Tag Archives: Computer Vision

MELON: Reconstructing 3D objects from images with unknown poses

Posted by Mark Matthews, Senior Software Engineer, and Dmitry Lagun, Research Scientist, Google Research

A person's prior experience and understanding of the world generally enables them to easily infer what an object looks like in whole, even if only looking at a few 2D pictures of it. Yet the capacity for a computer to reconstruct the shape of an object in 3D given only a few images has remained a difficult algorithmic problem for years. This fundamental computer vision task has applications ranging from the creation of e-commerce 3D models to autonomous vehicle navigation.

A key part of the problem is how to determine the exact positions from which images were taken, known as pose inference. If camera poses are known, a range of successful techniques — such as neural radiance fields (NeRF) or 3D Gaussian Splatting — can reconstruct an object in 3D. But if these poses are not available, then we face a difficult “chicken and egg” problem where we could determine the poses if we knew the 3D object, but we can’t reconstruct the 3D object until we know the camera poses. The problem is made harder by pseudo-symmetries — i.e., many objects look similar when viewed from different angles. For example, square objects like a chair tend to look similar every 90° rotation. Pseudo-symmetries of an object can be revealed by rendering it on a turntable from various angles and plotting its photometric self-similarity map.

Self-Similarity map of a toy truck model. Left: The model is rendered on a turntable from various azimuthal angles, θ. Right: The average L2 RGB similarity of a rendering from θ with that of θ*. The pseudo-similarities are indicated by the dashed red lines.

The diagram above only visualizes one dimension of rotation. It becomes even more complex (and difficult to visualize) when introducing more degrees of freedom. Pseudo-symmetries make the problem ill-posed, with naïve approaches often converging to local minima. In practice, such an approach might mistake the back view as the front view of an object, because they share a similar silhouette. Previous techniques (such as BARF or SAMURAI) side-step this problem by relying on an initial pose estimate that starts close to the global minima. But how can we approach this if those aren’t available?

Methods, such as GNeRF and VMRF leverage generative adversarial networks (GANs) to overcome the problem. These techniques have the ability to artificially “amplify” a limited number of training views, aiding reconstruction. GAN techniques, however, often have complex, sometimes unstable, training processes, making robust and reliable convergence difficult to achieve in practice. A range of other successful methods, such as SparsePose or RUST, can infer poses from a limited number views, but require pre-training on a large dataset of posed images, which aren’t always available, and can suffer from “domain-gap” issues when inferring poses for different types of images.

In “MELON: NeRF with Unposed Images in SO(3)”, spotlighted at 3DV 2024, we present a technique that can determine object-centric camera poses entirely from scratch while reconstructing the object in 3D. MELON (Modulo Equivalent Latent Optimization of NeRF) is one of the first techniques that can do this without initial pose camera estimates, complex training schemes or pre-training on labeled data. MELON is a relatively simple technique that can easily be integrated into existing NeRF methods. We demonstrate that MELON can reconstruct a NeRF from unposed images with state-of-the-art accuracy while requiring as few as 4–6 images of an object.


MELON

We leverage two key techniques to aid convergence of this ill-posed problem. The first is a very lightweight, dynamically trained convolutional neural network (CNN) encoder that regresses camera poses from training images. We pass a downscaled training image to a four layer CNN that infers the camera pose. This CNN is initialized from noise and requires no pre-training. Its capacity is so small that it forces similar looking images to similar poses, providing an implicit regularization greatly aiding convergence.

The second technique is a modulo loss that simultaneously considers pseudo symmetries of an object. We render the object from a fixed set of viewpoints for each training image, backpropagating the loss only through the view that best fits the training image. This effectively considers the plausibility of multiple views for each image. In practice, we find N=2 views (viewing an object from the other side) is all that’s required in most cases, but sometimes get better results with N=4 for square objects.

These two techniques are integrated into standard NeRF training, except that instead of fixed camera poses, poses are inferred by the CNN and duplicated by the modulo loss. Photometric gradients back-propagate through the best-fitting cameras into the CNN. We observe that cameras generally converge quickly to globally optimal poses (see animation below). After training of the neural field, MELON can synthesize novel views using standard NeRF rendering methods.

We simplify the problem by using the NeRF-Synthetic dataset, a popular benchmark for NeRF research and common in the pose-inference literature. This synthetic dataset has cameras at precisely fixed distances and a consistent “up” orientation, requiring us to infer only the polar coordinates of the camera. This is the same as an object at the center of a globe with a camera always pointing at it, moving along the surface. We then only need the latitude and longitude (2 degrees of freedom) to specify the camera pose.

MELON uses a dynamically trained lightweight CNN encoder that predicts a pose for each image. Predicted poses are replicated by the modulo loss, which only penalizes the smallest L2 distance from the ground truth color. At evaluation time, the neural field can be used to generate novel views.


Results

We compute two key metrics to evaluate MELON’s performance on the NeRF Synthetic dataset. The error in orientation between the ground truth and inferred poses can be quantified as a single angular error that we average across all training images, the pose error. We then test the accuracy of MELON’s rendered objects from novel views by measuring the peak signal-to-noise ratio (PSNR) against held out test views. We see that MELON quickly converges to the approximate poses of most cameras within the first 1,000 steps of training, and achieves a competitive PSNR of 27.5 dB after 50k steps.

Convergence of MELON on a toy truck model during optimization. Left: Rendering of the NeRF. Right: Polar plot of predicted (blue x), and ground truth (red dot) cameras.

MELON achieves similar results for other scenes in the NeRF Synthetic dataset.

Reconstruction quality comparison between ground-truth (GT) and MELON on NeRF-Synthetic scenes after 100k training steps.


Noisy images

MELON also works well when performing novel view synthesis from extremely noisy, unposed images. We add varying amounts, σ, of white Gaussian noise to the training images. For example, the object in σ=1.0 below is impossible to make out, yet MELON can determine the pose and generate novel views of the object.

Novel view synthesis from noisy unposed 128×128 images. Top: Example of noise level present in training views. Bottom: Reconstructed model from noisy training views and mean angular pose error.

This perhaps shouldn’t be too surprising, given that techniques like RawNeRF have demonstrated NeRF’s excellent de-noising capabilities with known camera poses. The fact that MELON works for noisy images of unknown camera poses so robustly was unexpected.


Conclusion

We present MELON, a technique that can determine object-centric camera poses to reconstruct objects in 3D without the need for approximate pose initializations, complex GAN training schemes or pre-training on labeled data. MELON is a relatively simple technique that can easily be integrated into existing NeRF methods. Though we only demonstrated MELON on synthetic images we are adapting our technique to work in real world conditions. See the paper and MELON site to learn more.


Acknowledgements

We would like to thank our paper co-authors Axel Levy, Matan Sela, and Gordon Wetzstein, as well as Florian Schroff and Hartwig Adam for continuous help in building this technology. We also thank Matthew Brown, Ricardo Martin-Brualla and Frederic Poitevin for their helpful feedback on the paper draft. We also acknowledge the use of the computational resources at the SLAC Shared Scientific Data Facility (SDF).

Source: Google AI Blog


Health-specific embedding tools for dermatology and pathology

Posted by Dave Steiner, Clinical Research Scientist, Google Health, and Rory Pilgrim, Product Manager Google Research

There’s a worldwide shortage of access to medical imaging expert interpretation across specialties including radiology, dermatology and pathology. Machine learning (ML) technology can help ease this burden by powering tools that enable doctors to interpret these images more accurately and efficiently. However, the development and implementation of such ML tools are often limited by the availability of high-quality data, ML expertise, and computational resources.

One way to catalyze the use of ML for medical imaging is via domain-specific models that utilize deep learning (DL) to capture the information in medical images as compressed numerical vectors (called embeddings). These embeddings represent a type of pre-learned understanding of the important features in an image. Identifying patterns in the embeddings reduces the amount of data, expertise, and compute needed to train performant models as compared to working with high-dimensional data, such as images, directly. Indeed, these embeddings can be used to perform a variety of downstream tasks within the specialized domain (see animated graphic below). This framework of leveraging pre-learned understanding to solve related tasks is similar to that of a seasoned guitar player quickly learning a new song by ear. Because the guitar player has already built up a foundation of skill and understanding, they can quickly pick up the patterns and groove of a new song.

Path Foundation is used to convert a small dataset of (image, label) pairs into (embedding, label) pairs. These pairs can then be used to train a task-specific classifier using a linear probe, (i.e., a lightweight linear classifier) as represented in this graphic, or other types of models using the embeddings as input.

Once the linear probe is trained, it can be used to make predictions on embeddings from new images. These predictions can be compared to ground truth information in order to evaluate the linear probe's performance.

In order to make this type of embedding model available and drive further development of ML tools in medical imaging, we are excited to release two domain-specific tools for research use: Derm Foundation and Path Foundation. This follows on the strong response we’ve already received from researchers using the CXR Foundation embedding tool for chest radiographs and represents a portion of our expanding research offerings across multiple medical-specialized modalities. These embedding tools take an image as input and produce a numerical vector (the embedding) that is specialized to the domains of dermatology and digital pathology images, respectively. By running a dataset of chest X-ray, dermatology, or pathology images through the respective embedding tool, researchers can obtain embeddings for their own images, and use these embeddings to quickly develop new models for their applications.


Path Foundation

In “Domain-specific optimization and diverse evaluation of self-supervised models for histopathology”, we showed that self-supervised learning (SSL) models for pathology images outperform traditional pre-training approaches and enable efficient training of classifiers for downstream tasks. This effort focused on hematoxylin and eosin (H&E) stained slides, the principal tissue stain in diagnostic pathology that enables pathologists to visualize cellular features under a microscope. The performance of linear classifiers trained using the output of the SSL models matched that of prior DL models trained on orders of magnitude more labeled data.

Due to substantial differences between digital pathology images and “natural image” photos, this work involved several pathology-specific optimizations during model training. One key element is that whole-slide images (WSIs) in pathology can be 100,000 pixels across (thousands of times larger than typical smartphone photos) and are analyzed by experts at multiple magnifications (zoom levels). As such, the WSIs are typically broken down into smaller tiles or patches for computer vision and DL applications. The resulting images are information dense with cells or tissue structures distributed throughout the frame instead of having distinct semantic objects or foreground vs. background variations, thus creating unique challenges for robust SSL and feature extraction. Additionally, physical (e.g., cutting) and chemical (e.g., fixing and staining) processes used to prepare the samples can influence image appearance dramatically.

Taking these important aspects into consideration, pathology-specific SSL optimizations included helping the model learn stain-agnostic features, generalizing the model to patches from multiple magnifications, augmenting the data to mimic scanning and image post processing, and custom data balancing to improve input heterogeneity for SSL training. These approaches were extensively evaluated using a broad set of benchmark tasks involving 17 different tissue types over 12 different tasks.

Utilizing the vision transformer (ViT-S/16) architecture, Path Foundation was selected as the best performing model from the optimization and evaluation process described above (and illustrated in the figure below). This model thus provides an important balance between performance and model size to enable valuable and scalable use in generating embeddings over the many individual image patches of large pathology WSIs.

SSL training with pathology-specific optimizations for Path Foundation.

The value of domain-specific image representations can also be seen in the figure below, which shows the linear probing performance improvement of Path Foundation (as measured by AUROC) compared to traditional pre-training on natural images (ImageNet-21k). This includes evaluation for tasks such as metastatic breast cancer detection in lymph nodes, prostate cancer grading, and breast cancer grading, among others.

Path Foundation embeddings significantly outperform traditional ImageNet embeddings as evaluated by linear probing across multiple evaluation tasks in histopathology.


Derm Foundation

Derm Foundation is an embedding tool derived from our research in applying DL to interpret images of dermatology conditions and includes our recent work that adds improvements to generalize better to new datasets. Due to its dermatology-specific pre-training it has a latent understanding of features present in images of skin conditions and can be used to quickly develop models to classify skin conditions. The model underlying the API is a BiT ResNet-101x3 trained in two stages. The first pre-training stage uses contrastive learning, similar to ConVIRT, to train on a large number of image-text pairs from the internet. In the second stage, the image component of this pre-trained model is then fine-tuned for condition classification using clinical datasets, such as those from teledermatology services.

Unlike histopathology images, dermatology images more closely resemble the real-world images used to train many of today's computer vision models. However, for specialized dermatology tasks, creating a high-quality model may still require a large dataset. With Derm Foundation, researchers can use their own smaller dataset to retrieve domain-specific embeddings, and use those to build smaller models (e.g., linear classifiers or other small non-linear models) that enable them to validate their research or product ideas. To evaluate this approach, we trained models on a downstream task using teledermatology data. Model training involved varying dataset sizes (12.5%, 25%, 50%, 100%) to compare embedding-based linear classifiers against fine-tuning.

The modeling variants considered were:

  • A linear classifier on frozen embeddings from BiT-M (a standard pre-trained image model)
  • Fine-tuned version of BiT-M with an extra dense layer for the downstream task
  • A linear classifier on frozen embeddings from the Derm Foundation API
  • Fine-tuned version of the model underlying the Derm Foundation API with an extra layer for the downstream task

We found that models built on top of the Derm Foundation embeddings for dermatology-related tasks achieved significantly higher quality than those built solely on embeddings or fine tuned from BiT-M. This advantage was found to be most pronounced for smaller training dataset sizes.

These results demonstrate that the Derm Foundation tooI can serve as a useful starting point to accelerate skin-related modeling tasks. We aim to enable other researchers to build on the underlying features and representations of dermatology that the model has learned.

However, there are limitations with this analysis. We're still exploring how well these embeddings generalize across task types, patient populations, and image settings. Downstream models built using Derm Foundation still require careful evaluation to understand their expected performance in the intended setting.


Access Path and Derm Foundation

We envision that the Derm Foundation and Path Foundation embedding tools will enable a range of use cases, including efficient development of models for diagnostic tasks, quality assurance and pre-analytical workflow improvements, image indexing and curation, and biomarker discovery and validation. We are releasing both tools to the research community so they can explore the utility of the embeddings for their own dermatology and pathology data.

To get access, please sign up to each tool's terms of service using the following Google Forms.

After gaining access to each tool, you can use the API to retrieve embeddings from dermatology images or digital pathology images stored in Google Cloud. Approved users who are just curious to see the model and embeddings in action can use the provided example Colab notebooks to train models using public data for classifying six common skin conditions or identifying tumors in histopathology patches. We look forward to seeing the range of use-cases these tools can unlock.


Acknowledgements

We would like to thank the many collaborators who helped make this work possible including Yun Liu, Can Kirmizi, Fereshteh Mahvar, Bram Sterling, Arman Tajback, Kenneth Philbrik, Arnav Agharwal, Aurora Cheung, Andrew Sellergren, Boris Babenko, Basil Mustafa, Jan Freyberg, Terry Spitz, Yuan Liu, Pinal Bavishi, Ayush Jain, Amit Talreja, Rajeev Rikhye, Abbi Ward, Jeremy Lai, Faruk Ahmed, Supriya Vijay,Tiam Jaroensri, Jessica Loo, Saurabh Vyawahare, Saloni Agarwal, Ellery Wulczyn, Jonathan Krause, Fayaz Jamil, Tom Small, Annisah Um'rani, Lauren Winer, Sami Lachgar, Yossi Matias, Greg Corrado, and Dale Webster.

Source: Google AI Blog


MobileDiffusion: Rapid text-to-image generation on-device

Posted by Yang Zhao, Senior Software Engineer, and Tingbo Hou, Senior Staff Software Engineer, Core ML

Text-to-image diffusion models have shown exceptional capabilities in generating high-quality images from text prompts. However, leading models feature billions of parameters and are consequently expensive to run, requiring powerful desktops or servers (e.g., Stable Diffusion, DALL·E, and Imagen). While recent advancements in inference solutions on Android via MediaPipe and iOS via Core ML have been made in the past year, rapid (sub-second) text-to-image generation on mobile devices has remained out of reach.

To that end, in “MobileDiffusion: Subsecond Text-to-Image Generation on Mobile Devices”, we introduce a novel approach with the potential for rapid text-to-image generation on-device. MobileDiffusion is an efficient latent diffusion model specifically designed for mobile devices. We also adopt DiffusionGAN to achieve one-step sampling during inference, which fine-tunes a pre-trained diffusion model while leveraging a GAN to model the denoising step. We have tested MobileDiffusion on iOS and Android premium devices, and it can run in half a second to generate a 512x512 high-quality image. Its comparably small model size of just 520M parameters makes it uniquely suited for mobile deployment.

      
Rapid text-to-image generation on-device.

Background

The relative inefficiency of text-to-image diffusion models arises from two primary challenges. First, the inherent design of diffusion models requires iterative denoising to generate images, necessitating multiple evaluations of the model. Second, the complexity of the network architecture in text-to-image diffusion models involves a substantial number of parameters, regularly reaching into the billions and resulting in computationally expensive evaluations. As a result, despite the potential benefits of deploying generative models on mobile devices, such as enhancing user experience and addressing emerging privacy concerns, it remains relatively unexplored within the current literature.

The optimization of inference efficiency in text-to-image diffusion models has been an active research area. Previous studies predominantly concentrate on addressing the first challenge, seeking to reduce the number of function evaluations (NFEs). Leveraging advanced numerical solvers (e.g., DPM) or distillation techniques (e.g., progressive distillation, consistency distillation), the number of necessary sampling steps have significantly reduced from several hundreds to single digits. Some recent techniques, like DiffusionGAN and Adversarial Diffusion Distillation, even reduce to a single necessary step.

However, on mobile devices, even a small number of evaluation steps can be slow due to the complexity of model architecture. Thus far, the architectural efficiency of text-to-image diffusion models has received comparatively less attention. A handful of earlier works briefly touches upon this matter, involving the removal of redundant neural network blocks (e.g., SnapFusion). However, these efforts lack a comprehensive analysis of each component within the model architecture, thereby falling short of providing a holistic guide for designing highly efficient architectures.


MobileDiffusion

Effectively overcoming the challenges imposed by the limited computational power of mobile devices requires an in-depth and holistic exploration of the model's architectural efficiency. In pursuit of this objective, our research undertakes a detailed examination of each constituent and computational operation within Stable Diffusion’s UNet architecture. We present a comprehensive guide for crafting highly efficient text-to-image diffusion models culminating in the MobileDiffusion.

The design of MobileDiffusion follows that of latent diffusion models. It contains three components: a text encoder, a diffusion UNet, and an image decoder. For the text encoder, we use CLIP-ViT/L14, which is a small model (125M parameters) suitable for mobile. We then turn our focus to the diffusion UNet and image decoder.


Diffusion UNet

As illustrated in the figure below, diffusion UNets commonly interleave transformer blocks and convolution blocks. We conduct a comprehensive investigation of these two fundamental building blocks. Throughout the study, we control the training pipeline (e.g., data, optimizer) to study the effects of different architectures.

In classic text-to-image diffusion models, a transformer block consists of a self-attention layer (SA) for modeling long-range dependencies among visual features, a cross-attention layer (CA) to capture interactions between text conditioning and visual features, and a feed-forward layer (FF) to post-process the output of attention layers. These transformer blocks hold a pivotal role in text-to-image diffusion models, serving as the primary components responsible for text comprehension. However, they also pose a significant efficiency challenge, given the computational expense of the attention operation, which is quadratic to the sequence length. We follow the idea of UViT architecture, which places more transformer blocks at the bottleneck of the UNet. This design choice is motivated by the fact that the attention computation is less resource-intensive at the bottleneck due to its lower dimensionality.

Our UNet architecture incorporates more transformers in the middle, and skips self-attention (SA) layers at higher resolutions.

Convolution blocks, in particular ResNet blocks, are deployed at each level of the UNet. While these blocks are instrumental for feature extraction and information flow, the associated computational costs, especially at high-resolution levels, can be substantial. One proven approach in this context is separable convolution. We observed that replacing regular convolution layers with lightweight separable convolution layers in the deeper segments of the UNet yields similar performance.

In the figure below, we compare the UNets of several diffusion models. Our MobileDiffusion exhibits superior efficiency in terms of FLOPs (floating-point operations) and number of parameters.

Comparison of some diffusion UNets.

Image decoder

In addition to the UNet, we also optimized the image decoder. We trained a variational autoencoder (VAE) to encode an RGB image to an 8-channel latent variable, with 8× smaller spatial size of the image. A latent variable can be decoded to an image and gets 8× larger in size. To further enhance efficiency, we design a lightweight decoder architecture by pruning the original’s width and depth. The resulting lightweight decoder leads to a significant performance boost, with nearly 50% latency improvement and better quality. For more details, please refer to our paper.

VAE reconstruction. Our VAE decoders have better visual quality than SD (Stable Diffusion).

Decoder   #Params (M)     PSNR↑     SSIM↑     LPIPS↓  
SD 49.5 26.7 0.76 0.037
Ours 39.3 30.0 0.83 0.032
Ours-Lite     9.8 30.2 0.84 0.032

Quality evaluation of VAE decoders. Our lite decoder is much smaller than SD, with better quality metrics, including peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), and Learned Perceptual Image Patch Similarity (LPIPS).

One-step sampling

In addition to optimizing the model architecture, we adopt a DiffusionGAN hybrid to achieve one-step sampling. Training DiffusionGAN hybrid models for text-to-image generation encounters several intricacies. Notably, the discriminator, a classifier distinguishing real data and generated data, must make judgments based on both texture and semantics. Moreover, the cost of training text-to-image models can be extremely high, particularly in the case of GAN-based models, where the discriminator introduces additional parameters. Purely GAN-based text-to-image models (e.g., StyleGAN-T, GigaGAN) confront similar complexities, resulting in highly intricate and expensive training.

To overcome these challenges, we use a pre-trained diffusion UNet to initialize the generator and discriminator. This design enables seamless initialization with the pre-trained diffusion model. We postulate that the internal features within the diffusion model contain rich information of the intricate interplay between textual and visual data. This initialization strategy significantly streamlines the training.

The figure below illustrates the training procedure. After initialization, a noisy image is sent to the generator for one-step diffusion. The result is evaluated against ground truth with a reconstruction loss, similar to diffusion model training. We then add noise to the output and send it to the discriminator, whose result is evaluated with a GAN loss, effectively adopting the GAN to model a denoising step. By using pre-trained weights to initialize the generator and the discriminator, the training becomes a fine-tuning process, which converges in less than 10K iterations.

Illustration of DiffusionGAN fine-tuning.

Results

Below we show example images generated by our MobileDiffusion with DiffusionGAN one-step sampling. With such a compact model (520M parameters in total), MobileDiffusion can generate high-quality diverse images for various domains.

Images generated by our MobileDiffusion

We measured the performance of our MobileDiffusion on both iOS and Android devices, using different runtime optimizers. The latency numbers are reported below. We see that MobileDiffusion is very efficient and can run within half a second to generate a 512x512 image. This lightning speed potentially enables many interesting use cases on mobile devices.

Latency measurements (s) on mobile devices.

Conclusion

With superior efficiency in terms of latency and size, MobileDiffusion has the potential to be a very friendly option for mobile deployments given its capability to enable a rapid image generation experience while typing text prompts. And we will ensure any application of this technology will be in-line with Google’s responsible AI practices.


Acknowledgments

We like to thank our collaborators and contributors that helped bring MobileDiffusion to on-device: Zhisheng Xiao, Yanwu Xu, Jiuqiang Tang, Haolin Jia, Lutz Justen, Daniel Fenner, Ronald Wotzlaw, Jianing Wei, Raman Sarokin, Juhyun Lee, Andrei Kulik, Chuo-Ling Chang, and Matthias Grundmann.

Source: Google AI Blog


HealthPulse AI Leverages MediaPipe to Increase Health Equity

A guest post by Rouella Mendonca, AI Product Lead and Matt Brown, Machine Learning Engineer at Audere

Please note that the information, uses, and applications expressed in the below post are solely those of our guest authors from Audere.


About HealthPulse AI and its application in the real world

Preventable and treatable diseases like HIV, COVID-19, and malaria infect ~12 million per year globally with a disproportionate number of cases impacting already underserved and under-resourced communities1. Communicable and non-communicable diseases are impeding human development by their negative impact on education, income, life expectancy, and other health indicators2. Lack of access to timely, accurate, and affordable diagnostics and care is a key contributor to high mortality rates.

Due to their low cost and relative ease of use, ~1 billion rapid diagnostic tests (RDTs) are used globally per year and growing. However, there are challenges with RDT use.

  • Where RDT data is reported, results are hard to trust due to inflated case counts, lack of reported expected seasonal fluctuations, and non-adherence to treatment regimens.
  • They are used in decentralized care settings by those with limited or no training, increasing the risk of misadministration and misinterpretation of test results.

HealthPulse AI, developed by a digital health non-profit Audere, leverages MediaPipe to address these issues by providing digital building blocks to increase trust in the world’s most widely used RDTs.

HealthPulse AI is a set of building blocks that can turn any digital solution into a Rapid Diagnostic Test (RDT) reader. These building blocks solve prominent global health problems by improving rapid diagnostic test accuracy, reducing misadministration of tests, and expanding the availability of testing for conditions including malaria, COVID, and HIV in decentralized care settings. With just a low-end smartphone, HealthPulse AI improves the accuracy of rapid diagnostic test results while automatically digitizing data for surveillance, program reporting, and test validation. It provides AI facilitated digital capture and result interpretation; quality, accessible digital use instructions for provider and self-tests; and standards based real-time reporting of test results.

These capabilities are available to local implementers, global NGOs, governments, and private sector pharmacies via a web service for use with chatbots, apps or server implementations; a mobile SDK for offline use in any mobile application; or directly through native Android and iOS apps.

It enables innovative use cases such as quality-assured virtual care models which enables stigma-free, convenient HIV home testing with linkage to education, prevention, and treatment options.

HealthPulse AI Use Cases

HealthPulse AI can substantially democratize access to timely, quality care in the private sector (e.g. pharmacies), in the public sector (e.g. clinics), in community programs (e.g. community health workers), and self-testing use cases. Using only an RDT image captured on a low-end smartphone, HealthPulse AI can power virtual care models by providing valuable decision support and quality control to clinicians, especially in cases where lines may be faint and hard to detect with the human eye. In the private sector, it can automate and scale incentive programs so auditors only need to review automated alerts based on test anomalies; procedures which presently require human reviews of each incoming image and transaction. In community care programs, HealthPulse AI can be used as a training tool for health workers learning how to correctly administer and interpret tests. In the public sector, it can strengthen surveillance systems with real-time disease tracking and verification of results across all channels where care is delivered - enabling faster response and pandemic preparedness3.


HealthPulse AI algorithms

HealthPulse AI provides a library of AI algorithms for the top RDTs for malaria, HIV, and COVID. Each algorithm is a collection of Computer Vision (CV) models that are trained using machine learning (ML) algorithms. From an image of an RDT, our algorithms can:

  • Flag image quality issues common on low-end phones (blurriness, over/underexposure)
  • Detect the RDT type
  • Interpret the test result

Image Quality Assurance

When capturing an image of an RDT, it is important to ensure that the image captured is human and AI interpretable to power the use cases described above. Image quality issues are common, particularly when images are captured with low-end phones in settings that may have poor lighting or simply captured by users with shaky hands. As such, HealthPulse AI provides image quality assurance (IQA) to identify adversarial image conditions. IQA returns concerns detected and can be used to request users to retake the photo in real time. Without IQA, clients would have to retest due to uninterpretable images and expired RDT read windows in telehealth use cases, for example. With just-in-time quality concern flagging, additional cost and treatment delays can be avoided. Examples of some adversarial images that IQA would flag are shown in Figure 1 below.

Images of malaria, HIV and COVID tests that are dark, blurry, too bright, and too small.
Figure 1: Images of malaria, HIV and COVID tests that are dark, blurry, too bright, and too small.

Classification

With just an image captured on a 5MP camera from low-end smartphones commonly used in Africa, SE Asia, and Latin America where a disproportionate disease burden exists, HealthPulse AI can identify a specific test (brand, disease), individual test lines, and provide an interpretation of the test. Our current library of AI algorithms supports many of the most commonly used RDTs for malaria, HIV, and COVID-19 that are W.H.O. pre-qualified. Our AI is condition agnostic and can be easily extended to support any RDT for a range of communicable and non-communicable diseases (Diabetes, Influenza, Tuberculosis, Pregnancy, STIs and more).

HealthPulse AI is able to detect the type of RDT in the image (for supported RDTs that the model was trained for), detect the presence of lines, and return a classification for the particular test (e.g. positive, negative, invalid, uninterpretable). See Figure 2.

Figure 2: Interpretation of a supported lateral flow rapid test.
Figure 2: Interpretation of a supported lateral flow rapid test.

How and why we use MediaPipe

Deploying HealthPulse AI in decentralized care settings with unstable infrastructure comes with a number of challenges. The first challenge is a lack of reliable internet connectivity, often requiring our CV and ML algorithms to run locally. Secondly, phones available in these settings are often very old, lacking the latest hardware (< 1 GB of ram and comparable CPU specs), and on different platforms and versions ( iOS, Android, Huawei; very old versions - possibly no longer receiving OS updates) mobile platforms. This necessitates having a platform agnostic, highly efficient inference engine. MediaPipe’s out-of-the-box multi-platform support for image-focused machine learning processes makes it efficient to meet these needs.

As a non-profit operating in cost-recovery mode, it was important that solutions:

  • have broad reach globally,
  • are low-lift to maintain, and
  • meet the needs of our target population for offline, low resource, performant use.

Without needing to write a lot of glue code, HealthPulse AI can support Android, iOS, and cloud devices using the same library built on MediaPipe.

Our pipeline

MediaPipe’s graph definitions allow us to build and iterate our inference pipeline on the fly. After a user submits a picture, the pipeline determines the RDT type, and attempts to classify the test result by passing the detected result-window crop of the RDT image to our classifier.

For good human and AI interpretability, it is important to have good quality images. However, input images to the pipeline have a high level of variability we have little to no control over. Variability factors include (but are not limited to) varying image quality due to a range of smartphone camera features/megapixels/physical defects, decentralized testing settings which include differing and non-ideal lighting conditions, random orientations of the RDT cassettes, blurry and unfocused images, partial RDT images, and many other adversarial conditions that add challenges for the AI. As such, an important part of our solution is image quality assurance. Each image passes through a number of calculators geared towards highlighting quality concerns that may prevent the detector or classifier from doing its job accurately. The pipeline elevates these concerns to the host application, so an end-user can be requested in real-time to retake a photo when necessary. Since RDT results have a limited validity time (e.g. a time window specified by the RDT manufacturer for how long after processing a result can be accurately read), IQA is essential to ensure timely care and save costs. A high level flowchart of the pipeline is shown below in Figure 3.

Figure 3: HealthPulse AI pipeline
Figure 3: HealthPulse AI pipeline

Summary

HealthPulse AI is designed to improve the quality and richness of testing programs and data in underserved communities that are disproportionately impacted by preventable communicable and non-communicable diseases.

Towards this mission, MediaPipe plays a critical role by providing a platform that allows Audere to quickly iterate and support new rapid diagnostic tests. This is imperative as new rapid tests come to market regularly, and test availability for community and home use can change frequently. Additionally, the flexibility allows for lower overhead in maintaining the pipeline, which is crucial for cost-effective operations. This, in turn, reduces the cost of use for governments and organizations globally that provide services to people who need them most.

HealthPulse AI offerings allow organizations and governments to benefit from new innovations in the diagnostics space with minimal overhead. This is an essential component of the primary health journey - to ensure that populations in under-resourced communities have access to timely, cost-effective, and efficacious care.


About Audere

Audere is a global digital health nonprofit developing AI based solutions to address important problems in health delivery by providing innovative, scalable, interconnected tools to advance health equity in underserved communities worldwide. We operate at the unique intersection of global health and high tech, creating advanced, accessible software that revolutionizes the detection, prevention, and treatment of diseases — such as malaria, COVID-19, and HIV. Our diverse team of passionate, innovative minds combines human-centered design, smartphone technology, artificial intelligence (AI), open standards, and the best of cloud-based services to empower innovators globally to deliver healthcare in new ways in low-and-middle income settings. Audere operates primarily in Africa with projects in Nigeria, Kenya, Côte d’Ivoire, Benin, Uganda, Zambia, South Africa, and Ethiopia.


1 WHO malaria fact sheets

StyleDrop: Text-to-image generation in any style

Posted by Kihyuk Sohn and Dilip Krishnan, Research Scientists, Google Research

Text-to-image models trained on large volumes of image-text pairs have enabled the creation of rich and diverse images encompassing many genres and themes. Moreover, popular styles such as “anime” or “steampunk”, when added to the input text prompt, may translate to specific visual outputs. While many efforts have been put into prompt engineering, a wide range of styles are simply hard to describe in text form due to the nuances of color schemes, illumination, and other characteristics. As an example, “watercolor painting” may refer to various styles, and using a text prompt that simply says “watercolor painting style” may either result in one specific style or an unpredictable mix of several.

When we refer to "watercolor painting style," which do we mean? Instead of specifying the style in natural language, StyleDrop allows the generation of images that are consistent in style by referring to a style reference image*.

In this blog we introduce “StyleDrop: Text-to-Image Generation in Any Style”, a tool that allows a significantly higher level of stylized text-to-image synthesis. Instead of seeking text prompts to describe the style, StyleDrop uses one or more style reference images that describe the style for text-to-image generation. By doing so, StyleDrop enables the generation of images in a style consistent with the reference, while effectively circumventing the burden of text prompt engineering. This is done by efficiently fine-tuning the pre-trained text-to-image generation models via adapter tuning on a few style reference images. Moreover, by iteratively fine-tuning the StyleDrop on a set of images it generated, it achieves the style-consistent image generation from text prompts.


Method overview

StyleDrop is a text-to-image generation model that allows generation of images whose visual styles are consistent with the user-provided style reference images. This is achieved by a couple of iterations of parameter-efficient fine-tuning of pre-trained text-to-image generation models. Specifically, we build StyleDrop on Muse, a text-to-image generative vision transformer.


Muse: text-to-image generative vision transformer

Muse is a state-of-the-art text-to-image generation model based on the masked generative image transformer (MaskGIT). Unlike diffusion models, such as Imagen or Stable Diffusion, Muse represents an image as a sequence of discrete tokens and models their distribution using a transformer architecture. Compared to diffusion models, Muse is known to be faster while achieving competitive generation quality.


Parameter-efficient adapter tuning

StyleDrop is built by fine-tuning the pre-trained Muse model on a few style reference images and their corresponding text prompts. There have been many works on parameter-efficient fine-tuning of transformers, including prompt tuning and Low-Rank Adaptation (LoRA) of large language models. Among those, we opt for adapter tuning, which is shown to be effective at fine-tuning a large transformer network for language and image generation tasks in a parameter-efficient manner. For example, it introduces less than one million trainable parameters to fine-tune a Muse model of 3B parameters, and it requires only 1000 training steps to converge.

Parameter-efficient adapter tuning of Muse.

Iterative training with feedback

While StyleDrop is effective at learning styles from a few style reference images, it is still challenging to learn from a single style reference image. This is because the model may not effectively disentangle the content (i.e., what is in the image) and the style (i.e., how it is being presented), leading to reduced text controllability in generation. For example, as shown below in Step 1 and 2, a generated image of a chihuahua from StyleDrop trained from a single style reference image shows a leakage of content (i.e., the house) from the style reference image. Furthermore, a generated image of a temple looks too similar to the house in the reference image (concept collapse).

We address this issue by training a new StyleDrop model on a subset of synthetic images, chosen by the user or by image-text alignment models (e.g., CLIP), whose images are generated by the first round of the StyleDrop model trained on a single image. By training on multiple synthetic image-text aligned images, the model can easily disentangle the style from the content, thus achieving improved image-text alignment.

Iterative training with feedback*. The first round of StyleDrop may result in reduced text controllability, such as a content leakage or concept collapse, due to the difficulty of content-style disentanglement. Iterative training using synthetic images, generated by the previous rounds of StyleDrop models and chosen by human or image-text alignment models, improves the text adherence of stylized text-to-image generation.

Experiments


StyleDrop gallery

We show the effectiveness of StyleDrop by running experiments on 24 distinct style reference images. As shown below, the images generated by StyleDrop are highly consistent in style with each other and with the style reference image, while depicting various contexts, such as a baby penguin, banana, piano, etc. Moreover, the model can render alphabet images with a consistent style.

Stylized text-to-image generation. Style reference images* are on the left inside the yellow box. Text prompts used are:
First row: a baby penguin, a banana, a bench.
Second row: a butterfly, an F1 race car, a Christmas tree.
Third row: a coffee maker, a hat, a moose.
Fourth row: a robot, a towel, a wood cabin.
Stylized visual character generation. Style reference images* are on the left inside the yellow box. Text prompts used are: (first row) letter 'A', letter 'B', letter 'C', (second row) letter 'E', letter 'F', letter 'G'.

Generating images of my object in my style

Below we show generated images by sampling from two personalized generation distributions, one for an object and another for the style.

Images at the top in the blue border are object reference images from the DreamBooth dataset (teapot, vase, dog and cat), and the image on the left at the bottom in the red border is the style reference image*. Images in the purple border (i.e. the four lower right images) are generated from the style image of the specific object.

Quantitative results

For the quantitative evaluation, we synthesize images from a subset of Parti prompts and measure the image-to-image CLIP score for style consistency and image-to-text CLIP score for text consistency. We study non–fine-tuned models of Muse and Imagen. Among fine-tuned models, we make a comparison to DreamBooth on Imagen, state-of-the-art personalized text-to-image method for subjects. We show two versions of StyleDrop, one trained from a single style reference image, and another, “StyleDrop (HF)”, that is trained iteratively using synthetic images with human feedback as described above. As shown below, StyleDrop (HF) shows significantly improved style consistency score over its non–fine-tuned counterpart (0.694 vs. 0.556), as well as DreamBooth on Imagen (0.694 vs. 0.644). We observe an improved text consistency score with StyleDrop (HF) over StyleDrop (0.322 vs. 0.313). In addition, in a human preference study between DreamBooth on Imagen and StyleDrop on Muse, we found that 86% of the human raters preferred StyleDrop on Muse over DreamBooth on Imagen in terms of consistency to the style reference image.


Conclusion

StyleDrop achieves style consistency at text-to-image generation using a few style reference images. Google’s AI Principles guided our development of Style Drop, and we urge the responsible use of the technology. StyleDrop was adapted to create a custom style model in Vertex AI, and we believe it could be a helpful tool for art directors and graphic designers — who might want to brainstorm or prototype visual assets in their own styles, to improve their productivity and boost their creativity — or businesses that want to generate new media assets that reflect a particular brand. As with other generative AI capabilities, we recommend that practitioners ensure they align with copyrights of any media assets they use. More results are found on our project website and YouTube video.


Acknowledgements

This research was conducted by Kihyuk Sohn, Nataniel Ruiz, Kimin Lee, Daniel Castro Chin, Irina Blok, Huiwen Chang, Jarred Barber, Lu Jiang, Glenn Entis, Yuanzhen Li, Yuan Hao, Irfan Essa, Michael Rubinstein, and Dilip Krishnan. We thank owners of images used in our experiments (links for attribution) for sharing their valuable assets.

*See image sources ↩

Source: Google AI Blog


Open sourcing Project Guideline: A platform for computer vision accessibility technology

Posted by Dave Hawkey, Software Engineer, Google Research

Two years ago we announced Project Guideline, a collaboration between Google Research and Guiding Eyes for the Blind that enabled people with visual impairments (e.g., blindness and low-vision) to walk, jog, and run independently. Using only a Google Pixel phone and headphones, Project Guideline leverages on-device machine learning (ML) to navigate users along outdoor paths marked with a painted line. The technology has been tested all over the world and even demonstrated during the opening ceremony at the Tokyo 2020 Paralympic Games.

Since the original announcement, we set out to improve Project Guideline by embedding new features, such as obstacle detection and advanced path planning, to safely and reliably navigate users through more complex scenarios (such as sharp turns and nearby pedestrians). The early version featured a simple frame-by-frame image segmentation that detected the position of the path line relative to the image frame. This was sufficient for orienting the user to the line, but provided limited information about the surrounding environment. Improving the navigation signals, such as alerts for obstacles and upcoming turns, required a much better understanding and mapping of the users’ environment. To solve these challenges, we built a platform that can be utilized for a variety of spatially-aware applications in the accessibility space and beyond.

Today, we announce the open source release of Project Guideline, making it available for anyone to use to improve upon and build new accessibility experiences. The release includes source code for the core platform, an Android application, pre-trained ML models, and a 3D simulation framework.


System design

The primary use-case is an Android application, however we wanted to be able to run, test, and debug the core logic in a variety of environments in a reproducible way. This led us to design and build the system using C++ for close integration with MediaPipe and other core libraries, while still being able to integrate with Android using the Android NDK.

Under the hood, Project Guideline uses ARCore to estimate the position and orientation of the user as they navigate the course. A segmentation model, built on the DeepLabV3+ framework, processes each camera frame to generate a binary mask of the guideline (see the previous blog post for more details). Points on the segmented guideline are then projected from image-space coordinates onto a world-space ground plane using the camera pose and lens parameters (intrinsics) provided by ARCore. Since each frame contributes a different view of the line, the world-space points are aggregated over multiple frames to build a virtual mapping of the real-world guideline. The system performs piecewise curve approximation of the guideline world-space coordinates to build a spatio-temporally consistent trajectory. This allows refinement of the estimated line as the user progresses along the path.

Project Guideline builds a 2D map of the guideline, aggregating detected points in each frame (red) to build a stateful representation (blue) as the runner progresses along the path.

A control system dynamically selects a target point on the line some distance ahead based on the user’s current position, velocity, and direction. An audio feedback signal is then given to the user to adjust their heading to coincide with the upcoming line segment. By using the runner’s velocity vector instead of camera orientation to compute the navigation signal, we eliminate noise caused by irregular camera movements common during running. We can even navigate the user back to the line while it’s out of camera view, for example if the user overshot a turn. This is possible because ARCore continues to track the pose of the camera, which can be compared to the stateful line map inferred from previous camera images.

Project Guideline also includes obstacle detection and avoidance features. An ML model is used to estimate depth from single images. To train this monocular depth model, we used SANPO, a large dataset of outdoor imagery from urban, park, and suburban environments that was curated in-house. The model is capable of detecting the depth of various obstacles, including people, vehicles, posts, and more. The depth maps are converted into 3D point clouds, similar to the line segmentation process, and used to detect the presence of obstacles along the user’s path and then alert the user through an audio signal.

Using a monocular depth ML model, Project Guideline constructs a 3D point cloud of the environment to detect and alert the user of potential obstacles along the path.

A low-latency audio system based on the AAudio API was implemented to provide the navigational sounds and cues to the user. Several sound packs are available in Project Guideline, including a spatial sound implementation using the Resonance Audio API. The sound packs were developed by a team of sound researchers and engineers at Google who designed and tested many different sound models. The sounds use a combination of panning, pitch, and spatialization to guide the user along the line. For example, a user veering to the right may hear a beeping sound in the left ear to indicate the line is to the left, with increasing frequency for a larger course correction. If the user veers further, a high-pitched warning sound may be heard to indicate the edge of the path is approaching. In addition, a clear “stop” audio cue is always available in the event the user veers too far from the line, an anomaly is detected, or the system fails to provide a navigational signal.

Project Guideline has been built specifically for Google Pixel phones with the Google Tensor chip. The Google Tensor chip enables the optimized ML models to run on-device with higher performance and lower power consumption. This is critical for providing real-time navigation instructions to the user with minimal delay. On a Pixel 8 there is a 28x latency improvement when running the depth model on the Tensor Processing Unit (TPU) instead of CPU, and 9x improvement compared to GPU.



Testing and simulation

Project Guideline includes a simulator that enables rapid testing and prototyping of the system in a virtual environment. Everything from the ML models to the audio feedback system runs natively within the simulator, giving the full Project Guideline experience without needing all the hardware and physical environment set up.

Screenshot of Project Guideline simulator.


Future direction

To launch the technology forward, WearWorks has become an early adopter and teamed up with Project Guideline to integrate their patented haptic navigation experience, utilizing haptic feedback in addition to sound to guide runners. WearWorks has been developing haptics for over 8 years, and previously empowered the first blind marathon runner to complete the NYC Marathon without sighted assistance. We hope that integrations like these will lead to new innovations and make the world a more accessible place.

The Project Guideline team is also working towards removing the painted line completely, using the latest advancements in mobile ML technology, such as the ARCore Scene Semantics API, which can identify sidewalks, buildings, and other objects in outdoor scenes. We invite the accessibility community to build upon and improve this technology while exploring new use cases in other fields.


Acknowledgements

Many people were involved in the development of Project Guideline and the technologies behind it. We’d like to thank Project Guideline team members: Dror Avalon, Phil Bayer, Ryan Burke, Lori Dooley, Song Chun Fan, Matt Hall, Amélie Jean-aimée, Dave Hawkey, Amit Pitaru, Alvin Shi, Mikhail Sirotenko, Sagar Waghmare, John Watkinson, Kimberly Wilber, Matthew Willson, Xuan Yang, Mark Zarich, Steven Clark, Jim Coursey, Josh Ellis, Tom Hoddes, Dick Lyon, Chris Mitchell, Satoru Arao, Yoojin Chung, Joe Fry, Kazuto Furuichi, Ikumi Kobayashi, Kathy Maruyama, Minh Nguyen, Alto Okamura, Yosuke Suzuki, and Bryan Tanaka. Thanks to ARCore contributors: Ryan DuToit, Abhishek Kar, and Eric Turner. Thanks to Alec Go, Jing Li, Liviu Panait, Stefano Pellegrini, Abdullah Rashwan, Lu Wang, Qifei Wang, and Fan Yang for providing ML platform support. We’d also like to thank Hartwig Adam, Tomas Izo, Rahul Sukthankar, Blaise Aguera y Arcas, and Huisheng Wang for their leadership support. Special thanks to our partners Guiding Eyes for the Blind and Achilles International.

Source: Google AI Blog


Scaling multimodal understanding to long videos

Posted by Isaac Noble, Software Engineer, Google Research, and Anelia Angelova, Research Scientist, Google DeepMind

When building machine learning models for real-life applications, we need to consider inputs from multiple modalities in order to capture various aspects of the world around us. For example, audio, video, and text all provide varied and complementary information about a visual input. However, building multimodal models is challenging due to the heterogeneity of the modalities. Some of the modalities might be well synchronized in time (e.g., audio, video) but not aligned with text. Furthermore, the large volume of data in video and audio signals is much larger than that in text, so when combining them in multimodal models, video and audio often cannot be fully consumed and need to be disproportionately compressed. This problem is exacerbated for longer video inputs.

In “Mirasol3B: A Multimodal Autoregressive model for time-aligned and contextual modalities”, we introduce a multimodal autoregressive model (Mirasol3B) for learning across audio, video, and text modalities. The main idea is to decouple the multimodal modeling into separate focused autoregressive models, processing the inputs according to the characteristics of the modalities. Our model consists of an autoregressive component for the time-synchronized modalities (audio and video) and a separate autoregressive component for modalities that are not necessarily time-aligned but are still sequential, e.g., text inputs, such as a title or description. Additionally, the time-aligned modalities are partitioned in time where local features can be jointly learned. In this way, audio-video inputs are modeled in time and are allocated comparatively more parameters than prior works. With this approach, we can effortlessly handle much longer videos (e.g., 128-512 frames) compared to other multimodal models. At 3B parameters, Mirasol3B is compact compared to prior Flamingo (80B) and PaLI-X (55B) models. Finally, Mirasol3B outperforms the state-of-the-art approaches on video question answering (video QA), long video QA, and audio-video-text benchmarks.

The Mirasol3B architecture consists of an autoregressive model for the time-aligned modalities (audio and video), which are partitioned in chunks, and a separate autoregressive model for the unaligned context modalities (e.g., text). Joint feature learning is conducted by the Combiner, which learns compact but sufficiently informative features, allowing the processing of long video/audio inputs.

Coordinating time-aligned and contextual modalities

Video, audio and text are diverse modalities with distinct characteristics. For example, video is a spatio-temporal visual signal with 30–100 frames per second, but due to the large volume of data, typically only 32–64 frames per video are consumed by current models. Audio is a one-dimensional temporal signal obtained at much higher frequency than video (e.g., at 16 Hz), whereas text inputs that apply to the whole video, are typically 200–300 word-sequence and serve as a context to the audio-video inputs. To that end, we propose a model consisting of an autoregressive component that fuses and jointly learns the time-aligned signals, which occur at high frequencies and are roughly synchronized, and another autoregressive component for processing non-aligned signals. Learning between the components for the time-aligned and contextual modalities is coordinated via cross-attention mechanisms that allow the two to exchange information while learning in a sequence without having to synchronize them in time.


Time-aligned autoregressive modeling of video and audio

Long videos can convey rich information and activities happening in a sequence. However, present models approach video modeling by extracting all the information at once, without sufficient temporal information. To address this, we apply an autoregressive modeling strategy where we condition jointly learned video and audio representations for one time interval on feature representations from previous time intervals. This preserves temporal information.

The video is first partitioned into smaller video chunks. Each chunk itself can be 4–64 frames. The features corresponding to each chunk are then processed by a learning module, called the Combiner (described below), which generates a joint audio and video feature representation at the current step — this step extracts and compacts the most important information per chunk. Next, we process this joint feature representation with an autoregressive Transformer, which applies attention to the previous feature representation and generates the joint feature representation for the next step. Consequently, the model learns how to represent not only each individual chunk, but also how the chunks relate temporally.

We use an autoregressive modeling of the audio and video inputs, partitioning them in time and learning joint feature representations, which are then autoregressively learned in sequence.

Modeling long videos with a modality combiner

To combine the signals from the video and audio information in each video chunk, we propose a learning module called the Combiner. Video and audio signals are aligned by taking the audio inputs that correspond to a specific video timeframe. We then process video and audio inputs spatio-temporally, extracting information particularly relevant to changes in the inputs (for videos we use sparse video tubes, and for audio we apply the spectrogram representation, both of which are processed by a Vision Transformer). We concatenate and input these features to the Combiner, which is designed to learn a new feature representation capturing both these inputs. To address the challenge of the large volume of data in video and audio signals, another goal of the Combiner is to reduce the dimensionality of the joint video/audio inputs, which is done by selecting a smaller number of output features to be produced. The Combiner can be implemented simply as a causal Transformer, which processes the inputs in the direction of time, i.e., using only inputs of the prior steps or the current one. Alternatively, the Combiner can have a learnable memory, described below.


Combiner styles

A simple version of the Combiner adapts a Transformer architecture. More specifically, all audio and video features from the current chunk (and optionally prior chunks) are input to a Transformer and projected to a lower dimensionality, i.e., a smaller number of features are selected as the output “combined” features. While Transformers are not typically used in this context, we find it effective for reducing the dimensionality of the input features, by selecting the last m outputs of the Transformer, if m is the desired output dimension (shown below). Alternatively, the Combiner can have a memory component. For example, we use the Token Turing Machine (TTM), which supports a differentiable memory unit, accumulating and compressing features from all previous timesteps. Using a fixed memory allows the model to work with a more compact set of features at every step, rather than process all the features from previous steps, which reduces computation.

We use a simple Transformer-based Combiner (left) and a Memory Combiner (right), based on the Token Turing Machine (TTM), which uses memory to compress previous history of features.

Results

We evaluate our approach on several benchmarks, MSRVTT-QA, ActivityNet-QA and NeXT-QA, for the video QA task, where a text-based question about a video is issued and the model needs to answer. This evaluates the ability of the model to understand both the text-based question and video content, and to form an answer, focusing on only relevant information. Of these benchmarks, the latter two target long video inputs and feature more complex questions.

We also evaluate our approach in the more challenging open-ended text generation setting, wherein the model generates the answers in an unconstrained fashion as free form text, requiring an exact match to the ground truth answer. While this stricter evaluation counts synonyms as incorrect, it may better reflect a model’s ability to generalize.

Our results indicate improved performance over state-of-the-art approaches for most benchmarks, including all with open-ended generation evaluation — notable considering our model is only 3B parameters, considerably smaller than prior approaches, e.g., Flamingo 80B. We used only video and text inputs to be comparable to other work. Importantly, our model can process 512 frames without needing to increase the model parameters, which is crucial for handling longer videos. Finally with the TTM Combiner, we see both better or comparable performance while reducing compute by 18%.

Results on the MSRVTT-QA (video QA) dataset.
Results on NeXT-QA benchmark, which features long videos for the video QA task.

Results on audio-video benchmarks

Results on the popular audio-video datasets VGG-Sound and EPIC-SOUNDS are shown below. Since these benchmarks are classification-only, we treat them as an open-ended text generative setting where our model produces the text of the desired class; e.g., for the class ID corresponding to the “playing drums” activity, we expect the model to generate the text “playing drums”. In some cases our approach outperforms the prior state of the art by large margins, even though our model outputs the results in the generative open-ended setting.

Results on the VGG-Sound (audio-video QA) dataset.
Results on the EPIC-SOUNDS (audio-video QA) dataset.

Benefits of autoregressive modeling

We conduct an ablation study comparing our approach to a set of baselines that use the same input information but with standard methods (i.e., without autoregression and the Combiner). We also compare the effects of pre-training. Because standard methods are ill-suited for processing longer video, this experiment is conducted for 32 frames and four chunks only, across all settings for fair comparison. We see that Mirasol3B’s improvements are still valid for relatively short videos.

Ablation experiments comparing the main components of our model. Using the Combiner, the autoregressive modeling, and pre-training all improve performance.

Conclusion

We present a multimodal autoregressive model that addresses the challenges associated with the heterogeneity of multimodal data by coordinating the learning between time-aligned and time-unaligned modalities. Time-aligned modalities are further processed autoregressively in time with a Combiner, controlling the sequence length and producing powerful representations. We demonstrate that a relatively small model can successfully represent long video and effectively combine with other modalities. We outperform the state-of-the-art approaches (including some much bigger models) on video- and audio-video question answering.


Acknowledgements

This research is co-authored by AJ Piergiovanni, Isaac Noble, Dahun Kim, Michael Ryoo, Victor Gomes, and Anelia Angelova. We thank Claire Cui, Tania Bedrax-Weiss, Abhijit Ogale, Yunhsuan Sung, Ching-Chung Chang, Marvin Ritter, Kristina Toutanova, Ming-Wei Chang, Ashish Thapliyal, Xiyang Luo, Weicheng Kuo, Aren Jansen, Bryan Seybold, Ibrahim Alabdulmohsin, Jialin Wu, Luke Friedman, Trevor Walker, Keerthana Gopalakrishnan, Jason Baldridge, Radu Soricut, Mojtaba Seyedhosseini, Alexander D'Amour, Oliver Wang, Paul Natsev, Tom Duerig, Younghui Wu, Slav Petrov, Zoubin Ghahramani for their help and support. We also thank Tom Small for preparing the animation.

Source: Google AI Blog


SANPO: A Scene understanding, Accessibility, Navigation, Pathfinding, & Obstacle avoidance dataset

Posted by Sagar M. Waghmare, Senior Software Engineer, and Kimberly Wilber, Software Engineer, Google Research, Perception Team

As most people navigate their everyday world, they process visual input from the environment using an eye-level perspective. Unlike robots and self-driving cars, people don't have any "out-of-body" sensors to help guide them. Instead, a person’s sensory input is completely "egocentric", or "from the self." This also applies to new technologies that understand the world around us from a human-like perspective, e.g., robots navigating through unknown buildings, AR glasses that highlight objects, or assistive technology to help people run independently.

In computer vision, scene understanding is the subfield that studies how visible objects relate to the scene's 3D structure and layout by focusing on the spatial, functional, and semantic relationships between objects and their environment. For example, autonomous drivers must understand the 3D structure of the road, sidewalks, and surrounding buildings while identifying and recognizing street signs and stop lights, a task made easier with 3D data from a special laser scanner mounted on the top of the car rather than 2D images from the driver’s perspective. Robots navigating a park must understand where the path is and what obstacles might interfere, which is simplified with a map of their surroundings and GPS positioning data. Finally, AR glasses that help users find their way need to understand where the user is and what they are looking at.

The computer vision community typically studies scene understanding tasks in contexts like self-driving, where many other sensors (GPS, wheel positioning, maps, etc.) beyond egocentric imagery are available. Yet most datasets in this space do not focus exclusively on egocentric data, so they are less applicable to human-centered navigation tasks. While there are plenty of self-driving focused scene understanding datasets, they have limited generalization to egocentric human scene understanding. A comprehensive human egocentric dataset would help build systems for related applications and serve as a challenging benchmark for the scene understanding community.

To that end, we present the Scene understanding, Accessibility, Navigation, Pathfinding, Obstacle avoidance dataset, or SANPO (also the Japanese word for ”brisk stroll”), a multi-attribute video dataset for outdoor human egocentric scene understanding. The dataset consists of real world data and synthetic data, which we call SANPO-Real and SANPO-Synthetic, respectively. It supports a wide variety of dense prediction tasks, is challenging for current models, and includes real and synthetic data with depth maps and video panoptic masks in which each pixel is assigned a semantic class label (and for some semantic classes, each pixel is also assigned a semantic instance ID that uniquely identifies that object in the scene). The real dataset covers diverse environments and has videos from two stereo cameras to support multi-view methods, including 11.4 hours captured at 15 frames per second (FPS) with dense annotations. Researchers can download and use SANPO here.

3D scene of a real session built using the provided annotations (segmentation, depth and camera positions). The top center video shows the depth map, and the top right shows the RGB or semantic annotations.

SANPO-Real

SANPO-Real is a multiview video dataset containing 701 sessions recorded with two stereo cameras: a head-mounted ZED Mini and a chest-mounted ZED-2i. That’s four RGB streams per session at 15 FPS. 597 sessions are recorded at a resolution of 2208x1242 pixels, and the remainder are recorded at a resolution of 1920x1080 pixels. Each session is approximately 30 seconds long, and the recorded videos are rectified using Zed software and saved in a lossless format. Each session has high-level attribute annotations, camera pose trajectories, dense depth maps from CREStereo, and sparse depth maps provided by the Zed SDK. A subset of sessions have temporally consistent panoptic segmentation annotations of each instance.

The SANPO data collection system for collecting real-world data. Right: (i) a backpack with ZED 2i and ZED Mini cameras for data collection (bottom), (ii) the inside of the backpack showing the ZED box and battery pack mounted on a 3D printed container (middle), and (iii) an Android app showing the live feed from the ZED cameras (top). Left: The chest-mounted ZED-2i has a stereo baseline of 12cm with a 2.1mm focal length, and the head-mounted ZED Mini has a baseline of 6.3cm with a 2.1mm focal length.

Temporally consistent panoptic segmentation annotation protocol

SANPO includes thirty different class labels, including various surfaces (road, sidewalk, curb, etc.), fences (guard rails, walls,, gates), obstacles (poles, bike racks, trees), and creatures (pedestrians, riders, animals). Gathering high-quality annotations for these classes is an enormous challenge. To provide temporally consistent panoptic segmentation annotation we divide each video into 30-second sub-videos and annotate every fifth frame (90 frames per sub-video), using a cascaded annotation protocol. At each stage, we ask annotators to draw borders around five mutually exclusive labels at a time. We send the same image to different annotators with as many stages as it takes to collect masks until all labels are assigned, with annotations from previous subsets frozen and shown to the annotator. We use AOT, a machine learning model that reduces annotation effort by giving annotators automatic masks from which to start, taken from previous frames during the annotation process. AOT also infers segmentation annotations for intermediate frames using the manually annotated preceding and following frames. Overall, this approach reduces annotation time, improves boundary precision, and ensures temporally consistent annotations for up to 30 seconds.

Temporally consistent panoptic segmentation annotations. The segmentation mask’s title indicates whether it was manually annotated or AOT propagated.

SANPO-Synthetic

Real-world data has imperfect ground truth labels due to hardware, algorithms, and human mistakes, whereas synthetic data has near-perfect ground truth and can be customized. We partnered with Parallel Domain, a company specializing in lifelike synthetic data generation, to create SANPO-Synthetic, a high-quality synthetic dataset to supplement SANPO-Real. Parallel Domain is skilled at creating handcrafted synthetic environments and data for machine learning applications. Thanks to their work, SANPO-Synthetic matches real-world capture conditions with camera parameters, placement, and scenery.

3D scene of a synthetic session built using the provided annotations (segmentation, depth and odometry). The top center video shows the depth map, and the top right shows the RGB or semantic annotations.

SANPO-Synthetic is a high quality video dataset, handcrafted to match real world scenarios. It contains 1961 sessions recorded using virtualized Zed cameras, evenly split between chest-mounted and head-mounted positions and calibrations. These videos are monocular, recorded from the left lens only. These sessions vary in length and FPS (5, 14.28, and 33.33) for a mix of temporal resolution / length tradeoffs, and are saved in a lossless format. All the sessions have precise camera pose trajectories, dense pixel accurate depth maps and temporally consistent panoptic segmentation masks.

SANPO-Synthetic data has pixel-perfect annotations, even for small and distant instances. This helps develop challenging datasets that mimic the complexity of real-world scenes. SANPO-Synthetic and SANPO-Real are also drop-in replacements for each other, so researchers can study domain transfer tasks or use synthetic data during training with few domain-specific assumptions.

An even sampling of real and synthetic scenes.

Statistics

Semantic classes

We designed our SANPO taxonomy: i) with human egocentric navigation in mind, ii) with the goal of being reasonably easy to annotate, and iii) to be as close as possible to the existing segmentation taxonomies. Though built with human egocentric navigation in mind, it can be easily mapped or extended to other human egocentric scene understanding applications. Both SANPO-Real and SANPO-Synthetic feature a wide variety of objects one would expect in egocentric obstacle detection data, such as roads, buildings, fences, and trees. SANPO-Synthetic includes a broad distribution of hand-modeled objects, while SANPO-Real features more “long-tailed” classes that appear infrequently in images, such as gates, bus stops, or animals.

Distribution of images across the classes in the SANPO taxonomy.

Instance masks

SANPO-Synthetic and a portion of SANPO-Real are also annotated with panoptic instance masks, which assign each pixel to a class and instance ID. Because it is generally human-labeled, SANPO-Real has a large number of frames with generally less than 20 instances per frame. Similarly, SANPO-Synthetic’s virtual environment offers pixel-accurate segmentation of most unique objects in the scene. This means that synthetic images frequently feature many more instances within each frame.

When considering per-frame instance counts, synthetic data frequently features many more instances per frame than the labeled portions of SANPO-Real.

Comparison to other datasets

We compare SANPO to other important video datasets in this field, including SCAND, MuSoHu, Ego4D, VIPSeg, and Waymo Open. Some of these are intended for robot navigation (SCAND) or autonomous driving (Waymo) tasks. Across these datasets, only Waymo Open and SANPO have both panoptic segmentations and depth maps, and only SANPO has both real and synthetic data.

Comparison to other video datasets. For stereo vs mono video, datasets marked with ★ have stereo video for all scenes and those marked ☆ provide stereo video for a subset. For depth maps, ★ indicates dense depth while ☆ represents sparse depth, e.g., from a lower-resolution LIDAR scanner.

Conclusion and future work

We present SANPO, a large-scale and challenging video dataset for human egocentric scene understanding, which includes real and synthetic samples with dense prediction annotations. We hope SANPO will help researchers build visual navigation systems for the visually impaired and advance visual scene understanding. Additional details are available in the preprint and on the SANPO dataset GitHub repository.


Acknowledgements

This dataset was the outcome of hard work of many individuals from various teams within Google and our external partner, Parallel Domain.

Core Team: Mikhail Sirotenko, Dave Hawkey, Sagar Waghmare, Kimberly Wilber, Xuan Yang, Matthew Wilson

Parallel Domain: Stuart Park, Alan Doucet, Alex Valence-Lanoue, & Lars Pandikow.

We would also like to thank following team members: Hartwig Adam, Huisheng Wang, Lucian Ionita, Nitesh Bharadwaj, Suqi Liu, Stephanie Debats, Cattalyya Nuengsigkapian, Astuti Sharma, Alina Kuznetsova, Stefano Pellegrini, Yiwen Luo, Lily Pagan, Maxine Deines, Alex Siegman, Maura O’Brien, Rachel Stigler, Bobby Tran, Supinder Tohra, Umesh Vashisht, Sudhindra Kopalle, Reet Bhatia.

Source: Google AI Blog


DynIBaR: Space-time view synthesis from videos of dynamic scenes

Posted by Zhengqi Li and Noah Snavely, Research Scientists, Google Research

A mobile phone’s camera is a powerful tool for capturing everyday moments. However, capturing a dynamic scene using a single camera is fundamentally limited. For instance, if we wanted to adjust the camera motion or timing of a recorded video (e.g., to freeze time while sweeping the camera around to highlight a dramatic moment), we would typically need an expensive Hollywood setup with a synchronized camera rig. Would it be possible to achieve similar effects solely from a video captured using a mobile phone’s camera, without a Hollywood budget?

In “DynIBaR: Neural Dynamic Image-Based Rendering”, a best paper honorable mention at CVPR 2023, we describe a new method that generates photorealistic free-viewpoint renderings from a single video of a complex, dynamic scene. Neural Dynamic Image-Based Rendering (DynIBaR) can be used to generate a range of video effects, such as “bullet time” effects (where time is paused and the camera is moved at a normal speed around a scene), video stabilization, depth of field, and slow motion, from a single video taken with a phone’s camera. We demonstrate that DynIBaR significantly advances video rendering of complex moving scenes, opening the door to new kinds of video editing applications. We have also released the code on the DynIBaR project page, so you can try it out yourself.



Given an in-the-wild video of a complex, dynamic scene, DynIBaR can freeze time while allowing the camera to continue to move freely through the scene.


Background

The last few years have seen tremendous progress in computer vision techniques that use neural radiance fields (NeRFs) to reconstruct and render static (non-moving) 3D scenes. However, most of the videos people capture with their mobile devices depict moving objects, such as people, pets, and cars. These moving scenes lead to a much more challenging 4D (3D + time) scene reconstruction problem that cannot be solved using standard view synthesis methods.



Standard view synthesis methods output blurry, inaccurate renderings when applied to videos of dynamic scenes.

Other recent methods tackle view synthesis for dynamic scenes using space-time neural radiance fields (i.e., Dynamic NeRFs), but such approaches still exhibit inherent limitations that prevent their application to casually captured, in-the-wild videos. In particular, they struggle to render high-quality novel views from videos featuring long time duration, uncontrolled camera paths and complex object motion.

The key pitfall is that they store a complicated, moving scene in a single data structure. In particular, they encode scenes in the weights of a multilayer perceptron (MLP) neural network. MLPs can approximate any function — in this case, a function that maps a 4D space-time point (x, y, z, t) to an RGB color and density that we can use in rendering images of a scene. However, the capacity of this MLP (defined by the number of parameters in its neural network) must increase according to the video length and scene complexity, and thus, training such models on in-the-wild videos can be computationally intractable. As a result, we get blurry, inaccurate renderings like those produced by DVS and NSFF (shown below). DynIBaR avoids creating such large scene models by adopting a different rendering paradigm.



DynIBaR (bottom row) significantly improves rendering quality compared to prior dynamic view synthesis methods (top row) for videos of complex dynamic scenes. Prior methods produce blurry renderings because they need to store the entire moving scene in an MLP data structure.


Image-based rendering (IBR)

A key insight behind DynIBaR is that we don’t actually need to store all of the scene contents in a video in a giant MLP. Instead, we directly use pixel data from nearby input video frames to render new views. DynIBaR builds on an image-based rendering (IBR) method called IBRNet that was designed for view synthesis for static scenes. IBR methods recognize that a new target view of a scene should be very similar to nearby source images, and therefore synthesize the target by dynamically selecting and warping pixels from the nearby source frames, rather than reconstructing the whole scene in advance. IBRNet, in particular, learns to blend nearby images together to recreate new views of a scene within a volumetric rendering framework.


DynIBaR: Extending IBR to complex, dynamic videos

To extend IBR to dynamic scenes, we need to take scene motion into account during rendering. Therefore, as part of reconstructing an input video, we solve for the motion of every 3D point, where we represent scene motion using a motion trajectory field encoded by an MLP. Unlike prior dynamic NeRF methods that store the entire scene appearance and geometry in an MLP, we only store motion, a signal that is more smooth and sparse, and use the input video frames to determine everything else needed to render new views.

We optimize DynIBaR for a given video by taking each input video frame, rendering rays to form a 2D image using volume rendering (as in NeRF), and comparing that rendered image to the input frame. That is, our optimized representation should be able to perfectly reconstruct the input video.

We illustrate how DynIBaR renders images of dynamic scenes. For simplicity, we show a 2D world, as seen from above. (a) A set of input source views (triangular camera frusta) observe a cube moving through the scene (animated square). Each camera is labeled with its timestamp (t-2, t-1, etc). (b) To render a view from camera at time t, DynIBaR shoots a virtual ray through each pixel (blue line), and computes colors and opacities for sample points along that ray. To compute those properties, DyniBaR projects those samples into other views via multi-view geometry, but first, we must compensate for the estimated motion of each point (dashed red line). (c) Using this estimated motion, DynIBaR moves each point in 3D to the relevant time before projecting it into the corresponding source camera, to sample colors for use in rendering. DynIBaR optimizes the motion of each scene point as part of learning how to synthesize new views of the scene.

However, reconstructing and deriving new views for a complex, moving scene is a highly ill-posed problem, since there are many solutions that can explain the input video — for instance, it might create disconnected 3D representations for each time step. Therefore, optimizing DynIBaR to reconstruct the input video alone is insufficient. To obtain high-quality results, we also introduce several other techniques, including a method called cross-time rendering. Cross-time rendering refers to the use of the state of our 4D representation at one time instant to render images from a different time instant, which encourages the 4D representation to be coherent over time. To further improve rendering fidelity, we automatically factorize the scene into two components, a static one and a dynamic one, modeled by time-invariant and time-varying scene representations respectively.


Creating video effects

DynIBaR enables various video effects. We show several examples below.


Video stabilization

We use a shaky, handheld input video to compare DynIBaR’s video stabilization performance to existing 2D video stabilization and dynamic NeRF methods, including FuSta, DIFRINT, HyperNeRF, and NSFF. We demonstrate that DynIBaR produces smoother outputs with higher rendering fidelity and fewer artifacts (e.g., flickering or blurry results). In particular, FuSta yields residual camera shake, DIFRINT produces flicker around object boundaries, and HyperNeRF and NSFF produce blurry results.




Simultaneous view synthesis and slow motion

DynIBaR can perform view synthesis in both space and time simultaneously, producing smooth 3D cinematic effects. Below, we demonstrate that DynIBaR can take video inputs and produce smooth 5X slow-motion videos rendered using novel camera paths.




Video bokeh

DynIBaR can also generate high-quality video bokeh by synthesizing videos with dynamically changing depth of field. Given an all-in-focus input video, DynIBar can generate high-quality output videos with varying out-of-focus regions that call attention to moving (e.g., the running person and dog) and static content (e.g., trees and buildings) in the scene.




Conclusion

DynIBaR is a leap forward in our ability to render complex moving scenes from new camera paths. While it currently involves per-video optimization, we envision faster versions that can be deployed on in-the-wild videos to enable new kinds of effects for consumer video editing using mobile devices.


Acknowledgements

DynIBaR is the result of a collaboration between researchers at Google Research and Cornell University. The key contributors to the work presented in this post include Zhengqi Li, Qianqian Wang, Forrester Cole, Richard Tucker, and Noah Snavely.

Source: Google AI Blog


Google Research embarks on effort to map a mouse brain

Posted by Michał Januszewski, Research Scientist, Google Research

The human brain is perhaps the most computationally complex machine in existence, consisting of networks of billions of cells. Researchers currently don’t understand the full picture of how glitches in its network machinery contribute to mental illnesses and other diseases, such as dementia. However, the emerging connectomics field, which aims to precisely map the connections between every cell in the brain, could help solve that problem. While maps have only been created for simpler organisms, technological advances for mapping even larger brains can enable us to understand how the human brain works, and how to treat brain diseases.

Today, we're excited to announce that the Connectomics team at Google Research and our collaborators are launching a $33 million project to expand the frontiers of connectomics over the next five years. Supported by the Brain Research Through Advancing Innovative Neurotechnologies (BRAIN) Initiative at the National Institutes of Health (NIH) and led by researchers at Harvard University, we'll be working alongside a multidisciplinary team of experts from the Allen Institute, MIT, Cambridge University, Princeton University and Johns Hopkins University, with advisers from HHMI’s Janelia Research Campus. Our project goal is to tackle an immense challenge in neuroscience: mapping a tiny fraction (2-3%) of the mouse brain. We will specifically target the hippocampal region, which is responsible for encoding memories, attention and spatial navigation. This project is one of 11 funded by the NIH's $150 million BRAIN Initiative Connectivity Across Scales (BRAIN CONNECTS) program. Google Research is contributing computational and analytical resources to this effort, and will not receive any funding from the NIH. Our project asks a critical question: Can we scale and speed up our technologies enough to map the whole connectome of a mouse brain?


The modern era of connectomics

This effort to map the connectome of a small part of the mouse brain builds on a decade of innovation in the field, including many advances initiated by the Connectomics team at Google Research. We hope to accomplish something similar to the early days of the Human Genome Project, when scientists worked for years to sequence a small portion of the human genome as they refined technologies that would enable them to complete the rest of the genome.

In 2021, we and collaborators at Harvard successfully mapped one cubic millimeter of the human brain, which we released as the H01 dataset, a resource for studying the human brain and scaling connectomics technologies. But mapping the entire human brain connectome would require gathering and analyzing as much as a zettabyte of data (one billion terabytes), which is beyond the current capabilities of existing technologies.

Analyzing a mouse connectome is the next best thing. It is small enough to be technically feasible and could potentially deliver insights relevant to our own minds; neuroscientists already use mice to study human brain function and dysfunction. By working together to map 10–15 cubic mm of the mouse brain, we hope to develop new approaches that will allow us to map the entire remainder of the mouse brain, and the human brain thereafter.

Neuroscientists have been working for decades to map increasingly larger and more complicated connectomes.


One of biology’s largest datasets

In this connectomics project, we will map the connectome of the hippocampal formation of the mouse brain, which converts short-term memories into long-term memories and helps the mouse navigate in space. The mouse hippocampal formation is the largest area of any brain we’ve attempted to understand in this way. Through mapping this region of the mouse brain, we will create one of the largest datasets in biology, combining about 25,000 terabytes, or 25 petabytes of brain data. For reference, there are about 250 billion stars in our Milky Way Galaxy. If each of those stars was a single byte, it would take 100,000 Milky Way Galaxies to match the 25 petabytes of data that the project will collect when mapping a small region of the mouse brain.

To illustrate the hippocampal project’s scale, we calculated the number of Pixel phones (shown as stacks of Pixels below) needed to store the image data from the completed connectome projects that mapped the roundworm and fruit fly brains, as well as for the mouse hippocampal region and entire mouse brain projects, which are just getting started.

Then, we compared the heights of each Pixel stack to familiar objects and landmarks. It would take a stack of 100 Pixels, as tall as a four-year-old girl, to store the image data for the fruit fly brain, the largest completed project thus far. In contrast, the mouse hippocampal connectome effort will require storage equivalent to more than 48,800 Pixels, reaching as high as the Empire State Building. The animation below shows how the mouse hippocampal project will surpass the scale of previous connectome projects.

We are partnering with several collaborators to build a connectome (a map of the connections between brain cells) for the hippocampal region of a mouse brain. This project will create the largest connectomic dataset ever, surpassing the scale of previous projects that mapped the smaller roundworm and fruit fly brains. We hope this effort will lead to the development of new approaches that will allow us to later map an entire mouse brain. This animation shows how the field of connectomics is scaling up by calculating the number of Pixel phones needed to store the data from various projects. It would take just two Pixels, the height of an olive, to store the roundworm connectome data, while it would take a stack of Pixels the size of Mount Everest to store the data from an entire mouse connectome.

Understanding the connectome of the mouse hippocampal formation could help illuminate the way our own brains work. For instance, we may find common features between this circuitry in the mouse brain and human brains that explain how we know where we are, how our brains associate memories with specific locations, and what goes wrong in people who can’t properly form new spatial memories.


Opening the petabyte pipeline

Over the last decade, our team has worked to develop tools for managing massive connectomic datasets, and extracting scientific value from them. But a mouse brain has 1,000 times more neurons than the brain of the Drosophila fruit fly, an organism for which we helped build a connectome for a large part of the brain. Starting the mouse brain connectome will challenge us to improve existing technologies to enable us to map more data faster than ever before.

We’ll continue to refine our flood-filling networks, which use deep learning to trace, or “segment”, each neuron’s path through three-dimensional brain volumes made from electron microscope data. We’ll also extend the capabilities of our self-supervised learning technology, SegCLR, which allows us to automatically extract key insights from segmented volumes, such as identifying cell type (e.g., pyramidal neuron, basket neuron, etc.) and parts of each neuron (e.g., axon, dendrite, etc.).

A flood filling network traces a neuron through three-dimensional brain space.

We will also continue to enhance the scalability and performance of our core connectomics infrastructure, such as TensorStore for storage and Neuroglancer for visualization, in order to enable all of our computational pipelines and human analysis workflows to operate at these new scales of data. We’re eager to get to work to discover what peering into a mouse’s mind might tell us about our own.


Acknowledgements

The mouse connectomics project described in this blog post will be supported in part by the NIH BRAIN Initiative under award number 1UM1NS132250. Google Research is contributing computational and analytical resources to the mouse connectome project, and will not receive funding from the NIH. Many people were involved in the development of the technologies that make this project possible. We thank our long-term academic collaborators in the Lichtman Lab (Harvard University), HHMI Janelia, and the Denk Lab (Max Planck Institute for Biological Intelligence), and acknowledge core contributions from the Connectomics Team at Google. We also thank John Guilyard for creating the illustrative animation in this post, and Elise Kleeman, and Erika Check Hayden for their support. Thanks to Lizzie Dorfman, Michael Brenner, Jay Yagnik and Jeff Dean for their support, coordination and leadership.

Source: Google AI Blog