The Holoscan SDK is part of NVIDIA Holoscan, the AI sensor processing platform that combines hardware systems for low-latency sensor and network connectivity, optimized libraries for data processing and AI, and core microservices to run streaming, imaging, and other applications, from embedded to edge to cloud. It can be used to build streaming AI pipelines for a variety of domains, including Medical Devices, High Performance Computing at the Edge, Industrial Inspection and more.

In previous releases, the prefix Clara was used to define Holoscan as a platform designed initially for medical devices. As Holoscan has grown, its potential to serve other areas has become apparent. With version 0.4.0, we're proud to announce that the Holoscan SDK is now officially built to be domain-agnostic and can be used to build sensor AI applications in multiple domains. Note that some of the content of the SDK (sample applications) or the documentation might still appear to be healthcare-specific pending additional updates. Going forward, domain specific content will be hosted on the HoloHub repository.

• Getting Started
• Building the SDK from source
  • Prerequisites
  • (Recommended) using the run script
  • Cross-compilation
  • (Advanced) Docker + CMake
  • (Advanced) Local environment + CMake
• Runtime Container
• Utilities
  • Testing
  • Linting
  • VSCode
• Troubleshooting
• Repository structure

Visit the Holoscan User Guide to get started with the Holoscan SDK: https://docs.nvidia.com/holoscan/sdk-user-guide/getting_started.html

⚠️ Disclaimer: we only recommend building the SDK from source if you are a developer of the SDK, or need to build the SDK with debug symbols or other options not used as part of the published packages. If you want to write your own operator or application, you can use the SDK as a dependency (and contribute to HoloHub). If you need to make other modifications to the SDK, file a feature or bug request. If that's not the case, prefer installing the SDK from published packages.

• Prerequisites for each supported platform are documented in the user guide.
• To build and run the SDK in a containerized environment (recommended) you'll need:
  • the NVIDIA Container Toolkit v1.12.2+
  • Docker, including the buildx plugin (docker-buildx-plugin)

Call ./run build within the repository to build the build container and the CMake project.

• If you encounter errors during the CMake build, you can execute ./run clear_cache to remove cache/build/install folders

• Execute ./run build --help for more information

• Execute ./run build --dryrun to see the commands that will be executed

• That command can be broken-up in more granular commands also:

  ./run check_system_deps  # ensure the system is properly configured for building
  ./run build_image        # create the build Docker container
  ./run build              # run the CMake configuration, build, and install steps

Call the ./run launch command to start and enter the build container.

• You can run from the install or build tree by passing the working directory as an argument (ex: ./run launch install)
• Execute ./run launch --help for more information
• Execute ./run launch --dryrun to see the commands that will be executed
• Execute ./run launch --run-cmd "..." to execute a bash command directly in the container

Run the examples inside the container by running their respective commands listed within each directory README file.

While the Dockerfile to build the SDK does not currently support true cross-compilation, you can compile the Holoscan SDK for the developer kits (arm64) from a x86_64 host using an emulation environment.

1. Install qemu
2. Clear your build cache: ./run clear_cache
3. Rebuild for linux/arm64 using --arch|-a or HOLOSCAN_BUILD_ARCH:
   • ./run build --arch arm64
   • HOLOSCAN_BUILD_ARCH=arm64 ./run build

You can then copy the install folder generated by CMake to a developer kit with a configured environment or within a container to use for running and developing applications.

The run script mentioned above is helpful to understand how Docker and CMake are configured and run, as commands will be printed when running it or using --dryrun. We recommend looking at those commands if you want to use Docker and CMake manually, and reading the comments inside the script for details about each parameter (specifically the build() and launch() methods).

⚠️ Disclaimer: this method of building the SDK is not actively tested or maintained. Instructions below might go out of date.

To build the Holoscan SDK on a local environment, the following versions of dev dependencies are needed (or tested). The last column refers to the stage (FROM) in the Dockerfile where respective commands can be found to build/install these dependencies.

Note: refer to the Dockerfile for other dependencies which are not needed to build, but might be needed for:

• runtime (openblas/mkl for torch, egl for headless rendering, cloudpickle for distributed python apps, cupy for some examples...)
• testing (valgrind, pytest, xvfb...)
• utilities (v4l-utils, ...)

For CMake to find these dependencies, install them in default system paths, or pass CMAKE_PREFIX_PATH, CMAKE_LIBRARY_PATH, and/or CMAKE_INCLUDE_PATH during configuration.

# Configure
cmake -S $source_dir -B $build_dir \
  -G Ninja \
  -D CMAKE_BUILD_TYPE=Release \
  -D CUDAToolkit_ROOT:PATH="/usr/local/cuda"

# Build
cmake --build $build_dir -j

# Install
cmake --install $build_dir --prefix $install_dir

The commands to run the examples are then the same as in the dockerized environment, and can be found in the respective source directory READMEs.

There are multiple containers associated with Holoscan:

• The build container generated by the top-level Dockerfile is designed to pull dependencies to build and test the SDK itself. The image does not contain the SDK itself, as it is mounted with during docker run to run the cmake build or run tests.
• The development container available at NGC | Holoscan Container which includes all the development tools and libraries needed to build Holoscan applications.
  • This image is ~13 GB when uncompressed. However, once a Holoscan application is created, it does not need all those same development tools just to run an application.
• To address this, a runtime container can now be generated with the runtime_docker/Dockerfile which contains only the runtime dependencies of the Holoscan SDK.
  • This Dockerfile is based on the CUDA-base image, which begins with Ubuntu:22.04 and installs the CUDA runtime and Compat package.
  • This image is ~8.7 GB on x86_64, and can be further reduced based on use cases (see below).

⚠️ Disclaimer: Currently iGPU is not supported by the runtime container

The run script contains the command build_run_image to build the runtime Holoscan SDK image:

./run build_run_image

Once this image is built, it can be run exactly as the Holoscan development container on NGC is. Simply follow the 'Running the container' instructions beginning at step #3 at NGC | Holoscan Container, but replace ${NGC_CONTAINER_IMAGE_PATH} by holoscan-sdk-run-<arch>[-<gpu>] in step #4 (name outputted at the end of the above command).

If you have a specific application you wish to deploy, you can further reduce this runtime image size in two ways:

1. Targeting different stages of the runtime Dockerfile.

   1. add --cpp to the command above to not pull in python dependencies.
   2. add --cpp-no-mkl to the command above to not pull in MKL (x86_64-only libtorch dependency) in addition to the above.

2. Modifying the Dockerfile

The runtime Dockerfile is thoroughly documented to indicate which dependency is used by which component of the Holoscan SDK. If you do not use some of these components (ex: Torch inference backend, ONNX Runtime inference backend, TensorRT inference backend, Python/Cupy, format_converter operator, etc...), comment out the appropriate line in the Dockerfile and run the build command above.

Some utilities are available in the scripts folder, others closer to the built process are listed below:

Existing tests are using GTest for C++ and pytest for Python, and can be found under tests and python/tests respectively. The Holoscan SDK uses CTest as a framework to build and execute these tests.

Run the tests using the following command:

./run test

Note: Run run test --help to see additional options.

Run the following command to run various linting tools on the repository:

./run lint # optional: specify directories

Note: Run run lint --help to see the list of tools that are used. If a lint command fails due to a missing module or executable on your system, you can install it using python3 -m pip install <tool>.

The source of the user guide hosted at https://docs.nvidia.com/holoscan/sdk-user-guide is located in docs. It can be built with the following commands:

• PDF: ./run build_pdf
• HTML: ./run build_html (auto-reload: ./run live_html)

Run ./run help for more commands related to the user guide documentation.

Visual Studio Code can be utilized to develop the Holoscan SDK. The .devcontainer folder holds the configuration for setting up a development container with all necessary tools and libraries installed.

The ./run script contains vscode and vscode_remote commands for launching Visual Studio Code in a container or from a remote machine, respectively.

• To launch Visual Studio Code in a dev container, use ./run vscode.
• To attach to an existing dev container from a remote machine, use ./run vscode_remote. For more information, refer to the instructions from ./run vscode_remote -h.

Once Visual Studio Code is launched, the development container will be built and the recommended extensions will be installed automatically, along with CMake being configured.

For manual configuration of CMake, open the command palette (Ctrl + Shift + P) and run the CMake: Configure command.

The source code in the development container can be built by either pressing Ctrl + Shift + B or executing Tasks: Run Build Task from the command palette (Ctrl + Shift + P).

To debug the source code in the development container, open the Run and Debug view (Ctrl + Shift + D), select a debug configuration from the dropdown list, and press F5 to initiate debugging.

Enable permissions to your X server from Docker, either:

• Passing -u $(id -u):$(id -g) to docker run, or
• Running xhost +local:docker on your host

You may encounter the error message if the Holoscan Application runs on a Virtual Machine (by a Cloud Service Provider) or without a physical display attached. If you want to run applications that use GPU on x11 (e.g., VNC or NoMachine), the following environment variables need to be set before executing the application to offload the rendering to GPU.

export __NV_PRIME_RENDER_OFFLOAD=1
export __GLX_VENDOR_LIBRARY_NAME=nvidia

Ensure all your application connections in the yaml file (nvidia::gxf::Connection) refer to entities or components defined within. This can occur when attempting to remove a component and not cleaning up the stale connections.

Ensure your entity or component is not an orphan, but is connected to a nvidia::gxf::Connection.

These errors indicate that you don't have AJA support in your environment.

2022-06-09 18:45:13.826 ERROR gxf_extensions/aja/aja_source.cpp@80: Device 0 not found.
2022-06-09 18:45:13.826 ERROR gxf_extensions/aja/aja_source.cpp@251: Failed to open device 0

Double check that you have installed the AJA ntv2 driver, loaded the driver after every reboot, and that you have specified --device /dev/ajantv20:/dev/ajantv20 in the docker run command if you’re running a docker container.

These errors may indicate that you need to reconfigure your format converter's num_block number.

2022-06-09 18:47:30.769 ERROR gxf_extensions/format_converter/format_converter.cpp@521: Failed to allocate memory for the channel conversion
2022-06-09 18:47:30.769 ERROR gxf_extensions/format_converter/format_converter.cpp@359: Failed to convert tensor format (conversion type:6)

Try increasing the current num_block number by 1 in the yaml file for all format converter entities. This may happen if your yaml file was configured for running with RDMA and you have decided to disable RDMA.

Some of those errors may occur when running the V4L2 codelet:

Failed to open device, OPEN: No such file or directory

Ensure you have a video device connected (ex: USB webcam) and listed when running ls -l /dev/video*.

Failed to open device, OPEN: Permission denied

This means the /dev/video* device is not available to the user from within docker. Give --group-add video to the docker run command.

You may encounter an error when trying to run the Holoviz operator on a laptop equipped with an integrated and a discrete GPU. By default these systems will be using the integrated GPU when running an application. The integrated GPU does not provide the capabilities the Holoviz operator needs and the operator will fail.

The following environment variables need to be set before executing the application to offload the rendering to the discrete GPU. See PRIME Render Offload for more information.

export __NV_PRIME_RENDER_OFFLOAD=1
export __GLX_VENDOR_LIBRARY_NAME=nvidia

The repository is organized as such:

• cmake/: CMake configuration files
• data/: directory where data will be downloaded
• examples/: source code for the examples
• gxf_extensions/: source code for the holoscan SDK gxf codelets
• include/: source code for the holoscan SDK core
• modules/: source code for the holoscan SDK modules
• patches/: patch files applied to dependencies
• python/: python bindings for the holoscan SDK
• scripts/: utility scripts
• src/: source code for the holoscan SDK core
• tests/: tests for the holoscan SDK