media3/libraries/decoder_iamf

IAMF decoder module

The IAMF module provides LibiamfAudioRenderer, which uses libiamf (the IAMF decoding library) to decode IAMF audio.

License note

Please note that whilst the code in this repository is licensed under Apache 2.0, using this module also requires building and including one or more external libraries as described below. These are licensed separately.

Build instructions (Linux, macOS)

To use the module you need to clone this GitHub project and depend on its modules locally. Instructions for doing this can be found in the top level README.

In addition, it's necessary to build the module's native components as follows:

• Set the following environment variables:

cd "<path to project checkout>"

IAMF_MODULE_PATH="$(pwd)/libraries/decoder_iamf/src/main"

• Download the Android NDK and set its location in an environment variable. This build configuration has been tested on NDK r27.

NDK_PATH="<path to Android NDK>"

• Fetch libiamf:

Clone the repository containing libiamf to a local folder of choice - preferably outside of the project checkout. Link it to the project's jni folder through symlink.

cd <preferred location for libiamf>


git clone https://github.com/AOMediaCodec/libiamf.git libiamf && \
cd libiamf && \
LIBIAMF_PATH=$(pwd)

• Symlink the folder containing libiamf to the project's JNI folder and run the script to convert libiamf code to NDK compatible format:

cd "${IAMF_MODULE_PATH}"/jni && \
ln -s $LIBIAMF_PATH libiamf && \
cd libiamf/code &&\
cmake . && \
make

• Build the JNI native libraries from the command line:

cd "${IAMF_MODULE_PATH}"/jni && \
${NDK_PATH}/ndk-build APP_ABI=all -j4

Build instructions (Windows)

We do not provide support for building this module on Windows, however it should be possible to follow the Linux instructions in Windows PowerShell.

Notes

• Every time there is a change to the libiamf checkout clean and re-build the project.
• If you want to use your own version of libiamf, place it in ${IAMF_MODULE_PATH}/jni/libiamf.

Using the module with ExoPlayer

Once you've followed the instructions above to check out, build and depend on the module, the next step is to tell ExoPlayer to use LibiamfAudioRenderer. How you do this depends on which player API you're using:

• If you're passing a DefaultRenderersFactory to ExoPlayer.Builder, you can enable using the module by setting the extensionRendererMode parameter of the DefaultRenderersFactory constructor to EXTENSION_RENDERER_MODE_ON. This will use LibiamfAudioRenderer for playback if MediaCodecAudioRenderer doesn't support the input format. Pass EXTENSION_RENDERER_MODE_PREFER to give LibiamfAudioRenderer priority over MediaCodecAudioRenderer.
• If you've subclassed DefaultRenderersFactory, add a LibiamfAudioRenderer to the output list in buildAudioRenderers. ExoPlayer will use the first Renderer in the list that supports the input media format.
• If you've implemented your own RenderersFactory, return a LibiamfAudioRenderer instance from createRenderers. ExoPlayer will use the first Renderer in the returned array that supports the input media format.
• If you're using ExoPlayer.Builder, pass a LibiamfAudioRenderer in the array of Renderers. ExoPlayer will use the first Renderer in the list that supports the input media format.

Note: These instructions assume you're using DefaultTrackSelector. If you have a custom track selector the choice of Renderer is up to your implementation, so you need to make sure you are passing a LibiamfAudioRenderer to the player, then implement your own logic to use the renderer for a given track.

Links

• Troubleshooting using decoding extensions