media3/extensions/flac/README.md

ExoPlayer Flac extension

The Flac extension provides FlacExtractor and LibflacAudioRenderer, which use libFLAC (the Flac decoding library) to extract and decode FLAC audio.

License note

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

Build instructions

To use this extension you need to clone the ExoPlayer repository and depend on its modules locally. Instructions for doing this can be found in ExoPlayer's top level README.

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

• Set the following environment variables:

cd "<path to exoplayer checkout>"
EXOPLAYER_ROOT="$(pwd)"
FLAC_EXT_PATH="${EXOPLAYER_ROOT}/extensions/flac/src/main"

• Download the Android NDK (version <= 17c) and set its location in an environment variable:

NDK_PATH="<path to Android NDK>"

• Download and extract flac-1.3.2 as "${FLAC_EXT_PATH}/jni/flac" folder:

cd "${FLAC_EXT_PATH}/jni" && \
curl https://ftp.osuosl.org/pub/xiph/releases/flac/flac-1.3.2.tar.xz | tar xJ && \
mv flac-1.3.2 flac

• Build the JNI native libraries from the command line:

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

Using the extension

Once you've followed the instructions above to check out, build and depend on the extension, the next step is to tell ExoPlayer to use the extractor and/or renderer.

Using FlacExtractor

FlacExtractor is used via ExtractorMediaSource. If you're using DefaultExtractorsFactory, FlacExtractor will automatically be used to read .flac files. If you're not using DefaultExtractorsFactory, return a FlacExtractor from your ExtractorsFactory.createExtractors implementation.

Using LibflacAudioRenderer

• If you're passing a DefaultRenderersFactory to ExoPlayerFactory.newSimpleInstance, you can enable using the extension by setting the extensionRendererMode parameter of the DefaultRenderersFactory constructor to EXTENSION_RENDERER_MODE_ON. This will use LibflacAudioRenderer for playback if MediaCodecAudioRenderer doesn't support the input format. Pass EXTENSION_RENDERER_MODE_PREFER to give LibflacAudioRenderer priority over MediaCodecAudioRenderer.
• If you've subclassed DefaultRenderersFactory, add a LibflacAudioRenderer 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 LibflacAudioRenderer instance from createRenderers. ExoPlayer will use the first Renderer in the returned array that supports the input media format.
• If you're using ExoPlayerFactory.newInstance, pass a LibflacAudioRenderer 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 an LibflacAudioRenderer to the player, then implement your own logic to use the renderer for a given track.

Links

• Javadoc: Classes matching com.google.android.exoplayer2.ext.flac.* belong to this module.