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README.md

Flac decoder module

The Flac module 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 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>"
FLAC_MODULE_PATH="$(pwd)/libraries/decoder_flac/src/main"
  • Download the Android NDK and set its location in an environment variable. This build configuration has been tested on NDK r21.
NDK_PATH="<path to Android NDK>"
  • Download and extract flac-1.3.2 as "${FLAC_MODULE_PATH}/jni/flac" folder:
cd "${FLAC_MODULE_PATH}/jni" && \
curl https://ftp.osuosl.org/pub/xiph/releases/flac/flac-1.3.2.tar.xz | tar xJ && \
mv flac-1.3.2 flac
  • Build the JNI native libraries from the command line:
cd "${FLAC_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.

Using the module

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 the extractor and/or renderer.

Using FlacExtractor

FlacExtractor is used via ProgressiveMediaSource. 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 with ExoPlayer

  • 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 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 ExoPlayer.Builder, 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.

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