media3/extensions/opus/README.md
olly 049d41db2a Add license notes for extensions with non-Google dependencies
Issue: #3197

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=166988657
2017-08-31 16:28:22 +01:00

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# ExoPlayer Opus extension #
The Opus extension provides `LibopusAudioRenderer`, which uses libopus (the Opus
decoding library) to decode Opus 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.
[Apache 2.0]: https://github.com/google/ExoPlayer/blob/release-v2/LICENSE
## 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="$(pwd)"
OPUS_EXT_PATH="${EXOPLAYER_ROOT}/extensions/opus/src/main"
```
* Download the [Android NDK][] and set its location in an environment variable:
```
NDK_PATH="<path to Android NDK>"
```
* Fetch libopus:
```
cd "${OPUS_EXT_PATH}/jni" && \
git clone https://git.xiph.org/opus.git libopus
```
* Run the script to convert arm assembly to NDK compatible format:
```
cd ${OPUS_EXT_PATH}/jni && ./convert_android_asm.sh
```
* Build the JNI native libraries from the command line:
```
cd "${OPUS_EXT_PATH}"/jni && \
${NDK_PATH}/ndk-build APP_ABI=all -j4
```
[top level README]: https://github.com/google/ExoPlayer/blob/release-v2/README.md
[Android NDK]: https://developer.android.com/tools/sdk/ndk/index.html
## Notes ##
* Every time there is a change to the libopus checkout:
* Arm assembly should be converted by running `convert_android_asm.sh`
* Clean and re-build the project.
* If you want to use your own version of libopus, place it in
`${OPUS_EXT_PATH}/jni/libopus`.
## 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 `LibopusAudioRenderer`.
How you do this depends on which player API you're using:
* 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
`LibopusAudioRenderer` for playback if `MediaCodecAudioRenderer` doesn't
support the input format. Pass `EXTENSION_RENDERER_MODE_PREFER` to give
`LibopusAudioRenderer` priority over `MediaCodecAudioRenderer`.
* If you've subclassed `DefaultRenderersFactory`, add a `LibopusAudioRenderer`
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
`LibopusAudioRenderer` 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 `LibopusAudioRenderer`
in the array of `Renderer`s. 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 `LibopusAudioRenderer` 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.opus.*`
belong to this module.
[Javadoc]: https://google.github.io/ExoPlayer/doc/reference/index.html