# ExoPlayer FFmpeg extension #

The FFmpeg extension provides `FfmpegAudioRenderer`, which uses FFmpeg for
decoding and can render audio encoded in a variety of formats.

## 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 (Linux, macOS) ##

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][]. The extension is not provided via JCenter (see [#2781][]
for more information).

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

* Set the following shell variable:

```
cd "<path to exoplayer checkout>"
FFMPEG_EXT_PATH="$(pwd)/extensions/ffmpeg/src/main/jni"
```

* Download the [Android NDK][] and set its location in a shell variable.
  This build configuration has been tested on NDK r20.

```
NDK_PATH="<path to Android NDK>"
```

* Set up host platform ("darwin-x86_64" for Mac OS X):

```
HOST_PLATFORM="linux-x86_64"
```

* Configure the formats supported by adapting the following variable if needed
  and by setting it. See the [Supported formats][] page for more details of the
  formats.

```
ENABLED_DECODERS=(vorbis opus flac)
```

* Fetch and build FFmpeg. For example, executing script `build_ffmpeg.sh` will
  fetch and build FFmpeg release 4.2 for armeabi-v7a, arm64-v8a and x86:

```
cd "${FFMPEG_EXT_PATH}" && \
./build_ffmpeg.sh \
  "${FFMPEG_EXT_PATH}" "${NDK_PATH}" "${HOST_PLATFORM}" "${ENABLED_DECODERS[@]}"
```

* Build the JNI native libraries, setting `APP_ABI` to include the architectures
  built in the previous step. For example:

```
cd "${FFMPEG_EXT_PATH}" && \
${NDK_PATH}/ndk-build APP_ABI="armeabi-v7a arm64-v8a x86" -j4
```

## Build instructions (Windows) ##

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

[Windows PowerShell]: https://docs.microsoft.com/en-us/powershell/scripting/getting-started/getting-started-with-windows-powershell

## 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 `FfmpegAudioRenderer`.
How you do this depends on which player API you're using:

* If you're passing a `DefaultRenderersFactory` to `SimpleExoPlayer.Builder`,
  you can enable using the extension by setting the `extensionRendererMode`
  parameter of the `DefaultRenderersFactory` constructor to
  `EXTENSION_RENDERER_MODE_ON`. This will use `FfmpegAudioRenderer` for playback
  if `MediaCodecAudioRenderer` doesn't support the input format. Pass
  `EXTENSION_RENDERER_MODE_PREFER` to give `FfmpegAudioRenderer` priority over
  `MediaCodecAudioRenderer`.
* If you've subclassed `DefaultRenderersFactory`, add an `FfmpegAudioRenderer`
  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 an
  `FfmpegAudioRenderer` 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 an `FfmpegAudioRenderer` 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 `FfmpegAudioRenderer` to the player,
then implement your own logic to use the renderer for a given track.

[top level README]: https://github.com/google/ExoPlayer/blob/release-v2/README.md
[Android NDK]: https://developer.android.com/tools/sdk/ndk/index.html
[#2781]: https://github.com/google/ExoPlayer/issues/2781
[Supported formats]: https://exoplayer.dev/supported-formats.html#ffmpeg-extension

## Using the extension in the demo application ##

To try out playback using the extension in the [demo application][], see
[enabling extension decoders][].

[demo application]: https://exoplayer.dev/demo-application.html
[enabling extension decoders]: https://exoplayer.dev/demo-application.html#enabling-extension-decoders

## Links ##

* [Troubleshooting using extensions][]
* [Javadoc][]: Classes matching `com.google.android.exoplayer2.ext.ffmpeg.*`
  belong to this module.

[Troubleshooting using extensions]: https://exoplayer.dev/troubleshooting.html#how-can-i-get-a-decoding-extension-to-load-and-be-used-for-playback
[Javadoc]: https://exoplayer.dev/doc/reference/index.html
