# ExoPlayer AV1 extension #

The AV1 extension provides `Libgav1VideoRenderer`, which uses libgav1 native
library to decode AV1 videos.

## 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][].

In addition, it's necessary to fetch cpu_features library and libgav1 with its
dependencies as follows:

* Set the following environment variables:

```
cd "<path to exoplayer checkout>"
EXOPLAYER_ROOT="$(pwd)"
AV1_EXT_PATH="${EXOPLAYER_ROOT}/extensions/av1/src/main"
```

* Fetch cpu_features library:

```
cd "${AV1_EXT_PATH}/jni" && \
git clone https://github.com/google/cpu_features
```

* Fetch libgav1:

```
cd "${AV1_EXT_PATH}/jni" && \
git clone https://chromium.googlesource.com/codecs/libgav1
```

* Fetch Abseil:

```
cd "${AV1_EXT_PATH}/jni/libgav1" && \
git clone https://github.com/abseil/abseil-cpp.git third_party/abseil-cpp
```

* [Install CMake][].

Having followed these steps, gradle will build the extension automatically when
run on the command line or via Android Studio, using [CMake][] and [Ninja][]
to configure and build libgav1 and the extension's [JNI wrapper library][].

[top level README]: https://github.com/google/ExoPlayer/blob/release-v2/README.md
[Install CMake]: https://developer.android.com/studio/projects/install-ndk
[CMake]: https://cmake.org/
[Ninja]: https://ninja-build.org
[JNI wrapper library]: https://github.com/google/ExoPlayer/blob/release-v2/extensions/av1/src/main/jni/gav1_jni.cc

## 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 `Libgav1VideoRenderer`.
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 `Libgav1VideoRenderer` for
  playback if `MediaCodecVideoRenderer` doesn't support decoding the input AV1
  stream. Pass `EXTENSION_RENDERER_MODE_PREFER` to give `Libgav1VideoRenderer`
  priority over `MediaCodecVideoRenderer`.
* If you've subclassed `DefaultRenderersFactory`, add a `Libvgav1VideoRenderer`
  to the output list in `buildVideoRenderers`. ExoPlayer will use the first
  `Renderer` in the list that supports the input media format.
* If you've implemented your own `RenderersFactory`, return a
  `Libgav1VideoRenderer` 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 `Libgav1VideoRenderer` 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.
You need to make sure you are passing a `Libgav1VideoRenderer` to the player and
then you need to implement your own logic to use the renderer for a given track.

## 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

## Rendering options ##

There are two possibilities for rendering the output `Libgav1VideoRenderer`
gets from the libgav1 decoder:

*   GL rendering using GL shader for color space conversion

    *   If you are using `SimpleExoPlayer` with `PlayerView`, enable this option
        by setting `surface_type` of `PlayerView` to be
        `video_decoder_gl_surface_view`.
    *   Otherwise, enable this option by sending `Libgav1VideoRenderer` a
        message of type `Renderer.MSG_SET_VIDEO_DECODER_OUTPUT_BUFFER_RENDERER`
        with an instance of `VideoDecoderOutputBufferRenderer` as its object.

*   Native rendering using `ANativeWindow`

    *   If you are using `SimpleExoPlayer` with `PlayerView`, this option is
        enabled by default.
    *   Otherwise, enable this option by sending `Libgav1VideoRenderer` a
        message of type `Renderer.MSG_SET_SURFACE` with an instance of
        `SurfaceView` as its object.

Note: Although the default option uses `ANativeWindow`, based on our testing the
GL rendering mode has better performance, so should be preferred

## Links ##

* [Javadoc][]: Classes matching `com.google.android.exoplayer2.ext.av1.*`
  belong to this module.

[Javadoc]: https://exoplayer.dev/doc/reference/index.html
