# ExoPlayer VP9 extension #

The VP9 extension provides `LibvpxVideoRenderer`, which uses libvpx (the VPx
decoding library) to decode VP9 video.

## 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="$(pwd)"
VP9_EXT_PATH="${EXOPLAYER_ROOT}/extensions/vp9/src/main"
```

* Download the [Android NDK][] and set its location in an environment variable.
  The build configuration has been tested with Android NDK r19c.

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

* Fetch libvpx:

```
cd "${VP9_EXT_PATH}/jni" && \
git clone https://chromium.googlesource.com/webm/libvpx libvpx
```

* Checkout the appropriate branch of libvpx (the scripts and makefiles bundled
  in this repo are known to work only at specific versions of the library - we
  will update this periodically as newer versions of libvpx are released):

```
cd "${VP9_EXT_PATH}/jni/libvpx" && \
git checkout tags/v1.8.0 -b v1.8.0
```

* Run a script that generates necessary configuration files for libvpx:

```
cd ${VP9_EXT_PATH}/jni && \
./generate_libvpx_android_configs.sh
```

* Build the JNI native libraries from the command line:

```
cd "${VP9_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 libvpx checkout:
  * Android config scripts should be re-generated by running
    `generate_libvpx_android_configs.sh`
  * Clean and re-build the project.
* If you want to use your own version of libvpx, place it in
  `${VP9_EXT_PATH}/jni/libvpx`. Please note that
  `generate_libvpx_android_configs.sh` and the makefiles may need to be modified
  to work with arbitrary versions of libvpx.

## 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 `LibvpxVideoRenderer`.
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
  `LibvpxVideoRenderer` for playback if `MediaCodecVideoRenderer` doesn't
  support decoding the input VP9 stream. Pass `EXTENSION_RENDERER_MODE_PREFER`
  to give `LibvpxVideoRenderer` priority over `MediaCodecVideoRenderer`.
* If you've subclassed `DefaultRenderersFactory`, add a `LibvpxVideoRenderer`
  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
  `LibvpxVideoRenderer` 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 `LibvpxVideoRenderer`
  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 `LibvpxVideoRenderer` to the
player, then implement your own logic to use the renderer for a given track.

`LibvpxVideoRenderer` can optionally output to a `VpxVideoSurfaceView` when not
being used via `SimpleExoPlayer`, in which case color space conversion will be
performed using a GL shader. To enable this mode, send the renderer a message of
type `LibvpxVideoRenderer.MSG_SET_OUTPUT_BUFFER_RENDERER` with the
`VpxVideoSurfaceView` as its object, instead of sending `MSG_SET_SURFACE` with a
`Surface`.

## Links ##

* [Javadoc][]: Classes matching `com.google.android.exoplayer2.ext.vp9.*`
  belong to this module.

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