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# 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 (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 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.
This build configuration has been tested on NDK r20.
```
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 && \
${NDK_PATH}/ndk-build APP_ABI=all -j4
```
[top level README]: https://github.com/google/ExoPlayer/blob/release-v2/README.md
[Android NDK]: https://developer.android.com/tools/sdk/ndk/index.html
## Build instructions (Windows) ##
We do not provide support for building this extension on Windows, however it
should be possible to follow the Linux instructions in [Windows PowerShell][].
[Windows PowerShell]: https://docs.microsoft.com/en-us/powershell/scripting/getting-started/getting-started-with-windows-powershell
## Notes ##
* Every time there is a change to the libvpx checkout:
* Android config scripts should be re-generated by running
`generate_libvpx_android_configs.sh`
* Clean and re-build the project.
* If you want to use your own version of libvpx, place it in
`${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 `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 `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 `ExoPlayer.Builder`, 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.
## 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 `LibvpxVideoRenderer`
gets from the libvpx 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 `LibvpxVideoRenderer` a message of
type `C.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 `LibvpxVideoRenderer` a message of
type `C.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.vp9.*`
belong to this module.
[Javadoc]: https://exoplayer.dev/doc/reference/index.html