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# AV1 decoder module
The AV1 module 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 module also requires building and including one or
more external libraries as described below. These are licensed separately.
[Apache 2.0]: ../../LICENSE
## Build instructions (Linux, macOS)
To use the module you need to clone this GitHub project and depend on its
modules locally. Instructions for doing this can be found in the
[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 project checkout>"
AV1_MODULE_PATH="$(pwd)/libraries/decoder_av1/src/main"
```
* Fetch cpu_features library:
```
cd "${AV1_MODULE_PATH}/jni" && \
git clone https://github.com/google/cpu_features
```
* Fetch libgav1:
```
cd "${AV1_MODULE_PATH}/jni" && \
git clone https://chromium.googlesource.com/codecs/libgav1
```
* Fetch Abseil:
```
cd "${AV1_MODULE_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 module automatically when run
on the command line or via Android Studio, using [CMake][] and [Ninja][] to
configure and build libgav1 and the module's [JNI wrapper library][].
[top level README]: ../../README.md
[Install CMake]: https://developer.android.com/studio/projects/install-ndk
[CMake]: https://cmake.org/
[Ninja]: https://ninja-build.org
[JNI wrapper library]: src/main/jni/gav1_jni.cc
## Build instructions (Windows)
We do not provide support for building this module 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 module with ExoPlayer
Once you've followed the instructions above to check out, build and depend on
the module, 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 `ExoPlayer.Builder`, you
can enable using the module 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.
## 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 `ExoPlayer` with `PlayerView`, enable this option by
setting the `surface_type` of the view to be
`video_decoder_gl_surface_view`.
* Otherwise, enable this option by sending `Libgav1VideoRenderer` a
message of type `Renderer.MSG_SET_VIDEO_OUTPUT` with an instance of
`VideoDecoderOutputBufferRenderer` as its object.
`VideoDecoderGLSurfaceView` is the concrete
`VideoDecoderOutputBufferRenderer` implementation used by `PlayerView`.
* Native rendering using `ANativeWindow`
* If you are using `ExoPlayer` with `PlayerView`, this option is enabled
by default.
* Otherwise, enable this option by sending `Libgav1VideoRenderer` a
message of type `Renderer.MSG_SET_VIDEO_OUTPUT` 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
* [Troubleshooting using decoding extensions][]
[Troubleshooting using decoding extensions]: https://developer.android.com/media/media3/exoplayer/troubleshooting#how-can-i-get-a-decoding-library-to-load-and-be-used-for-playback