# AndroidX (ExoPlayer)

## Supported stream format

1. The solution utilizes`MediaCodec`for  decoding the base video stream so any codec supported by `MediaCodec` on the device can be supported for its LCEVC enhanced stream. Please consult [this page](https://developer.android.com/media/platform/supported-formats) to understand Android native codec support. For example, LCEVC enhanced H264 stream in local file (MPEG-TS `.ts`, MPEG-4 `.mp4`), as well as in HLS and DASH, are well supported. However, formats such as AV1 are only available on Android 10 and later, so playback of LCEVC-enhanced AV1 streams in this implementation faces the same limitation.
2. LCEVC data can be carried within the single video track using the SEI NAL unit type for MPEG codecs such as H.264, HEVC, and VVC. Alternatively, it can be contained within separate tracks, as seen in an `.mp4` video source where one track carries the base video stream and another track carries the LCEVC video stream. However, it's crucial to note that the current implementation only supports the use of a single video track carried within SEI data.

### Supported AndroidX (ExoPlayer) version

Since ExoPlayer version 2.13, the `MediaCodecAdapter`interface has been introduced and remained stable. The implementation of the LCEVC decoder extension relies on this interface, enabling seamless integration of the solution into media applications using ExoPlayer 2.13 and later versions. 

## Design overview

The provided class diagram offers a high-level depiction of how LCEVC decoding and rendering are integrated into the AndroidX framework:

1. LCEVC decoding and rendering is added into ExoPlayer as a decoder extension library, by use the LCEVC decoder native library.
2. `LCEVCSynchronousMediaCodecAdapter` is the entry point class, which inherits the interface `MediaCodecAdapter`defined in ExoPlayer core library. Its implementation is by use `MediaCodec` API to decode the base video stream, use LCEVC decoder native library to decode LCEVC video stream and render the final full resolution video frame.

<figure><img src="/files/Eg0Q27lFruD6Na9kAItg" alt=""><figcaption><p>decoder_lcevc extension architecture</p></figcaption></figure>

## How to deploy

### Get decoder\_lcevc extension library

For media application already migrated to AndroidX project the integration can be quite straight forward:

1. Fetch specific version of Google AndroidX libraries in your project build.gradle i.e.

   ```
   def mediaVersion = "1.0.1"
   implementation "androidx.media3:media3-exoplayer:$mediaVersion"
   implementation "androidx.media3:media3-exoplayer-dash:$mediaVersion"
   ```
2. Fetch the matching version of V-Nova decoder\_lcevc library  by adding following into build.gradle i.e:

   ```
   def lcevcDecoderExtensionVersion = “1.0.1.hashcode”
   implementation "androidx.media3:media3-decoder-lcevc:$lcevcDecoderExtensionVersion "
   ```

### Code to enable LCEVC

Once you've followed the instructions above to fetch the AndroidX and decoder\_lcevc libraries, the next step is to tell ExoPlayer to use decoder\_lcevc by creating the `LcevcRenderersFactory` and create ExoPlayer instance:

```
renderersFactory = LcevcRenderersFactory(applicationContext)
player = ExoPlayer.Builder(this)
            .setRenderersFactory(renderersFactory)
            .build()
```


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