The Dolby Vision codec selection library is for Android developers who are adding support for Dolby Vision user-generated content to their applications. The library helps to ensure that an application can adapt to various Android mobile device capabilities and support Dolby Vision content in playback and transcoding use cases.
The library retrieves track information from an input video file and checks the capabilities of the device to support Dolby Vision. It selects the appropriate track and codec for decoding the video content based on the device's capabilities and the chosen output format (HEVC, AVC, or Dolby Vision Profile 8.4). It uses standard Android classes including MediaExtractor, MediaFormat, and MediaCodec (see the import statements in CodecBuilderImpl.java for all Android classes used).
It is important to note that the Dolby Vision codec selection library also considers whether decoding and subsequent color space conversion processes (for example, Dolby Vision Profile 8.4 to SDR) are based on a GPU (graphics processing unit) or a DPU (display processing unit). These processes are straightforward when the DPU is available and capable of performing the necessary HDR to SDR color mapping. In this case, the MediaFormat class used to configure the MediaCodec decoder needs only to have the KEY_COLOR_TRANSFER_REQUEST field set to the appropriate value (COLOR_TRANSFER_SDR_VIDEO for SDR). However, when the GPU is used for decoding Dolby Vision and color mapping, it is necessary to configure additional decoder parameters (vendor.dolby.codec.transfer.value) with specific color transfer type (for example, transfer.sdr.normal for SDR). The Dolby Vision codec selection library provides a more straightforward interface for selecting and configuring the appropriate Dolby Vision codec, whether it uses the GPU or the DPU.
The code available in this repository can be opened as an Android Studio project. Once this is done, build the application as usual. By default, the output will not be an APK (Android Package Kit) file, but instead an AAR (Android Archive) file. This archive file can then be linked to another project, allowing the codec selector to be used as a library.
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The CodecBuilderImpl class extends the CodecBuilder interface and implements codec selection functionality.
To access CodecBuilderImpl and other codec selection library classes, import the codecselection package:
import com.dolby.vision.codecselection;
The constructor for CodecBuilderImpl instantiates a builder for an Android context, an output format, and an input file URI:
public CodecBuilderImpl(Context context, String outputFormat, Uri uri) throws IOException;The static method getSupportStatus of the CodecBuilderImpl class returns an enumerated value indicating the type of processor for the platform. The method and its enumerated return type are declared as follows:
public static enum PlatformSupport
{
NONE,
GPU,
DPU
}
public static PlatformSupport getSupportStatus() {...}There are two static methods of the CodecBuilderImpl class to determine whether the decoder name is the name for a specific type of processor (GPU or DPU):
public static boolean isDolbyGPUDecoder(String decoderName) {...}
public static boolean isDolbyDPUDecoder(String decoderName) {...}The isDolbySupported method returns a boolean value indicating whether Dolby Vision is supported:
public boolean isDolbySupported() {...}The getDolbyCodecMapping method returns a HashMap with with Dolby Vision profile numbers mapped to lists of codecs, and can be used to get codecs for a profile:
public HashMap<Integer, ArrayList<String>> getDolbyCodecMapping() {...}The printDolbyCodecSupport method returns a String with a return-separated list of supported Dolby Vision profile names:
public String printDolbyCodecSupport() {...}The getDecodedFormat method returns a MediaFormat that is the decoder format indicated by the builder:
public MediaFormat getDecodedFormat() {
return this.decoderFormat;
}The getCodecName method returns the name of the codec for the format of the track:
public String getCodecName() throws ... {...}The MainActivity.java file defines a class MainActivity that extends the Android class AppCompatActivity and uses a CodecBuilderImpl instance when opening a MP4 video file upon creation (onCreate).
First, the builder is instantiated and its methods are called to get the codec name and to check for Dolby support (with logging of return values omitted):
CodecBuilderImpl builder = new CodecBuilderImpl(context, "placeholder", inputUri.getData());
builder.printDolbyCodecSupport();
String codecName = builder.getCodecName();
boolean dolby = builder.isDolbySupported();Next, an ExampleDecoder is instantiated and used to create a codec, and the builder creates and configures a MediaExtractor for the codec that can be used to play the video:
ExampleDecoder decoder = new ExampleDecoder();
decoder.createCodec(MediaCodec.createByCodecName(codecName));
MediaExtractor extractor = builder.configure(decoder.getCodec(), null, decoder, 1);This project is licensed under the BSD-3 License - see the LICENSE file for details.
See the dolby-vision-editor project.
See the VideoDecoder and FrameHandler classes for uses of the CodecBuilderImpl class.