W3cubDocs

/Web APIs

MediaCapabilities: decodingInfo() method

The MediaCapabilities.decodingInfo() method, part of the Media Capabilities API, returns a promise with the tested media configuration's capabilities info. This contains the three boolean properties supported, smooth, and powerefficient, which describe whether decoding the media described would be supported, smooth, and powerefficient.

Syntax

decodingInfo(configuration)

Parameters

configuration

An object with a property type and either a video or audio property containing a configuration of the appropriate type:

type

The type of media being tested. This takes one of three values:

file: Represents a configuration that is meant to be used for a plain file playback.
media-source: Represents a configuration that is meant to be used for playback of a MediaSource.
webrtc: Represents a configuration that is meant to be received using RTCPeerConnection.

video

Configuration object for a video media source. This has the following properties:

contentType: String containing a valid video MIME type, and (optionally) a codecs parameter.
width: The width of the video.
height: The height of the video.
bitrate: The number of bits used to encode one second of the video file.
framerate: The number of frames making up one second of video playback.

audio

Configuration object for an audio media source. This has the following properties:

contentType: String containing a valid audio MIME type, and (optionally) a codecs parameter.
channels: The number of channels used by the audio track.
bitrate: The number of bits used to encode one second of the audio file.
samplerate: The number of audio samples making up one second of the audio file.

Return value

A Promise fulfilling with an object containing three Boolean attributes:

supported: true if the media content can be decoded at all. Otherwise, it is false.
smooth: true if playback of the media will be smooth (of high quality). Otherwise it is false.
powerEfficient: true if playback of the media will be power efficient. Otherwise, it is false.

Browsers will report a supported media configuration as smooth and powerEfficient until stats on this device have been recorded. All supported audio codecs are reported to be power efficient.

Exceptions

TypeError: Thrown if the configuration passed to the decodingInfo() method is invalid, either because the type is not video or audio, the contentType is not a valid codec MIME type, the media decoding configuration is not a valid value for the type (file, media-source, or webrtc), or any other error in the media configuration passed to the method, including omitting any values.

Examples

This example shows how to create a media configuration for an audio file and then use it in MediaCapabilities.decodingInfo().

//Create media configuration to be tested
const mediaConfig = {
  type: "file", // or 'media-source' or 'webrtc'
  audio: {
    contentType: "audio/ogg; codecs=vorbis", // valid content type
    channels: 2, // audio channels used by the track
    bitrate: 132700, // number of bits used to encode 1s of audio
    samplerate: 5200, // number of audio samples making up that 1s.
  },
};

// check support and performance
navigator.mediaCapabilities.decodingInfo(mediaConfig).then((result) => {
  console.log(
    `This configuration is ${result.supported ? "" : "not "}supported,`,
  );
  console.log(`${result.smooth ? "" : "not "}smooth, and`);
  console.log(`${result.powerEfficient ? "" : "not "}power efficient.`);
});

Similarly, the code below shows the configuration for a video file.

const mediaConfig = {
  type: "file",
  video: {
    contentType: "video/webm;codecs=vp8", // valid content type
    width: 800, // width of the video
    height: 600, // height of the video
    bitrate: 10000, // number of bits used to encode 1s of video
    framerate: 30, // number of frames making up that 1s.
  },
};

Specifications

Specification
Media Capabilities # ref-for-dom-mediacapabilities-decodinginfo

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`decodingInfo`	66 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]	79 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]	63 ["The `webrtc` value of the `type` option is named `transmission`.", "Before Firefox 101, `decodingInfo()` ignored `codecs` parameter options for `av01` codecs (treating them as `av1`)."]	No	53 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]	13	66 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]	66 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]	63 ["The `webrtc` value of the `type` option is named `transmission`.", "Before Firefox 101, `decodingInfo()` ignored `codecs` parameter options for `av01` codecs (treating them as `av1`)."]	48 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]	13	9.0 ["`codecs` string can contain any subset of optional parameters (should be all or none).", "Errors if `codecs` string contains unexpected characters (should evaluate string up to character)."]