Syntax

Parameters

config

A dictionary object containing the following members:

codec

A string containing a valid codec string. See "codecs" parameter for details on codec string construction.

width Optional

An integer representing the width of each output EncodedVideoChunk in pixels, before any ratio adjustments.

height Optional

An integer representing the height of each output EncodedVideoChunk in pixels, before any ratio adjustments.

displayWidth Optional

An integer representing the intended display width of each output EncodedVideoChunk in pixels when displayed.

displayHeight Optional

An integer representing the vertical dimension of each output EncodedVideoChunk in pixels when displayed.

hardwareAcceleration

A hint that configures the hardware acceleration method of this codec. One of:

• "no-preference"
• "prefer-hardware"
• "prefer-software"

bitrate

An integer containing the average bitrate of the encoded video in units of bits per second.

framerate

An integer containing the expected frame rate in frames per second.

alpha

A string indicating whether the alpha component of the VideoFrame inputs should be kept or discarded prior to encoding. One of:

• "discard" (default)
• "keep"

scalabilityMode

A string containing an encoding scalability mode identifier as defined in WebRTC.

bitrateMode Optional

A string containing a bitrate mode. One of:

"constant"

The encoder will target constant bitrate.

"variable" (default)

The encoder will target a variable bitrate, allowing more space to be used for complex signals and less space for less complex signals.

"quantizer"

The encoder will disregard the bitrate option and instead it will use codec-specific quantizer values specified for each frame in the options parameter to VideoEncoder.encode().

latencyMode Optional

A string containing a value that configures the latency behavior of this codec. One of:

"quality" (default)

The encoder should optimize for encoding quality.

"realtime"

The encoder should optimize for low latency and may even drop frames to honor framerate.

Return value

None (undefined).

Exceptions

TypeError

Thrown if the provided config is invalid.

InvalidStateError DOMException

Thrown if the state is "closed".

NotSupportedError DOMException

Thrown if the provided config is valid but the user agent cannot provide a codec that can decode this profile.

Examples

The following example creates a new VideoEncoder and configures it with some of the available options.

const init = {
  output: handleChunk,
  error(e) {
    console.log(e.message);
  },
};

let config = {
  codec: "vp8",
  width: 640,
  height: 480,
  bitrate: 2_000_000, // 2 Mbps
  framerate: 30,
};

let encoder = new VideoEncoder(init);
encoder.configure(config);

Specifications

Browser compatibility

See also

• VideoEncoder.isConfigSupported()
• Codec String Support Table