AV1 WebCodecs Registration

W3C Group Draft Note,

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Paul Adenot (Mozilla)
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This registration is entered into the [webcodecs-codec-registry]. It describes, for AV1, the (1) fully qualified codec strings, (2) the codec-specific EncodedVideoChunk [[internal data]] bytes, (3) the codec-specific extensions to VideoEncoderConfig, (4) the VideoDecoderConfig.description bytes, (5) the values of EncodedVideoChunk [[type]], and (6) the codec-specific extensions to VideoEncoderEncodeOptions.

The registration is not intended to include any information on whether a codec format is encumbered by intellectual property claims. Implementers and authors are advised to seek appropriate legal counsel in this matter if they intend to implement or use a specific codec format. Implementers of WebCodecs are not required to support the AV1 codec.

This registration is non-normative.

Status of this document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

Feedback and comments on this specification are welcome. GitHub Issues are preferred for discussion on this specification. Alternatively, you can send comments to the Media Working Group’s mailing-list, public-media-wg@w3.org (archives). This draft highlights some of the pending issues that are still to be discussed in the working group. No decision has been taken on the outcome of these issues including whether they are valid.

This document was published by the Media Working Group as a Group Draft Note using the Note track.

Group Draft Notes are not endorsed by W3C nor its Members.

This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

The W3C Patent Policy does not carry any licensing requirements or commitments on this document.

This document is governed by the 2 November 2021 W3C Process Document.

1. Fully qualified codec strings

The codec string begins with the prefix "av01.", followed by a variable length suffix as described in Section 5 of [AV1-ISOBMFF].

2. EncodedVideoChunk data

EncodedVideoChunk [[internal data]] is expected to be data compliant to the "low-overhead bitstream format" as described in Section 5 of [AV1].

3. VideoDecoderConfig description

description is not used for this codec.

4. EncodedVideoChunk type

If an EncodedVideoChunk's [[type]] is key, then the EncodedVideoChunk is expected to contain a frame with a frame_type of KEY_FRAME as defined in Section 6.8.2 of [AV1].

5. VideoEncoderConfig extensions

partial dictionary VideoEncoderConfig {
  AV1EncoderConfig av1;

av1, of type AV1EncoderConfig
Contains codec specific configuration options for the AV1 codec.

5.1. AV1EncoderConfig

dictionary AV1EncoderConfig {
  boolean forceScreenContentTools = false;

forceScreenContentTools, of type boolean, defaulting to false
Indicates whether the encoder should force use of screen content coding tools. The default value (false) indicates that use of screen content coding tools is not forced. A value of true (corresponding to setting seq_force_screen_content_tools to SELECT_SCREEN_CONTENT_TOOLS in Section 5.5.1 of [AV1]) indicates that use of screen content coding tools is forced.

6. VideoEncoderEncodeOptions extensions

partial dictionary VideoEncoderEncodeOptions {
  VideoEncoderEncodeOptionsForAv1 av1;

av1, of type VideoEncoderEncodeOptionsForAv1
Contains codec specific encode options for the [AV1] codec.

6.1. VideoEncoderEncodeOptionsForAv1

dictionary VideoEncoderEncodeOptionsForAv1 {
  unsigned short? quantizer;

quantizer, of type unsigned short, nullable
Sets per-frame quantizer value. In [AV1] the quantizer threshold can be varied from 0 to 63

7. Privacy Considerations

Please refer to the section Privacy Considerations in [WEBCODECS].

8. Security Considerations

Please refer to the section Security Considerations in [WEBCODECS].


Document conventions

Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]

Examples in this specification are introduced with the words “for example” or are set apart from the normative text with class="example", like this:

This is an example of an informative example.

Informative notes begin with the word “Note” and are set apart from the normative text with class="note", like this:

Note, this is an informative note.


Terms defined by this specification

Terms defined by reference


Normative References

S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL: https://datatracker.ietf.org/doc/html/rfc2119
Paul Adenot; Bernard Aboba. WebCodecs. 6 July 2023. WD. URL: https://www.w3.org/TR/webcodecs/
Edgar Chen; Timothy Gu. Web IDL Standard. Living Standard. URL: https://webidl.spec.whatwg.org/

Informative References

AV1 Bitstream & Decoding Process Specification. URL: https://aomediacodec.github.io/av1-spec/
AV1 Codec ISO Media File Format Binding. URL: https://aomediacodec.github.io/av1-isobmff/
Chris Cunningham; Paul Adenot; Bernard Aboba. WebCodecs Codec Registry. 10 October 2022. NOTE. URL: https://www.w3.org/TR/webcodecs-codec-registry/

IDL Index

partial dictionary VideoEncoderConfig {
  AV1EncoderConfig av1;

dictionary AV1EncoderConfig {
  boolean forceScreenContentTools = false;

partial dictionary VideoEncoderEncodeOptions {
  VideoEncoderEncodeOptionsForAv1 av1;

dictionary VideoEncoderEncodeOptionsForAv1 {
  unsigned short? quantizer;