u-law PCM WebCodecs Registration

Editor’s Draft,

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Paul Adenot (Mozilla)
Bernard Aboba (Microsoft Corporation)
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Chris Cunningham (Google Inc.)
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This registration is entered into the [webcodecs-codec-registry]. It describes, for u-law encoded PCM, the (1) fully qualified codec strings, (2) the codec-specific EncodedAudioChunk [[internal data]] bytes, (3) the AudioDecoderConfig.description bytes, and (4) the values of EncodedAudioChunk [[type]].

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 u-law PCM 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 an Editor’s Draft. The group does not expect this document to become a W3C Recommendation.

Publication as an Editor’s Draft does not imply endorsement by W3C and its Members.

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

This document is governed by the 03 November 2023 W3C Process Document.

1. Fully qualified codec strings

The codec string is "ulaw".

2. EncodedAudioChunk data

EncodedAudioChunk [[internal data]] is expected to be a sequence of bytes of arbitrary length, where each byte is a u-law encoded PCM sample as defined by Table 2a and 2b in [ITU-G.711].

3. AudioDecoderConfig description

The description is expected to be omitted from the AudioDecoderConfig.

4. EncodedAudioChunk type

The [[type]] for an EncodedAudioChunk containing u-law PCM is always "key".

5. Privacy Considerations

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

6. 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 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; Eugene Zemtsov. WebCodecs. URL: https://w3c.github.io/webcodecs/

Informative References

G.711 : Pulse code modulation (PCM) of voice frequencies. November 1988. URL: https://www.itu.int/rec/T-REC-G.711/
Chris Cunningham; Paul Adenot; Bernard Aboba. WebCodecs Codec Registry. URL: https://w3c.github.io/webcodecs/codec_registry.html