Linear PCM is the raw audio format used
in WebCodecs and does not require decoding. The motivation for registering
the Linear PCM codec is to enable passthrough "decoding" of PCM content as
an architectural simpliciation for WebCodecs applications.
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.
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.
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 codec’s string begins with the prefix "pcm-", followed by a suffix that
indicates the sample format. The complete list of strings and associated
formats is as follows.
Linear pulse code modulation (linear PCM) describes a format where the audio
values are sampled at a regular interval, and where the quantization levels
between two successive values are linearly uniform.
EncodedAudioChunk[[internal data]] is expected to be
a sequence of bytes of arbitrary length, with a sample occuring every N
bits, where N is defined by the codec string. For multichannel PCM, samples from different channels are interleaved.
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: