pcm_codec_registration.src.html

<pre class='metadata'>
Title: Linear PCM WebCodecs Registration
Repository: w3c/webcodecs
Status: NOTE-ED
Shortname: webcodecs-pcm-codec-registration
Level: none
Group: mediawg
ED: https://w3c.github.io/webcodecs/pcm_codec_registration.html
TR: https://www.w3.org/TR/webcodecs-pcm-codec-registration/
Editor: Chris Cunningham, w3cid 114832, Google Inc. https://www.google.com/
Editor: Paul Adenot, w3cid 62410, Mozilla https://www.mozilla.org/
Editor: Bernard Aboba, w3cid 65611, Microsoft Corporation https://www.microsoft.com/

Abstract: This registration is entered into the [[webcodecs-codec-registry]].
    It describes, for Linear PCM, the (1) fully qualified codec strings,
    (2) the codec-specific {{EncodedAudioChunk}}
    [=EncodedAudioChunk/[[internal data]]=] bytes, (3) the
    {{AudioDecoderConfig.description}}, and (4) the values of
    {{EncodedAudioChunk}} [=EncodedAudioChunk/[[type]]=].

    Linear PCM is the [[webcodecs#audio-sample-formats|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.

Markup Shorthands:css no, markdown yes, dfn yes
!Participate: <a href="https://github.com/w3c/webcodecs">Git Repository.</a>
!Participate: <a href="https://github.com/w3c/webcodecs/issues/new">File an issue.</a>
!Version History: <a href="https://github.com/w3c/webcodecs/commits">https://github.com/w3c/webcodecs/commits</a>
</pre>

<pre class='anchors'>
spec: WEBCODECS; urlPrefix: https://w3c.github.io/webcodecs/#
    type: attribute
        text: AudioDecoderConfig.description; url: dom-audiodecoderconfig-description
    type: dfn
        for: EncodedAudioChunkType; text: key; url: dom-encodedaudiochunktype-key
        for: EncodedAudioChunk; text: [[internal data]]; url: dom-encodedaudiochunk-internal-data-slot
        for: EncodedAudioChunk; text: [[type]]; url: dom-encodedaudiochunk-type-slot
        text: sample; url: sample
        text: interleaved; url: interleaved
        text: section on sample magnitude; url: audio-samples-magnitude
    type: interface
        text: EncodedAudioChunk; url: encodedaudiochunk
        text: AudioData; url: audiodata-interface
    type: dictionary
        text: AudioDecoderConfig; url: dictdef-audiodecoderconfig
        text: AudioEncoderConfig; url: dictdef-audioencoderconfig
    type: enum
        text: AudioSampleFormat; url: enumdef-audiosampleformat
        text: u8; url: dom-audiosampleformat-u8
        text: s16; url: dom-audiosampleformat-s16
        text: s24; url: dom-audiosampleformat-s24
        text: s32; url: dom-audiosampleformat-s32
        text: f32; url: dom-audiosampleformat-f32
</pre>


Fully qualified codec strings {#fully-qualified-codec-strings}
==============================================================

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.

* pcm-u8, using format {{u8}}
* pcm-s16, using format {{s16}}
* pcm-s24, using three [[WEBIDL#idl-octet|byte]] (24-bit) [=samples=] with
    [=interleaved=] [[webcodecs#audio-buffer-arrangement|channel arrangement]].
* pcm-s32, using format {{s32}}
* pcm-f32, using format {{f32}}

NOTE: [[WEBCODECS]] does not define a 24-bit {{AudioSampleFormat}}. 24-bit
    samples are permitted within an {{EncodedAudioChunk}}, but such samples will
    be "decoded" in {{AudioData}} objects as either {{s32}} of {{f32}}. Please
    see [[WEBCODECS]] [=section on sample magnitude=] for addtional details.

EncodedAudioChunk data {#encodedaudiochunk-data}
================================================

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}} [=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=].


AudioDecoderConfig description {#audiodecoderconfig-description}
================================================================

An {{AudioDecoderConfig.description}} is expected to be omitted from the
{{AudioDecoderConfig}}.

EncodedAudioChunk type {#encodedaudiochunk-type}
================================================

The [=EncodedAudioChunk/[[type]]=] for an {{EncodedAudioChunk}} containing
Linear PCM is always "[=EncodedAudioChunkType/key=]".

Privacy and Security Considerations {#privacy-and-security-considerations}
==========================================================================

Please refer to the [[WEBCODECS#privacy-considerations|Privacy Considerations]]
and [[WEBCODECS#security-considerations|Security Considerations]] sections in
[[WEBCODECS]].