h263_codec_registration.src.html

<pre class='metadata'>
Title: H.263 WebCodecs Registration
Repository: w3c/webcodecs
Status: NOTE-ED
Shortname: webcodecs-h263-codec-registration
Level: none
Group: mediawg
ED: https://w3c.github.io/webcodecs/h263_codec_registration.html
TR: https://www.w3.org/TR/webcodecs-h263-codec-registration/
Editor: Yahweasel, Wereweasel https://wereweasel.com/

Abstract: This registration is entered into the [[webcodecs-codec-registry]].
    It describes, for H.263, (1) the fully qualified codec strings, (2) the
    codec-specific {{EncodedVideoChunk}} [=EncodedVideoChunk/[[internal
    data]]=] bytes, (3) the {{VideoDecoderConfig.description}} bytes, (4) the
    values of {{EncodedVideoChunk}} [=EncodedVideoChunk/[[type]]=], and (5)
    the naming convention used in this document.

    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 H.263 codec.

    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: EncodedVideoChunkMetadata.decoderConfig; url: dom-encodedvideochunkmetadata-decoderconfig
        for: EncodedVideoChunkType; text: key; url: dom-encodedvideochunktype-key
        text: VideoDecoderConfig.description; url: dom-videodecoderconfig-description
    type: dfn
        for: EncodedVideoChunk; text: [[internal data]]; url: dom-encodedvideochunk-internal-data-slot
        for: EncodedVideoChunk; text: [[type]]; url: dom-encodedvideochunk-type-slot
        for: VideoEncoder; text: [[output callback]]; url: dom-videoencoder-output-callback-slot
    type: interface
        text: EncodedVideoChunk; url: encodedvideochunk
        text: VideoEncoder; url: videoencoder
    type: dictionary
        text: VideoEncoderConfig; url: dictdef-videoencoderconfig
        text: VideoDecoderConfig; url: dictdef-videodecoderconfig
</pre>

<pre class='biblio'>
{
  "H.263v1": {
    "href": "https://www.itu.int/rec/T-REC-H.263-199603-S/en",
    "title": "H.263: Video coding for low bit rate communication (03/96)",
    "publisher": "ITU-T"
  },
  "H.263v2": {
    "href": "https://www.itu.int/rec/T-REC-H.263-199802-S/en",
    "title": "H.263: Video coding for low bit rate communication (02/98)",
    "publisher": "ITU-T"
  },
  "H.263v3": {
    "href": "https://www.itu.int/rec/T-REC-H.263-200501-I/en",
    "title": "H.263: Video coding for low bit rate communication (01/2005)",
    "publisher": "ITU-T"
  }
}
</pre>

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

The codec string begins with the prefix `"h263."`, with a suffix of 1 character
describing the version of the specification: `"h263.1"` for the first revision
([[H.263v1]]), `"h263.2"` for the second revision ([[H.263v2]]), or `"h263.3"`
for the third revision ([[H.263v3]]). As the specifications are backwards
compatible, an encoder can encode using an earlier revision than specified, and
a decoder can decode using a later revision than specified.

`"h263.3"`, but no prior revision, can further be suffixed with a `"."` and a
one-character profile number, as specified in Annex X.2 of [[H.263v3]]. If a
profile is not specified, then an encoder can use any optional features and a
decoder needs to support all optional features. This can further be suffixed by
a `"."` and a two-character level, as described in Table X.2 of [[H.263v3]]. If
a level is not specified, then an encoder can support any level or can support
formats other than those in any specified level, and a decoder needs to support
any level and can support formats other than those in any specified level.

As revisions of H.263 prior to H.263v3 do not have profiles or levels, if
`"h263.1"` or `"h263.2"` is specified, then an encoder can support any optional
features in the specified revision, and a decoder needs to support all optional
features in the specified revision. The non-normative profiles and levels
specified in Appendix II are not used.

EncodedVideoChunk data {#encodedvideochunk-data}
================================================

{{EncodedVideoChunk}} [=EncodedVideoChunk/[[internal data]]=] is expected to be
a picture as described in Section 5.1 of [[H.263v1]], [[H.263v2]], or
[[H.263v3]], as appropriate for the used specification revision.

VideoDecoderConfig description {#videodecoderconfig-description}
================================================================

{{VideoDecoderConfig.description}} is not used for this codec.

EncodedVideoChunk type {#encodedvideochunk-type}
================================================

If an {{EncodedVideoChunk}}'s [=EncodedVideoChunk/[[type]]=] is
{{EncodedVideoChunkType/key}}, then the {{EncodedVideoChunk}} is expected to
contain an `INTRA` picture. The precise definition depends on the specification
revision:

H.263v1: `PTYPE`'s bit 9 (Picture Coding Type) is 0 (`INTRA`), as defined in
Section 5.1.3 of [[H.263v1]].

H.263v2, H.263v3: If `PTYPE`'s bits 6-8 are not set to 111, then `PTYPE`'s bit
9 (Picture Coding Type) is 0 (`INTRA`), as defined in Section 5.1.3. If
`PTYPE`'s bits 6-8 are set to 111, as defined in Section 5.1.3, then
`PLUSPTYPE`'s `MPPTYPE`'s bits 1-3 (Picture Type Code) are 000 (`INTRA`), as
defined in Section 5.1.4.3. Section numbers refer to [[H.263v2]] if the second
revision is used, or [[H.263v3]] if the third revision is used.

Notes on codec naming {#notes-on-codec-naming}
==============================================

This registration codifies only the unamended H.263 specification revisions as
published by ITU-T. Each specification is named "H.263", so they are
differentiated by revision numbers. The specifications do not formally have
revision numbers, but the revision numbers used in this registration are
commonly used. Each revision is materially identical to the previous revision
with several separately published annexes added. This registration provides no
means of specifying the annexes independently of the specification revisions in
which they were included, so it is not possible to, for instance, specify
baseline H.263 with Annexes A through J but not L through T. H.263v1 includes
Annexes A through H, H.263v2 includes Annexes A through T, and H.263v3 includes
Annexes A through X.

H.263v2 is also known as H.263+ or H.263 1998. H.263v3 is also known as H.263++
or H.263 2005.

MPEG-4 Part 2 specifies a video encoding format which is backwards compatible
with H.263 (H.263 streams can be decoded as MPEG-4 Part 2), but it is not
forwards compatible (MPEG-4 Part 2 streams do not decode as H.263), and it is
not covered by this registration.

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]].