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This specification defines a Media Source Extensions byte stream format specification based on the WebM container format.
This document is merely a W3C-internal document. It has no official standing of any kind and does not represent consensus of the W3C Membership.
This specification describes a byte stream format based on the WebM container format. It defines the MIME-type parameters used to signal codecs, and provides the necessary format specific definitions for initialization segments, media segments, and random access points required by the byte stream formats section of the Media Source Extensions spec.
This section specifies the parameters that can be used in the MIME-type passed to isTypeSupported()
or addSourceBuffer()
.
Codec ID | Valid with "audio/webm" | Valid with "video/webm" |
---|---|---|
vorbis | true | true |
opus | true | true |
vp8 | false | true |
vp9 | false | true |
Examples of valid MIME-types with a codecs parameter.
A WebM initialization segment must contain a subset of the elements at the start of a typical WebM file.
The user agent must run the append error algorithm with the decode error parameter set to true if any of the following conditions are not met:
The user agent must accept and ignore any elements other than an EBML Header or a Cluster that occur before, in between, or after the Segment Information and Tracks elements.
The user agent must source attribute values for id, kind, label and language for AudioTrack
, VideoTrack
and
TextTrack
objects as described for WebM in the in-band tracks spec [INBANDTRACKS].
A WebM media segment is a single Cluster element.
The user agent uses the following rules when interpreting content in a Cluster:
The user agent must run the append error algorithm with the decode error parameter set to true if any of the following conditions are not met:
The user agent must accept and ignore Cues or Chapters elements that follow a Cluster element.
A SimpleBlock element with its Keyframe flag set signals the location of a random access point for that track. Media segments containing multiple tracks are only considered a random access point if the first SimpleBlock for each track has its Keyframe flag set. The order of the multiplexed blocks must conform to the WebM Muxer Guidelines.