- From: David Evans via GitHub <sysbot+gh@w3.org>
- Date: Fri, 09 Dec 2016 14:31:28 +0000
- To: public-html-media@w3.org
bbcrddave has just created a new issue for https://github.com/w3c/media-source: == Allow non-ISO/IEC14496-12 top-level boxes in ISOBMFF Byte Streams == The [Segment Parser Loop](https://w3c.github.io/media-source/index.html#sourcebuffer-segment-parser-loop) states the following: "If the input buffer contains bytes that violate the SourceBuffer byte stream format specification, then run the append error algorithm and abort this algorithm." The [ISO BMFF Byte Stream Format](https://www.w3.org/TR/mse-byte-stream-format-isobmff/) states: "Valid top-level boxes defined in ISO/IEC 14496-12 other than ftyp, moov, styp, moof, and mdat are allowed to appear between the end of an initialization segment or media segment and before the beginning of a new media segment. These boxes MUST be accepted and ignored by the user agent and are not considered part of the media segment in this specification. " This appears to imply only valid top-level boxes defined in 14496-12 are allowed to appear in a stream, and that strictly compliant implementations should reject input buffers containing any other top-level boxes. MPEG-DASH (ISO/IEC 23009-1:2014) specifies a new box (`emsg`) as a mechanism for signalling both generic in-band metadata related to the media and DASH-specific operations. It further constrains this new box to be placed before the `moof` - i.e. at the top level. It seems that the byte stream format specification needs either to be less strict in general in terms of extensions, or include references other than 14496-12 in the list. Note: at least one implementation has already included `emsg` in its list of valid top-level boxes [1]. See also: 1. https://bugs.chromium.org/p/chromium/issues/detail?id=276303 2. https://bugzilla.mozilla.org/show_bug.cgi?id=1322587 Please view or discuss this issue at https://github.com/w3c/media-source/issues/174 using your GitHub account
Received on Friday, 9 December 2016 14:31:35 UTC