18601 2012-08-17 13:07:23 +0000 Contradictory requirements for initialization segments 2012-11-28 18:40:41 +0000 1 1 1 Unclassified HTML WG Media Source Extensions unspecified PC Linux RESOLVED FIXED tpac2012 P2 normal --- 1 philipj acolwell acolwell adrianba mike public-html-media watsonm public-html-bugzilla oldest_to_newest 72353 0 philipj 2012-08-17 13:07:23 +0000 The spec seems confused about whether or not initialization segments are mandatory or not. http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#source-buffer-basic-append "The first segment appended MUST be an initialization segment." (IMHO, this entire section should be non-normative, but currently it isn't.) http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#dom-append A bunch of steps here are triggered by the first initialization segment. http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#byte-stream-formats "A byte stream format specification MAY define initialization segments and MUST define media segments." 72354 1 philipj 2012-08-17 13:08:12 +0000 I don't have a strong opinion on the fix, but if no one is planning to support a format without initialization segments, then it doesn't make sense to spend too much time on it at this point. 72355 2 philipj 2012-08-17 13:17:03 +0000 Further down, there's also this paragraph: "Initialization segments are an optimization. They allow a byte stream format to avoid duplication of information in Media Segments that is the same for many Media Segments. Byte stream format specifications need not specify Initialization Segment formats, however. They may instead require that such information is duplicated in every Media Segment." 72371 3 acolwell 2012-08-17 20:41:37 +0000 (In reply to comment #0) > The spec seems confused about whether or not initialization segments are > mandatory or not. > > http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#source-buffer-basic-append > > "The first segment appended MUST be an initialization segment." I could soften this to the following: "If the format defines an initialization segment format, the first segment appended must be an initialization segment." > > (IMHO, this entire section should be non-normative, but currently it isn't.) > > http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#dom-append > > A bunch of steps here are triggered by the first initialization segment. > > http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#byte-stream-formats > > "A byte stream format specification MAY define initialization segments and MUST > define media segments." I'm CC'ing Mark Watson because I believe he is the one that wanted to make initialization segments optional. All the formats we currently support have initialization segments so I'd be fine with dropping the "init segments are optional" text until we have a more concrete idea of how a format w/o init segments would work. 76867 4 adrianba 2012-10-22 01:14:05 +0000 Discussed during call: http://www.w3.org/2012/09/25-html-media-minutes.html#item06 Current proposal is to remove the text making initialization segments optional. Even "self initializing" media formats will likely be indistinguishable from formats that have distinct initialization and media segments. The main goal is to avoid appending media data without initialization for those formats where this might otherwise be possible. 79024 5 acolwell 2012-11-28 18:40:41 +0000 Changes committed. http://dvcs.w3.org/hg/html-media/rev/0c638da9a67a Based on TPAC decisions, I've removed the text that says initialization segments are optional.