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[media-source] ISO BMFF Byte Stream format should support layered (scalable) encodings

From: None via GitHub <sysbot+gh@w3.org>
Date: Thu, 10 Sep 2015 16:49:54 +0000
To: public-html-media@w3.org
Message-ID: <issues.opened-105850928-1441903793-sysbot+gh@w3.org>
mwatson2 has just created a new issue for 

== ISO BMFF Byte Stream format should support layered (scalable) 
encodings ==
ISO/IEC 14496-15 describes the carriage of layered (scalable) 
encodings in ISO Base Media File Format. Examples include SVC and MVC.

Such layered encodings can be encoded within a single track, or with 
multiple tracks, for example one for each layer. In the multi-layer 
case, when Movie Fragments are used, there are two ways the data can 
be organized into movie fragments:
(1) A single moof / mdat(s) pair can contain the data for the several 
tracks for each media segment
(2) The several tracks can be split into several consecutive moof / 
mdat(s) pairs

Option (1) is supported by our existing MSE byte stream format, but 
option (2) is not because we require that each "media segment" 
consists of a single moof and mdat(s). Option (2) has advantage 
because, typically, the sequence of moof / mdat(s) containing the 
"base layer" can be processed by a device which does not understand 
the scalable encoding.

So, I propose we modify our definition of Media Segment for the ISO 
BMFF byte stream format to consist of a sequence of one or more ( 
moof, mdat (, mdat)* ) structures where:
- all data referred to in each moof appears in the immediately 
following sequence of mdats
- all presentation timestamps fall within the range specified in the 
first moof of the sequence

If this is agreeable, I'll prepare the PR.

See https://github.com/w3c/media-source/issues/7
Received on Thursday, 10 September 2015 16:49:56 UTC

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