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MSE byte-stream format initialization segment boxes

From: David Singer <singer@apple.com>
Date: Tue, 18 Feb 2014 09:54:09 -0800
Message-id: <45F3418A-EBB1-461E-8580-4B9354E40BEC@apple.com>
To: public-html-media@w3.org
Hi guys

there is a sentence in 

http://www.w3.org/2013/12/byte-stream-format-registry/isobmff-byte-stream-format.html#iso-init-segments

which is causing us some problems, notably the ‘ignore' here:

> Valid top-level boxes such as ftyp, styp, and sidx are allowed to appear before the moov box. 
> These boxes must be accepted and ignored by the user agent and are not considered part of the initialization segment in this specification.

This is causing some implementations to strip these boxes before they get to the media engine, and then we’ve lost important compatibility information (notably the claims of compatibility made by the ftyp and styp boxes) and, if we want to index, the indexing information.  I suppose they think we’re going to conform to the apparent requirement (though it’s expressed as a statement of fact, rather than as an option or requirement) to ignore.  But why?

Should this be re-phrased?

These boxes *are* considered part of the initialization segment in this specification and must be accepted and passed by the user-agent to the media engine; they may be ignored or processed as desired.


Can someone explain why it’s written the way it is?


David Singer
Multimedia and Software Standards, Apple Inc.
Received on Tuesday, 18 February 2014 17:54:39 UTC

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