[Mp4-tech] Re: MP4 file format and H.264 CBR streams

[Dave Singer]

The MP4 specification formally says that you shouldn't put filler 
data in the MP4 file, as that 'transport environment' doesn't need 
padding to CBR, and we decided that it should contain the 
'irreducible' media data.  Padding to CBR should be done in 
transports where it is needed (and therefore, e.g., in hint tracks).
However, there is nothing physically stopping you from doing it, it's 
perfectly possible.  It might even make the sample tables more 
compact (though I feel sure that the space consumed by the filler 
data will be greater than the space thus saved).
At 9:27  +0100 24/01/08, Tchi Southivong wrote:
>Hello,
>
>I was wondering if it is possible and correct to store a H.264 CBR
>stream in a MP4 file?
>
>Indeed, the MP4 file format doesn't allow filler data nal units.
>However, they actually can be present in a CBR stream that fulfills the
>HRD requirements (to prevent under/overflows).
>
>I would be tempted to store the CBR stream in the MP4 file by filtering
>out the filler nal units. But that isn't really satisfactory since it
>would be quite inconvenient to recover the original stream if I need to
>export it to another container (like Transport Stream).
>
>I would be really interested to get your comments and advice on this
>situation.
>
>Thanks.
>
>Best Regards,
>Tchi.
>
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-- 
David Singer
Apple/QuickTime