Re: [AVT] Working group last call: JPEG-2000 payload format

[Dave Singer <singer at apple.com>]

I think we are in general agreement here, that we should recommend a 
clock rate, and lay out the factors that go into the choice, so that 
sources choose well.

You asked for a reason to pick another rate.  An obvious one is when 
you are given a file to send (e.g. a QuickTime movie, MP4, 3GP file) 
in which the media track has a clock that is not the same as 90 kHz, 
but is nonetheless suitable.  If I choose the same clock for RTP, I 
am assured I won't have any conversion problems as I am not doing 
conversion -:)

For example, files with a clock at 24000 are not uncommon (for film 
material).  It *may be* that all the timestamps are, in fact, 
integral when converted to 90 kHz, but I cannot tell that without 
scanning the file.

I think the example of source material timed at 27 MHz is probably similar.


--
David Singer
Apple Computer/QuickTime

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