[Mp4-tech] Query for mp4 Box--stco entries

[Dave Singer]

At 10:11  +0530 15/02/08, Praveen Singh wrote:
>Hi experts,
>After converting a audio (AMRNB) 3gp file into mp4 file through i 
>observed that it has changed the offset values in "stco" box.
>In 3gp file, the sample size box contains individdual size entries 
>for all samples, but in mp4 file the size entry if common for all 
>samples. and corrosponding sample entries are changed in stco box.
>I just want to know whether its necessary for mp4 file or mp4box did 
>it for some other reason?
>
>Thanks
>Praveen

It sounds as if maybe there was a better way to pack the tables than 
was implemented in the original file.  Without seeing the details, 
it's impossible to say.  It may also be that the file was 
"re-chunked", which is also legal (and sometimes desirable).  Offsets 
will, of course, change if the moov box precedes the data, and the 
moov box changes size.
-- 
David Singer
Apple/QuickTime
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