[FFmpeg-devel] MPEG-4 container header identification
ohookins at gmail.com
Fri Apr 5 15:13:02 CEST 2013
Ah, that makes sense. Many apologies for wasting your time, I'm only just
starting out with this container format.
On 5 April 2013 14:58, Paul B Mahol <onemda at gmail.com> wrote:
> On 4/5/13, Oliver <ohookins at gmail.com> wrote:
> > Hi,
> > I've been trying to wrap my head around the MPEG-4 container format and
> > while the specifications I've read have been very complete, nothing seems
> > to mention the purpose or meaning of the first 4 bytes in the file. From
> > what I've seen, these typically are 0x0000001C, 0x00000018 or 0x00000014
> > (e.g., listed here: http://www.garykessler.net/library/file_sigs.html).
> > This page: http://xhelmboyx.tripod.com/formats/mp4-layout.txt indicates
> > that the first 4 bytes are an "offset" but I haven't found any other
> > reference to back this up, and my reading of the ffmpeg codebase
> > unfortunately didn't shed any light on the subject for me either (mostly
> > due to my unfamiliarity with it).
> > I was hoping someone might know the purpose of these 4 bytes before the
> > ftyp box marker, and if you could point me in the right direction it
> > be much appreciated.
> Aren't it size of ftyp box?
> > Best Regards,
> > Oliver
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