[FFmpeg-cvslog] r11935 - in trunk/libavformat: nut.h nutdec.c

[Michael Niedermayer]

On Fri, Feb 15, 2008 at 11:32:54PM +0100, Nico Sabbi wrote:
> Il Friday 15 February 2008 19:03:29 Michael Niedermayer ha scritto:
> > On Fri, Feb 15, 2008 at 04:49:40PM +0100, Nico Sabbi wrote:
> > > On Friday 15 February 2008 16:47:52 Rich Felker wrote:
> > > > On Fri, Feb 15, 2008 at 03:36:09AM +0100, michael wrote:
> > > > > Author: michael
> > > > > Date: Fri Feb 15 03:36:09 2008
> > > > > New Revision: 11935
> > > > >
> > > > > Log:
> > > > > Elision header demuxing support.
> > > >
> > > > The word is "elided". Elision is the process of eliding.
> > > >
> > > > Rich
> > > 
> > > this header elision process will  make remuxing to other formats
> > > a  _real_ challenge, just like in ffmpeg (think of H264 to and from TS 
> > > and MP4) ...
> > 
> > huh? elaborate please
> > 
> > 
> > [...]
> 
> 
> If I understand correctly what this header-elision stuff is about
> (in the case of mpeg2video I think it's the removal of sequence+gop+extension headers
> and of all startcodes because frames are mapped 1:1 to nut packets payloads , right? )
> the reversal of this process needed to remux from nut to another
> format will require reinserting the headers in a codec-specific way.
> Or did I misunderstand what this header-elision stuff does?

Yes you did misunderstand it
There simply is a table of byte sequences in the main NUT header, and each
frame code can point to one of them.
If the demuxer sees such a frame code it outputs that byte sequence, and
then reads and outputs the rest of the packet.
There is nothing codec specific in the demuxer for this. The muxer though
does need to know a little about the codecs to be able to effectively use
this. But then the muxer doesnt have to use it if it doesnt want ...

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
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