[mpeg2] Re: docs

[Warren Young <warren@etr-usa.com>]

Kees Cook wrote:
> 
> Does anyone have the MPEG2-PS format documentation?  

Yes, ANSI has these docs, and they will let _you_ have a copy for about
$400.  That's for the first three sections, which are the main ones. 
(System, video and audio.)  http://webstore.ansi.org/  Search for ISO
13818, sections 1 through 3.

For this simple task, you might find a copy of the Mitchell book more
approachable.  It can be had for about $120.  It doesn't replace the
MPEG standards, but it's a whole lot easier to read.
 
> From what I understand, if
> I drop sections between I-frames, I can do this safely.  As in, if I had:
> 
> ...IBBPBBPBBPIBBPBBPBBPI...
> 
> I could make it
> 
> ...II...

You might do it that way, but usually you chop out the whole GOP,
including the associated I frame.  In other words, while you can leave
an I frame in the stream alone, you usually want to chop whole GOPs out.

> (I realize that it's actually IPBBPBBPBBI.)

Actually, that's the playback view.  In the stream itself, the frames
are given as IBBP....

> My trouble is that I need to drop the audio sections as well.  And to do
> this, I need to parse sync information, and possibly rebuild the entire
> Program Stream.

You will also need to know how to parse MPEG-1 audio layer "frames". 
The Mitchell book has almost nothing to say about MPEG audio.  Luckily,
there is a whole lot of free MPEG audio code out there which you could
study.

> Does anything like this exist?  

For Windows, yes.  Visit the link below and see the MPEG editing article
for info on that subject.  None of the programs mentioned work on Linux,
however, which I assume is your aim since you're posting here.
-- 
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