[mpeg2] Re: docs

[Kees Cook <kees@outflux.net>]

On Mon, Oct 01, 2001 at 10:45:54AM -0600, Warren Young wrote:
> 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.

Gah.  How wonderful to have open standards that cost money.

> 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.

Maybe I can skim it at Barnes and Noble...

> 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.

Okay, cool.  I was under the impression that the B and P frames might 
forward-reference a starting I-frame.  But GOP boundries makes sense.

> > (I realize that it's actually IPBBPBBPBBI.)
> 
> Actually, that's the playback view.  In the stream itself, the frames
> are given as IBBP....

"playback"?  Or decode view?  The _visual_ playback should be IBBP, right?
(And, by the way, if the decode view is IPBB, why isn't the stream IPBB?)

> 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.

Agreed.  I have a simple task, IMHO, but I can't do it without format 
information.

> 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.
> = MPEG articles: http://tangentsoft.net/video/mpeg/

Ah, yes, this is exactly the kind of article I was looking for.  So, the 
formal description is "I want to write a GOP-accurate MPEG editor for 
linux."  :)

Now, if I "reverse engineer" the MPEG formats I'm interested in, and
"publish" this documentation, will ISO trying to beat me up?  Because I
can't believe I'm the only person trying to find details on MPEG file
formats.

Thanks!

-- 
Kees Cook                                            @outflux.net