Re: [Dvdauthor-users] OT: What MPEG editor can you use under linux that doesn't reencode the stream?

[Roger I. <ri...@ri...>]

On Mon, 31 Jan 2005, Scott T. Smith wrote:
> On Mon, 2005-01-31 at 06:58 -0800, Roger Ivie wrote:
>>> 2) What happens to the audio stream?  My understanding is that the audio
>>> appears later in the VOB file than the video (due to the video decoder
>>> reading 3 or 4 frames ahead), so what happens at the start and end of
>>> your new stream when you "cat" a subset of the tiny vobs together?
>>
>> I blithely assume everything will work out fine.
>
> Unfortunately it won't.  You will likely get A/V sync issues as you pass
> through cuts.  Each cut will make the A/V sync worse.  It's possible
> (depending on how you do it) that skipping directly to that chapter will
> then make the A/V sync line up again, making it very difficult to figure
> out what's going on.  Worse yet, it might work on one DVD player but not
> another.  Trust me, I've been there.

I have no doubt that if I were doing actual *editing*, I'd have a mess
of trouble. But all I'm really doing is lopping off the end of a
chapter or pasting the end of one chapter onto the beginning of the
next.

In lopping off the end of a chapter, the worst that I can see is that I
might miss a bit of audio from the final GOP in the chapter. But then I
might already be missing a bit of audio (since the audio frames and
video frames don't necessarily line up at chapter boundaries), so I
don't see how this is any different than what I started with.

In pasting a few GOPs from the end of one chapter onto the next, all
that should happen is that I fill in the missing start of the first frame 
of audio in the chapter and move the partial frame at the beginning of
the chapter to the beginning of the first GOP I moved. Since the
chapters involved are adjacent, the final audio frame in the first 
chapter fills in the partial audio frame at the beginning of the next
(again, because audio frame boundaries don't happen cleanly at chapter
breaks), and the pasting should Just Work.

In short, gopinator should work for the limited things I'm currently
doing. When I need to do something more sophisticated, I'm sure I'll
need more sophisticated software.
-- 
Roger Ivie
ri...@ri...
http://anachronda.webhop.org/
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