[vdr] Re: cutting frame accurate?

["Rienecker, Fa. Evenio, ITS P, M" <C.Rienecker@deutschepost.de>]

There are only a few frames, that hold the complete information of one
single frame. Those are the I-frames (i.e. appx. every 12th frame)
P- and B- Frames only make sense with respect to the following or/and
previous frame respectivly. The don't contain a complete set of inbformation
to to hold a single frame.
E.g. have a look at http://www.thefab.net/topics/computing/co03_mpeg.htm

That means:
* A stream _MUST_ start with an I-frame.
* A stream should stop after an I-frame or an P-frame.

Otherwise you will not be able to reconstruct all frames.
Therefore, if you want to cut on exact frame boundaries you will have to
decode part of the stream to reconstruct an I-frame that starts the new
stream.

CU,
Christian.

PS: That's the reason why switching a channel in DVB can take up to half a
second until you see a picture, you have to wait for the next I-frame.


> -----Original Message-----
> From: Andy Coates [mailto:andy@bribed.net]
> Sent: Tuesday, December 03, 2002 1:28 PM
> To: vdr@linuxtv.org
> Subject: [vdr] Re: cutting frame accurate?
> 
> 
> > Does someone know about a linux/opensource solution for frame 
> > accurate cutting of MPEG-2 Streams? On Windows you can use M2-Edit 
> > (commercial), which reencodes the B/P-Frames around the 
> cutting point 
> > to the next I-Frames. Maybe in the meantime someone made a 
> > linux-solution for this problem?
> 
> I'm not aware what all the frames mean when it comes to MPEG2 - whats
> the difference between cutting around the B/P-Frames and the I-Frames?
> 
> I too am looking for an MPEG2 editor, so please if anyone does know of
> one for linux let us know :-)
> 
> TIA,
> Andy.
> 
> 
> 
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