[linux-dvb] Re: Cutting

[Christoph Ackermann <ackermann@cms.tecmath.com>]

Hello Daniel,

here some explanations.

Daniel Schneider wrote:
> 
> >If you want to connect two clips with reencoded starts/ends you have a
> >problem, because the GOP-sequence is not circular and you get a "jitter
> >effect" at the editpoint.
> 
> Can't this jitter effect be avoided? Isn't this the goal of the not closed
> GOP-mode (but I think for DVD authoring you need closed GOP).

Thats right - but only used by a few and expensive Editstations like
AVID and others.


> Wouldn't it be possible to reencode the (B/P) frames in the cut GOP as
> I-Frames to avoid the jitter effect at the editpoint (for example:
> IBPBBPBBPBBP IBPBBPBBPBBP IIIII IBPBBPBBPBBP IBPBBPBBPBBP).

If you do this you have no Constant-Bit-Rate behaviour because an
I-Frame contains much more Data than B- or P-Frame. 

> 
> Reencoding the whole clip isn't ideal, I guess no matter what encoding
> algorithm you use there's always a loss of quality.

Not all the time if you stay in MPEG2 domain. Converting between MPEG2
and DV can produce a lot of artefacts in your video.

> 
> Regards,
> Daniel

For more Details read this document:

	http://www.tektronix.com/Measurement/App_Notes/mpegfund/25W_11418_3.pdf

Sorry its about 1,7 MB but very good.

Regards
Christoph

-- 

________________________________________________________________________

Christoph Ackermann                                    ] t e c m a t h [
System Integration Engineer          Content Management Systems Division
phone +49 6301 606-200      Sauerwiesen 2, 67661 Kaiserslautern, Germany
fax   +49 6301 606-209                            http://www.tecmath.com
________________________________________________________________________


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