[vdr] Re: cutting frame accurate in VDR?

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

"Rienecker, Fa. Evenio, ITS P, M" wrote:
> 
> > > >  > I-Frames to avoid the jitter effect at the editpoint (for example:
> > > >  > IBPBBPBBPBBP IBPBBPBBPBBP IIIII IBPBBPBBPBBP IBPBBPBBPBBP).
> > > >
> > > >That would have been my first idea, too.
> > > >However, I haven't yet found any code that converts a GOP into
> > > >all I-frames. If we were able to perform that conversion, I believe
> > > >doing the cutting the way you described shouldn't be a problem.
> > > >
> > > >Klaus
> > > >--
> > >
> > > Maybe someone knows how to convert a GOP into all I-frames? Then
> > > maybe frame accurate cutting could be integrated in VDR, that would
> > > be the nicest solution anyway...
> >
> > I know, how to convert a GOP into all I-frames: By reencoding the GOPs
> > where the cuts occur.
> >
> > Setting only I-frames btw. is a bad solution, as it requires a lot of
> > unnecessary bandwith. You can simply use a shorter GOP
> > instead as a GOP
> > does not have to have a fixed size. Example (| marks the cut point):
> > Before: ...IBPBBPBBPBBP IBPBB|... {commercial break} ...|PBBP
> > IBPBBPBBPBBP...
> > After:  ...IBPBBPBBPBBP IBPBP     {no more break :-)}    IBBP
> > IBPBBPBBPBBP...
> > where IBPBP and IBBP are reencoded.
> >
> > But as I mentioned before: How to sync the audio?
> 
> Is there any need to sync audio.
> Actually you just need to replace at most two frames.
> 
> At the a start of the new stream we need to replace the B- or P-frame with an I-frame and at the End of the new stream we only need to replace the last frame if it's a B-frame, as P-frames don't need to now anything about follwing frames.
> 
> If you want to optimize this you don't even need to replace the last B-frame if you provide the next I-frame on which the B-frame is dependend on. But this may result in strange behaviour when replaying the end.
> 
> CU,
> Christian.

If you want to do frame accurate cutting you *must* convert the entire GOP into
a sequence of I-frames, because that's the only way you can arbtrarily position
a cutting mark and display each individual frame.

Klaus
-- 
_______________________________________________________________

Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
_______________________________________________________________


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