[linux-dvb] Re: GOP to I-frame converter?

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

Carsten Koch wrote:
> 
> MK wrote:
> ....
> > I-frames only mpegs have a seemingly justified reputation for lousy quality.
> 
> The reason for that being that you have to choose a much higher
> compression for the I-frame when you cannot use B- and P- frames
> and you want the overall bitrate of the file to remain constant.
> 
> So I do not believe this applies to Klaus' problem because a) we're
> dealing with VBR files anyway and b) Klaus does not want to turn the
> entire file into an "I-frames only mpeg", but just part of the GOP
> at the cut point. Usually a GOP is less than 2 seconds.

Carsten is right, I don't need to (nor want to) decode the entire
recording, but only those frames needed to perform frame accurate
editing. I would not expect any quality degardation in doing so,
since the expanded P- and B-frames could have roughly the same size as
the I-frame of their GOP. There's probably no problem if the MPEG stream
contains a small sequence of "all I-frames".

> Back to the question: The obvious solution that I can see is to
> decompress the entire GOP and recompress the part of it that turns
> out to be needed.
> 
> For an open source MPEG2 (de)compression software, see
>       http://heroinewarrior.com/mpeg.html

Thanks, will do.

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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