[linux-dvb] Re: AW: HOWTO create SVCDs on Linux

[Peter Hofmann <junk@pxh.de>]

Hi,

On Apr 18,  8:19, Nils Heidorn wrote:
> Subject: [linux-dvb] AW: HOWTO create SVCDs on Linux
> How about the encoding time, is it somehow comparable with the advanced
> PC-Tools ( the free tmpeg or the *notatall* free cee ) ?

In the beginning I did some tests with FlaskMPEG/bbMPEG and DVD2AVI/TMPGEnc
before the discovering the MJPEG project with its modified MPEG encoder.

Even though I did not do any formal timing my impression is that the
transcoding time is about the same (at least in the same order of magnitude).

The MPEG encoder from MJPEG does include a lot of performance optimizations
such as MMX, 3DNOW etc., so it should already be quite good. Additionally you
could play with the options - the ones that I have been using try to optimize
quality at the cost of speed.

> One problem ( from reading your manual swiftly ) seems to be that you have
> to cut the video into pieces by vdr before you start encoding, normally you
> want to do so before starting to encode ( on pc side with pvacut ) or to cut
> the 1 file output mpeg file.
> The normal method implies to get 2 or 3 SVCD's in good Quality, so you want
> a cutting that divides the movie in 2 or three equal parts, i even like to
> do an overlapping cut ( like many channels do for commercials, repeat the
> last 10 seconds of the movie, so you can get *in* again ).
>-- End of excerpt from Nils Heidorn

I know that it is a gross hack to use VDR like that, but it was just the
easiest way for me. If you come up with a different method I would be happy to
include that in my HOWTO.

The VDR method has the deficiency that the MPEG system stream is only cut into
equal length files which have a different number of frames and therefore
playback time. This leads to varying stream sizes after transcoding, since the
MPEG audio has constant bitrate anyway and the mpeg2enc video encoder also
produces a quite constant bitrate on the average (even though I use variable
bitrate encoding for the video).

A solution to cut the .vdr files that produced files with equal length in time
would be preferable. The overlapping features also is a good idea.

Peter

-- 
Peter Hofmann                  e-mail: junk@pxh.de


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