[vdr] Re: Announce: tosvcd 0.5

[Werner Schweer <ws@seh.de>]

On Sunday 05 May 2002 19:34, Carsten Koch wrote:
> Werner wrote:
> ...
>
> > i've just uploaded version 0.5 of tosvcd to
> >       http://muse.seh.de/tosvcd/
>
> Hi Werner,
>
> thank you very much for this useful tool that allows
> me to archives recordings and to share FTA snippets
> with other people.
>
> I have two questions:
>
> 1) Is there an option to NOT re-encode the MPEG-2 data?
>    I have a Yamakawa DVD player which is quite flexible
>    regarding allowed resolutions and data rates, so I would
>    like to save the many hours and the quality lost by re-
>    encoding.

this is not possible with the current program. I'm not an
mpeg expert but i believe there is a difference between the
DVB mpeg2 format and the svcd mpeg2 (other than max. data rate and
resolution). Of course there may be better ways of transcode
mpeg2 to mpeg2 than to decode to yuv and recode again.

>
> 2) Are you planning to do better data balancing soon?
>    I have just created SVCD images with the follwing
>    command:
>
>    tosvcd -v -o p -s 732 -q 1 -c 3
>
>    and the 3 resulting bin files are:
> -rw-r--r--    1 cko      users    791154000 May  5 18:55 p-1.bin
> -rw-r--r--    1 cko      users    790723584 May  5 18:58 p-2.bin
> -rw-r--r--    1 cko      users     3822000 May  5 18:58 p-3.bin
>
>    Which is 754.5 MB, 754.1 MB and 3.6 MB.

tosvcd uses the mpeg2enc encoder which is a 1 pass encoder. The size
of the encoder output is adjustable with -q parameter but depends on
the movie (quality/noise/motion) and is not predictable.

If you give -q and -c parameter you trigger a special case: tosvcd
transcodes with the fixed quantisation (quality) given with -q and
does nothing with -c.
If you give only -c parameter (number of CD's), tosvcd tries to
fill these CD's much as possible by estimating the output size
and trying higher -q values if the output size exceeds the capacity
of the CD's (another paramter sets the size of a CD; default is a
80min CD).
Maybe someday the author or mpeg2enc extends the encoder with a second
pass which would enable to ensure exact streamrates over a movie.


Werner