Re: [transcode-users] How to cut a mpeg2 sniplet from vob?

[Francesco Romani <fromani@xxxxxxxxx>]

On Fri, 23 Dec 2005 19:27:31 +0100
Hans-Peter Jansen <hpj@xxxxxxxxx> wrote:

> > You want a just slice of your VOB? Just use dd, should fit this
> > need. If you want a slice of one of streams (say, N-th audio track
> > or M-th video track) you can use a pipe with tcextract and dd.
> Yes, say I want frame 2000..3000 from the vob. Just using tcextract 
> doesn't do well here (transcode 1.0.2):
> 
> tcextract -i ../vts_01_1.vob -t vob -a 0 -x mpeg2 -C 2000-3000 -d 0 > 
> 1.mpeg

Yes, MPEG handling code in transcode is quite problematic now.
We have some plans to greatly enhance MPEG support[1], but nothing
is ready, yet.

[...]
> Two questions: 
> What is the easiest way to get both video and audio?
> How comes dd into play here?

The 'dd' solution is in fact a quick 'n' dirty hack to bypass the
deficiences mentioned above.
If you want to do a benchmark with a VOB source, say, on 3000 frames,
a solution can be:
1) extract a rough slice
dd if=/path/to/your.vob of=/path/to/test.vob bs=xM
you should experiment a bit to find the value of 'x' right for your
purposes, since dd itself just copies bytes, it don't knows anything
about internal format.
Let's assume that we use x=500. This will give a 500 MB test.vob which
will contain, say, 344 frames (warning: totally invented numbers).
2) now you can use transcode's option -c to fine-tune the frame range.
Of course you can't use more than 344 frames, but it's easy to round
down test frame number to 300: -c 0-301

Unfortunately this isn't a precise solution :\

Hope this helps, until transcode itself was enhanced or a better
solution pops out :)

+++

[1] promo: http://fromani.exit1.org/mpeglib/index.html
Unfortunately I've been really busy with some other business in last
weeks :\ but development should restart in the first weeks of 2006.

Regards and happy holydays,

-- 
Francesco Romani -- Ikitt 
'people always complain, no matther what you do' 
IM contact: (drop me a note via email first, I have antispam default
deny!) jabber://ikitt-at-jabber-dot-linux-dot-it icq://27-83-87-867