On Tue, 4 Oct 2005, Frank Albrecht wrote:
It might be a better idea to reply to this list (especially with
lavrec or V4L problems - I abandoned the Bt878 card several years
some time ago).
> > Perhaps others who capture to mjpeg can help with some ideas - but
> > I thought 'lavrec' was the usual method used to capture mjpeg data.
>
> I spent much time for trying out lavrec. With a BT878
> (software-encoding) and a 2.4 GHz/512MB Machine i can't get a
> good quality. Either dropped frames or quality(<50) goes down.
Couple things can cause that - an unsteady source (VHS decks in
particular are very jittery) or the mjpeg compression routines are
taking just a little too long to get the job done.
The kernel driver(s) are the same for both lavrec and streamer so the
problem is probably not in the kernel.
Is this from a VHS tape deck? Maybe a signal stabilizer would help,
something like:
http://www.kramerelectronics.com/indexes/item.asp?desc=98
or a TBC but that's probably more money than you want to spend ;)
If it's a matter of the software mjpeg compression taking too long
(are you using the jpeg-mmx routines?) maybe capturing to 4:2:2
uncompressed ( I think the Bt878 and drivers are capable of this)
might be better - at the cost of MUCH more diskspace (not to mention
I think the general YUV handling in the lavtools is broken ;)).
> Streamer can also write mjpeg avis, cuttable by glav, but if
> size goes > 2GB, neither lav2yuv nor avisplit can handle that
> avi. Streamer can't create with %01d mjpegtools can.
If someone knows of a good replacement for the lavtools/avilib.c
which implements the ODML extensions (or at least provides some
code that can be "borrowed") then the lav* programs can support
> 2GB files.
The better long term solution is to find out why streamer can't
write quicktime files - but I see that's in the next mail item ;)
Cheers,
Steven Schultz
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