[Ffmpeg-devel] Re: new grab interface breaks bktr grabing

Ramiro Ribeiro Polla ramiro
Mon Apr 2 22:00:59 CEST 2007


Nikns Siankin wrote:
> First I tried:
> ffmpeg -y -f bktr -i /dev/bktr0 -an -vcodec wmv2 -tvstd pal /root/test.wmv
> /dev/bktr0: Error while opening file
> Then I remembered that even with old ffmpeg there was such error if no frame
> size specified, but running:
> ffmpeg -y -f bktr -i /dev/bktr0 -an -vcodec wmv2 -tvstd pal -s cif /root/test.wmv
> didn't help either.
> Hovewer, specifying "-s" in front of args finnaly started capturing:
> ffmpeg -y -s cif -f bktr -i /dev/bktr0 -an -vcodec wmv2 -tvstd pal /root/test.wmv
> Input #0, bktr, from '/dev/bktr0':
>   Duration: N/A, bitrate: N/A
>   Stream #0.0: Video: rawvideo, yuv420p, 352x288, 25.00 fps(r)
> Output #0, asf, to '/root/test.wmv':
>   Stream #0.0: Video: wmv2, yuv420p, 352x288, q=2-31, 200 kb/s, 25.00 fps(c)
> Stream mapping:
>   Stream #0.0 -> #0.0
> Press [q] to stop encoding
> but grabing status isn't shown and 'ffplay test.wmv' showed only one frame.
> I guess that, removed prepare_grab() from ffmpeg.c did some magic that
> made bktr video grabbing work.
> Anyway - would be good idea to set default frame size for bktr,
> so that it would work wihout specifying "-s" and/or example in
> manpage would be very usefull too.
> Anyone have success grabing from bktr with new grab interface?

The new grab interface should not be any problem. Notice that now you 
might need to pass the new -isync option.
Someone mentioned that FFmpeg used to set a default input size if there 
was none. Could you check this out for us on the cvslog?

Anyways, the grabbing formats need input size to be specified. Maybe 
because of hardware scaling, altough, IMHO, I think they should set the 
card's default size if none was set. I'd look into that, but I won't 
right now...

Ramiro Polla

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