On 22/11/2009, at 2:55 AM, Jan Stary wrote:
Some time ago, when I looked into something similar, all the
supported
cards that I found could only record incomming video at 1/2 res
max.
Whether this is a limitation of the bt848 chipset, I didnt bother
to
verify.
...
Seems I am experiencing something similar.
A google search indicated that this card cannot capture at greater than
320x240.
If I don't specify any -target option, I just get the 320x240 mpeg4
stream. If I specify -target dvd, I get
Output #0, dvd, to '/media/NEW/video.avi':
Stream #0.0: Video: mpeg2video, yuv420p, 720x576, q=2-31, 6000 kb/s,
90k tbn , 25 tbc
Does that mean ffmpeg somehow scales the captured 320x240 to 720x576
on the fly, as it writes video.avi? If that is the case, am I better
off saving just the 320x240 stream and do the scaling/converting later,
in non-real time, with clever ffmpeg options?
I'm no expert, and a little hazy here, but it's my impression that the
DVD
video standard (if there is such a thing) has a very small number of
predefined resolutions (pal, ntsc). So ffmpeg is scaling to the
appropriate
dvd size.
You can probably create 'non-standard' sized dvd video streams with
other
software but may well have compatibility issues with many players.
So it depends on your requirements - if you can generate a stream with a
lower data rate (due to it's smaller frame size), which can be scaled
up to
a suitable size at acceptable quality on your output device, then this
is
probably good.
paulm
