Hi -
On Wed, 29 Dec 2004, Ray Cole wrote:
Possible to hit the <return> key once in a while? :-)
> > Hmmm, the 'yuvycsnoise' filter could probably be dropped - even when I
>
> I noticed a big difference in quality with my Bt878 card, particularly with
> credits and other white text that appears. I love this filter :-)
So the saying "your mileage may vary" is true ;)
It is a commentary on the quality of the Bt878 chipset (at least the
color separation portion) though ... ;(
> > If you're capturing at full frame square pixel (which for a Bt878 is
> > 640x480) then you are scaling/resampling to 704x480 and not 720x480...
>
> I'm not actually using it to scale. I'm just using it to crop the edges.
> I could do that in a number of places, but just chose to stay with yuvscaler.
> I'm actually using 'nuppelrec' to capture (actually with a couple of
> modifications I've made over the past year to record raw frames only, and at
That application I'm not familiar with. The underlying hardware
can support Rec.601 pixels BUT it's up to the application to put the
device into that mode.
A very common sequence has been to "capture, encode and display on a
_computer_" (either locally or over a streaming server, etc) . So
the applications use the square sampling specs - that way you get
the 640x480 and 320x240 sizes which are the 4/3 image. For video
though you need 704x480 10:11 pixels to make the same 4/3 image.
Looking at the kernel source tree (happens to be 2.6.8) I see there
is mention of the Rec.601 13.5Mhz sampling rate in bt832.h but that
is for a CMOS digital camera from the looks of it.
> 48K rather than 44.1K for audio, as well as some modifications to some other
In the course of your modifications did you notice what mode the
card was being placed in?
> I tell it to capture at 720x480 and I haven't noticed any distortion.
Perfect circles are a good test pattern to use ;)
IF you're not seeing 8 black pixels on each side then the capturing
process is "expanding" the 704x480 to fill the requested size (720x480)
and those pixels are NOT part of the original data (I don't know if
the application/card/whatever is expanding, replicating, scaling).
> Should I really be capturing at 704x480 instead? I don't do any scaling
704x480 is the full frame unless you're dealing with DV which has an
extra 8 pixels on each border. After doing a capture with a analog
to DV box I plainly see the 'full frame' (704x480) inside the DV
720x480 frame.
> me, so I assume I'm OK, but could give capturing at 704x480 a shot.
Or 640x480 and resample with y4mscaler to 704x480 :)
Cheers,
Steven Schultz
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