Frame buffer field reversal with AJA Kona LHe/Mac Pro
by Alan Okey
on
Oct 29, 2008 at 9:01:54 pm
C* 2008 on Mac Pro w/AJA Kona LHe card.
Annoying behavior:
When using the AJA Kona LHe NTSC DV frame buffer output (720x486@60i) to display DV-resolution comps (720x480@60i), field order is reversed. I suspect it's because the driver (not sure if it's on the AJA side or the C* side) doesn't shift the 720x480 output up or down one scan line to maintain proper field order, and the 720x480 frame is centered on the 720x486 frame, with 3 blank scan lines on top and on bottom. Shifting a comp's footage layer up or down by one scan line fixes the issue, but final output is then incorrectly rendered unless the footage layer position is reset.
This doesn't happen in other applications, i.e. FInal Cut Pro or Motion. Other applications on the same system display 720x480 comps or clips with a one-line shift applied, so field order appears correct.
Is this behavior dictated by AJA's driver, or Combustion's frame buffer driver?
Re: Frame buffer field reversal with AJA Kona LHe/Mac Pro by Jeff Brown on Oct 29, 2008 at 11:37:32 pm
I think you're just seeing what is actually there: reversed fields
You can: shift the footage one line as you've found.
Or--
Interpret the fields (lower first) for both the 720 footage (footage/source settings), and the comp. Then preview using (right-click) fields:show both. You should then see the proper fielding you would get if rendered. If you preview with fields "none", then you'll see both without proper interpretation, which is my guess as to what's causing the kerfuffle.
You could also (i think) work with a DV comp (720x480), and use a 480 high preview. Can't remember for sure if that's a choice in the framebuffer settings...
Re: Frame buffer field reversal with AJA Kona LHe/Mac Pro by Alan Okey on Oct 30, 2008 at 3:13:45 am
The funny thing is, I used Combustion 4 with a Blackmagic Decklink SDI card a few years ago and it displayed 720x480 comps with the proper field order.
The C* 2008 frame buffer list with the Kona card installed shows only two options for NTSC - 525i29.97 10-bit and 525i29.97 8-bit.
I'm guessing that it might be a function of AJA's driver, but I'm not sure.
Re: Frame buffer field reversal with AJA Kona LHe/Mac Pro by Alan Okey on Oct 30, 2008 at 11:00:21 pm
[Jeff Brown]"Maybe there's an updated driver?
I just checked on my Xena/Combustion (PC) setup; there is a choice for 480 comps in the framebuffer config. "
Unfortunately, no. I'm using the latest Kona drivers, latest version of OS X and the latest version of C* 2008. No choice for 480 comps in the framebuffer listings. Must just be a Mac thing...
