Combustion (Mac) frame buffer field order reversal
by Alan Okey
on
Oct 29, 2008 at 9:03:29 pm
Combustion 2008 on Mac Pro w/AJA Kona LHe card.
Annoying behavior:
When using the AJA Kona LHe NTSC 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: Combustion (Mac) frame buffer field order reversal by Jeremy Garchow on Oct 29, 2008 at 10:29:09 pm
I am not familiar with Combustion at all, but are there multiple output selects to choose from? For instance, with video output in AE and a Kona (before the Adobe plugins) you could choose 525i29.97, but then you choose the resolution. You can choose 525i29.97 - RGB or 525i29.97 DV -RGB. IS there a similar menu within Combustion?
Re: Combustion (Mac) frame buffer field order reversal by Alan Okey on Oct 30, 2008 at 3:16:59 am
[Jeremy Garchow]"You can choose 525i29.97 - RGB or 525i29.97 DV -RGB. IS there a similar menu within Combustion? "
Jeremy -
Unfortunately, no. There are only two NTSC choices in the Combustion frame buffer list, 525i29.97 10-bit and 525i29.97 8-bit. No discrete settings for 720x486 and 720x480.
I'm not sure how to go about reporting this to the responsible developers - do you think it's more a function of the Kona drivers, or Combustion's frame buffer support?
Re: Combustion (Mac) frame buffer field order reversal by Jeremy Garchow on Oct 30, 2008 at 4:03:27 am
Sorry, Alan, I just don't know enough about how it all works at that level in the chain.
I'd start with AJA as you are probably more likely to get a yes or a no, and also I'd imagine that they are plugging in to Combustion's output so I am sure they have a bit of control as to what happens to that.
Again, I have no experience with Combustion so I have no idea if it's easy or difficult to get a hold of someone on the other line.
