Re: FxPlug adding color cast.
Re: FxPlug adding color cast.
- Subject: Re: FxPlug adding color cast.
- From: Paul Schneider <email@hidden>
- Date: Wed, 14 Feb 2007 00:06:13 -0500
Hi, all,
I spoke with Emile offline, and we figured out that his issue doesn't
have anything to do with FxPlug. His media was coming into Final Cut
as (254, 0, 0) and not (255, 0, 0) - that is, the color shift
happened on import, with no effects applied. This seems to be
because (255, 0, 0) is either not a valid YUV value, or is truncated
when compressed with the DV-NTSC codec. I was able to get (255, 0,
0) by switching to an RGB render using the Animation (lossless)
codec. We have not quite figured out what is going on here, but we
have ruled out FxPlug.
I've also been trying to reproduce Trevor's problem, without
success. I have tried a passthrough filter on several types of media
on both Intel and PowerPC, and one of our QA engineers has also run
some pretty extensive tests. We haven't found any color shifts,
except for the 8-bit YUV issue I mentioned earlier.
Here is the passthrough filter I used in my testing. It can run on
either the GPU or the CPU; I tested on both. I tested using the
Digital Color Meter application (in /Applications/Utilities) to
compare pixel values with and without the filter.
Attachment:
JustCopy.zip
Description: Zip archive
Trevor, can you try with this filter and see if you still see the
problem? Also, if you could send me the media and project you see
the problem with, that would be very helpful. If they are too big to
email, let me know and I will find another way. If your media is
sensitive, it would be very helpful if you could reproduce the
problem with benign media.
Has anyone else on this list seen this issue? If you have, please
let me know, and include media and projects if possible.
Thanks,
- Paul
On Feb 13, 2007, at 12:14 PM, Paul Schneider wrote:
Hi, list,
I think I may have misspoken earlier. We recently found an issue
with running YUV FxPlugs on PowerPC in 8-bit, where the image would
be darkened by one after going through the FxPlug. This is
something that will be fixed in an upcoming version. This issue
only happened in 8-bit YUV renders on PowerPC.
It sounds like the issue that Trevor reports happens with RGB
effects as well as YUV, and in float as well as 8-bit. This is not
something we're aware of, and not something we've seen internally.
You don't say if the issue happens on x86 as well; is this
something you're able to test?
Also, what kind of image are you applying the effect to? Does it
have a fully opaque alpha channel? Are the red and blue channels
significantly brighter than the green channel?
Thanks,
- Paul
On Feb 13, 2007, at 9:48 AM, Gabriele de Simone wrote:
So is this true in all cases? In other words, the workaround to
fix it under FCP 5.1.2 would be to add 1 to the output whenever
the plug-in is asked to render in 8 bit RGB/YUV, on PowerPC?
Emile: the color shift is actually visible on the computer screen,
but it is understandably quite small so you'll catch it easily
only with bright scenes (e.g. a sky) or by building a passthrough
filter and keeping an eye on the scope and toggling the filter on/
off.
On Feb 12, 2007, at 7:31 PM, Paul Schneider wrote:
Hi, all,
sorry I was silent on this topic - it somehow didn't come across
my radar.
This is in fact a bug in Final Cut, which only happens on
PowerPC. We've identified the problem, and a fix should appear
in an upcoming version. Sorry about the inconvenience!
- Paul
On Feb 12, 2007, at 7:10 PM, Dave Howell wrote:
Begin forwarded message:
From: Emile Tobenfeld <email@hidden>
Date: February 12, 2007 4:09:09 PM PST
To: Trevor Anderson <email@hidden>, Gabriele de Simone
<email@hidden>, email@hidden, pro-apps-
email@hidden
Subject: Re: FxPlug adding color cast.
At 3:29 PM -0800 2/12/07, Trevor Anderson wrote:
I found the problem. I logged the pixel data by running two
plugins,
one after the other. Final cut is decreasing all values by
one. If you
simply pass back the input values in the plugin, FC then
subtracts one
from them, after fixing this in the plugin, passing back the
input
data plus one, the cast went away and everything works as
expected.
Seems like there is a bug in there somewhere, and it's in
Final Cut
after it gets the frame back from the plugin.
Thanks to everyone who helped me out, I'm glad it was this
simple, as
I really wanted to avoid the workaround.
Trevor
Good catch, Trevor -- though it sounds like the shift affects
all RGB colors and is not really a cast.
I'd noticed some 254's in my debugging code where I expected
255's , but had been too busy with other issues to dig further.
Dave, et al,
Can you comment on this. We don't really want to bump our input
values by 1 every time we are called.
--
"Now, here, you see, it takes all the running you can do, to
keep in the same place. If you want to get somewhere else, you
must run at least twice as fast as that!" -- The Red Queen
Emile Tobenfeld, Ph. D.
Video Producer Image Processing Specialist
Video for your HEAD! Boris FX
http://www.foryourhead.com http://www.borisfx.com
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