Re: getInputBitmap:withInfo:atTime: produces darker images in FCP
Re: getInputBitmap:withInfo:atTime: produces darker images in FCP
- Subject: Re: getInputBitmap:withInfo:atTime: produces darker images in FCP
- From: Piers Goodhew <email@hidden>
- Date: Tue, 4 Nov 2008 09:51:26 +1100
I recall reading somewhere quite recently (like maybe even here on pro-
apps-dev) that FCP has some sort of "Assumption table" for which RGB
movies/codecs it treats as 1.8 gamma and which are 2.2. And I've seen
plenty of gamma shifts when you park a frame in FCP, not much help I
know but they may be related.
Ah, this was it: http://support.apple.com/kb/HT2912
Again, could be a total red herring, but I thought I'd share ..
PG
On 04/11/2008, at 9:40 AM, Stonewall Ballard wrote:
Paul,
This is very odd. It turned out that the darkening happens only with
certain clips, in particular, the one I was using to test my plugin.
This darkens in both your test plugin and mine.
I cut a 1 sec. section out of it and put it here:
<http://stonetics.com/GammaExhibit.mov>. About 3.9MB.
I don't know why this one is different. I made it in AE by adding
noise to an ArtBeats freebie movie. The original clip from ArtBeats
does not show this effect. It's compressed using Photo JPEG, though.
This clip is DV/DVCPRO NTSC. Other clips with the same compressor
that I tried do not show the darkening.
I also found that using R408 pixels bypassed the problem.
Can you tell why this clip is darkened when fetched by the Temporal
API? I suppose it could be something mangled in this clip, but I
don't see what it is.
Thanks.
- Stoney
On Nov 3, 2008, at 4:37 PM, Paul Schneider wrote:
Hi Stoney,
This isn't a known problem, and I can't reproduce it with a simple
test plugin. Here's the plugin I'm using to test:
<TemporalAPI.zip>
I believe that one difference between FCP and Motion is that if you
request a non-existent frame (a frame that is before the start of
the media or after the end), Motion will clamp to the nearest
available frame while FCP will return an all-zero bitmap. Are you
averaging multiple frames together? That could produce darker
frames if some of the images aren't there.
- Paul
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