I'm having an issue with rendering properly in SpeedGrade.
The grade is finished, but every time I render it generates random noticable flickering in the results. The flickers occur on every few frames in an irregular pattern and consist of a saturation decrease on the frame.
The most frustrating thing about it is the random nature which it occurs. For example, if I render out an entire timeline it might occur on certain clips, while rendering those clips separately may alleviate the issue...though rendering those same individual clips once again may cause some of the results to flicker once more. In short, I can't render the whole project and rendering the separate elements (in addition to being very tedious) is a crapshoot. I suppose with enough rendering I'll eventually get enough usable clips to finish the product, but the point here is whats happening.
The project is pretty simple. Mostly Primary/Secondary Color layers, a LUT (cinema + 3strip), sharpening, and masked Gaussean blur on the edges of a few clips. All effects and color are on separate layers above the Source layer.
First, I tried messing with the order of layers and even turning some off, but the flicker remained (randomly) in most cases without completely removing the grade all together.
I then thought the issue might be in the quicktime render, so I tried many flavors of DPX, TIF etc. Flicker still in every render, though on different clips. Again unpredictable.
Moved to maybe an embedded alpha in the source material might be to blame. The original project used 1920x1080 PRORES444 source material, so I retranscoded and tried rebuilding the reels with PRORESHQ, TIF Sequences and even the original Red R3d's. Random flicker still present on render.
I then exported each clip out separately thinking that the issue might be how speedgrade handles memory. Each clip rendered quickly. There seemed to be less clips with the flickering but still there. Another similar clip by clip render would yield different results each time.
After trying to troubleshoot with several very experienced visual tech guys and professional colorists yesterday, at least one other person who had the time to experiment experienced the same flickering in their results, but was also unable to determine why it was happening.
Now I think this may be some other non-source, non-footage issue. Maybe a graphics card incompatibility or bug of some sort.
Here is my system specs for reference:
Model Name: Mac Pro
Model Identifier: MacPro2,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 3 GHz
Number of Processors: 2
Total Number of Cores: 8
L2 Cache (per Processor): 8 MB
Memory: 18 GB
Bus Speed: 1.33 GHz
ATI Radeon HD 5770:
Chipset Model: ATI Radeon HD 5770
VRAM (Total): 1024 MB