--- Operating System, Graphics card ---
Windows 8 64-bits, NVIDIA GT 540M
--- Blender version with error, and version that worked ---
Broken on 2.69 and 2.68a.
--- Short description of error ---
When rendering with a scene overlaid on top of a movie (Over Drop/Alpha Over scene strip over a movie strip), the movie gets whitish on second render forward.
--- Steps for others to reproduce the error (preferably based on attached .blend file) ---
Open attached .blend file. Press F12 to render (renders fine). Press F12 to render again (renders with white tint). Compare both renders.
Notes: The attached .avi is for reference and is very short (it is not corrupted). It was cut just to show the problem (the full file also shows it, but is very big). The file was created with VLC screen capture and cut with Avidemux. Some movie files from different sources don't show this problem.
Sample renders in http://blenderartists.org/forum/showthread.php?316990-Rendering-with-a-movie-background-shows-inconsistent-results&p=2511120&viewfull=1#post2511120
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It looks like the problem is some sort of issue in the video scaling or some related thing.
I found two workarounds:
1) In this case, the video and the render were 1024x768. If I increased or decreased one pixel in any direction, the problem was gone.
2) In this process, I found that enabling the "Image Offset" option of the strip disabled the auto-scaling and the problem vanished too (without changing the render size).
Both workarounds involve setting a scaling different from the original movie size, though I have no idea what triggers the white tinting, specially since it only happens when there's a scene overlapping the movie, and it doesn't happen with every movie.