Random rainbow frames during deinterlacing with QTGMC?

[Kugelfang]

Dear All,

i recently captured all my VHS using Huffyuv as codec. In order to prepare the videos for watching on my PC i want to deinterlace them. After lots of reading i found that QTGMC would be the way to go for me. Therfore i prepared a small script for avisynth which i intent to capture via VirtualDUB as a direct steam copy.

Quote:

SetMTMode(3, 8)
AVISource("E:\test.avi")
SetMTMode(2)
AssumeTFF()
QTGMC(Preset="slow", EdiThreads=4)

However i encountered a weird behaviour. on some frames I get a strage rainbow discoloration. To make thinks even more strage, if i "Save as avi" the file two consecutive times with identical settings, different frames seem to be affected. Enclosed you can finde screenshots of the identical frame which exhibited the discoluration during the first export but not during the second.

It would be great if someone could help me with this.

[msgohan]

I would bet your problems will go away if you use the regular, single-threaded Avisynth.

BTW, "Direct Stream Copy" from an Avisynth script will just give you uncompressed video. You're better off using Fast Recompress to a lossless codec if you're wanting an intermediate.

[Kugelfang]

great point, ill give it a shot tonight, thanks for the input!

-- update --

You were right, using single treaded Avisynth fixed the problem. Question now is why? Any idea?

[themaster1]

avisynth 2.6MT can be buggy at times but qtgmc work ok there , you have to play with setmemory max and setmode try something like:

SetMemoryMax(900)
SetMTMode(2,4)
avisource()
QTGMC(Preset="fast", edithreads=4) # edithreads = numbers of threads/cores

[Kugelfang]

so i did some more tryouts and even gave the precise settings you supposed a shot but still im getting some random rainbow colored frames using multitreading

[lordsmurf]

I never use MT mode for Avisynth. It's more trouble than it's worth, and I've rarely found it to be faster.

The rainbow probably existed on the interlaced footage, but was simply harder to see. Now that the interlace is gone, the issue is obvious.

Add this to your script:

chubbyrain2(th=1, radius=15)

Tweak as needed. Just be aware that it will never 100% perfectly remove the noise. I used this on a video last year, and it probably removed 90%+ of the error. The obnoxious video was now watchable and non-obnoxious.

It's an .avsi, and requires other plugins.

See also: http://avisynth.nl/index.php/ChubbyRain2

[Kugelfang]

Thanks for the input. Ill give it a try tomorrow. But how come that if the error is present in the source material already it does not show up in the same frame verey time?