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Flicker in MPEG-2???

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Ryan Hinkle
Flicker in MPEG-2???
on Nov 15, 2005 at 4:06:22 pm

I shot a number of interviews in a studio setting, using a GL2 in "Frame Mode". Captured and Edited in FCP5, and it looks clean and crisp. Final output is to DVD, so I export using Compressor 2, MPEG-2 and the quality goes berserk. The person in the picture being interviewed is fine, but the unmoving draped neutral-toned background flickers (subtle but noticeable, and completely unacceptable) from light to dark, about 2 times /sec. It shows major compression changes, bad pixelation. There should be no change in the unmoving sections of the video. Please help. I've messed with all the settings, GOP, Motion estimation, Bit rate, I just can't get it right. Does anyone know what I'm doing wrong?



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andygoodman
Re: Flicker in MPEG-2???
on Nov 17, 2005 at 1:50:13 pm

Hello Ryan.
I'm having similar problems to you-
I'm using compressor to encode MPEG-2 from uncompressed QT. Quality looks great, but i'm getting pixelated boxes at intermittan times and 'fuzz' around the subjects edges when he moves against a static background. Tried all the bit rates, GOP, etc but nothing appears to be working.
I was just wondering if you had found a way around your problem (without any replies I noticed), or whether it may be a bug in compressor.
any help would be greatly appreciated
Regards
Andy Goodman


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Ryan Hinkle
Re: Flicker in MPEG-2???
on Nov 17, 2005 at 8:54:56 pm

Hey Andy, well no I haven't figured it out entirely, but I'm getting closer. In my situation, I discovered a few potential problem sources.

1. I used studio tungsten lights mixed with ambient light from the window. Perhaps the two light sources made the camera's sensors record askew. I also had the camera's exposure on +6dB, which did introduce some unwanted noise. (I doubt that either of these are the case because my WB was manually set to a white board prior to every shot, and the strange flickering didn't appear until AFTER compression to MPEG-2)

2. I recorded with my Canon GL2 in "Frame Mode" and captured as 30P. I've since discovered that you should still capture as 29.97. My field dominance was set to None when captured, yet the Item Properties in FCP insist they are "Even (Upper)" My sequence settings were also at Timecode 30, Field Dominance "none", yet it won't playback to my external TV monitor without having the Timecode set to 29.97. I believe this is because of the conflict with the file properties.

I just notice that MPEG2 in essence tries too hard to compress every pixel. Comparing Sorensen or H.264 at 320x240, I notice that if a part of the image is unmoving, the pixels are NOT refreshing. They are stagnant, as well they should be. The movement looks great, and the perceived quality is far better (even though it's throwing away more information.) I just wish MPEG2 would do this. I'm not letting it stop me though. Starting this morning, our production team shot without the "Frame Mode" and leaving simply as 29.97 interlaced, and imported/edited the same. Also we made sure the exposure was +0dB. Though we haven't yet finalized to MPEG2 (keeping our fingers crossed) I hope we'll see better results.

If you find a solution that works for you, let me know. Till then, good luck.



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Austoka
Re: Flicker in MPEG-2???
on Nov 23, 2005 at 12:20:08 am

Hi guys,

Have you tried setting the field dominance to upper (odd) in FCP and exporting through compressor again?



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