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H264 gives better results than ProRes 422(HQ) or Uncompressed?!
H264 gives better results than ProRes 422(HQ) or Uncompressed?!
I have a peculiar problem and was wondering if anyone could chime in. I have some footage that I need to send to a colorist and want to export it to 10-bit uncompressed. But the export always ends up with some weird, pixelated color-smearing in one particular scene when I export to either uncompressed or ProRes 422HQ. Curiously, the footage looks fine if I export via H.264. Why doesn’t uncompressed or PR give superior results?
Here are the particulars:
- Footage originated on Panny AF100 8-bit, 4:2:0 but we added some VFX layers and exported new footage as 10 bit QT files
- I converted the above 10-bit files to ProRes 422 HQ for editing
- My FCP 7.03 sequence set to Render ALL YUV in high precision YUV
- Before exporting I set sequence to uncompressed 10-bit
- I have tried exporting as self-contained QT movie or sending to Compressor and get identical results either way
- Hardware is Intel MacPro, 8-processors, 12 GB RAM
The problematic scene is in a desert and has some blown-out highlights, especially on the chrome trim of a car and some snow-capped mountains in the background. That scene looks fine in my FCP timeline – the aforementioned highlights are certainly hot, but no weird color smears.
But when I output to either uncompressed or ProRes 422HQ, the highlights get smeared with pixellated rainbow colors, like some 8-bit Atari video game. When I output to H.264, no smearing, the footage looks as good as it does in my FCP timeline.
What could be causing this and how could I get around it? I don’t want to send H.264 compressed footage to the colorist.
I would upload some frame-grabs, but I’m not authorized as clip contains some name actors and producers would not be happy.
Any input much appreciated!
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27 Replies
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Are you rendering ALL YUV stuff in High Precision?
You shoud do that wen exporting to any 10b codec.
rafael -
Yes, as mentioned in my bullet points:
– My FCP 7.03 sequence set to Render ALL YUV in high precision YUV
I’m really scratching my head on this issue!
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Ok. This is a pretty crazy workflow.
First, AVCHD to ProRes. (1)
Then VFX and export to 10b UC. (2) maybe (3)
Those then converted to HQ for editing. (4)
Then exported back to 10b UC (5)
That’s perhaps 5 generations not including any I missed. Considering your already highly compressed 24ish megabit/sec source, this is unnecessary.
Please post a screen grab of what you are seeing so we can speak objectively about what you might be happening.
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Okay, here is a screen grab with cropping to highlight the problem areas. Note the purple splotches on frame left (car windshield) and on actresse’s right arm and chest. The two actors in back seat also have the color smear, as does a thin band on hood of car.
In my timeline, these color splotches are not there. Those areas simply look a bit hot but otherwise normal. And if I send to H.264, those areas also look normal. They only look like in this pic if I send to uncompressed or ProRes 422HQ.
In terms of editing, what workflow do you recommend?
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These look like transcode errors of some sort.
Let’s start from the beginning.
Did you log and transfer the AVCHD footage? To what?
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I believe the assistant editor logged and transferred the AVCHD right to ProRes 422HQ
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Excellent.
Then when you do the VFX, what’s the workflow there? Where do you do the VFX?
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After editing the final cut, the entire movie was exported to TIFF sequences (I know another step!) so that we could move it to Windows for VFX work in Combustion.
Work was done in 16-bit in Combustion and then exported to 10-bit MOV animation for re-import back into FCP on Mac.
After all the above steps, the footage looks great playing in FCP. It’s only when I try to export again that I get the color smears on that one scene.
Oh – and just to test, I went back to the very earliest cut of the movie, before any work had been done (other than the original transcode to ProRes422 HQ), and tried exporting that particular scene to a self-contained movie. Same problem, whether I do self-contained or send to Compressor. The H.264 looks fine. The unocomp and PR looks like the above pic.
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And as another test, I opened the original media clip (the first transcode from AVCHD to ProRes422 HQ) and it plays fine in Quicktime Player. Screen grab below:
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Just posted the original screen grab in the thread for your ref.
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