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Compressor output losing quality? QTX Deinterlacing?
I’m transcoding from a 720×480 Anamorphic DV video to a square-pixel ProRes version, and it appears to have lowered the quality– more than I would think ProRes would. At first I thought it was a QTX display quirk, because it seemed to be applying some sort of blending deinterlace in addition to the quality loss.
Before:
After:
Then I took a look at it in QT7, and the deinterlace seems to be gone, but the quality is still noticeably lower.
Before:
After:
Thoughts?
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16 Replies
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Well you’re starting out with a very low quality DV original to begin with and then recompressing that to another codec. DV is 5:1 compressed footage and I believe it’s 4:1:1 color space so you’re missing a lot of information in the picture.
When you convert that footage to another format, it will degrade just as a result of the recompression. When we want to convert formats here, we do this through AJA Kona 3 hardware because it’s much cleaner than using software to perform the conversions.
That being said, this is software out there that will do a better job with much more control over the final image than Compressor. Telestream Episode is one, Innobits makes some nice products and Sorenson Squeeze is also a top converter.
Walter Biscardi, Jr.
Editor, Colorist, Director, Writer, Consultant, Author, Chef.
HD Post and Production
Biscardi Creative Media“Foul Water, Fiery Serpent” featuring Sigourney Weaver coming soon.
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Thanks, Walter. I think there’s something else at work though, because when I JUST do a ProRes conversion, there’s no degradation. It only happens when I also convert to square pixels. Maybe I’ll try working in the Frame Controls?…
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Hm, well boosting the Frame Controls quality seems to have helped the degradation issue. The before and after now both look pretty much the same in QT7.
So I guess the one thing I want to be sure of is, what’s happening in QTX? Is it deinterlacing and blending the before? If so, why not the after?
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[Zak Ray] “It only happens when I also convert to square pixels. Maybe I’ll try working in the Frame Controls?…”
Well ProRes is not square pixels in SD I don’t believe. Been so long since I used ProRes in SD I honestly can’t remember and I’m not near an FCP system today.
Set up a ProRes anamorphic SD timeline. What does it say there with the pixels? That’s what your setting should be in Compressor.
Walter Biscardi, Jr.
Editor, Colorist, Director, Writer, Consultant, Author, Chef.
HD Post and Production
Biscardi Creative Media“Foul Water, Fiery Serpent” featuring Sigourney Weaver coming soon.
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Normally you’d be right, ProRes maintains the PAR of it’s source which in my case would be DV Anamorphic PAR, but I’m doing this conversion to make a square-pixel version, so I set the resolution to 853×480 and the PAR to 1.0.
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[Zak Ray] “so I set the resolution to 853×480”
That doesn’t sound like a resolution that would call for square pixels. Again, not near an FCP system, but 640 x 480 is a square pixel format. 853 would not be a square pixel format so you would want to avoid square pixels I believe.
Walter Biscardi, Jr.
Editor, Colorist, Director, Writer, Consultant, Author, Chef.
HD Post and Production
Biscardi Creative Media“Foul Water, Fiery Serpent” featuring Sigourney Weaver coming soon.
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Pretty sure 853 is the anamorphic equivalent of 640.
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That is the square conversion from 720×480 anamorphic but normally you go down instead of you 720×405 (not 270 as I had it before the edit) might give you better results. But the question that has to be asked is why are you going to a square version of a codec that is meant for broadcast or editing?
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Wouldn’t lowering the vertical resolution mess up the interlacing?
I’m converting them because their only application is to the web, and it’s easier for me to work with square pixels for what I’m doing.
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Is this a bad idea? I mean, they’re never going to broadcast and they’re never going to be re-cut, I just think it makes more sense to make them square pixels in an increasingly-square-pixel world.
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