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Quality loss exporting to QT Ref
Hi,
I have found heaps of comments on how exporting QT reference files do not impair the quality of the video, however…
… At work I’m burning subtitles in the video with FCP. We use a piece of software that exports an XML file and creates a TIFF picture per subtitle block. We import the XML in FCP, relink the files and we’re done importing subtitles!
Once I’ve layered the video underneath, I export the sequence as a QT Ref. I end up with perfectly sharp subtitles over slightly pixelised video. The pixelisation translates into awful aliasing when compressing to SD MPEG2 from Compressor.
When I send the sequence to Compressor straight from FCP, without creating a QT Ref, the compressed SD video does not show such artifacts.
My conclusion is that something happens around the QT Ref conversion. Is it really lossless? Does it take bandwidth from the video to burn in the subtitles?
FWIW, the original video material in this case is 50Mb/s XDCAM and does not show pixelisation. It seems that XDCAM does not support more than a 50Mb/s rate which is what got me thinking that the subtitles were using too much of the bandwidth. Is that even possible?
I would understand if the whole video would be a little less sharp once the subtitles get burnt-in, but the difference between the sharpness of the subtitles’ text and the pixelisation of the video is quite surprising.
Any idea on the matter would be greatly appreciated. I’ll particularly appreciate little hints like a link to “video compression explained” or more specific articles such as “how FCP creates new video from several sources”.
Thanks for your time!
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10 Replies
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What you’re seeing is something strange with XDCam, or so I think. I am consulting with several clients encountering big problems when making DVDs from their XDCam sources. Frame controls in Compressor serms to help, but is still less than perfect.
David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
https://www.drwfilms.comPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Business & Marketing and Apple Final Cut Pro forums. Formerly host of the Apple Final Cut Basics, Indie Film & Documentary, and Film History & Appreciations forums.
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[David Roth Weiss] “What you’re seeing is something strange with XDCam, or so I think. I am consulting with several clients encountering big problems when making DVDs from their XDCam sources.”
Agreed. Adobe has run into some bizarre problems with Apple’s XDCAM codec, too (see https://forums.adobe.com/message/3020754),which they have had to work around somehow.
Perhaps a ProRes-transcode workflow is justified?
Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events -
Thanks for conforming Walter. For the record, though I haven’t tried transcoding to ProRes, rendering to ProRes does nothing major to help.
David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
https://www.drwfilms.comPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Business & Marketing and Apple Final Cut Pro forums. Formerly host of the Apple Final Cut Basics, Indie Film & Documentary, and Film History & Appreciations forums.
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I don’t think is nothing related with XDCAM or DVDs
I bet that your sequence are not fully rendered before exporting the Ref Movies.[Justin Huss] “I have found heaps of comments on how exporting QT reference files do not impair the quality of the video, however…”
Not sure if you have clear the concept “Reference Movie”.
rafael -
[Rafael Amador] “I bet that your sequence are not fully rendered before exporting the Ref Movies.”
Trust me Rafa, I’ve been working on these issues for nearly a month now, and I fully render everything here all the time.
David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
https://www.drwfilms.comPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Business & Marketing and Apple Final Cut Pro forums. Formerly host of the Apple Final Cut Basics, Indie Film & Documentary, and Film History & Appreciations forums.
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David,
Since February 2008 the only thing I do are DVDs from EX-1 footage.
Since last year I’m shooting with the NANO (XDCAM HD 422, 35/280Mbps), and no issues.
Of course I never edit on any XDCAM sequence.
Always Prores.
Rafael -
My clients are using some of the newer and beefier XDCam cameras. I suspect Sony has changed something with regard to the way fields are handled. Without frame controls turned on and fields forced to progressive, DVDs from perfect XDCam progressive sources are being interpreted incorrectly.
David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
https://www.drwfilms.comPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Business & Marketing and Apple Final Cut Pro forums. Formerly host of the Apple Final Cut Basics, Indie Film & Documentary, and Film History & Appreciations forums.
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You may be right David.
The fact is that I’m using BitVice for the MPGE-2s.
Also I’m working fully progressive.
However for what you are explaining now, to me its sounds more like a Compressor bug.BTW MAKE SURE YOU ARE setting the proper field order here on VIDEO FORMAT.
You must set it to Progressive too.
Rafael -
[Rafael Amador] “You must set it to Progressive too.”
Yes, but not typically necessary with other source footage. This is peculiar to XDCam source material, and it’s a problem waiting to happen to most who aren’t quite as well versed in problem-solving as you and I.
David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
https://www.drwfilms.comPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Business & Marketing and Apple Final Cut Pro forums. Formerly host of the Apple Final Cut Basics, Indie Film & Documentary, and Film History & Appreciations forums.
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Yeah, if you “Send to Compressor”, no problem: Compressor read the setting directly from the FCs sequence.
When importing Self-contained or Reference movies, is necessary to pay attention to this control.However David, about issues with XDCAM, I fly everyday few times to the EX Forum and other XDCAM related sites and haven’t heard complains.
In fact one of the most appreciated XDCAM advantages has been the rock solid Field-Order flag.
rafael
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