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DV Codecs and compression explained
I’m an old school Betacam guy who has recently jumped into the DV world with a DV camera and FCP. I am trying to get an understanding of how DV codecs work when moving footage around to different applications. I understand DV’s 5:1 compression, 4:1:1 sampling and 25 mbs data rate. But what exactly happens when I transfer my footage into FCP using the DV codec, then export a QT file for After Effects using the DV coded, render out of AE using DV codec, re-import into FCP with DV codec, and then cut to DV tape? Obviously the footage does not get compressed 5:1 and resampled at 4:1:1 each time it moves applications, because the end product would be 30:1 compression. Is the DV codec recogonized by all parties involved and passed along untouched? What if the codec is changes midstream, say while rendering out of AE?
Thanks
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1 Reply
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You are correct, partly. The parts of your edit that don’t have titles or have any filters will be identical to the original footage all the way through the edit and on final DV tape master. Any titles effects or re-compressing from other programs such as AE will hurt the image quality.This being said, the hit is not as bad as some tape formats. Some people composite DV footage in AE at 10bit uncompressed to lessen the noticeable effects of re-compression. Graphics mainly take the biggest hit, in my experience. Workflow will depend on your clients quality needs. We used to be a BetaSP shop, now we shoot and edit HDV/DV and our clients don’t see any difference. We don’t do broadcast so if that is your client base maybe someone with that client set can commit how to maintain quality.
As for working in AE and re-compressing this is what gets re-compressed. Footage imported from capture scratch is original and not affected. Once you export out of AE it will re-compress. Importing the file into FCP from AE will not affect it, given that it matches your timeline settings for DV. Add any titles, filters or effects on the timeline the AE import will be re-comressed again. That could be 2 re-compressions but I still think it looks good. Some have higher standards needs. We just go to DVD for our clients and they love it.
Hope this helps-
Matthew
Quad 2.5 G5
OSX 10.4.X
Ram 4GB
FCP 5.1/AE 6.5/DVDSP4
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