[ This article was first published in the August, 2008, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]
Jonathan Kirsch writes:
I don’t work in HD (yet) so I’m not that familiar with it, but reading EditWell and your newsletter has got me thinking. I’ve read instances where people say they shoot uncompressed HD and bring it in to FCP as ProRes to edit in, then export it as uncompressed HD. How is that possible? Am I remembering what I read correctly?
Isn’t ProRes a form of H.264, which is lower quality than uncompressed HD? If so, once you capture in a low quality, how to you export to high quality?
My first guess is by recapturing everything in the uncompressed HD. Isn’t that a waste of time? It seems so many people who shoot, for example, HDV, edit in ProRes. Well, isn’t that a lower quality than the HDV? What am I not understanding?
Larry replies: Jonathan, these are great questions. There’s a lot of confusion about ProRes out there.
First, ProRes is NOT a form of H-264. It is a new codec, developed by Apple, that provides high-quality, frame-accurate editing. H.264 is a distribution codec for finished work. ProRes is an editing codec to provide very high-quality images without taking a lot of storage space.
Apple, and others, describe ProRes as visually loss-less. That means that while data is being removed during compression, the resulting images do not suffer from image degradation. Based on what I’ve seen, images which have been converted to ProRes and copied 10 generations show virtually no loss in image quality. Unlike, say, images copied in JPEG or HDV for 10-generations.
Uncompressed HD can requires up to 250 MB per second — far exceeding the ability of a single hard drive to support. ProRes needs less than 30 MB per second. While this is more than a single drive FireWire 400 or even 800 can comfortably support, this is well within the range of even inexpensive RAIDs.
Here’s a quick comparison between HDV and ProRes:
|8-bit depth||10-bit depth||10-bit is better|
|GOP-compressed||I-frame compressed||I-frame is better and much faster|
|Rectangular pixels||Square pixels||Don’t need to convert pixel aspect ratios|
|Needs conforming before output||Doesn’t need conforming||Not conforming is better|
|4:2:0 chroma-subsampling||4:2:2 chroma-subsampling||4:2:2 makes for better chroma-keys and color correction|
The currently accepted HD workflow for professional-grade work in FCP is: shoot in whatever format you want (HDV, XDCAM HD, DVCPRO HD) then transcode into ProRes during capture, or as soon thereafter as possible.
Edit your sequence in ProRes, then output to D5 or HDCAM for distribution. The output would require a capture card from Blackmagic Design or AJA to convert the ProRes into a release format.
If you are going to the web, editing native HDV is fine, though much slower. If you are planning on projecting your images to a large screen, keep in mind that HDV often has problems with images, or camera shots, that are moving quickly. Shooting in a different video format might be a wiser choice.
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