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April 20, 2007

In depth look at ProRes 422

Please note, this blog has been archived and now lives at www.discretecosine.com

Apple has posted a white paper on the ProRes codec. A white paper on a video compression codec? Name one thing more exciting than that, I dare you.

Truth be told, the document doesn't contain a whole lot of new information. ProRes is an I-frame online VBR codec, operating internally at 10bit 4:2:2.

A few interesting details came up though. First off, FCP6 will have a new preference that allows long gop formats to be rendered in ProRes. So you can capture your HDV, apply effects, and render them into ProRes. This is really nice, as it means you don't suffer the generation loss issues of long-gop reencoding, and it should be quite a bit faster as well.

Speaking of generation loss, the white paper shows that there is essentially no drop in PSNR after the first generation of encodes. That is, of course, how a codec should ideally behave - if the decoder matches the encoder, successive reencodes won't suffer generation loss issues. However, that's rarely the case in reality.

We still don't know much about how the codec operates internally, though I'm sort of guessing it's a DCT (rather than DWT) based codec with some fancy intelligent quantization routines and good entropy coding.

I'm looking forward to giving it a try.

Posted by at April 20, 2007 12:03 PM | News

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