24 Nov 2019

Why can't there just be one, really good, codec?

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Why can't there just be one, really good, codec? Why can't there just be one, really good, codec? RedShark


RedShark Replay: The one where Phil Rhodes doesn't mince his words in wondering why not!

For some reason(!) the world has failed to take any notice of the article I wrote a while ago on the subject of uncompressed images. To be completely fair, this might be that NAND flash chips have failed to increase in size and speed by the order of magnitude that would have actually made uncompressed workflows practical in the interim.

Codecs on the Brain

What brought the subject of codecs back to my forebrain, however, was a refreshingly honest and interesting discussion with Al Mooney, product manager at Adobe for Premiere Pro, at IBC. Apparently, they get quite a lot of requests from people to develop an intermediate or mezzanine codec in the vein of Avid's DNxHD and Apple's ProRes, presumably because those asking for it are under the impression that the ability of things like Media Composer and Final Cut to do certain desirable things are based on something that's special about DNxHD or ProRes.

Mezzanine Codecs

This is immediately reminiscent of some of the points I made in support of uncompressed workflows in the previous article, but it's probably worth a quick intermission here to think about what these mezzanine codecs actually are, technically. Neither Avid nor Apple's pet codec is anything very new or special, technologically. Both are based on the discrete cosine transform used in image compression since JPEG, and thus have a lot in common with MJPEG, DV, DVCPRO-HD, Theora, and others. The advantage of them is that they are implemented to handle currently-popular frame sizes, bit depths, and frame rates, and are constrained in such a way that nonlinear edit software can make assumptions that lead to technological efficiencies. If forced to choose, DNxHD is probably the more egalitarian since it's standardised as SMPTE VC-3, but given the huge market penetration of ProRes, the choice is made for us in many circumstances.

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Phil Rhodes

Phil Rhodes is a Cinematographer, Technologist, Writer and above all Communicator. Never afraid to speak his mind, and always worth listening to, he's a frequent contributor to RedShark.

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