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Monday, January 13, 2014

ProRes 422 VS AVChd 24

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Real image from real job in progress right now. 1080p24 ProRes 422 (record on ninja2 via HDMI ) vs AVChd 24 on C100. Winner is ? You tell me ! both images are keyed using Ultra Keyer in Premiere Pro CC 7.2. Do you see any real difference ? Look hard. Guess what, on a still frame there is no real difference. When playing I can see some compression artifacts in the AVChd version but they are small. Both key equally as well. Impossible ? no. The green means that the AVChd codec isn't working nearly as hard as if it had an image filled with detail to compress. The codec is working easy and produced some great results for what it was even with 4:2:0 color space. This of course comes back to what I say a lot - get it right in camera and even a 8bit 4:2:0 GOP codec can be ok. Its only when you start pushing that codec with extreme color corrections, too much detail and motion that it can fall apart. Under these circumstances 422 intraframe codecs may do better. may do better, maybe not. I'm not totally sold that just because its more bits that it will produce a better image automatically. In fact given the GOP efficiency it might not matter.

Sometimes I think I see some very minor differences in the skin tones. I think the ProRes has a bit more gradation than the AVChd....sometimes. I can see the noise in the image is a bit cleaner in ProRes vs some compression artifacts in the AVChd. This is watching the images on a 42" LG screen closer than I should be looking.

Do you know what I'd like to see ? a short GOP h.264 codec of say 5 frames, 4:2:2 and 10bit. Certainly possible in the spec, you just have to set your encoder to do it. With this sort of compression at 150-200mbits I bet it would make for very reasonable file sizes and outstanding quality. You could even push it to 12bit for RAW recording. Anyone tried it yet ?