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But at this point, there's no compelling reason to leave the current codec. It meets broadcast spec, it's easy to edit, and it looks pretty darn good at higher bitrates. I sincerely hope the next jump is to wavelet and not AVC based. |
EX codec doesn't meet EBU broadcast specs, needs to 50 mb/s.
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Steve |
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I feel 1 megapixel may be the best compromise for 1/3" chips - twice the number of photosites as the HPX170, but without compromising individual photosite size too severely. But best of all are obviously full 2 megapixel (1920x1080) on a 1/2" chip. Regrettably only Sony seems to offer that in a prosumer grade camera. Quote:
And the mosquito noise can be argued to be more objectionable than codec failings due to motion - it's there all the time, often "twinkling" around the edges of static detail. The ratio of I frames to difference frames in a codec is not fixed, it's easy to see how static performance can be traded off for better motion performance. With AVCCAM they seem to weight in favour of motion. What is really needed for the prosumer is a camera styled like JVCs HM700, but 1/2", full 1920x1080 chips, and a codec to the standard of XDCAM 50Mbs or AVC-Intra 100. And ideally recording to both "full spec" media (P2 or SxS) AND consumer memory like SDHC or CF. There is no technical reason why that is not possible. Nothing currently meets all the criteria. Of what's available, I'd argue the EX is the obvious first choice at the moment, since at least you can get it to meet those criteria with an external recorder. |
Perhaps you are looking at Panasonic's consumer AVCHD? Apparently the pro cameras get a much better AVCHD encoder (branded as AVCCAM) than the consumer camcorders (or the GH1, for that matter). Barry Green did a very direct comparison of AVCCAM AVCHD (the branded AVCHD for the pro cams), by attaching an AG-HMR10 to an EX1, recording XDCAM EX in-camera and Panasonic's AVCCAM AVCHD with the AG-HMR10 (recording from exactly the same source coming off the imaging block - true apples to apples comparison). In the article he wrote, he showed comparison frame grabs, where the codecs were stressed, and the AVC looked a tad better on the whole. He didn't post frame grabs of the more typical ("unstressed") footage, but did state that both codecs produced very good images that were quite comparable in most of the footage. When I look at blown up images shot with my HMC40 (full raster chips), it looks awfully good (just a whale of a lot better than HDV) and does seem (to me) somewhat difficult to imagine XDCAM EX encoding being a whole bunch better at maintaining image fidelity from the imaging block. I don't shoot 1080i though.
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I'd love to see a similar (apples to apples) test (XDCAM EX vs AVCCAM with an EX1 or EX3) panning a res chart slowly.
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I've also seen that effect personally on an HMC150 in 1080i mode. There are many ways of "stressing a codec" other than with motion, and the two most obvious are fine detail/sharp edges, and slowly changing gradients (especially coloured). Just because a codec performs well in one respect doesn't mean it will in the others. (And different coders, different hardware, can give widely differing results, even if they are the same codec and same bitrate.) Quote:
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An HMC150 is going to show aliasing in 1080 line recordings of detailed images, even if recording uncompressed. The imaging block just can't resolve a high level of detail (low res chips).
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This wasn't aliasing, it was a compression issue. If it had been aliasing it would have been just as visible in 720 mode as 1080 - it wasn't. I was able to step frame by frame through the material and see a constant mosquito noise pattern for a number of frames before the pattern jumped, then be constant for a number more frames, then another jump.
I'm pretty sure the jumps corresponded to GOP intervals. Hence pretty sure that the codec is fairly fragile in respect of static detail, whilst being quite robust with respect to inter-frame movement. Of course, this only applies to the coder in the HMC150 which is several years old in design now. That in the forthcoming Canon camera is newer, hence likely to be better. |
I believe aliasing should show up more on 1080 line recordings (which goes beyond the HMC150 imaging block's ability to resolve detail cleanly).
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