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October 12th, 2009, 07:20 PM | #31 | |
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I was under the impression that AVC-Intra 100 was h.264 based, therefore MPEG-4, DV, and DVCPRO HD are DCT-based and HDV and XDCAM HD MPEG-2. XDCAM 422 is a very good codec, good color space, full sample, however it's an 8-bit codec not 10-bit color depth like AVC-Intra 100. I believe that's an important difference. Jeff Regan Shooting Star Video www.ssv.com |
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October 13th, 2009, 05:33 PM | #32 | ||
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What's important is that there are two ways to get banding - insufficient bitdepth, and too heavy compression. Just try compressing a gradient in Photoshop with JPEG quality set to min, and watch it turn in to a step chart. Hence it's conceivable that a 10 bit system may involve heavier basic compression unless the bitrate is correpondingly increased - and that compression may negate the effects of greater bitdepth! Is that the case here? I don't know, but that's why I keep saying don't worry about the numbers, the subject is so complicated - the EBU have given both codecs a high rating, they are both good. Yes, 10 bit is desirable in isolation, but only if the bitrate is up to it. It may be argued that if 10 bit is really important to you, you should be using HDCAM-SR anyway. A bit like going into a car showroom and the salesman saying how important built in satnav is in car A. Maybe, but what if he's not telling you that it means they can't afford ABS braking? You MAY decide that if the cost of the car forces a choice, you'd rather have ABS than satnav, and buy car B. More you look into it, more complicated the subject is. |
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October 13th, 2009, 06:08 PM | #33 |
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David, interesting info, however, this is what Wikipedia has for AVC-Intra:
"fully compliant with the H.264/MPEG-4 AVC standard", "permitting full resolution, 10-bit field capture of high quality HD imagery in one piece camera-recorders." "It defines 10-bit intra-frame only compression, which is easy for editing and preserves maximum video quality. The new standard significantly outperforms the older HDV(MPEG2 based) and DVCPRO HD(DV based) formats, allowing the codec to maintain better quality in 2x less storage." I assume the last part is about AVC-Intra 50. I don't see AVC-Intra as being MPEG-2 based, just H.264/MPEG-4. So, DCT is used in JPEG and MPEG and DV, but MPEG-2 is different from MPEG-4/H.264, is it not? Wikipedia for XDCAM 422: "Third generation XDCAM uses the 4:2:2 profile MPEG-2 codec, which has double the chroma-resolution of the previous generations. To accommodate the chroma-detail, the maximum video bit-rate has been increased to 50 Mbit/s." Obviously, all these compression schemes are scalable and "adding tools" adds to computational complexity, requiring more powerful processors. I think the key is that AVC-Intra 100 is higher quality at the same bit rate as DVCPRO HD and XDCAM 422 is higher quality than HDCAM, the latter requiring a much higher bit rate than the former. I like the idea of 10-bit and I-Frame, and believe that AVC-Intra 100 is a very high quality codec, that can be graded and color corrected more severely than other 4:2:2 codecs. So far my editor is very happy with AVC-Intra vs. DVCPRO HD. Jeff Regan Shooting Star Video |
October 14th, 2009, 05:03 PM | #34 | |||
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It could be either, though it's fairly sloppily written. What I think they are intending to make out is that you can get comparable quality with an AVC-I codec compared to MPEG2 at half the bitrate. Of course, they miss out that the comparison is actually with I-frame only MPEG2.
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As I said before, MPEG2 is based on DCT, and H264/MPEG4 is based on MPEG2. (And AVC-Intra is a subset of H264.) ALL of them are based on DCT, though H264 codecs allow the block size to be varied, and a lot more variations. See H.264/MPEG-4 AVC - Wikipedia, the free encyclopedia and "Features" - that shows the extra tools that are available to enhance the efficiency. (Though not all are likely to be implemented in any one coder, and note that many are only applicable to long-GOP H264. Because of that, you can't expect the improvement over MPEG2 to be as great with I-frame only as with long-GOP, which I why I'm dubious about the 2x figure given for AVC-I v I-frame MPEG2. There's a big oversimplification to just say 2x as a catch all figure, it will vary widely depending on many factors.) Quote:
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Look, nothing I've said is anything other than praise for AVC-Intra, all I've said is intended to give evidence that XDCAM 422 is also extremely good. That was earlier called a "wonky" codec, and nothing could be further from the truth as the EBU trials prove. Simon sums it up nicely a few pages back when he says that ".....it is swings and roundabouts with regard to which codec is best. Either is acceptable, and really the choice of camera should be down to which suits the production best." |
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October 14th, 2009, 11:53 PM | #35 |
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Thanks for the good information David. I think that Panasonic is smart to make AVC-Intra available in a low priced camera, the HPX300, as well as the P2 Portable deck. Sony has yet to allow XDCAM 422 to migrate down to affordable cameras, probably will try to keep product separation.
I saw on the Wiki link you provided for h.264/MPEG4 that it's conceivable that a codec could have up to 14-bits and 4:4:4 color space. Maybe Panasonic will be able to upgrade P2 cards again for higher throughput than the E series for "AVC-Ultra" in the future? Jeff Regan Shooting Star Video |
October 15th, 2009, 06:06 AM | #36 | |
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October 15th, 2009, 11:32 AM | #37 | |
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But whatever it is, it'll work on today's cards. And yesterday's cards. |
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October 15th, 2009, 05:26 PM | #38 |
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The EBU approvals of XDCAM422 and AVC-Intra 100 do say for "general broadcast HD acquisition", they don't say that better than either of them wouldn't be a good thing for top end work such as high end drama. Or that XDCAM 35Mbs or AVC-Intra 50 may not be a more suitable choice for such as news. Sony would no doubt say that they fill the first requirement with HDCAM-SR, AVC-Intra 200 would be Panasonics direct competitor.
And yes, SxS and P2 should each respectively be capable of handling those data rates. I'm sure both manufacturers will be keen in the future to promote them to encourage the purchasing of ever bigger capacity cards. (Even a 32GB P2 card will only last about 15 minutes at 200Mbs.) |
October 18th, 2009, 12:26 AM | #39 |
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Thanks for the clarification on data rate for P2 cards. I see that they can handle up to 640Mbps, so 4:4:4 would be no problem--as long as memory capacity is increased every year.
Jeff Regan Shooting Star Video |
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