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Old October 12th, 2009, 08:20 PM   #31
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Originally Posted by David Heath View Post
I don't see how that can be the case. Using Region50 figures, the raw rates for 720p/50 are about 50megapixels/second (approx 1 megapixel, 50 times a second), and for both 1080i/25 and 1080p/25 it's roughly the same - though now 2 megapixels, 25 times a second. Hence 100 Mbs needed in both cases for comparable compression. Go to 720p/25 and it's now approx 25 megapixels per second, hence yes, drop the data rate to 50Mbs.

The same must apply in Region60 countries, though OK, 1080p/24 is only 5/6 the raw rate of 1080p/30 or 720p/60, so it could drop to about 85Mbs for equivalent compression.

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Which is best? Frankly it's irrelevant. BOTH of them have been given a big seal of approval by the EBU - go to EBU Technical Review , click on "Digital Compression", and then "HDTV production codec tests" if you want full details. BOTH of them have, in the words of the EBU:

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A user doesn't need to worry about using either XDCAM422 or AVC-Intra 100 on quality grounds for general acquisition, end of story.

If you mean because it causes less processing work during editing, then maybe yes. But the AVC nature causes an overhead of it's own - it's swings and roundabouts.
David, thank you for the information/clarification/correction. I didn't mean to imply that Native rates for 1080 will require only 40Mbps. 1080/24p yields about 1.3 minutes per Gb, so your 85Mbps sounds correct.

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.

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Old October 13th, 2009, 06:33 PM   #32
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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.
At heart, they are all based on DCT. But MPEG2 allows extra facilities to be used ADDITIONALLY. Same with H264, at heart it is MPEG2, but allows extra tools additionally. The more tools you use, the greater the efficiency, but the greater the complexity - use none of them and it's MPEG2! The way your post reads it implies DCT, MPEG2, and H264 are completely separate technologies - they're not, one builds upon the other. Excuse me if that's not what you intended.
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..........however it's an 8-bit codec not 10-bit color depth like AVC-Intra 100. I believe that's an important difference.
It may be, but again I'm afraid it may not be that simple. I'm assuming you desire 10bit such that contour banding on graded footage etc will be minimised.

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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Old October 13th, 2009, 07:08 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.

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Old October 14th, 2009, 06:03 PM   #34
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I assume the last part is about AVC-Intra 50.
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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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?
No, that's not true. Not if you think H264 is based on completely different principles to DCT. (As indeed, JPEG2000 and Dirac are.)

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.)
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Obviously, all these compression schemes are scalable and "adding tools" adds to computational complexity, requiring more powerful processors.
Yes, exactly so. If we start with I-frame only MPEG2, both Sony and Panasonic have decided they want a more efficient solution. Sony approach has been to say keep it MPEG2, but go long-GOP. Panasonics has been to say keep it I-frame only, but use H264 tools. Both solutions are more efficient than I-frame MPEG2, but both require more processing power. It's two ways to skin the same cat, and I wouldn't like to say either of them is better than the other.
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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.
Well, if we're talking about DVCProHD, then undoubtably yes. If we're talking about HDCAM-SR, then undoubtably no. If we're talking about XDCAM422 50Mbs, the EBU trials don't seem to point up much difference.

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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Old October 15th, 2009, 12:53 AM   #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?

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Old October 15th, 2009, 07:06 AM   #36
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Originally Posted by Jeff Regan View Post
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
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From what I've read that's not necessary to utilize an upcoming Avc-ultra, you can use all the previous cards except the first ones. Correct me if I'm wrong though...
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Old October 15th, 2009, 12:32 PM   #37
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Originally Posted by Jeff Regan View Post
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
Not necessary to upgrade them; they've already announced AVC-Ultra as being a 200mbps codec, which will work with all existing P2 cards. They haven't specified exactly what they'll do with AVC-Ultra, other than to say it'll be used for things beyond normal ATSC video, such as 3-D, or 4:4:4 12-bit 1080p, or 1080/60p, or 2K.

But whatever it is, it'll work on today's cards. And yesterday's cards.
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Old October 15th, 2009, 06:26 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.)
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Old October 18th, 2009, 01:26 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.

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