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Old January 30th, 2007, 03:56 PM   #1
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AVC-Intra question

I understand that DVCPRO HD is based on the same DCT method that
ordinary JPEG still images use, and that the compression
characteristics of the two formats should therefore be loosely
comparable. I understand also that JPEG2000 is the current state of
the art (or very nearly) in still image compression, and that its
performance is only about 20% better than ordinary JPEG. Isn't it
therefore a little ambitious to hope that AVC-Intra at 50 Mbps will
compare favourably with DVCPRO HD, or has still image compression
advanced significantly beyond what JPEG2000 is capable of? Or are my
comparisons and reasoning just way off?

Since this is my first post, here's a little about me. I'm
considering videography as a hobby, but somewhat intimidated by the
price of the HVX200/P2. I like 720p/50, and none of the HDV cameras
can record this*, so I'm hoping (as I'm sure many of you are too) for
a true progressive scan HD capable DVX100 replacement recording AVCHD
(or perhaps even AVC-Intra at moderate bitrates) to SD cards. Hey, I
can dream, can't I?

*Yes, I know the JVC could do this with HD-SDI and a RAID array, but
this wouldn't be practical for me.
Geoffrey Robson is offline   Reply With Quote
Old February 2nd, 2007, 03:15 PM   #2
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AFAIK from talking with Panny reps, AVC-Intra has the same data flow as DVCPRO HD...

And JVC records 720 natively.

Xcept from that...

If you compare the next DVCPRO-HD solution to the HVX (pricevice) and consider the i-frame compression.... It is really a no-brainer.

Main problem is that Panny has decided that a feature of varicam, HDX900 & the upcomming 2000 cameras of shifting more bits to the lowlights at lowlight situations is not a general DVCPRO HD. That is a major stupid decission.

Gunleik
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Old February 2nd, 2007, 03:56 PM   #3
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AVC-Intra will be used at two bitrates. 50 Mbps is supposed to be similar to DVCPRO HD, and 100 Mbps similar to D5 HD.
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Old February 2nd, 2007, 04:43 PM   #4
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Quote:
Originally Posted by Geoffrey Robson
I like 720p/50, and none of the HDV cameras
can record this*, .........

*Yes, I know the JVC could do this with HD-SDI and a RAID array, but
this wouldn't be practical for me.
The HD200 series (but not the 100 series) can do this to HDV tape.

Regarding JPEG2000, I understand that it's quoted advantage over such as AVC is not that it is vastly more efficient in terms of filesize, but when the compression starts to fall over, JPEG2000 goes soft, whereas AVC (like MPEG) goes blocky. The softness is supposed to be less objectionable.
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Old February 3rd, 2007, 02:51 AM   #5
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AVC-Intra on New Panny AJ-HPX2000

Geoffrey,

Be careful what you are saying. Panasonic is not promising that the camera's cost effective 50mbs AVC-Intra mode is as good as dvcprohd. They're promising that the quality of AVC-Intra is comparable to dvcprohd using half the bit rate. Actually, this camera is a dvcprohd camera with the optional AVC-Intra board when it's available, and it can do just about everything. The 50mbs cost effective mode records 1440 x 1080i/4:2:0 (same as hdv, only hdv is 25mbs using inefficient MPEG 2 compression). On the other hand, the dvcprohd records 1440 x 1080i with the better 4:2:2. Based on the highly efficient H.264 compression sceme, The AVC-Intra cost saving 50mbs might look like dvcprohd but with half the color information. In other words, it will not hold up as well doing compositing, chroma keying and post editing. Of course its higher quality AVC-Intra 100mbs is like D5 quality as you reported, 4:2:2/with full 1920 x 1080i. Oh, This camera does do 720P and multiple frame rates. I just left those out for the sake of this example.

John
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Old February 3rd, 2007, 02:55 AM   #6
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AVC-Intra New Panny AJ-HPX2000

Oh, I just noticed you did say "similar". I must be getting tired. Sorry, my bad.

John
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