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AVCHD Format Discussion
Inexpensive High Definition H.264 encoding to DVD, Hard Disc or SD Card.

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Old April 4th, 2009, 01:26 PM   #16
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Originally Posted by Robin Davies-Rollinson View Post
the HMC151 It's also got a three CMOS chips, good audio features etc.
In fact one of its main selling features (for me) was that it *doesn't* have CMOS chips Robin.
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Old April 5th, 2009, 03:22 PM   #17
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Mea maxima culpa...
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Old April 5th, 2009, 05:35 PM   #18
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Originally Posted by Jon McGuffin View Post
I've often wondered though if you're going to reach as high as the Z7 (nearly twice the price of the HMC150) why not go with the EX1?
I was thinking that - and last time I looked the price for the EX1 was about 50% more than the HMC151, about 4,100 v 2,600. (It's twice as much only if you buy it with SxS cards, and now most people seem to be using SDHC with an adaptor, there's no need to do that.)

As far as codecs go, then it's difficult to say that one has an inherent advantage over another - it becomes a matter of bitrate and the actual hardware doing the encoding. At the same bitrate, AVC-HD would be expected to outperform MPEG2, and I would expect the HMC151 bitrate to outperform HDV. My own experiences though are that the EX codec outperforms 21Mbs AVC-HD for quality.

And quality is only one aspect. As others have said, the drawback to AVC-HD is increased complexity, and the need for increased processing power. The effective necessity to transcode to edit to an extent that is not necessary with MPEG2.

I think AVC-HD is absolutely the right way to go for consumer cameras, but it's worth remembering why it was initially adopted for what became the HMC151. Panasonic recognised the desire to get high quality results using much cheaper than P2 memory, but said that to use SD cards and to keep reasonable quality, AVC-HD was essential to get the data rate low enough. So the drawbacks to AVC-HD may have been seen as worthwhile if it meant SDHC as opposed to P2.

But then along comes the ability to use SDHC in an EX, and then native use of SDHC in the new JVC cameras. It becomes evident that SDHC are capable of handling much more than 21Mbs. Yes, the 151 will record 90 minutes to a 16GB card, versus about 50 minutes of the XDCAM-EX codec, but personally I don't think that's worth the lesser quality and the greater processing needed for a semi-pro camera.

If you can't afford the EX, then the 151 is a good choice. But if you've got the money, the EX gives a lot more for not that much extra cost, and not just in terms of codec or resolution.
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Old April 5th, 2009, 06:56 PM   #19
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Originally Posted by Larry Horwitz View Post
The trade off indicated in the comment:

"converting to a more robust codec gives you more overhead (more calculation accuracy), resulting in fewer quality losses while applying any kind of effects. If you edit AVCHD footage on an AVCHD timeline you could suffer quality losses from effects more significant than those from doing transcoding, so the quality issue is a wash and transcoding is more practical"

is only partially true, and that is because today's NLEs have not been specifically built or optimized to handle AVCHD or other h.264 especially well in native format.
Maybe I misspoke, but editing video in a decompressed workspace should be preferable to applying effects which must be immediately rendered back to the source format. In any case, the performance advantages of decompressing AVCHD before editing can be significant, so if the quality results are acceptable then decompressing first has practical benefits.

With HDV (another inter-frame codec), I can work with 2-3 layers of decompressed footage on my laptop - which can barely handle one layer of native footage.
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