Re: PDW-700 vs HPX 2000 -Workflow, cost of operation over time.

[john sharaf] "Panasonic AVC-I is really four times as good as that on the XDCAM."

With respect, the relative quality levels of the competing codecs are not even close to 4 times different. You have to look at these apples and oranges from several perspectives to come to any even speculative conclusions, and we'll have to wait for the real proof of the pudding when we can compare them directly. The fact that the Panasonic is intraframe and the Sony interframe makes a huge difference. The old rule of thumb when looking at MPEG2 compression is that interframe (long GOP) compression is approximately 2.5 times more efficient than intraframe compression (I-frame), just harder for the NLE to work with.

All compression schemes are conscious compromises. Since MPEG2 compression is perhaps a little more efficient in intraframe than the intraframe DCT compression used in DVCProHD, there is very little difference in quality between the 35 mbps XDCAM HD interframe codec and the 100 mbps DVCPRO HD intraframe codec, except where the respective companies decided to compromise. Panasonic went for 4:2:2 color space for improved color resolution and vibrancy and Sony went for 4:2:0 color space to improve the spacial resolution. These choices have been born out in the practical applications of shooters, who for the most part agree that XDCAM HD is sharper than DVCPRO HD but that DVCPRO HD images have a color vibrancy superior to XDCAM HD. This assumes that camera heads are equal which of course they never are, which is another reason that we have to look at things in the real world.

Now both Sony and Panasonic have new codecs, a 50 mbps, 4:2:2, interframe MPEG2 XDCAM HD codec for Sony and a variant of MPEG4, 50 and 100 mbps, AVC intraframe codec for Panasonic. The old rules of thumb don't directly apply anymore because the AVC codec, if we are to believe Panasonic (and let us do so for simplicity), is twice as efficient as DVCPRO HD. If the old competing codecs were roughtly equivalent in quality, then the new competing codecs will give the edge to Panasonic, because it is twice as efficient as the old, while the new Sony is approximately a 1.5 times improvement. But that means that the Panasonic codec is perhaps 30-50% better than the Sony, not 4 times better.

We will have to wait and see how this works out in the field, but my suspicion is that there will be little real difference in the quality, such that other things like work flow and the subjective response to the camcorders' imagery will be of greater importance than any mostly non visible differences in codec quality. Another thing to watch out for is the relative ease or difficulty of dealing with the respective codecs in the nle. We already know that long GOP XDCAM HD is harder to deal with, and we know that AVC-I takes more CPU horsepower to decode than MPEG2, but I at least haven't heard how much. It may be a wash or it may not?

Ron Shook
Shoulder-High Eye Productions
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