Fair enough (interesting link by the way), so I'll gladly accept the correction. The important thing for editing is the lack of interframe compression. For those to whom this is gobbldeygook, this means that a frame contains only the information that has changed from the previous frame. After several frames, there may be a noticeable error buildup. So every second or so, a full frame (key frame) is presented to get everything right again. This is a pain for editing, since odds are pretty good that you're not cutting on key frames. The editing software will generally do a decent job of reconstructing the frame, but there will still be accumulated errors in those frames that may affect the overall appearance of the video. And of course other details of the compression algorithm are important. While loss in the color signal is not trivial, it's generally more acceptable to loose a bit of color fidelity than to lose detail. The DCT compression is excellent at maintaining clear sharp edges. The overall bit rate of DV is about 36MBit per second, according to the WIKI article. The highest bit rate for DVD is about 10 Mbit per second, but most commercial DVDs will be lower. Quick calculation on the Sanyo recorder I mentioned in last night's post gives me a bit over 800 Kilobits per second for that format. And Chuck, your comment about obsolete formats brings one caution to mind. We're just about to go through another VHS/Betamax mess. There are two incompatible high-definition DVDs coming on to the market. One is called Blu-Ray and the other is HD-DVD. Prepare for years of hearing why your old DVDs aren't any good anymore as the film companies convince you to buy movies you've already bought twice before. In truth, both formats are better than the current format, and each can claim some advantages over the other. But we don't need both. We may end up with players that can handle both formats, but that will take a while. And of course, we're supposed to eliminate NTSC television (the format that's been in place from the beginning) and go all digital by the end of the decade. The changeover was originally supposed to have happened already, but there was justified squawking and the process was delayed. There are a lot of high- definition TVs sold over the last few years that may not work without converter boxes. Given that the FCC nowadays is populated by idiots, I'm waiting this one out and keeping the money in my pocket until the industry has some adult supervision.

Not compressed? That may depend on how you define "compression". The DV formats I'm aware of do store video in a compressed format--just not a "highly compressed" format. :-) The video data recorded on a DV tape (and uploaded to a computer via firewire) isn't compressed temporally, which is why it works so well for nonlinear editing, but each individual frame *is* compressed with both 4:1:1 chroma subsampling and a DCT. http://en.wikipedia.org/wiki/DV25

Chris

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Michael Carnes MichaelCarnes@earthlink.net home.earthlink.net/~michaelcarnes