Digital Video Questions? Answers from an Expert
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DMN: Talking about rendering, I think a common misconception is that rendering always happens when the video is compressed. When it's time to render, isn't the video uncompressed when the rendering takes place, and then the video is compressed back into the chosen codec?
Bryant: Sometimes, sometimes not. It depends on the codec. There is MPEG-2 and there's also DV. If you look at DV, like Sonic Foundry's DV codec they use in Vegas Video -- they keep it in the DV codec, completely, all the time. They never take it out of it, so it's never uncompressed, always in the DV codec. That's a codec that you can actually work in. Other codecs like MPEG-2, because there are IBP frames, some of them aren't real, and the temporal and spatial differences between frames make it so you can't be frame-accurate. So almost nobody does MPEG-2 editing except for straight cuts and simple stuff, because you never know what you're getting. It's like the old days of going from 30 frames per second to 24 frames per second. You never knew if you had a real frame or not, but now we've gotten the art down to where we can figure that out.
I think there are some codecs that lend themselves to be used and rendered in and then there's others that don't. HDCam, I wouldn't want to be in that codec, but you could. What they do with the bits makes it bad. DVCPro is not too bad, because it's a DV derivation, it's in 4:2:2 color space, so you can figure it out and work with it fairly easily, and then you have Sony pushing MPX and the other stuff, which is kind of like an MPEG-2 derivation. I think some codecs lend themselves to be rendered in the native codec and others, you just can't. You have to get out of it, do your stuff, and then re-encode it.
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Charlie White has been writing about new media and digital video since it was the laughingstock of the television industry. A technology journalist and columnist for the past eight years, White is also an Emmy-winning producer, video editor and shot-calling PBS TV director with 27 years broadcast experience. Talk back -- Send Chazz a note at cwhite@digitalmedianet.com.Prev 1 2 3 4
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