RE: dvgrab
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From: Alastair M. <ala...@ww...> - 2000-04-14 20:46:28
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A couple of days ago Bryan Stillwell mentioned that he was getting scrambled images (eg http://www.verinet.com/~arcane/screwedup.jpg ). Compare that to the slide of how a DV packet is assembled by taking chunks (8x32) from different areas of the image: http://desktopvideo.miningco.com/compute/desktopvideo/library/graphics/dvpres/bgSlide23.GIF (sorry for the ridiculously long URL) The little black rectangles mixed in with the purple and orange ones show where the pixel data for the first video segment comes from. The scrambled image above exhibits a similar arrangement of pixel blocks. I think (from a quick glance over the code) that dvgrab just puts the DV data into the AVI file in the order in which it was received, and that some AVI-playing software is smart enough to reassemble the chunks into correct order for display (if it recognizes the frames as DV). Part of making a more general DV codec will of course be shifting this stuff around into pixel-orders more recognizable by other graphic pgms, and vice versa. If I have enough time this weekend I'll get dvgrab running on my system and start working on code to do that. -- Alastair |