On Wednesday 16 July 2003 23:04, Billy Biggs wrote: >Vidiot (brown@xxxxxxxxxxxxxxxxxx): >> > One annoyance with DV for NTSC is that it's 4:1:1 and converting >> > from 4:1:1 to the 4:2:0 you need for MPEG-1/2 is a pain to do >> > well. Still, that sort of annoyance is best left to those >> > seeking ultra-correctness. >> >> Not had a problem so far. Unfortunately at this point it has all >> been done under Windbloze. But, a friend has been playing with >> Linux tools and as far as I know, hasn't had a problem either. > > At some point, someone has to convert from 4:1:1 to 4:2:0. Linux >tools currently seem to simply duplicate chroma samples horizontally > and drop vertically, resulting in poorer colour than could be > achieved with a better filter. Test images to show problems would > likely have jagged blue or red edges. > >> >> BTW, before going to VCD and/or DVD, the NTSC setup level needs >> >> to be removed. So whatever tool you use, make sure that it can >> >> remove NTSC setup, as the MPEG-1/2 standard does not use it and >> >> leaving it in will cause problems. >> > >> > What are you talking about here? The Y'CbCr specs for MPEG-1/2 >> > are the same as for DV. Please clarify. >> >> Please read what I wrote. I said that the "NTSC setup" needs to >> be removed. Most consumer, and even pro-sumer, devices will not >> remove NTSC setup when fed an analog signal for conversion to DV. >> The setup is left intact in the DV data. My DVCAM decks are like >> that. No switch to tell it to remove, or add, setup. It records >> what you feed it. > > Ok I see what you mean. We discussed this before about how to >properly cut it off. So, let's say I'm trying to get rid of the > setup. Should I record at like 768x480 and then estimate where the > setup ends, and then resample the active area with 720 samples ? I > can't see how to do this though without messing up the aspect ratio > of the content. > You are missing the point Billy. 'Setup' in the NTSC vernacular, doesn't have a thing to do with the operating resolution, none, nada, zip. Setup is a small step upwards in the black level during active picture time, and on a scale where peak white=100, should be set to maintain the videos black level at 7.5% of this 100 IRE peak white when looking at the waveform monitoring scope. Effectively it makes the blackest area of the picture into a medium grey since the eye is a bit logarithmic. We've been trying to get the FCC to remove it for about 3 decades now. -- Cheers, Gene AMD K6-III@500mhz 320M Athlon1600XP@1400mhz 512M 99.26% setiathome rank, not too shabby for a WV hillbilly Yahoo.com attornies please note, additions to this message by Gene Heskett are: Copyright 2003 by Maurice Eugene Heskett, all rights reserved.
