On Thu, Feb 26, 2004 at 09:31:07AM -0800, Ben Barrett wrote: > For some reason, I thought that s-video carried audio as well. I've no > experience there, so "no blood no foul"...
That wouldn't make much sense given the evolving standards for both. Aside from the PAL vs. NTSC vs. SECAM issue, video currently comes in these major flavors: - Composite (single RCA plug, usually yellow) - S-Video (mini-DIN connector, seperate chroma and luma) - Component video - YCrCb as 3 RCA plugs - RGB (sync on green) - 3 RCA plugs (some pro gear uses BNC) - VGA connector - RGBHV (seperate sync) - 5 RCA plugs (some pro gear uses BNC) - VGA connector These are from worst to best, acutally. The most flexible is the five signal RGB cable since it it gives equal colorspace to the three primary light colors and offers seperate sync for various resolutions and timings. This is basically VGA/SVGA. Older fixed frequency gear (and anything designed to work with today's televisions is fixed frequency) can get by just fine without any vsync signal and depending only on the hsync which is multiplexed into the green wire. Adapters to use old Sun monitors with normal video cards do this multiplexing, and adapters to use multisync monitors on old Suns extract the hsync and use some intelligence to create a vsync. I digress.. YCrCb is interesting because it applies the technique used by broadcast television. When color TVs came out, B&W had been established and they wanted compatibility. So, they left the B&W signal alone and added the colorburst signal B&W TVs didn't even see. Basically, color TVs treat the B&W signal as brightness and then use a signal for the difference between the brightness and the red, and another the brightness and the blue. What's left once you subtract these out is green. This leaves you with high green resolution but pretty low red/blue. The Y (Luma) signal contains the brightness and sync, the other two contain the color differences. S-Video is what happens when you combine the two color information lines together into one signal and put the result in a single connector. It's not quite as good as component video, but it's still pretty good. Most say it's good enough. Four pins are used--two signal and two ground. No idea why they adopted a single connector for both, but anyone who remembers the old Commadore 64 color monitor has seen S-Video done as two seperately shielded RCA plugs. Someone just decided to make one connector out of it along the way. Composite is the two S-Video signals mixed, giving you one signal. Short of RF modulation, it's the worst thing you can do to the signal. If you haven't guessed yet, Composite happened when someone decided to not bother to modulate and demodulate the TV signal. S-Video happened when someone decided not to mix Luma and Chroma. YCrCb composite happened when someone else decided to output the signal without mixing the Chroma channels together. RGB simply was what all of these things were before we tried to make them sane for both B&W and color. THANKFULLY, Audio is more sane. Sortof. - Analog - Signal level - Line level (what you're used to) - Mic level (weaker, you won't use it, usually needs preamp) - Connector madness - XLR (you won't use this) - RCA (1-6 depending on channels) - Headphone type - Size - 1/4 inch (dying except for mono for musical instruments) - 35 mm (probably only stereo anymore for computers/headphones) - Bizarre sizes and 3+ channels for camcorders and other weirdness - Channels - Mono - Stereo (seperate or combined connector) - Rat's nest of (almost always) RCA plugs for 3, 4, 4.1, 5.1, etc - Digital - Signal conduit - Coaxial copper (RCA plug) - plastic fibre (TOSlink) - Signal type - Stereo PCM - AC3 (basically multi-channel MPEG audio) Currently, non-embarassing AV gear accepts S-Video and stereo RCA. S-Video plus TOSlink patch cables are becoming more common, but I think those won't last because DVD players are making people start to demand component video over S-Video more and more often. TOSlink will win over coax because it's cooler (not because it matters since the signal is already digital) and YCrCb vs. RGB is still up in the air. Both have a strong push behind them. Although DVDs happen to be encoded in the YCrCb format, the playback devices quite often render them to an RGB framebuffer before re-encoding them for display. This is amusingly wasteful, but lossless. ;) > So, what are some reasonably good ways to determine how many milliseconds > out of sync one's audio and video are? When you figure this out, talk to the people making DVDs. Note that the beginning of Fellowship of the Ring was out of sync in the theatrical DVD. Most weren't terribly annoyed and those who don't work with digital AV didn't even notice. ;) _______________________________________________ EuG-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug