Posted By
TLC
on 2010-10-31
15:20:31
|  Re: interesting'n'funny stuff
MMS: well... I don't remember trying how the C64 behaves in this subject (wouldn't be surprised if the results were similar, due to the similar construction of the video-out circuit), but the Plus/4's s-video out is certainly ugly.
Precisely speaking, there's no problem with bad bandwidth (seemingly washed out edges) or high level of noise (noisy image), there's a high level of crosstalk between the luma and chroma signals. ...It's so bad that some composite displays would show a _color_ image out of the _luma_ signal alone. This is due to crosstalk ie. some amount of the chroma signal mixed onto the top of the luma signal. The problem must be somewhere in the RF-modulator (...where buffering + impedance matching of the luma/chroma outs are done, beside generating RF). The crosstalk would appear as a typical moire-like image all over coloured fields of the screen, if s-video connection (separate luma + chroma) were used.
Edit: Nah, Chicken was faster :). BTW, the page linked by him holds two images (amongst others); both were taken from a TFT. The first is RF (note the poor image but the clean, flat blue field), the second is separate luma/chroma (...note the sharp edges, with the noticeable vertical bars on the blue field... we're talking about this one here, this distortion is because of crosstalk. You wouldn't see these bars if there were a third image, showing how composite looks like -- yeah, I also won't make a bet that the edges would remain that sharp as seen here).
That makes it for three possibilities:
-- RF. Worst of all, especially with modern digital TVs.
-- Composite. ...Bearable. My current choice. No unusual distortions but only what you're already used to, if you had dealt with composite displays before.
-- Separate luma-chroma ie. s-video. Sharpest image of all, unfortunately with those slightly-moire-ridden coloured* fields.
Please note that I still don't have any digital TVs (not even 100Hz CRTs, let alone LCDs), ie. I only ever had but little (...bad) experience with these displays. These do some digital filtering and tricks in order to enhance (...better said: to display a bearable result of) the digitized analog image. As I noticed, the digital filtering method usually differs for different sorts of video sources (which is probably one of the reasons why RF performs _that_ bad in spite of a Commodore computer + modern LCD displays). ...With that in mind, I'd say, "YMMV" (your mileage may vary). ...You might find out that you like either of s-video or composite better, depending on your setup (even though we know that the "s-video out" of the Plus/4 is not perfect).
*The problem only affects coloured fields, as the chroma signal is constant (amplitude = 0) for all colourless (ie. white, gray, black) fields, ie. it won't disturb our luma signal, even if there were (is) some level of crosstalk.
Edit #2: Weheee, err... check dis... :)
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