Re: VOC output to AV Mac: Excellent!!!

[dalloff@freenet.columbus.oh.us (Dave Althoff)]

Joseph Lee (nugundam@netcom.com) wrote:
: FermiLevel (fermilevel@aol.com) wrote:
: : almost like the IIGS monitor!  Big question:  why is the NTSC composite
: : output on the VOC so much better than the IIGS???

: The VOC has chromo-crosstalk filters that clean up the NTSC signal out
: which the GS doesn't.  Also I think the GS outputs composite (which has
: audio mixed in, degrading video bandwidth) which the VOC doesn't do.

Half-right.  Yes, the VOC has some additional filtering, which I believe
is related to getting a nice clean key over the input video.

Yes, the GS video output port is a composite video signal.  What that
means is that the brightness, the sync, and the color burst are all
carried on a single conductor, in conformance with the revised RS-170
standard.  This has nothing at all to do with audio.  There is no audio on
the GS monitor port.  Just composite video.

In composite video, it is essentially a black-and-white luminance signal,
spaced with the line- and field-sync pulses.  Color is generated by a
burst signal just after the field sync, and I'm still a little fuzzy on
how it is encoded.

By comparison, an analog RGB monitor (such as the "standard" GS monitor)
has three black-and-white video luminance signals (for red, green, and
blue) transmitted simultaneously and in sync; and a fourth signal to carry
the line and field sync signals.  Since there is no decoding required for
the color, and since each color signal is given the full bandwidth of the
carrier, the image can be sharper with no color blur.

--Dave Althoff, ][.
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