From: dhavill@rucs2.sunlab.cs.runet.edu (Adrian Havill)
Subject: Re{visted}: [Genesis/Neo-Geo] A/V connector
Organization: Radford University
Date: Wed, 27 Jan 1993 00:09:14 GMT

In email to me, chandler@wc.novell.com writes:
>In <C1GrBA.3F8@rucs2.sunlab.cs.runet.edu> you write:
>>
>>You most likely have composite inputs with RCA phono-type plug inputs on
>>your TV. Use the composite cable that came with your Genesis/Neo Geo. This
>
>
>Are you referring to the "optional" $10 cable that they mention in the
>Genesis documentation?

Whoops! I've been informed that the composite cable is not standard equipment
on the Genesis (it is on the Neo Geo, though). Looks like Sega wants US $10
buckaroos for the sucker.

>>will provide you with a much better picture than going through the RF
>>modulator (the gizmo that converts a video game audio and video into a
>>radio frequency that the TV can pick up on channels 2/3/4)

Actually, just channels 3 and 4. The old Atari 2600 RF modulators did
channels 2 and 3, but we'll leave that for the people on
alt.video.games.classic to ponder over, eh? ^_^

>>iie. doo itashimashite.
>
>So, we should chuck that funky "box" and pony-up the $10 for the cable,
>right?  (I'm a bit confused.)

I've received other mail saying people don't understand me. I'll try to
clarify. "iie. doo itashimashite" means "you're welcome" in japanese. (Some
people thought I was experiencing modem noise and asked me to re-type it :)

To make a long story very short:

1. Yes, pony-up the ten bucks if you have line ins on your TV for video and
   audio and $10 won't put you in debt.

To make a long story short:

1. Everything that processes analog signals slightly distorts it and
   adds noise to it.
2. Noise and distortion are cumulative (in an analog signal), thus
3. The less transformations a signal undergoes, the truer it is to the
   original form.

To make a long story long:

An extremely simplified diagram of the audio/video path in a Genesis or
Neo-Geo, with major liberties taken: (for example, the "multiplexors" (MUXs)
aren't REALLY MUXs, but I'm no ASCII artist, and the real diagram was too
much of a pain)

	      RGB line out (A/V)
		    ^
                    |
/------------\      +           /---------------\
| video chip +-> Red   Signal ->+ Multiplexor   |
|  in your   +-> Green Signal ->+ that combines |
| video game +-> Blue  Signal ->+ these into    |
|  system    +-> Sync  Signal ->+ one signal    |
\------------/                  \------+--------/
                                       v
/-------------\                        +----->--------> video line out (A/V)
| Multiplexor |         /----->--->----|----->--------> audio line out (A/V)
|   merges    |         |              v
| stereo into |         +       /------+----------\
|   mono      |-> Mono Signal ->+ Radio Frequency |
\-------------/                 |   Modulator     |--> antenna out
   ^      ^                     \--------+--------/
   |      |                               \____<_____< antenna in
  Left  Right
   ^      ^           /---------------------\
   |      +---------->+   Mini amplifier    +--------> stereo headphones out
   +------|---------->+ to drive headphones |
/--+------+--\        \---------+-----------/
| sound chip |                  |
|  in your   |           [volume control]
| video game |
\------------/

Applying rule 3, the closer the "tap" is from the video and audio chips, the
closer the audio and video is going to look like to it's true form.

Thus, an RGB cable gives the best signal, the composite (video line out)
cable gives the next best, and the antenna out is the worst (the process
of modulating the composite and audio together and the TV then demodulating
it distorts the signal way more than a composite signal distorts the original
RBG source)

Granted, you could be lucky and the total distortion/noise you see via
the antennae out method may be so minimal that you can't tell the difference.
Or the other way around: your TV has such a bad focus/picture/sharpness that
it wouldn't matter if you had a fiber optic digital link to you TV the
picture would still make you feel like you had cataracts. As far as you know
a squirrel could be behind you set chewing on your RF cable and you wouldn't
see a picture difference. (My set :)

However, RGB monitors are such an order of magnitude better picture that if
you opt for the RGB cable/monitor setup, you will see an incredible
difference in picture.
in
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