Re: IIGS composite video->VCR

[mjmahon@aol.com (Michael J. Mahon)]

Hal Bouma replied:

>mjmahon@aol.com (Michael J. Mahon) wrote in message
>news:<20020828205023.22191.00004908@mb-mv.aol.com>...
>> Mitchell Spector replied:
>> 
>> >DoNOT@feed.the.trolls (SlickRBCD) wrote:
>> >
>>  <snip>
>> >
>> >>but why wouldn't the text screen work in color?
>> >
>> >    It's a feature, which unfortunately cannot be changed using the
>> >Control Panel settings.
>> 
>> Since the bandwidth of the NTSC composite chroma signal is
>> less than 2MHz, you couldn't even get 40 characters across the
>> screen.  That's why the color burst is turned off in text mode.
>> 
>> If the burst is on, as with mixed text/graphics screens, the
>> high dot bandwidth of the luminance signal aliases into myriad
>> of fuzzy colors on a composite display, producing a colorful but
>> very hard-to-read display.  It would be impossible to produce
>> more than about 24 characters of any _particular_ color without
>> a much more clever video generator (with two-pixel wide dots
>> and anti-aliasing).
>> 
>> -michael
>
>Thats not totally true. Seven and a half years ago I made some video
>tapes of the IIGS programs I had written for my resumes to get into
>the game industry. (For some strange reason, nobody owned Apple IIGS
>computers anymore. Don't ask me why! ;) The only way I could show them
>my work was with video tapes. Of course, I had someone with expensive
>video editing equipment help me but we were able to record 80 column
>text after he made some adjustments. (I had written a text mode
>basketball game.) We were also able to record my 3200 color demo as
>well. But you are correct that the color text settings are not
>applied. Black background with white text is all you get.
>
>Hal Bouma
>Software Engineer @ High Voltage Software

That's what I meant when I said "if the burst is on".  If color burst is
present, it signals the monitor that there is a chrominance subcarrier,
and high frequency luminance (black & white) data will be interpreted
as color information, blurring and distorting the text.  If the burst is
off, the composite signal is interpreted as black & white, and the full
bandwidth of the monitor is available for displaying data.  For NTSC,
this is generally limited to 4.25MHz, so 80-column text will not be
particularly sharp, but it _is_ possible to read it.  (Most 80-column
monitors have a bandwidth of over 10MHz.)  If the color burst were
on, the text would be virtually unreadable, unless the chrominance
(saturation) was turned all the way down (to produce black & white).

-michael

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