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Re: RT.SYNTH -- anybody tried it?
sicklittlemonkey wrote:
I understand what you're saying above, Michael. As long as they're
running at a multiple of the same frequency it doesn't matter if
they're out of sync.
Exactly. (However, I misspoke in saying that each 46 cycle pulse
would span two 23-cycle sample intervals. That happens only in the
case of exact alignment. In the general case, each pulse is at least
partly in three 23-cycle intervals, and shares one of them with the
adjacent 46-cycle pulse. Still no problem, on the average.
But (and no offense to Linards, as I'm interested in his emulation
efforts too) I'm surprised that his naive "value assignment algorithm"
is perfect! Isn't it effectively converting frequency into amplitude?
Actually, it's converting duty cycle (in the sample period) into
amplitude, which is the equivalent of averaging over all 23 1MHz
bi-level samples.
Also, Linards, can you clarify what you mean by the speaker being "on".
In my mind each access to $C03X, if sufficiently separated, should
result in toggling of the sample output values between a min and max
(e.g. 0 and 255). In other words, there is no "on", but it's the
transition between two states that makes a waveform.
No, each reference complements the state of the speaker toggle, with
the initial state undefined. So each reference causes the level to
switch from 0 to 255 or from 255 to 0, depending on its current level.
(The initial state may, in fact, be defined. But after loading ProDOS
<click> and getting a few "beeps", it's anyone's guess what the state
is--unless all speaker sounds use an *even* number of transitions!)
-michael
Music synthesis for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it is seriously underused."