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Old 02 December 2013, 04:30   #28
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Join Date: Jan 2012
Location: USA
Posts: 281
Originally Posted by xArtx View Post
Whether or no Paula can do this and can't do that,
the music we hear in demos is all sample based mod,
with no programatic reproduction of audio, only sequencing of samples.
So at best, we'd hear synthesised samples in some games, maybe...

Can you simply tell Paula to play a sine wave tone at a specified frequency without
providing the sample to play back? So the tone would be continuous?
Or would you have to loop a recorded sample to play it continuously?
While a sample of a sine wave could be obtained by sampling and recording a pure tone, a sine wave can be produced analytically so there is no need to sample one. The CPU is perfectly capable of computing and filling a block of memory with those values needed by Agnus+Paula to produce a sine wave.

Once a block of memory has been filled with one cycle of the computed sine wave, Agnus+Paula can be set so as to play that one cycle repeatedly at a variety of possible frequencies to produce a continuous pure tone until the channel is turned off.

The same thing can be done to produce all the waveforms typically found in old synth chips like the sawtooth waveform, triangle waveform, and square wave waveform. These waveforms are all easy for the CPU to compute and store. There's no need to sample or record them. Once stored, Agnus+Paula can use them to output sounds at a variety of frequencies.

Of course samples could be used as base waveforms and often are. This has given rise to the belief that Agnus+Paula can only play samples. But Agnus+Paula can play arbitrary waveforms that would be nearly impossible to obtain by sampling a real signal.

Paula is even capable of using one channel to FM and AM modulate another. Rarely used, though, since it reduces the number of available voices and it's a simple matter to use the CPU to alter the frequency or volume of a channel while it's playing. There's no need to recompute a new waveform. Paula will automatically output the waveform at the new frequency and volume.
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