[PD] smallest possible value of a delay-time

Frank Barknecht fbar at footils.org
Fri May 14 07:51:15 CEST 2004

Roman Haefeli hat gesagt: // Roman Haefeli wrote:

> this discussion went up when we talked about the karplus-strong-sythesis. so
> it is not about getting this short delay in realtime. it is about a sythesis
> that tries to simulate string and other percussive instruments. the problem
> is, that the frequency of the sythesized sound is dependent from a
> delay-time (frequency=1/delaytime). if the quantization of the delaytime is
> 1 sample, you can't play any frequency you want with this sythesis (for
> example: you want freq of 5000. how many samples long is the delay: 44100 /
> 5000 = 8.82 samples delaytime > 8.82 truncated> 9. freq with 9 samples delay
> = 44100 / 9 = 4900 >>> you get an error size of 100Hz or 2%) .

A delay simply is a sound recorder and player. In earlier times, they
were done with tapes, that were just shorter than tapes for real
recordings, and looped. 

Thinking of tapes as simple sample recorder/players or even as some
kind of adc/dac combination, they must follow the same rules as other
samle players, that is: the max frequency they can record or play is
Nyquist frequency, that is half sample rate. The shortest possible
delay time then in theory is 1/nyquist[Hz] seconds.

The second question then is: Can you have delays not quantized on
samples? This looks as if it's the same problem as a basic wavetable
oscillator has, like tabplay~. They also play a short buffer for a
certain time, that doesn't have to be exactly on a sample, but can be
in between.

 Frank Barknecht                               _ ______footils.org__

More information about the Pd-list mailing list