always a variable celay will cause a transposition, but this depends on time that happens the variation and the delta between a time of dely and the other.
while the time of variation is longer and the delta is shorter the transposition during this period will be smaller. (read about doppler effect)
Andrés Ferrari G.
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And conversely, a delay buffer with a ordinary movable read point (which is what I guess you really want in this case) will always cause a click since there's no reason why jumps between arbitrary samples will be smooth. Of course there will be no trasposition since the read location changes instead of the rate.
Transposition may be desirable, but clicks rarely are. As it stands you can either have smoothness with transposition, or no transposition and clicks.
It seems reasonable that if the position changes infrequently one could make a vari-delay to crossfade between two buffers, which would then be an overlapped timestretch process.
For short (time period) effects there are several variations on this general idea of crossfading between parallel but slightly offset static delay buffers. It depends on what effect you want to achieve.
On Thu, 5 Jun 2008 13:52:16 -0700 (PDT) Andres Ferrari anfex@yahoo.com wrote:
always a variable celay will cause a transposition, but this depends on time that happens the variation and the delta between a time of dely and the other.
while the time of variation is longer and the delta is shorter the transposition during this period will be smaller. (read about doppler effect)
Andrés Ferrari G.
http://puredata.org/Members/anfex
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On Thu, 2008-06-05 at 22:36 +0100, Andy Farnell wrote:
And conversely, a delay buffer with a ordinary movable read point (which is what I guess you really want in this case) will always cause a click since there's no reason why jumps between arbitrary samples will be smooth. Of course there will be no trasposition since the read location changes instead of the rate.
Transposition may be desirable, but clicks rarely are. As it stands you can either have smoothness with transposition, or no transposition and clicks.
iirc, there is a technique described in millers book, which i don't recall the name of, which is used to avoid discontinuities, when jumping from one to another time point in an audio stream. this is achieved by adding a ramp to the signal, that smoothes out the difference between the samples at the jump. i used this technique to create clickless loops with arbitrary length. i assume, it would also work for a non-continuous, but clickfree changeable delay (without transposition).
however, if jamie wants it to be continuous, then probably the technique as shown in 3.audio.examples/I07.phase.vocoder.pd could be used, which is very cpu-time consuming, though.
roman
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Yes, that's a great point. IIRC that is mainly for slow moving envelope/control signals. I wonder, if you did it with audio then you'd have a limited number of times to apply it in a given interval because the worst case means you get an accumulating DC offset that will go out of bounds. (?)
On Fri, 06 Jun 2008 16:58:32 +0200 Roman Haefeli reduzierer@yahoo.de wrote:
On Thu, 2008-06-05 at 22:36 +0100, Andy Farnell wrote:
And conversely, a delay buffer with a ordinary movable read point (which is what I guess you really want in this case) will always cause a click since there's no reason why jumps between arbitrary samples will be smooth. Of course there will be no trasposition since the read location changes instead of the rate.
Transposition may be desirable, but clicks rarely are. As it stands you can either have smoothness with transposition, or no transposition and clicks.
iirc, there is a technique described in millers book, which i don't recall the name of, which is used to avoid discontinuities, when jumping from one to another time point in an audio stream. this is achieved by adding a ramp to the signal, that smoothes out the difference between the samples at the jump. i used this technique to create clickless loops with arbitrary length. i assume, it would also work for a non-continuous, but clickfree changeable delay (without transposition).
however, if jamie wants it to be continuous, then probably the technique as shown in 3.audio.examples/I07.phase.vocoder.pd could be used, which is very cpu-time consuming, though.
roman
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On Fri, 06 Jun 2008 16:58:32 +0200 Roman Haefeli reduzierer@yahoo.de wrote:
On Thu, 2008-06-05 at 22:36 +0100, Andy Farnell wrote:
And conversely, a delay buffer with a ordinary movable read point (which is what I guess you really want in this case) will always cause a click since there's no reason why jumps between arbitrary samples will be smooth. Of course there will be no trasposition since the read location changes instead of the rate.
Does it need to be sampel accurate timing; would snapping to a nearby same-direction zero-crossing work?
On Fri, 2008-06-06 at 16:07 +0100, Andy Farnell wrote:
Yes, that's a great point. IIRC that is mainly for slow moving envelope/control signals. I wonder, if you did it with audio then you'd have a limited number of times to apply it in a given interval because the worst case means you get an accumulating DC offset that will go out of bounds. (?)
yeah.. so the rate should be limited to 1/(period of the ramp). actually i only tried it with audio. you still get kind of clicks sometimes, if the direction of the signal suddenly changes, but they sound very different and - IMO - far not as bad as the noisy sample-jumps with lots of high frequencies.
roman
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