Hi again helpful forum!

For those who don`t know, B.14 sampler.rockafella.pd in pd extended(audio examples, help file) performs time stretching/contraction via looped samples..

Effectively, it allows you to change speed without changing pitch..

My question is, how is this possible? I thought this was a feature reserved for fft and granular synthesis..

I suspect it may have something to do with this expression :[expr (pow(2, $f1/120) -$f3)/$f2]
(I do not thoroughly understand the expression nor its function)

My second question is, how could one modify the patch as to avoid the temporary change in pitch when adjusting the chunk size?

I say temporary as whilst one changes the chunk size you can hear the pitch change, however, it corrects itself and returns to the original or chosen pitch.

Thanks in advance as always!

Just a friendly little bump as I posted this on a sunday a couple weeks ago and it didn`t get any love..

Thanks in advance.

@lovelovevideo Damn...... I thought someone else would reply. It has to do with old technologies and ways of reproducing them on computers.
In ancient times this effect was achieved by speeding up and slowing down the tape (a very long plastic film coated with........ enough..... see here https://en.wikipedia.org/wiki/Magnetic_tape)
Obviously that would also change the pitch. But if the tape head (reading the information) was a complete circle (for domestic stuff like "cassettes" it was a small arc of a circle) then the head could be revolving slowly in one sense or the other, and so read the information at a different speed....... and so compensate for the change in speed of the tape.
Of course in the digital sampling domain the solution has to be different.... but only slightly.
In the analogue example the number of samples (ferrite bits stuck to the tape) being read every second by the revolving head was irrelevant. Not so in the digital domain...... the sample rate being necessarily constant.
To get around this constraint extra copies of samples need to be added when the speed is slow, and some need to be removed when the "tape is running fast" so as to keep the sample rate stable.
Hence the "chunk size" (a revolution of the head) and the continuous re-adjustment of the phase so as to insert (copies) and drop samples as necessary by continuously updating the read point of tabplay......
Of course, when in doubt ask @katjav .........http://www.katjaas.nl/pitchshift/pitchshift.html
David.

@whale-av Awesome answer and great resource, cheers....will have to really soak that one in(link).

So then, effectively, avoiding the temporary change in pitch is not possible barring some temporary proportionate pitch shift countermeasure? (its the only thing that occurs to me).

Thanks a million again...

@lovelovevideo I just read the op again and realized also that you said "avoiding the temporary change in pitch"............... and you meant when you change the chunk size rather than the precision......
Sorry!...... I was carried away by joyful memories!
Yes, you can solve that. The solution is in the text comment of B12.sampler.transpose.........
David.

@whale-av Haha, no worries...I love your informative responses...

Cheers, will look into it now..