Hi all,

I'm currently developping a beamforming array of 12 loudspeaker and a need to delay each input to change the angle of the directivity pattern. The problem is that these delays are very small ( around 0.005ms) and I would like to know if PD allows to deal with this order of magnitude and if yes, how? I tried with [delwrite] and [delread] but it looks like it doesn't work...

Thank you.

@SgtChipo Even if you reduce the block size you still need 64 samples for the codecs.... so total 64/44100x2=2.9ms. With a block size of 1 you could make a small delay, but you still need to wait to push it through the dac.
Someone more knowledgeable than me (many on this forum) might know how to shift the phase via fft though (.... the same thing).

@katjav 's site would be a good place to start..... http://www.katjaas.nl/home/home.html

I think you will be disappointed even if you achieve small delays in your patch. You will still have a minimum of 2.9ms from input to output on your computer, but maybe that is acceptable (as a delay in the processing) and as you actually need only the difference between 2 channels..... not overall....... then maybe..........but I am not sure that it is possible in Pd.....!?

Dedicated 1-bit dsp hardware and assembly language are the usual requirements....
David.

It's possible to delay by 1 sample without changing the block size using del write~ and delread~. (see the example G05.execution.order.pd in the docs)

However, to get a delay of .005 ms you would need a very large sample rate (200000).
If your output sample rate is fixed at a lower rate (less than 200,000), the best you can hope for is putting out samples at that lower rate, and maybe using lagrange interpolation via [vd~] to get values that are slightly phase-shifted from each other. I also have a hermite-spline delay line interpolator [vdhs~] in my lib

You can also use an FIR filter to interpolate using more samples than 4 (in this case using a windowed since function as an interpolator):
http://www.labbookpages.co.uk/audio/beamforming/fractionalDelay.html