[PD] minimum delay time for delread4~

[Orm Finnendahl]

Hi,

 the help of delread4~ states the "delay time is at least one sample",
but it seems the lower limit is one block (and the lowest blocksize I
can use on linux seems to be 64 samples). I assume this is related to
the dsp scheduling order introducing one sample block latency.

The pd sources (d_delay.c) suggests to me that latency compensation in
the signal chain is taken care of, but I'm hitting a wall on my
machine. For a flanger-like application this means the highest
obtainable frequency here is 689 Hz at 44100 samplerate, which limits
its usability.

Attached is a patch to demonstrate the highest obtainable frequency
(here it is somewhere around f'' or Midi 78).

Can someone check whether this is a general problem or it is only on
my machine? I tested with newest pd (0.52) and 0.50.

--
Orm
-------------- next part --------------
#N canvas 907 238 618 640 12;
#X obj 30 325 delwrite~ \$0-test 2000;
#X obj 14 160 noise~;
#X obj 48 212 *~;
#X obj 66 161 line~;
#X msg 66 110 0.1 \, 0 30;
#X obj 51 291 dac~;
#X obj 169 191 delread4~ \$0-test 200;
#X obj 180 393 *~;
#X obj 311 242 line~;
#X msg 401 309 \$1 50;
#X obj 399 130 vsl 15 128 0 0.9999 0 0 empty empty empty 0 -9 0 10
#fcfcfc #000000 #000000 0 1;
#X floatatom 399 266 5 0 0 0 - - - 0;
#X floatatom 169 117 0 0 1000 0 - - - 0;
#X obj 169 167 line~;
#X msg 399 79 0 \, 0.999 500;
#X obj 399 103 line;
#X obj 65 82 bng 15 250 50 0 empty empty empty 17 7 0 10 #fcfcfc #000000
#000000;
#X text 91 80 <- click to test;
#X obj 169 142 pack 0 100;
#X obj 399 55 bng 15 250 50 0 empty empty empty 17 7 0 10 #fcfcfc #000000
#000000;
#X text 421 53 <- clear delay;
#X text 204 116 delay time in ms;
#X obj 554 11 loadbang;
#X msg 554 35 \; pd dsp 1;
#X connect 1 0 2 0;
#X connect 2 0 0 0;
#X connect 2 0 5 0;
#X connect 2 0 5 1;
#X connect 3 0 2 1;
#X connect 4 0 3 0;
#X connect 6 0 7 0;
#X connect 7 0 0 0;
#X connect 7 0 5 0;
#X connect 7 0 5 1;
#X connect 8 0 7 1;
#X connect 9 0 8 0;
#X connect 10 0 11 0;
#X connect 11 0 9 0;
#X connect 12 0 18 0;
#X connect 13 0 6 0;
#X connect 14 0 15 0;
#X connect 15 0 10 0;
#X connect 16 0 4 0;
#X connect 18 0 13 0;
#X connect 19 0 14 0;
#X connect 22 0 23 0;
#X connect 22 0 19 0;