Results with latency tests

[Martin Marier]

Hello,

	I've been trying to perform a latency test with PD.
I use the PD 0.32 for linux (unpatched kernel)with ALSA drivers
0.5.9 for my M-audio Delta-66.
To test the latency I use a patch that sends an
impulse to an output that is looped to an input.
I've tested both S/PDIF and analog I/O.
The patch is joined.


	Here are a few results I get :
(-rt and -alsa are also there in my .pdrc)

-audiobuf	latency_with_s/pdif	latency_with_analog	conversion_time
--------------------------------------------------------------------------------
20		37.7324			39.1837			1.45125
19		37.7324			39.1837			1.45125
18		37.7324			39.1837			1.45125
17		37.7324			39.1837			1.45125
16		20.3175			21.7687			1.45125
15		20.3175			21.7687			1.45125
14		24.6712			26.1224			1.45125
13		27.5737			29.0249			1.45125
12		23.22			24.6712			1.45125
11		20.3175			21.7687			1.45125
10		23.22			24.6712			1.45125
9		21.7687			23.22			1.45125
8		23.22			24.6712			1.45125


	There must be something I don't understand.
Can anyone explain these results ?  Does my test
make sense ?
Thanks

Martin Marier


(here's the patch)


#N canvas 468 248 505 403 10;
#X graph graph2 0 -1 3 1 399 396 499 346;
#X array click 4 float;
#X pop;
#X msg 399 309 \; click resize 4 \; click 0 1 0 0 0;
#X obj 37 48 tabplay~ click;
#X msg 37 28 bang;
#X obj 37 67 *~ 0.9;
#X obj 126 48 threshold~ 0.4 0 40 0;
#X obj 101 66 timer;
#X text 36 13 latency with analog;
#X obj 37 86 dac~ 1;
#X obj 126 29 adc~ 1;
#X obj 34 154 tabplay~ click;
#X msg 34 134 bang;
#X obj 34 173 *~ 0.9;
#X obj 123 154 threshold~ 0.4 0 40 0;
#X obj 98 172 timer;
#X text 33 119 latency with s/pdif;
#X obj 34 192 dac~ 10;
#X obj 123 135 adc~ 10;
#X obj 399 289 loadbang;
#X obj 98 193 print latency_with_s/pdif;
#X obj 101 87 print latency_with_analog;
#X obj 326 169 print conversion;
#X obj 347 78 -;
#X connect 2 0 4 0;
#X connect 3 0 2 0;
#X connect 3 0 6 0;
#X connect 4 0 8 0;
#X connect 5 0 6 1;
#X connect 6 0 20 0;
#X connect 6 0 22 0;
#X connect 9 0 5 0;
#X connect 10 0 12 0;
#X connect 11 0 10 0;
#X connect 11 0 14 0;
#X connect 12 0 16 0;
#X connect 13 0 14 1;
#X connect 14 0 19 0;
#X connect 14 0 22 1;
#X connect 17 0 13 0;
#X connect 18 0 1 0;
#X connect 22 0 21 0;