I’ve been using play~ to play back sounds loaded into a buffer~, and
have discovered that the sound quality seems to be a problem. The
playback sounds like it is being slightly ring-modulated, or that it is
showing the effects of a sample-rate mismatch. In any case, to test out
the problem, I tried playing the buffer back with wave~, and the issue
did not occur. I am driving play~ with a line~ object, and thought that
that might also be the problem, so I replaced the line~ with a phasor~
but the problem persisted.

The attached patch demonstrates the issue. Load a 1 minute stereo sample
in the buffer, and then turn on the DAC. Both play~ and wave~ will
playback simultaneously, but you can x-fade between the two to hear the
sound quality difference. Any insight as to why this might be happening
and what I could do to prevent it would be greatly appreciated. Many
thanks in advance.

Best,

Peter Traub

Best,

Peter

max v2;
#N vpatcher 275 65 876 807;
#P window setfont “Sans Serif” 9.;
#P window linecount 1;
#P hidden message 181 85 20 196617 50;
#P hidden newex 72 31 48 196617 loadbang;
#P message 354 89 55 196617 0.016666;
#P flonum 179 204 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P flonum 290 204 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P message 450 83 17 196617 0.;
#P hidden newex 77 248 35 196617 *~ 1.;
#P hidden flonum 172 249 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P hidden newex 123 246 35 196617 *~ 1.;
#P hidden newex 147 210 27 196617 + 1.;
#P hidden newex 147 187 34 196617 * -1.;
#P hidden newex 342 251 35 196617 *~ 1.;
#P hidden newex 295 251 35 196617 *~ 1.;
#P hidden newex 235 198 40 196617 / 100.;
#P user hslider 181 172 18 128 101 1 0 0;
#P newex 354 113 46 196617 phasor~;
#P newex 354 151 108 196617 wave~ buf 0 60000 2;
#P user ezdac~ 221 550 265 583 0;
#P user meter~ 196 390 213 514 50 0 168 0 103 103 103 255 153 0 255 0 0
217 217 0 153 186 0 12 3 3 3 3;
#P user meter~ 283 390 300 514 50 0 168 0 103 103 103 255 153 0 255 0 0
217 217 0 153 186 0 12 3 3 3 3;
#P user gain~ 254 391 24 100 158 0 1.071519 7.94321 10.;
#P user gain~ 221 391 24 100 158 0 1.071519 7.94321 10.;
#P newex 72 145 61 196617 play~ buf 2;
#P message 72 84 86 196617 0 , 60000 60000;
#P newex 72 111 32 196617 line~;
#P message 386 395 30 196617 read;
#P newex 386 423 103 196617 buffer~ buf 60000 2;
#P comment 155 153 194 196617 x-fade between play~ and wave~ objects;
#P window setfont “Sans Serif” 12.;
#P window linecount 2;
#P comment 387 355 158 196620 read a 1 minute stereo sample in here first;
#P window linecount 7;
#P comment 13 392 174 196620 Directions: read in a one minute stereo
sample to buffer. start DAC. playback should begin immediately. crossade
between play~ and wave~ objects to hear sound quality difference.;
#P hidden connect 28 0 6 0;
#P connect 6 0 5 0;
#P connect 5 0 7 0;
#P hidden connect 7 0 23 0;
#P hidden connect 20 0 23 1;
#P hidden connect 7 1 21 0;
#P hidden connect 16 0 19 0;
#P hidden connect 19 0 20 0;
#P hidden connect 20 0 21 1;
#P hidden connect 20 0 22 0;
#P hidden connect 20 0 26 0;
#P hidden connect 28 0 29 0;
#P hidden connect 29 0 15 0;
#P hidden connect 8 0 11 0;
#P hidden connect 17 0 8 0;
#P hidden connect 23 0 8 0;
#P connect 8 0 12 0;
#P hidden connect 15 0 16 0;
#P hidden connect 8 1 9 0;
#P hidden connect 18 0 9 0;
#P hidden connect 21 0 9 0;
#P connect 9 0 12 1;
#P hidden connect 9 0 10 0;
#P hidden connect 16 0 25 0;
#P hidden connect 13 0 17 0;
#P hidden connect 16 0 17 1;
#P hidden connect 13 1 18 0;
#P hidden connect 28 0 27 0;
#P connect 27 0 14 0;
#P connect 14 0 13 0;
#P hidden connect 16 0 18 1;
#P connect 4 0 3 0;
#P connect 24 0 14 1;
#P pop;

I tried the patch you sent and couldn’t reproduce the effect.
Sometimes with long sound files there is a problem with the bit depth
of the playback signal that results in playback degradation, but “ring
modulated” isn’t really how I would describe the sound… anyway, you
could try Joshua’s hi-res objects
(http://cycling74.com/twiki/bin/view/Share/JoshuaKitClayton) to see if
that fixes your problem. Otherwise the only thing I can suggest is to
make your one minute sound file available somewhere on the web so that
we can test that.

Ben

Yes, I suppose bit-depth degradation might be a better description of
the sound, and it does happen over time. In my actual application, I’m
using a 10 min. buffer and not the 1 min. one in my test file, so the
problem is even more accute. In any case, I’ve uploaded a 1 min. test
sound to the web that you can download and hear the issue with. It is at:

http://www.people.virginia.edu/~pmt4u/testsnd.aif

After about 15 seconds of playback in the test patch, try hard x-fading
between the play~ and wave~ output (i.e., listen fully to one and then
the other), and the difference between the two should become quite
audible. It becomes more audible over time. I will check out the hi-res
objects you suggest, but I’m curious why this problem exists with play~
in the first place and if there is some sort of workaround? Many thanks.

Best,

Peter

Peter McCulloch

Upon reading the docs for the hi.res objects, it seems that it is a bit
resolution issue. I have replaced my core playback module, that used
line~, play~, and pong~ with the hi.res objects hr.line~, hr.play~, and
hr.wrap~. They appear to do the trick in both the test application I
posted to the list and my main application. However, they do appear to
incur the cost of higher CPU utilization, meaning my poly~ instrument
that uses these playback objects can’t have as many instances of them.

Btw, I did try playing with the interp modes for wave~, but interp 0,
while giving noticeably diminished quality, did not give the same sort
of effect as I was hearing with play~. Many thanks.

Best,

Peter

Stefan

–

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Stefan Tiedje
Klanggestalter
Electronic Composition
&
Improvisation

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