Using BufChannels throws ERROR

Questions Code Review
1

I thought I can retrieve the number of channels with the UGen BufChannels like this:

(
b = Buffer.read(s, Platform.resourceDir +/+ "sounds/a11wlk01.wav");
{
	PlayBuf.ar(BufChannels.kr(b), b)
}.play
)

But this throws this error:

ERROR: Non Boolean in test.
RECEIVER:
Instance of BinaryOpUGen

Can any one spot the problem in my code?

2

Some arguments to Ugens will accept other Ugens, some only accept static data - that is, data known when the synthdef is compiled. The channel count of everything must be static - in other words, it must a language side, not server side.

BufChannels.kr is a dynamic (Ugen/server-side) way of getting the number of channels, what you want to the language side (static) way - b.numChannels.

However you will get sync problems here. Do this instead:

(
s.waitFotBoot {
   var buffer = Buffer.read(s, Platform.resourceDir +/+ "sounds/a11wlk01.wav");
   s.sync;
   { PlayBuf.ar(buffer.numChannels, buffer) }.play
}
)
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3

So if I understood you correctly BufChannels is not supposed to be used as an argument to PlayBuf. How can I know (for any ugen) which arguments are supposed to be static, which not? Is this documented any where?

4

Check out the help doc on PlayBuf.

numChannels
Number of channels that the buffer will be. This must be a fixed integer. The architecture of the SynthDef cannot change after it is compiled.

Meaning the value should be static with respect to the synth def.

1 Like