Why does playing on channels higher then 0 and 1 saturate?

Questions
1

I’m new to SC, so please forgive the dumb question.
I’m trying to send audio to my DAW (Bitwig) through ASIO Link Pro.
Everything works fine if I use output channels 0 and 1, but when I set Out.ar to use higher channels it sorts of breaks ASIO Link. It doesn’t happen with other audio applications (for example VCV Rack) so I suspect something strange happens between SC and ASIO Link Pro.

As you can see in the GIF below the channel never returns to 0 on the side of Bitwif ASIO server. If I send a sine wave with constant amplitude the channel becomes, and remains, red (completely saturated).

s.options.device_("ASIO : ASIO Link Pro");
s.options.numOutputBusChannels=4;
s.options.numInputBusChannels=0;
s.reboot;

SynthDef(\trigtest2, {arg freq, amp, dur=1, t_trig;
	var signal, env;
	env = EnvGen.ar(Env.perc(0.01, dur, amp), t_trig, doneAction:0);
	signal = SinOsc.ar(freq) * env;
	Out.ar(3, signal);
}).add

a = Synth(\trigtest2, [\freq, 333, \amp, 1, \t_trig, 1]);

bitwig_asiolinkpro
bitwig_asiolinkpro1909×1068 416 KB

Again, this doesn’t happen on channel 0 and 1, and doesn’t happen when the same setup is used with other audio applications.
Am I using the other channels in SC the wrong way?

2

What’s not clear to me is why channel 4 in the scsynth.exe window does go down to 0 (so, ASIO Link is getting silence from the server) but it’s different in bitwig.

hjh

3

Exactly @jamshark70 this is what I’m wondering too… and everything works fine if I use chanells 0 and 1.

4

My point was, if scsynth is providing 0s for silence and ASIO Link is passing nonzero values to Bitwig – I do hear you that it isn’t happening with other software but… the point at which silence is becoming non-silence appears to be outside of SC.

Btw what is the sample rate that scsynth is reporting when booting the server? That’s not visible in your GIF.

hjh

5

the sample rate is 44100, which is the same as the sample rate reported by my Focusrite ASIO driver (that’s being used by ASIO Pro Link).

Requested devices:
  Out (matching device found):
  - ASIO : ASIO Link Pro


Booting with:
  Out: ASIO : ASIO Link Pro
  Sample rate: 44100.000
  Latency (in/out): 0.012 / 0.012 sec
SC_AudioDriver: sample rate = 44100.000000, driver's block size = 64
SuperCollider 3 server ready.
Requested notification messages from server 'localhost'
localhost: server process's maxLogins (1) matches with my options.
localhost: keeping clientID (0) as confirmed by server process.
Shared memory server interface initialized
server 'localhost' disconnected shared memory interface
Shared memory server interface initialized
6

Asio Link Pro is still a mistery to me. Now everything seems to work fine without any apparent change…

If anyone knows what the Route OUT to IN is supposed to do please let me know. I turned it on/off several times both from the Asio Link Pro Tool and the SC client, and nothing apparently happens. I went back to the initial configuration in the end… and now the buffer goes to zero also on the server (Bitwig) side.