[sc-users] buffer sync question...

[Travis Weller]

All,

I might be missing something, but I think I've scoured help files and 
mailing list archives long enough. I'm still getting the hang of SC.

I have a SynthDef that loops sections of a buffer (the boundaries of 
which are selected and manipulated via a GUI). That much works great. 
I'm using Lance Putnam's LoopBuf because some of the stuff I'm doing 
with the buffer is difficult to accomplish with PlayBuf.

My problem comes in when I want to overdub in that buffer in 
realtime. So far, I'm been able to record into the section of the 
buffer that I'm playing back, but the recording point is often 
different from the playback point which makes it difficult to predict 
the results of overdubbing. Below, you will find the SynthDef and 
some messages extracted from the classes I'm writing. I can send both 
classes, but they are long and I figured this would get the point 
across.

Please note that in some cases the playback from LoopBuf is jumping 
around quite a bit. In those cases, there is no need for record and 
playback to be in sync, and the SynthDef below works fine for those 
situations. However, in other cases, I would like to emulate the old 
"tape loop" effect (read: Echoplex Digital Pro) where record and 
playback happen at the same point in the buffer with variable 
regeneration. It would work fine to maintain this state on the lang 
side (ie. switching in and out of 'sync' mode). I'm not quite sure 
how to get there using this setup.

Any ideas?

Thanks in advance,
Travis

--

SynthDef(\tcwloopBuf,{
	arg	buffer,
		rate = 1,
		glide = 0,
		gate = 1,
		t_loopGate = 1,
		startPos = 0,
		startLoop,
		endLoop,
		ipol = 4,
		envlen = 0.01,
		rec = 0,
		regenLevel = 1,
		amp = 1.0;
	var env, signal, phase;
	rate = Lag.kr(rate, glide);
	env = EnvGen.ar(Env.asr(envlen, 1, envlen), gate, doneAction: 2);
	signal = LoopBuf.ar(1,buffer, BufRateScale.kr(buffer) * rate,
		(1 - t_loopGate), startPos, startLoop, endLoop, ipol);
	phase = Phasor.ar(buffer, BufRateScale.kr(buffer), startLoop, endLoop);
	BufWr.ar((AudioIn.ar(1) * rec) + ((BufRd.ar(1, buffer, phase) 
* regenLevel)),
		buffer, phase);
	Out.ar(0, ((signal * env) * amp).dup);
}).send(server);

// ...and some out-of-context examples of messages...

server.sendMsg("/s_new", \tcwloopBuf, this.nodeID, 0, 0,
	\buffer, bufnum,
	\startPos, startArg,
	\startLoop, startArg,
	\endLoop, endArg,
	\t_loopGate, 1,
	\envlen, 2

server.sendMsg("/n_set", this.nodeID,
	\startPos, resetPos,
	\t_loopGate, 1

server.sendMsg("/n_set", this.nodeID,
	\startPos, mySelectionStart,
	\startLoop, mySelectionStart,
	\endLoop, (mySelectionStart + mySelectionSize),
	\t_loopGate, 1

server.sendMsg("/n_set", this.nodeID, \rec, 1, \regenLevel, 0.5);

server.sendMsg("/n_set", this.nodeID, \rec, 0, \regenLevel, 1);

server.sendMsg("/n_set", this.nodeID,
	\startPos, resetPos,
	\t_loopGate, 1

server.sendMsg("/n_set", this.nodeID, \gate, -1);