use the playbackRate when computing the offset of a synced player

fixes #349

Tone/source/Player.js

@@ -198,8 +198,16 @@ Tone.Player.prototype._start = function(startTime, offset, duration){
 
 	//compute the values in seconds
 	offset = this.toSeconds(offset);
+	
+	//if it's synced, it should factor in the playback rate for computing the offset
+	if (this._synced){
+		offset *= this._playbackRate;
+	}
+
+	//compute the duration which is either the passed in duration of the buffer.duration - offset
 	var computedDuration = Tone.defaultArg(duration, Math.max(this._buffer.duration - offset, 0));
 	computedDuration = this.toSeconds(computedDuration);
+
 	//scale it by the playback rate
 	computedDuration = computedDuration / this._playbackRate;
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "tone",
-  "version": "13.7.0",
+  "version": "13.8.0",
   "description": "A Web Audio framework for making interactive music in the browser.",
   "main": "build/Tone.js",
   "files": [

test/source/Player.js

@@ -450,6 +450,24 @@ describe("Player", function(){
 			});
 		});
 
+		it("starts at the correct position when Transport is offset and playbackRate is not 1", function(){
+			return Offline(function(Transport){
+				//make a ramp between 0-1
+				var ramp = new Float32Array(Math.floor(Tone.context.sampleRate * 0.3));
+				for (var i = 0; i < ramp.length; i++){
+					ramp[i] = (i / (ramp.length));
+				}
+				var buff = Buffer.fromArray(ramp);
+				var player = new Player(buff).toMaster();
+				player.playbackRate = 0.5;
+				player.sync().start(0);
+				//start halfway through
+				Transport.start(0, 0.15);
+			}, 0.05).then(function(buffer){
+				expect(buffer.getValueAtTime(0)).to.be.closeTo(0.25, 0.01);
+			});
+		});
+
 		it("starts with an offset when synced and started after Transport is running", function(){
 			return Offline(function(Transport){
 				var ramp = new Float32Array(Math.floor(Tone.context.sampleRate * 0.3));