refactor: remove Play L/R button, route A/B to stereo channels

sync_audio_test.py

@@ -269,7 +269,6 @@ class SyncWindow(QtWidgets.QMainWindow):
         self.btn_play_a = QtWidgets.QPushButton("Play A")
         self.btn_play_b = QtWidgets.QPushButton("Play B+lag")
         self.btn_play_mix = QtWidgets.QPushButton("Play Mix")
-        self.btn_play_split = QtWidgets.QPushButton("Play L/R")
         self.btn_stop = QtWidgets.QPushButton("Stop")
 
         ctr2.addWidget(QtWidgets.QLabel("Duration:"))
@@ -282,10 +281,10 @@ class SyncWindow(QtWidgets.QMainWindow):
         self.play_dur.setMaximumWidth(80)
         ctr2.addWidget(self.play_dur)
 
-        for b in [self.btn_play_a, self.btn_play_b, self.btn_play_mix, self.btn_play_split, self.btn_stop]:
+        for b in [self.btn_play_a, self.btn_play_b, self.btn_play_mix, self.btn_stop]:
             ctr2.addWidget(b)
         if not HAS_SD:
-            for b in [self.btn_play_a, self.btn_play_b, self.btn_play_mix, self.btn_play_split, self.btn_stop]:
+            for b in [self.btn_play_a, self.btn_play_b, self.btn_play_mix, self.btn_stop]:
                 b.setEnabled(False)
                 b.setToolTip("sounddevice not installed — run make install (optional)")
             ctr2.addWidget(QtWidgets.QLabel("(sounddevice missing — playback disabled)"))
@@ -308,7 +307,6 @@ class SyncWindow(QtWidgets.QMainWindow):
         self.btn_play_a.clicked.connect(lambda: self.play("a"))
         self.btn_play_b.clicked.connect(lambda: self.play("b"))
         self.btn_play_mix.clicked.connect(lambda: self.play("mix"))
-        self.btn_play_split.clicked.connect(lambda: self.play("split"))
         self.btn_stop.clicked.connect(self.stop_play)
 
         self.update_labels()
@@ -509,15 +507,17 @@ class SyncWindow(QtWidgets.QMainWindow):
         try:
             sd.stop()
             if which == "a":
-                sd.play(a_seg, samplerate=sr)
+                # A on left, silence on right
+                stereo = np.column_stack([a_seg, np.zeros_like(a_seg)])
+                sd.play(stereo, samplerate=sr)
             elif which == "b":
-                sd.play(b_seg, samplerate=sr)
+                # Silence on left, B on right
+                stereo = np.column_stack([np.zeros_like(b_seg), b_seg])
+                sd.play(stereo, samplerate=sr)
             elif which == "mix":
-                mix = (a_seg + b_seg) / 2.0
-                sd.play(mix, samplerate=sr)
-            elif which == "split":
-                # A on left, B on right
-                stereo = np.column_stack([a_seg, b_seg])
+                # A on left, B on right (stereo split)
+                ml = min(len(a_seg), len(b_seg))
+                stereo = np.column_stack([a_seg[:ml], b_seg[:ml]])
                 sd.play(stereo, samplerate=sr)
         except Exception as e:
             print(f"playback failed {e}", file=sys.stderr)