chore: increase default volume to 70 and switch play mode to stereo L/R split

verify_sync.py

@@ -423,7 +423,7 @@ class VerifyWindow(QtWidgets.QMainWindow):
 
         ctrl.addWidget(QtWidgets.QLabel("Play:"))
         self.play_mode = QtWidgets.QComboBox()
-        self.play_mode.addItems(["A+B mix", "A only", "B only"])
+        self.play_mode.addItems(["A left, B right", "A only", "B only"])
         self.play_mode.setCurrentIndex(0)
         self.play_mode.setFixedWidth(90)
         ctrl.addWidget(self.play_mode)
@@ -599,15 +599,15 @@ class VerifyWindow(QtWidgets.QMainWindow):
         vol_b = self.vol_b_slider.value() / 100.0
 
         mode = self.play_mode.currentIndex()
-        if mode == 0:  # A+B mix
+        if mode == 0:  # A left, B right
             ml = min(len(a_seg), len(b_seg))
-            mix = (a_seg[:ml] * vol_a + b_seg[:ml] * vol_b) / 2.0
+            stereo = np.column_stack([a_seg[:ml] * vol_a, b_seg[:ml] * vol_b])
         elif mode == 1:  # A only
-            mix = a_seg * vol_a
+            stereo = np.column_stack([a_seg * vol_a, np.zeros_like(a_seg)])
         else:  # B only
-            mix = b_seg * vol_b
+            stereo = np.column_stack([np.zeros_like(b_seg), b_seg * vol_b])
 
-        self.audio_player.play(mix, self.sr)
+        self.audio_player.play(stereo, self.sr)
         self.playing_a_b = True
         self.btn_play.setText("Pause")