fix: skip mpv gracefully when video file unavailable

verify_sync.py

@@ -484,6 +484,10 @@ class VerifyWindow(QtWidgets.QMainWindow):
 
     def _start_mpv(self):
         """Launch mpv in its own window, controlled via IPC socket."""
+        if not self.video_path or not os.path.exists(self.video_path):
+            print(f"mpv skipped: no video file available", file=sys.stderr)
+            self.info_label.setText(self.info_label.text() + " | mpv: unavailable")
+            return
         print(f"Launching mpv: {self.video_path}")
         try:
             self.mpv = MpvController(self.video_path)
@@ -776,8 +780,6 @@ def main():
             stem_b = os.path.splitext(os.path.basename(video_b))[0]
             wav_b = os.path.join(out_dir_extract, f"{stem_b}_audio.wav")
 
-        if not video_a or not os.path.exists(video_a):
-            print(f"ERROR: video A not found: {video_a}", file=sys.stderr); sys.exit(1)
         if not wav_a or not os.path.exists(wav_a):
             print(f"ERROR: wav A not found: {wav_a}", file=sys.stderr); sys.exit(1)
         if not wav_b or not os.path.exists(wav_b):
@@ -790,8 +792,13 @@ def main():
             if os.path.exists(extracted_video):
                 video_path = extracted_video
                 print(f"Using extracted video: {video_path}")
+            elif video_a and os.path.exists(video_a):
+                pass  # use original
             else:
-                print(f"WARNING: extracted video not found ({extracted_video}), using original", file=sys.stderr)
+                print(f"WARNING: no video found (extracted or original) for A, mpv will be unavailable", file=sys.stderr)
+        else:
+            if not video_a or not os.path.exists(video_a):
+                print(f"ERROR: video A not found: {video_a}", file=sys.stderr); sys.exit(1)
         temp_dir = None
         cache_key_a = None
         cache_key_b = None