fix: pre-transcode video to H.264 and try VAAPI encoder

Makefile

@@ -84,7 +84,7 @@ sync:
 	@if [ -x $(PY) ]; then $(PY) apply_sync.py --config $(CONFIG) --lag $(LAG); else python3 apply_sync.py --config $(CONFIG) --lag $(LAG); fi
 
 verify:
-	@if [ -x $(PY) ]; then QT_QPA_PLATFORM=xcb QT_FFMPEG_DECODING_HW_DEVICE_TYPES=vaapi QT_XCB_GL_INTEGRATION=xcb_egl QT_STYLE_OVERRIDE=Fusion $(PY) verify_sync.py --config $(CONFIG) --lag $(LAG); else QT_QPA_PLATFORM=xcb QT_FFMPEG_DECODING_HW_DEVICE_TYPES=vaapi QT_XCB_GL_INTEGRATION=xcb_egl QT_STYLE_OVERRIDE=Fusion python3 verify_sync.py --config $(CONFIG) --lag $(LAG); fi
+	@if [ -x $(PY) ]; then QT_STYLE_OVERRIDE=Fusion $(PY) verify_sync.py --config $(CONFIG) --lag $(LAG); else QT_STYLE_OVERRIDE=Fusion python3 verify_sync.py --config $(CONFIG) --lag $(LAG); fi
 
 ast:
 	@AUDIO_A=$$(python3 -c "import tomllib; c=tomllib.load(open('config.toml','rb')); print(c['extract'].get('file_a',''))" 2>/dev/null); \
@@ -100,7 +100,7 @@ ast:
 	else \
 		echo "=> extracted wavs exist ($$OUT/$${STEM_A}_audio.wav, $$OUT/$${STEM_B}_audio.wav), skipping extract"; \
 	fi
-	@if [ -x $(PY) ]; then QT_QPA_PLATFORM=xcb QT_FFMPEG_DECODING_HW_DEVICE_TYPES=vaapi QT_XCB_GL_INTEGRATION=xcb_egl QT_STYLE_OVERRIDE=Fusion $(PY) sync_audio_test.py --config $(CONFIG); else QT_QPA_PLATFORM=xcb QT_FFMPEG_DECODING_HW_DEVICE_TYPES=vaapi QT_XCB_GL_INTEGRATION=xcb_egl QT_STYLE_OVERRIDE=Fusion python3 sync_audio_test.py --config $(CONFIG); fi
+	@if [ -x $(PY) ]; then QT_STYLE_OVERRIDE=Fusion $(PY) sync_audio_test.py --config $(CONFIG); else QT_STYLE_OVERRIDE=Fusion python3 sync_audio_test.py --config $(CONFIG); fi
 
 clean:
 	rm -rf $(VENV) __pycache__ .pytest_cache

verify_sync.py

@@ -27,13 +27,6 @@ import numpy as np
 
 warnings.filterwarnings("ignore", category=RuntimeWarning, module="pyqtgraph")
 
-# Force X11/xcb on Wayland without EGL — QVideoWidget can't render without it
-for k, v in {"QT_QPA_PLATFORM": "xcb",
-             "QT_STYLE_OVERRIDE": "Fusion",
-             "QT_FFMPEG_DECODING_HW_DEVICE_TYPES": "vaapi",
-             "QT_XCB_GL_INTEGRATION": "xcb_egl"}.items():
-    os.environ.setdefault(k, v)
-
 try:
     import tomllib
 except ModuleNotFoundError:
@@ -117,24 +110,33 @@ def extract_audio_from_mkv(mkv_path: str, stream_index: int, out_wav: str, sr: i
 
 def transcode_to_h264_sdr(src: str, dst: str, duration: float = 0) -> bool:
     """Transcode video to H.264 SDR MP4 for QMediaPlayer compatibility.
-    If duration > 0, only transcode that many seconds."""
+    Tries VAAPI hardware encoding first, falls back to CPU x264."""
-    cmd = ["ffmpeg", "-y", "-i", src]
+    for encoder in ["h264_vaapi", "libx264"]:
-    if duration > 0:
+        cmd = ["ffmpeg", "-y", "-i", src]
-        cmd += ["-t", f"{duration:.3f}"]
+        if duration > 0:
-    cmd += [
+            cmd += ["-t", f"{duration:.3f}"]
-        "-map", "0:v:0",
+        cmd += ["-map", "0:v:0", "-an"]
-        "-an",
+        if encoder == "h264_vaapi":
-        "-c:v", "libx264", "-preset", "ultrafast", "-crf", "20",
+            cmd += ["-vaapi_device", "/dev/dri/renderD128",
-        "-pix_fmt", "yuv420p",
+                    "-vf", "format=nv12,hwupload",
-        "-vf", "scale=trunc(iw/2)*2:trunc(ih/2)*2",
+                    "-c:v", "h264_vaapi", "-qp", "20"]
-        "-movflags", "+faststart",
+        else:
-        dst,
+            cmd += ["-c:v", "libx264", "-preset", "ultrafast", "-crf", "20",
-    ]
+                    "-pix_fmt", "yuv420p",
-    try:
+                    "-vf", "scale=trunc(iw/2)*2:trunc(ih/2)*2"]
-        r = subprocess.run(cmd, capture_output=True, timeout=600)
+        cmd += ["-movflags", "+faststart", dst]
-        return r.returncode == 0 and os.path.exists(dst)
+        try:
-    except Exception:
+            r = subprocess.run(cmd, capture_output=True, timeout=600)
-        return False
+            if r.returncode == 0 and os.path.exists(dst):
+                print(f"  encoded with {encoder}")
+                return True
+            print(f"  {encoder} failed, trying next...", file=sys.stderr)
+            if os.path.exists(dst):
+                os.remove(dst)
+        except Exception:
+            if os.path.exists(dst):
+                os.remove(dst)
+    return False
 
 
 def apply_lag(a: np.ndarray, b: np.ndarray, lag_samples: int) -> tuple[np.ndarray, np.ndarray]:
@@ -406,9 +408,6 @@ class VerifyWindow(QtWidgets.QMainWindow):
         # Wait for media loaded to get actual duration
         self.media_player.durationChanged.connect(self._on_duration_changed)
 
-        # Handle video decode errors — transcode and retry
-        self.media_player.errorOccurred.connect(self._on_media_error)
-
     def _on_duration_changed(self, dur_ms):
         """QMediaPlayer reports actual video duration in ms."""
         vid_dur = dur_ms / 1000.0
@@ -427,30 +426,6 @@ class VerifyWindow(QtWidgets.QMainWindow):
             self.btn_play.setText("Play")
             self.audio_player.stop()
 
-    def _on_media_error(self, error, message):
-        """Handle video decode failure — transcode to H.264 and retry."""
-        if getattr(self, "_transcode_attempted", False):
-            print(f"Video error even after transcode: {message}", file=sys.stderr)
-            return
-        print(f"Video decode error ({error.name}): {message}", file=sys.stderr)
-        print("Attempting fallback: transcoding to H.264 SDR...", file=sys.stderr)
-        self._transcode_attempted = True
-
-        if self.temp_dir is None:
-            self.temp_dir = tempfile.mkdtemp(prefix="verify_sync_")
-        preview_path = os.path.join(self.temp_dir, "preview.mp4")
-        transcode_dur = 30.0 if self.mode == "short" else 0
-
-        if not transcode_to_h264_sdr(self.video_path, preview_path, transcode_dur):
-            print("Transcode also failed — video will remain black", file=sys.stderr)
-            return
-
-        # Reload with the transcoded file
-        self.video_path = preview_path
-        from PyQt6.QtCore import QUrl
-        self.media_player.setSource(QUrl.fromLocalFile(os.path.abspath(preview_path)))
-        print(f"Retrying with transcoded preview: {preview_path}")
-
     def _draw_waveforms(self):
         max_pts = 200_000 if self.mode == "full" else 80_000
 
@@ -688,6 +663,21 @@ def main():
                 print(f"WARNING: extracted video not found ({extracted_video}), using original", file=sys.stderr)
         temp_dir = None
 
+    # Always transcode to H.264 SDR — QMediaPlayer can't reliably decode
+    # HEVC HDR/DV, FFV1 yuv444p, or other exotic codecs
+    temp_dir = temp_dir or tempfile.mkdtemp(prefix="verify_sync_")
+    preview_path = os.path.join(temp_dir, "preview.mp4")
+    if not os.path.exists(preview_path):
+        transcode_dur = 30.0 if args.mode == "short" else 0
+        print(f"Transcoding to H.264 SDR ({'%.1fs' % transcode_dur if transcode_dur else 'full'})...")
+        if not transcode_to_h264_sdr(video_path, preview_path, transcode_dur):
+            print(f"ERROR: transcode failed", file=sys.stderr)
+            sys.exit(1)
+        print(f"Preview ready: {preview_path}")
+    else:
+        print(f"Using cached preview: {preview_path}")
+    video_path = preview_path
+
     print(f"Mode:    {args.mode}")
     print(f"Video:   {video_path}")
     print(f"WAV A:   {wav_a}")