ffmpeg fix

cht/stream/ffmpeg.py

@@ -72,27 +72,23 @@ def extract_scene_frames(input_path, output_dir, scene_threshold=0.10,
     meaningfully vs the previous frame. No periodic fallback so static content
     produces no spurious frames.
 
-    start_time/duration: applied via the select filter expression (NOT as -ss/-t
-    input options, which break h264 scene detection on MKV).
+    Uses -ss input seeking for O(1) startup regardless of file size.
+    pts_time in showinfo output is relative to the seek point.
     Returns (stdout, stderr) as decoded strings for timestamp parsing.
     """
     scene_expr = f"gt(scene,{scene_threshold})"
 
-    # Add time range filter if specified (incremental processing)
-    time_conditions = []
-    if start_time > 0:
-        time_conditions.append(f"gte(t,{start_time})")
+    # With -ss input seeking, t starts at 0 from the seek point.
+    # Only need end boundary (duration), start is handled by -ss.
     if duration is not None:
-        time_conditions.append(f"lte(t,{start_time + duration})")
+        scene_expr = f"({scene_expr})*lte(t,{duration})"
 
-    if time_conditions:
-        time_filter = "*".join(time_conditions)
-        select_expr = f"({scene_expr})*{time_filter}"
-    else:
-        select_expr = scene_expr
+    input_kwargs = {}
+    if start_time > 0:
+        input_kwargs["ss"] = start_time
 
-    stream = ffmpeg.input(str(input_path))
-    stream = stream.filter("select", select_expr).filter("showinfo")
+    stream = ffmpeg.input(str(input_path), **input_kwargs)
+    stream = stream.filter("select", scene_expr).filter("showinfo")
 
     output = (
         ffmpeg.output(

cht/stream/manager.py

@@ -68,6 +68,7 @@ class StreamManager:
         self._segment_offsets = {0: 0.0}  # segment_index → global_offset
         self.scene_threshold = SCENE_THRESHOLD
         self.readonly = False  # True when loaded from existing session
+        self.telemetry = None  # set by window after start
         log.info("Session: %s", session_id)
 
     @classmethod
@@ -306,6 +307,8 @@ class StreamManager:
 
     def _detect_scenes(self, start_time, end_time):
         """Run ffmpeg scene detection on a time range. Returns list of new frame entries."""
+        import time as _time
+        t0 = _time.monotonic()
         duration = end_time - start_time
         start_number = self._next_frame_number()
 
@@ -335,7 +338,8 @@ class StreamManager:
                 continue
             pts_match = re.search(r"pts_time:\s*([\d.]+)", line)
             if pts_match:
-                pts_time = float(pts_match.group(1))
+                # pts_time is relative to -ss seek point, add start_time for local offset
+                pts_time = float(pts_match.group(1)) + start_time
                 frame_id = f"F{frame_num:04d}"
                 frame_path = self.frames_dir / f"{frame_id}.jpg"
                 if frame_path.exists():
@@ -350,6 +354,20 @@ class StreamManager:
                 frame_num += 1
 
         index_path.write_text(json.dumps(index, indent=2))
+
+        elapsed_ms = (_time.monotonic() - t0) * 1000
+        tel = getattr(self, "telemetry", None)
+        if tel:
+            tel.metric("scene_detection", {
+                "start": start_time, "end": end_time,
+                "duration": duration,
+                "frames_found": len(new_frames),
+                "total_frames": len(index),
+                "threshold": self.scene_threshold,
+                "elapsed_ms": round(elapsed_ms),
+                "file_duration": self._estimate_safe_duration() or 0,
+            })
+
         return new_frames
 
     def capture_now(self, on_new_frames=None):