Add granular logging for frame processing and ffmpeg

inference.py

@@ -1309,6 +1309,7 @@ def run_inference(
         except Exception as e:
             logging.exception("Writer loop failed")
         finally:
+            logging.info("Writer loop finished. Wrote %d frames (target %d)", next_idx, total_frames)
             writer_finished = True
 
     writer_thread = Thread(target=writer_loop, daemon=True)
@@ -1332,6 +1333,8 @@ def run_inference(
             queue_in.put((frames_fed, frame)) # Blocks if full
             frames_fed += 1
             
+        logging.info("Feeder finished. Fed %d frames (expected %d)", frames_fed, total_frames)
+
         # Update total_frames to actual count so writer knows when to stop
         if frames_fed != total_frames:
             logging.info("Updating total_frames from %d to %d (actual fed)", total_frames, frames_fed)

utils/video.py

@@ -50,7 +50,11 @@ def _transcode_with_ffmpeg(src_path: str, dst_path: str) -> None:
     ]
     process = subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, check=False)
     if process.returncode != 0:
-        raise RuntimeError(process.stderr.decode("utf-8", errors="ignore"))
+        err_msg = process.stderr.decode("utf-8", errors="ignore")
+        logging.error("ffmpeg failed with code %d: %s", process.returncode, err_msg)
+        raise RuntimeError(err_msg)
+    else:
+        logging.info("ffmpeg success")
 
 
 def write_video(frames: List[np.ndarray], output_path: str, fps: float, width: int, height: int) -> None: