Update app.py

app.py

@@ -195,29 +195,71 @@ except ImportError:
     print("[warn] mcap / mcap_protobuf not installed; abc-teleop conversion disabled.")
 
 
+# def convert_mcap_camera(mcap_path: str, topic: str, tmp_dir: str, label: str) -> str:
+#     """Extract one camera topic from mcap and encode to mp4. Returns output path."""
+#     temp_h264 = os.path.join(tmp_dir, f"{label}.h264")
+#     output    = os.path.join(tmp_dir, f"{label}.mp4")
+
+#     with open(temp_h264, "wb") as out:
+#         with open(mcap_path, "rb") as f:
+#             reader = make_reader(f, decoder_factories=[DecoderFactory()])
+#             for schema, channel, msg, decoded in reader.iter_decoded_messages():
+#                 if channel.topic != topic:
+#                     continue
+#                 out.write(decoded.data)
+
+#     subprocess.run(
+#         ["ffmpeg", "-y",
+#          "-framerate", str(FPS),
+#          "-i", temp_h264,
+#          "-c:v", "libx264", "-preset", "fast",
+#          "-crf", "18", "-pix_fmt", "yuv420p",
+#          "-movflags", "+faststart",
+#          output],
+#         check=True, capture_output=True,
+#     )
+#     os.remove(temp_h264)
+#     return output
+
 def convert_mcap_camera(mcap_path: str, topic: str, tmp_dir: str, label: str) -> str:
-    """Extract one camera topic from mcap and encode to mp4. Returns output path."""
     temp_h264 = os.path.join(tmp_dir, f"{label}.h264")
     output    = os.path.join(tmp_dir, f"{label}.mp4")
 
+    timestamps = []
     with open(temp_h264, "wb") as out:
         with open(mcap_path, "rb") as f:
             reader = make_reader(f, decoder_factories=[DecoderFactory()])
             for schema, channel, msg, decoded in reader.iter_decoded_messages():
                 if channel.topic != topic:
                     continue
+                timestamps.append(msg.log_time)  # nanoseconds
                 out.write(decoded.data)
 
-    subprocess.run(
+    # derive fps from median inter-frame interval
+    if len(timestamps) >= 2:
+        intervals = [timestamps[i+1] - timestamps[i] for i in range(len(timestamps) - 1)]
+        median_ns  = sorted(intervals)[len(intervals) // 2]
+        fps = round(1e9 / median_ns) if median_ns > 0 else FPS
+    else:
+        fps = FPS
+
+    print(f"[{label}] detected {fps} fps from {len(timestamps)} frames")
+
+    result = subprocess.run(
         ["ffmpeg", "-y",
-         "-framerate", str(FPS),
+         "-err_detect", "ignore_err",
+         "-framerate", str(fps),
          "-i", temp_h264,
          "-c:v", "libx264", "-preset", "fast",
          "-crf", "18", "-pix_fmt", "yuv420p",
          "-movflags", "+faststart",
          output],
-        check=True, capture_output=True,
+        capture_output=True, text=True,
     )
+    if result.returncode != 0:
+        print(f"[ffmpeg stderr] {result.stderr[-2000:]}")
+        raise RuntimeError(f"ffmpeg failed (exit {result.returncode})")
+
     os.remove(temp_h264)
     return output