[feat] Add make_mcap_metadata.py and document it in bag2edex README

tools/python_tools/cuvslam_tools/bag2edex/README.md

@@ -83,6 +83,34 @@ rosbag_extract_urdf \
 ```
 
 
+## Generating Missing `metadata.yaml` for MCAP Files
+
+`make_mcap_metadata.py` regenerates the `metadata.yaml` file that `rosbag2` requires next to an `.mcap` file. Use it when you have a standalone `.mcap` file without its companion `metadata.yaml` — for example, after downloading only the `.mcap` from a recording system or after the metadata file was accidentally deleted.
+
+**Prerequisites:** `ros2` must be on `PATH` (the script calls `ros2 bag info` internally).
+
+**Usage:**
+```sh
+./make_mcap_metadata.py path/to/rosbag.mcap
+```
+
+The script writes `metadata.yaml` into the same directory as the `.mcap` file. Once generated, the directory can be used with the extraction tools above.
+
+**Optional argument:**
+- `--version <int>` — sets the `rosbag2_bagfile_information.version` field in the metadata (default: `9`). Only change this if you need to match a specific rosbag2 version.
+
+**Example:**
+```sh
+./make_mcap_metadata.py /data/bags/my_recording/my_recording_0.mcap
+# Wrote: /data/bags/my_recording/metadata.yaml
+
+rosbag_extract_edex \
+    --config configs/my_config.yaml \
+    --rosbag_path /data/bags/my_recording \
+    --output_path /data/edex/my_recording
+```
+
+
 ## License
 
 Copyright (c) 2025, NVIDIA CORPORATION. All rights reserved.

tools/python_tools/cuvslam_tools/bag2edex/make_mcap_metadata.py

@@ -0,0 +1,109 @@
+#!/usr/bin/env python3
+# Copyright (c) 2026, NVIDIA CORPORATION. All rights reserved.
+#
+# NVIDIA software released under the NVIDIA Community License is intended to be used to enable
+# the further development of AI and robotics technologies. Such software has been designed, tested,
+# and optimized for use with NVIDIA hardware, and this License grants permission to use the software
+# solely with such hardware.
+# Subject to the terms of this License, NVIDIA confirms that you are free to commercially use,
+# modify, and distribute the software with NVIDIA hardware. NVIDIA does not claim ownership of any
+# outputs generated using the software or derivative works thereof. Any code contributions that you
+# share with NVIDIA are licensed to NVIDIA as feedback under this License and may be incorporated
+# in future releases without notice or attribution.
+# By using, reproducing, modifying, distributing, performing, or displaying any portion or element
+# of the software or derivative works thereof, you agree to be bound by this License.
+
+import argparse
+import re
+import subprocess
+from pathlib import Path
+
+
+def ns_from_seconds(seconds: str) -> int:
+    return int(round(float(seconds) * 1_000_000_000))
+
+
+def ns_from_epoch(sec: str, nsec: str) -> int:
+    return int(sec) * 1_000_000_000 + int(nsec.ljust(9, "0")[:9])
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("mcap", help="Path to .mcap file")
+    parser.add_argument("--version", type=int, default=9)
+    args = parser.parse_args()
+
+    mcap_path = Path(args.mcap).resolve()
+    bag_dir = mcap_path.parent
+    metadata_path = bag_dir / "metadata.yaml"
+
+    result = subprocess.run(
+        ["ros2", "bag", "info", "--storage", "mcap", str(mcap_path)],
+        check=True,
+        text=True,
+        capture_output=True,
+    )
+
+    text = result.stdout
+
+    duration = re.search(r"Duration:\s+([0-9.]+)s", text)
+    start = re.search(r"Start:.*\((\d+)\.(\d+)\)", text)
+    messages = re.search(r"Messages:\s+(\d+)", text)
+
+    if not duration or not start or not messages:
+        raise RuntimeError("Could not parse ros2 bag info output")
+
+    duration_ns = ns_from_seconds(duration.group(1))
+    start_ns = ns_from_epoch(start.group(1), start.group(2))
+    total_messages = int(messages.group(1))
+
+    topic_re = re.compile(
+        r"Topic:\s+(.+?)\s+\|\s+Type:\s+(.+?)\s+\|\s+Count:\s+(\d+)\s+\|\s+Serialization Format:\s+(\S+)"
+    )
+
+    topics = topic_re.findall(text)
+
+    if not topics:
+        raise RuntimeError("No topics found in ros2 bag info output")
+
+    rel_file = mcap_path.name
+
+    yaml = []
+    yaml.append("rosbag2_bagfile_information:")
+    yaml.append(f"  version: {args.version}")
+    yaml.append("  storage_identifier: mcap")
+    yaml.append("  duration:")
+    yaml.append(f"    nanoseconds: {duration_ns}")
+    yaml.append("  starting_time:")
+    yaml.append(f"    nanoseconds_since_epoch: {start_ns}")
+    yaml.append(f"  message_count: {total_messages}")
+    yaml.append("  relative_file_paths:")
+    yaml.append(f"    - {rel_file}")
+    yaml.append("  files:")
+    yaml.append(f"    - path: {rel_file}")
+    yaml.append("      starting_time:")
+    yaml.append(f"        nanoseconds_since_epoch: {start_ns}")
+    yaml.append("      duration:")
+    yaml.append(f"        nanoseconds: {duration_ns}")
+    yaml.append(f"      message_count: {total_messages}")
+    yaml.append("  topics_with_message_count:")
+
+    for name, msg_type, count, serialization in topics:
+        yaml.append("    - topic_metadata:")
+        yaml.append(f"        name: {name}")
+        yaml.append(f"        type: {msg_type}")
+        yaml.append(f"        serialization_format: {serialization}")
+        yaml.append('        offered_qos_profiles: ""')
+        yaml.append(f"      message_count: {count}")
+
+    yaml.append('  compression_format: ""')
+    yaml.append('  compression_mode: ""')
+    yaml.append("  custom_data: {}")
+    yaml.append("")
+
+    metadata_path.write_text("\n".join(yaml))
+    print(f"Wrote: {metadata_path}")
+
+
+if __name__ == "__main__":
+    main()