Rerun

CLI Reference for MCAP

This reference guide covers all command-line options and workflows for working with MCAP files in Rerun.

Basic commands basic-commands

Direct viewing direct-viewing

Open MCAP files directly in the Rerun Viewer:

# View a single MCAP file
rerun data.mcap

# View multiple specific files
rerun file1.mcap file2.mcap file3.mcap

# Use glob patterns to load all MCAP files in a directory
rerun recordings/*.mcap

# Recursively load all MCAP files from a directory
rerun mcap_data/

File conversion file-conversion

Convert MCAP files to Rerun's native RRD format:

# Convert MCAP to RRD format for faster loading
rerun mcap convert input.mcap -o output.rrd

# Convert with custom output location
rerun mcap convert data.mcap -o /path/to/output.rrd

Decoder selection decoder-selection

Using specific decoders using-specific-decoders

Control which processing decoders are applied during conversion:

# Use only protobuf decoding and file statistics
rerun mcap convert input.mcap -d protobuf -d stats -o output.rrd

# Use only ROS2 semantic interpretation for robotics data
rerun mcap convert input.mcap -d ros2msg -o output.rrd

# Add robot geometry from ROS robot_description topics
rerun mcap convert input.mcap -d ros2msg -d urdf -o output.rrd

# Combine multiple decoders for comprehensive data access
rerun mcap convert input.mcap -d ros2msg -d raw -d recording_info -o output.rrd

Available decoder options available-decoder-options

Decoding:

  • raw: Preserve original message bytes
  • schema: Extract metadata and schema information
  • stats: Compute file and channel statistics
  • metadata: Extract metadata records into RRD __properties, if present
  • protobuf: Decode protobuf messages using into generic Arrow data without Rerun visualization components
  • recording_info: Extract recording session metadata
  • urdf: Use Rerun's built-in URDF loader when a ROS 2 /robot_description topic is present

Semantic:

  • foxglove: Semantic interpretation of Foxglove Protobuf messages
  • ros2msg: Semantic interpretation of ROS2 messages

Default behavior default-behavior

When no -d flags are specified, all available decoders are used:

# These commands are equivalent (default uses all decoders):

rerun mcap convert input.mcap -o output.rrd

rerun mcap convert input.mcap \
    -d raw \
    -d schema \
    -d stats \
    -d metadata \
    -d protobuf \
    -d recording_info \
    -d urdf \
    -d ros2msg \
    -d foxglove \
    -o output.rrd
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