A Config can help you convert HDF5 to MCAP files

config_aloha_unified.yaml

# config_aloha_unified.yaml
# Along this config, you also need a urdf
# Unified configuration for bidirectional ALOHA HDF5 ↔ MCAP conversion
# This single configuration file works for both conversion directions

# Global sampling rate (Hz) - default for all datasets
sampling_rate: 20.0

joint_states:
  hdf5_paths:
    position: "/observations/qpos"
    velocity: "/observations/qvel" # Optional
    effort: "/observations/effort" # Optional
  mcap_topic: "/joint_states"
  # sampling_rate: 20.0  # Optional: override global sampling rate for joint states

  # Unified joint mapping: URDF joint name → HDF5 column index
  # Works for both conversion directions
  joint_mappings:
    # Arm 1 - Map URDF names to HDF5 qpos/qvel columns 0-5
    "arm1_waist": 0
    "arm1_shoulder": 1
    "arm1_elbow": 2
    "arm1_forearm_roll": 3
    "arm1_wrist_angle": 4
    "arm1_wrist_rotate": 5
    # Arm 2 - Map URDF names to HDF5 qpos/qvel columns 7-12
    "arm2_waist": 7
    "arm2_shoulder": 8
    "arm2_elbow": 9
    "arm2_forearm_roll": 10
    "arm2_wrist_angle": 11
    "arm2_wrist_rotate": 12

  # Optional: Explicit joint order for HDF5 output
  # If not specified, derived automatically from joint_mappings
  # joint_order:
  #   - "arm1_waist"
  #   - "arm1_shoulder"
  #   - "arm1_elbow"
  #   - "arm1_forearm_roll"
  #   - "arm1_wrist_angle"
  #   - "arm1_wrist_rotate"
  #   - "arm1_left_finger"
  #   - "arm2_waist"
  #   - "arm2_shoulder"
  #   - "arm2_elbow"
  #   - "arm2_forearm_roll"
  #   - "arm2_wrist_angle"
  #   - "arm2_wrist_rotate"
  #   - "arm2_left_finger"

cameras:
  - hdf5_path: "/observations/images/cam_high"
    mcap_topic: "/camera/high/image_compressed"
    frame_id: "world" # Used for HDF5→MCAP, ignored for MCAP→HDF5
    format: "jpeg"
    # sampling_rate: 20.0  # Optional: override global sampling rate
  - hdf5_path: "/observations/images/cam_left_wrist"
    mcap_topic: "/camera/arm1_wrist/image_compressed"
    frame_id: "arm1_ee_gripper_link"
    format: "jpeg"
  - hdf5_path: "/observations/images/cam_right_wrist"
    mcap_topic: "/camera/arm2_wrist/image_compressed"
    frame_id: "arm2_ee_gripper_link"
    format: "jpeg"

# Unified gripper configurations with bidirectional value mapping
gripper:
  - # Gripper for Arm 1
    urdf_joint_name: "arm1_left_finger"
    hdf5_path: "/observations/qpos"
    hdf5_index: 6
    # Bidirectional value mapping (no "reverse" needed)
    value_mapping:
      hdf5_range: [0.0, 1.0]      # HDF5: 0=closed, 1=open
      urdf_range: [0.021, 0.057]  # URDF: 0.021=closed, 0.057=open
    description: "Arm 1 gripper mapping from normalized HDF5 to URDF position"

  - # Gripper for Arm 2
    urdf_joint_name: "arm2_left_finger"
    hdf5_path: "/observations/qpos"
    hdf5_index: 13
    value_mapping:
      hdf5_range: [0.0, 1.0]
      urdf_range: [0.021, 0.057]
    description: "Arm 2 gripper mapping from normalized HDF5 to URDF position"

# Unified custom topics (direction auto-detected)
custom_topics:
  - mcap_topic: "/action"
    hdf5_path: "/action"
    handler_name: "aloha_action_handler"
    # No handler_function needed - auto-detected based on conversion direction
    # No script_path needed - resolved from handler_name and input directory
    message_type: "std_msgs/msg/Float64MultiArray"
    description: "Robot action commands for dual arm system"
    # Custom parameters for this handler (optional)
    data_scaling: 1.0  # Scale factor applied to action values
    
  - mcap_topic: "/base_action"
    hdf5_path: "/base_action"
    handler_name: "aloha_base_action_handler"
    message_type: "std_msgs/msg/Float64MultiArray"
    description: "Base movement commands [linear_velocity, angular_velocity]"
    # Custom parameters for this handler (optional)
    velocity_limit: 2.0  # Maximum velocity magnitude (m/s or rad/s)
    
  - mcap_topic: "/compress_len"
    hdf5_path: "/compress_len"
    handler_name: "aloha_compress_len_handler"
    message_type: "std_msgs/msg/Float64MultiArray"
    description: "Compression length values for data processing"
    # Custom parameters for this handler (optional)
    min_compression_length: 0.0  # Minimum allowed compression length

# Optional: TF topic configuration
# tf_topic: "/tf"