Configuration Schema

Codec configuration files are YAML mappings. Each field name maps to a field configuration, and each field configuration needs a codec key unless it is created by ROS field inference.

field_name:
  codec: string
  max_length: 16

Common Field Keys

codec

Codec alias used to encode the field. See Codec Aliases.

fields

Nested field mapping for dict and msg codecs.

min_value and max_value

Numeric bounds used by integer and quantized float codecs.

precision

Number of decimal places preserved by the float codec.

resolution

Step size for linspace_float values. linspace_float can also be configured with num_values or num_bits instead.

num_bits

Fixed bit width for fixedint and padding.

max_length

Maximum number of characters, bytes, or array elements for variable-length codecs.

length

Number of elements for fixed_len_array.

element_type

Codec alias used for array elements.

element_params

Nested configuration passed to the element codec for an array.

nullable

When true on variable_len_array, an empty list is encoded as a single absent/present bit.

target_fields

Field mapping controlled by an optional field.

ros_type

ROS message type for msg fields. ROS 1 and ROS 2 type names are accepted.

Structured Fields

Nested dictionaries use fields:

status:
  codec: dict
  fields:
    mode:
      codec: uint8
    label:
      codec: string
      max_length: 12

Nested ROS messages use ros_type and may optionally provide fields:

point:
  codec: msg
  ros_type: geometry_msgs/Point
  fields:
    x:
      codec: float32
    y:
      codec: float32
    z:
      codec: float32

Arrays

Variable-length arrays include a length prefix:

samples:
  codec: variable_len_array
  max_length: 8
  element_type: uint16

Fixed-length arrays omit the length prefix:

orientation:
  codec: fixed_len_array
  length: 4
  element_type: float32

Array element codecs that require their own settings use element_params:

names:
  codec: variable_len_array
  max_length: 4
  element_type: string
  element_params:
    max_length: 16

Arrays of ROS messages use element_type: msg:

points:
  codec: variable_len_array
  max_length: 5
  element_type: msg
  element_params:
    ros_type: geometry_msgs/Point
    fields:
      x:
        codec: float32
      y:
        codec: float32
      z:
        codec: float32

Top-Level Options

ltcodecs.dict_codec.DictCodec and ltcodecs.ros_message_codec.RosMessageCodec accept an optional checksum argument. Supported values are crc8 and crc32.

codec = ltcodecs.DictCodec(fields, checksum="crc32")

The checksum is appended after the payload and validated during decoding.