mcap_protobuf.reader module

the mcap_protobuf.reader module is deprecated. For similar functionality, instantiate the mcap.reader.McapReader with a mcap_protobuf.decoder.DecoderFactory instance, eg:

>>> from mcap.reader import make_reader
>>> from mcap_protobuf.decoder import DecoderFactory
>>> reader = make_reader(open("proto.mcap", "rb"), decoder_factories=[DecoderFactory()])
>>> for schema_, channel_, message_, proto_msg in reader.iter_decoded_messages():
>>>     print(proto_msg)
MyProtoClass(data="hello")
MyProtoClass(data="goodbye")
class mcap_protobuf.reader.McapProtobufMessage(proto_msg: Any, message: Message, channel: Channel)[source]

Bases: object

Contains a single protobuf message and associated metadata from an MCAP file.

Variables:

  • proto_msg – the decoded protobuf message.

  • sequence_count – the message sequence count if included in the MCAP, or 0 otherwise.

  • topic – the topic that the message was published on.

  • channel_metadata – the metadata associated with this protobuf topic, if any.

  • log_time_ns – the time this message was logged by the recorder, as a POSIX nanosecond timestamp.

  • publish_time_ns – the time this message was published, as a POSIX nanosecond timestamp.

property log_time: datetime

The timestamp representing when this message was logged by the recorder.

property publish_time: datetime

The timestamp representing when this message was published.

mcap_protobuf.reader.read_protobuf_messages(source: str | bytes | PathLike[str] | McapReader | IO[bytes], topics: Iterable[str] | None = None, start_time: int | datetime | None = None, end_time: int | datetime | None = None, log_time_order: bool = True, reverse: bool = False) → Iterator['McapProtobufMessage'][source]

High-level generator that reads protobuf messages out of an MCAP.

Parameters:

  • source – some source of MCAP file data. Supply a stream of bytes, an McapReader instance, or the path to a valid MCAP file in the filesystem.

  • topics – an optional list of topics to read from the MCAP file.

  • start_time – if not None, messages logged before this time will not be included.

  • end_time – if not None, messages logged at this timestamp or after will not be included.

  • log_time_order – if True, messages will be yielded in ascending log time order. If False, messages will be yielded in the order they appear in the MCAP file.

  • reverse – if both log_time_order and reverse are True, messages will be yielded in descending log time order.

Yields:

an McapProtobufMessage instance for each protobuf message in the MCAP file.

Note

this generator assumes the source MCAP contains only Protobuf-encoded messages. If you need to decode protobuf messages from a file containing other encodings, use the mcap.reader.McapReader.iter_messages() function to iterate through Message records in your MCAP, and decode the protobuf messages with the mcap_protobuf.decoder.Decoder class.