LCM
LCM Log File format

Conceptually, an LCM Log file is an ordered list of events. Each event has four fields:

Field Name Field Description
event number monotonically increasing 64-bit integer that identifies each event. It should start at zero, and increase in increments of one.
timestamp monotonically increasing 64-bit integer that identifies the number of microseconds since the epoch (00:00:00 UTC on January 1, 1970) at which the event was received.
channel UTF-8 string identifying the LCM channel on which the message was received.
data binary blob consisting of the exact message received.

Event Encoding

Each event is encoded as a binary structure consisting of a header, followed by the channel and the data.

The header is 28 bytes and has the following format:

 0      7 8     15 16    23 24    31
+--------+--------+--------+--------+
|   LCM Sync Word                   |
+--------+--------+--------+--------+
|   Event Number (upper 32 bits)    |
+--------+--------+--------+--------+
|   Event Number (lower 32 bits)    |
+--------+--------+--------+--------+
|   Timestamp (upper 32 bits)       |
+--------+--------+--------+--------+
|   Timestamp (lower 32 bits)       |
+--------+--------+--------+--------+
|   Channel Length                  |
+--------+--------+--------+--------+
|   Data Length                     |
+--------+--------+--------+--------+

LCM Sync Word is an unsigned 32-bit integer with value 0xEDA1DA01

Event Number and Timestamp fields of the header are as described above.

Channel Length is an unsigned 32-bit integer describing the length of the channel name.

Data Length is an unsigned 32-bit integer describing the length of the data.

Each header is immediately followed by the UTF-8 encoding of the LCM channel, and then the message data. The channel is not NULL-terminated.

All integers are packed in network order (big endian)