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Messages, Channels and Schemas

MCAP organizes its data via messages, channels, and schemas.

Message

The unit of communication between nodes in the pub/sub system.

Channel

A stream of messages which have the same type, or schema. Often corresponds to a connection between a publisher and a subscriber.

Schema

A description of the structure and contents of messages on a channel, e.g. a Protobuf FileDescriptorSet or JSON Schema.

Info

The @foxglove/schemas repo provides pre-defined schema definitions for Foxglove Studio visualizations. Write messages that adhere to these schemas to an MCAP file, then visualize and debug this data using Studio’s panels.