Open Sensor Format

The Open Sensor Format (OSF) is an extensible file format for storing time-series data, based on FlatBuffers.

Compared to pcap, it offers the following advantages:

  • Messages can more easily be randomly-accessed because an index from message timestamp to the file offset of the chunk containing the message is contained within the file.

  • Full frames of lidar data are meant to be compressed as individual channels (using lossless PNG-based compression by default,) resulting in smaller file sizes for the same data.

  • Sensor configuration is contained within the file.

The Ouster SDK provides both Python and C++ methods for working with OSF files.

Reading and writing OSF files

Reading, writing, and recording new OSF files are all possible with the Ouster SDK and the Ouster SDK CLI.

Getting example OSF files

The sample data page has instructions for obtaining sample datasets. Sample datasets are available in OSF format in addition to pcap.

OSF format details

Typically, users of the Ouster SDK won’t have to worry about the implementation details of OSF. The following is a very basic overview of the structure of an OSF file.

An OSF file generally contains the following:

  1. A header, which contains the location of the OSF metadata.

  2. A series of “chunks”, each of which contain one or more messages, typically containing lidar scans - see LidarScan reference.

  3. Metadata, a collection of generic buffers usually containing the following:

    1. An index of chunks (meant to provide the file offset, in bytes, for a chunk given a timestamp.)

    2. An ouster/v1/streaming/StreamingInfo, which contains the start, end timestamps and number of messages for each chunk as well as some statistics.

    3. An ouster/v1/os_sensor/LidarSensor, which contains the configuration of the sensor used to collect the data contained in a stream of lidar scans.

    4. An ouster/v1/os_sensor/LidarScanStream, which indicates which fields are present in each lidar scan.

For more details of the structure of an OSF file, consult the definition files found in the ouster_osf/fb directory of the Ouster SDK repository.