Files & recordings
Play back a recording as if it were live, with the same channels, charts and tests.
Three types are built in:
| Type | What it is |
|---|---|
csv | rows under a header |
jsonl | one JSON object per line |
jsonl_watch | a folder you drop .jsonl files into |
Add one on Inputs (how). For MCAP, ROS 2 bags, CAN logs, NI TDMS or PX4 flight logs, install a connector from Connectors, then add it on Inputs the same way. Those connectors are listed at the end of this page.
| Field | Required | Example |
|---|---|---|
| File path | yes | /path/to/telemetry.csv |
| Loop (true/false) | no | true |
t,output_v,current_a,temp_c
1721037600,0.0,25.1,31.4
1721037601,0.8,25.1,31.6Each column except the time becomes a channel, with a / in front:
/output_v, /current_a, /temp_c.
| Time column | |
|---|---|
| Name | t, ts, time, timestamp, time_ns, t_ns or event_time — found by name, not position |
| A plain number | seconds, milliseconds, microseconds or nanoseconds since 1970, judged by its size |
| A written-out time | needs sub-second digits: 2024-07-15T10:00:00.000000Z |
Without sub-second digits it is not read as a time, and rows are stamped by row number instead.
| Field | Required | Example |
|---|---|---|
| File path | yes | /path/to/stream.jsonl |
| Tail (true/false) | no | true |
{"t_us":1721037600000000,"/imu/accel_z":9.81,"mode":"drive"}
{"t_us":1721037600100000,"/imu/accel_z":9.79,"mode":"drive"}Each key except the time becomes a channel: a number, true/false, or text. A
key without a leading / gets one, so mode becomes /mode.
- Time comes from
t_us(microseconds),t_ns(nanoseconds) ort(judged by its size). A line with none is stamped when it is read. - Nested objects and arrays are skipped. Bad lines are dropped.
- After a restart, reading continues where it stopped.
A drop folder: each .jsonl file you put in it is read once.
| Field | Required | Example |
|---|---|---|
| Directory | yes | /path/to/drops |
Lines are read the same way as jsonl. A file is picked up once it stops
growing. Finished files are remembered across restarts.
Loop and follow
| Field | Types | Effect |
|---|---|---|
| Loop (true/false) | csv | starts over at the end, timed as if arriving now |
| Tail (true/false) | jsonl | keeps reading lines as they are added |
Both are text boxes: type true. A connector's recordings have their own
Loop checkbox.
Nothing appears until the whole file has loaded. A big recording takes a while, then plays at its original speed.
Without Loop, a recording keeps the times it was recorded at. Find it on Replay, not Live: set the time control to All history, or pick the day it was recorded. It is not listed by file name; that list only holds runs you recorded.
#Connectors
Install one on Connectors and it becomes an input type here. Each page has its setup and fields.
MCAPReplay MCAP recordings in any schema.mcapPX4 ULogImport PX4 flight logs (.ulg).ulg
ROS 2Replay ROS 2 bags or stream live topics.mcap · .db3Updated