Recording and playback

Choose a recorder for the signal you need to save:

SigMF stores samples in .sigmf-data and frequency, sample rate, timing, and annotations in .sigmf-meta. Keep both files together.

Record IQ

1. Connect Device IQ to Recorder IQ.
2. Start the radio and press Record.
3. Press Stop to finish the files.

For multi-lane radios, the connected port selects the lane. Connect GPS position to include location metadata. The recorder shows elapsed time, bytes, dropped samples, and write errors.

A clean server shutdown finalises active recordings. Forcibly ending the process can leave an incomplete capture.

Record a channel's audio

Connect channel audio outputs to Audio recorder. Press Record beside each channel you want to save, then Stop to finish its WAV file.

Each channel gets a separate file after squelch, filtering, noise reduction, and AGC. Closed squelch writes silence to preserve timing. Mode and device-rate changes do not stop audio recording; removing a channel does. Headers update during capture so interrupted files remain playable through the last finalised data.

Audio and IQ recording can run independently at the same time.

Record a channel's baseband

Connect channel baseband outputs to Baseband recorder. Start and stop each channel separately.

Files contain IQ after frequency translation and filtering, before squelch. They preserve the channel frequency and sample rate and use less storage than full-device IQ. Completed files appear in the IQ library for playback.

A channel rebuild, including a mode or device-rate change, finishes the recording. Removing the channel also finishes it.

The IQ time machine

Capture a signal after it happens:

1. Connect Device IQ to Time machine, with optional GPS position.
2. Set a buffer duration and press Arm.
3. Press Capture to save the buffer and continue recording live IQ.
4. Press Stop to finish and remain armed, or Disarm to release the buffer.

Memory use is seconds × sample rate × 8 bytes, up to the server's 1 GiB limit. The display shows the required memory and maximum duration.

Sample rate is locked while armed. Retuning starts a new SigMF capture segment. The first timestamp belongs to the oldest buffered sample.

Storage

Recordings default to sdrmm/recordings under the platform data directory. Override it with:

sdrmm --recordings-dir /srv/sdrmm/recordings

Containers use /data/recordings; persist /data. The library rebuilds its IQ index from valid SigMF pairs on disk. Audio files live in the audio subdirectory.

Tags and notes

In Library → Recordings, choose Annotate and enter comma-separated tags and a note. Search matches names, tags, and notes; click a tag to search for it.

Annotations are stored in SigMF metadata as sdrmm:tags and core:description, so they survive downloads and index rebuilds. Duplicate tags merge while keeping the first spelling.

Download and export

Download IQ as the original SigMF archive or a stereo float WAV with I and Q as separate channels. WAV preserves samples but only part of the capture metadata. Channel audio provides the audio WAV downloads.

Downloads stream from disk. Failed exports abort instead of returning an apparently complete, truncated file.

Play a recording

Choose Open as source in Library → Recordings. Connect the new playback Device to channels and displays as you would a radio.

Playback uses the capture's centre frequency and sample rate. Use play, pause, stop, and seek to review the same samples with different decoder settings. Recording playback is available in release builds.

Decoder logs are separate

For messages, identifiers, and positions, connect channel events to Decoder log. Add Export for CSV or JSON. Logs store decoded results in SQLite; IQ files store the signal needed to decode again.