The rt-mbms-modem can work with sample files (recorded I/Q signals) in two ways: capture, which records a signal from a Software Defined Radio (SDR) and therefore needs an SDR and a live 5G Broadcast signal; and run (replay), which plays back an existing sample file and needs no SDR. See Sample Files for downloadable files and the filename convention.
Before capturing or running a sample file, make sure that MBMS Modem isn't running in the background. If it is, stop MBMS Modem with systemctl stop 5gmag-rt-modem.
Capture a sample file
Capturing needs an SDR and a live 5G Broadcast signal. Run the command below to record the raw I/Q data from the SDR to a file:
modem -w "PathToSample/samplefile.raw"
Run a sample file
Important: For correct pre-configuring of the MBMS Modem at system startup, it has to be run through systemd once, see https://github.com/5G-MAG/rt-mbms-modem#configuration
Based on the structure of the Service Announcement file the configuration file in /etc/5gmag-rt.conf needs to be adjusted. For details refer to the corresponding documentation.
To start MBMS Modem with a downloaded sample file, run the following command (no SDR required):
modem -f "PathToSample/samplefile.raw" -b 10
Notice:
-b 10is the bandwidth (in MHz) that the sample file was captured at, which is encoded in the filename (see Sample Files). So for a 5 MHz bandwidth sample file you need to adjust the command to-b 5.
Next steps
- To play a received HLS stream end to end, see SDR - HLS Playback over 5G Broadcast.
- Return to the Tutorials index.