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Raw

Raw files

The raw file input is for developers who have recorded I/Q sample files. You can use it to analyse your recordings or to test welle.io.

Open the settings, disable Auto detect and select Open RAW file. Select the sample format of the file, e.g. u8 for the output of rtl_sdr or cf32 for the File Sink of GNU Radio.

Raw file settings

From the command line, welle-io --raw-file <file> --raw-format <format> opens a file directly.

File formats

All formats use a sample rate of 2048000 samples/s. Possible values of --raw-format: auto, u8, s8, s16le, s16be and cf32. With auto (the default) the format is taken from the end of the file name, e.g. recording.s16le.iq; other files are read as u8.

u8: 8 bit unsigned

The I/Q samples are 8-bit unsigned values in the following order:

u8 format

  • Size: 8-bit unsigned per I and Q sample
  • Sources: rtl_sdr, rtl_tcp, qt-dab (*.raw)

s8: 8 bit signed

Like u8, but with 8-bit signed values.

  • Size: 8-bit signed per I and Q sample
  • Source: odr-dabmod

s16le: 16 bit signed little endian

The I/Q samples are 16-bit signed little endian values in the following order:

s16le format

  • Size: 16-bit signed little endian per I and Q sample
  • Source: qt-dab (*.sdr)

s16be is the same with big endian values.

cf32: 32 bit float

The I/Q samples are 32-bit float values (complex float), as written by the File Sink of GNU Radio.

Recording a raw file

welle.io (all input devices)

welle.io records the I/Q samples of the selected input device itself. Enable the expert mode in the settings and add the view RAW Recorder to the dashboard with the + button.

  1. Play a station or tune to a channel with Manual channel.
  2. Choose a Duration. With Until stopped the recording runs until you press Stop, otherwise it stops by itself. The card shows the estimated file size and warns if the folder has less space.
  3. Press Record. While recording the card shows the elapsed time and the current file size.

The file is saved in the folder shown in the card (by default the Downloads folder, Change selects another one) with the name welle-io_<channel>_<date>-<time>.<format>.iq, e.g. welle-io_11D_20261021-153000.u8.iq. Because the format is part of the name, the RAW file input opens it with the format auto.

The format depends on the input device, the sample rate is always 2048000 samples/s:

Input device Format Size
rtl-sdr, rtl_tcp, Linux kernel SDR with an RTL-SDR u8 4.1 MB/s, 246 MB/min
RAW file the format of the file
Airspy, SoapySDR, LimeSDR, other Linux kernel SDR devices cf32 16.4 MB/s, 983 MB/min

The recording stops when you change the channel, stop the playback or select another input device: one file always contains one channel. If the disk is too slow, the card shows how much data was lost.

rtl_sdr (format u8)

You can use the command line tool rtl_sdr to record a file with an rtl-sdr device:

rtl_sdr -f <frequency> -s 2048000 -n <sample count> <file>
# e.g.
rtl_sdr -f 174928000 -s 2048000 -n 10000 yourfile.iq

The script dab_raw_record.sh is more convenient. This command records 10 s of channel 5C into a file named <date and time>_5C.iq:

dab_raw_record.sh -c 5C -t 10

odr-dabmod (format s8)

To test your Opendigitalradio broadcasting set-up without broadcast hardware, you can create an I/Q file. Use odr-dabmod with this INI file:

odr-dabmod DabMod.ini

The input file has to be DabMux.eti, the output file is DabMod.iq.

Other tools

You can also use the following tools to record a raw file: