steve-m/librtlsdr — pull request #9 by sm0svx (2014-07-31 07:46:00+00:00)
Title: Added a frequency error calibration mode to rtl_fm

The rtl_fm utility may now be used to calibrate the frequency error of a
DVB-T dongle using the "-c" command line switch:

```
[-c] Do frequency error calibration
Frequency error calibration will only work for FM.
Use a higher sample rate, like -s170k, to handle
large frequency errors. A strong and noise free
signal is needed for good results. For example, use a
broadcast FM station for calibration. Let the
calibration run for some minutes until the values
have stabilized. Rerun with -p option using the
suggested ppm_error. Try this on a couple of stations.
Repeat until the error is stable at about zero.
Example: rtl_fm -f99.3M -s170k -r48k -c - | aplay -r48k -fS16_LE -
```