domenica 1 luglio 2018

welle.io / DAB


Searching for a DAB/DAB+ decoder I found this useful software running on Windows 10, Linux, macOS, Android. The picture above show a DAB signal ( OFDM modulation: Orthogonal Frequency Division Multiplexing ) with a bandwidth of 1,536 MHz, 1536 carriers at 1 kHz spacing and a symbol rate of 800 Hz.

welle.io is an open source software with support for rtl-sdr (RTL2832U) and airspy. I tested the software with an AirSpy sdr receiver. After the program launch, welle.io detected automatically the sdr and start to scan the frequencies for any possibile DAB transmission.
The scanning frequency was very quickly and after few minutes I found 2 DAB carriers ( 30 stations ).



The second picture show the program window with many useful informations about the DAB signal: a stations list ( in this case 30 stations - channels 12A and 12C ), station name, signal strenght, error code, program type, Kbps, DAB audio mode, an image of the current audio program ( normally a cover of the on air song… ) and other technical informations:

- Sdr device
- Channel and frequency
- Frequency corrections
- SNR
- Frames error
- RS Error
- AAC error
- Frame Synchronization
- FIC CRC

The three rectangles are an indicator for the signal quality and decoding, from left to right:

1. Signal sysnchronization: red = out of sync / green: sync
2. FIC CRC Fast Information Channel Checksum: red = NO CRC / green = CRC OK
3. Frame errors: red = Error / green: No error

Another interesting feature is the "waveform visualizer" window useful to have an "eye quality" view of the signal.



More info here : https://www.welle.io/

Sources:
Please visit the GitHub repository: https://github.com/albrechtl/welle.io