dabs

dabs is a DAB/DAB+ decoder. (Well, actually only DAB+.)

It uses an SDR (software-defined radio) device to receive data over the air transmitted by, well, a DAB/DAB+ emitter, and extracts audio content from it, playing it in your computer.

It supports USRP devices (I use a B210) and RTL-SDR devices.

(It doesn't work very well with RTL-SDR for the moment because of bad coarse frequency offset estimation and no use of Reed-Solomon stuff.) (This coarse offset thing also made things worse on my computer with the B210. You can edit dabs.c and look for the commented line coarse_freq_offset = 0; and uncomment it to get rid of the coarse offset stuff and maybe have a better behavior.)

Status: decodes local radio channels around Nice/France. May fail to work for other locations. Slow, basic documentation (README file).

Download

2021-11-28: dabs-1.0.tar.bz2 [README]

Old releases

dabs-0.9.tar.bz2
dabs-0.8.tar.bz2
dabs-0.7.tar.bz2
dabs-0.5.tar.bz2
dabs-0.5-pre1.tar.bz2
dabs-0.4.tar.bz2
dab-0.3.tar.bz2
dab-0.1.tar.bz2
dab-0.0.tar.bz2

Sample DAB+ data

Here is a DAB+ recording (format: IQ data, 16 bits for I, 16 bits for Q, little endian): rec-for-optim.raw The file is 131 MiB, will take some time to download.

Documentation

The specifications I used are:

ETSI EN 300 401: Radio Broadcasting Systems; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers

ETSI TS 102 563: Digital Audio Broadcasting (DAB); DAB+ audio coding (MPEG HE-AACv2)

ETSI TS 101 756: Digital Audio Broadcasting (DAB); Registered Tables

I also found Introduction to DAB Receiver [source], which provided nice information.

As for websites, I looked at:

• worlddab.org for the specifications
• wikipedia about band 3 in France
• DAB Ensembles Worldwide for the available channels around me
• DAB radio design and implementation
• dsp.stackexchange.com for Carrier frequency offset (CFO) estimation using cyclic prefix (sorry for this link, it was very useful though)
• ML Estimation of Time and Frequency Offset in OFDM Systems
• wikipedia for Viterbi decoder (not very useful)
• The Viterbi Algorithm: A Personal History
• Error Bounds for Convolutional Codes and an Asymptotically Optimum Decoding Algorithm the article of Viterbi (I didn't understand a shit in there)
• Coding and decoding with convolutional codes.The Viterbi Algorithm not very clear either
• tutorial on Viterbi decoder definitely the best source of information for Viterbi decoding that I found! My brain can get the theoretical stuff, but if it's not backed by the correct intuition, I'm doomed, and this website gave me the correct intuition

Those links were functional 2021-09-07.

Related work

Free software for receiving DAB/DAB+

Here are some other implementations of DAB/DAB+ receiving. They are way more featured than mine.

• qt-dab (you can find dab-cmdline there as well) is the ultimate free software DAB/DAB+ receiver. Unfortunately I couldn't make it run on my system, too complex (seriously? Qt?). But I did read the code and without it my program would probably not exist.
• sdrangel (I could not find a proper website, sorry, github...) was the program I used to see that my local dumps were decodable! and so my program did not work. It's a nice GUI thing. For DAB/DAB+ it uses dab-cmdline code from what I understand.
• dablin was also a good source of information. I did not run the program, just read the source (the link is not to dablin itself but the, what, company? organization? making dablin, or distributing/maintening it, I don't really know). It was a good source of information too.

Those links were functional 2021-09-07.

There are surely others. This is what I found.

Free software for transmitting DAB/DAB+

There is a transmitting free software thing also, ODR mmbTools. Looks very complex to me, but they claim to be production ready, so, well, there it is. I didn't look at it, I simply know it exists.

This link was functional 2021-09-07.

I don't know of other transmitting DAB/DAB+ free software.

Contact: see this

Created: 2021-07-25
Last update (more or less accurate): 2021-11-28