Re: [Discuss-gnuradio] Digital Audio Broadcast (DAB), anybody running gr-dab?

[Ruben Undheim]

Hi Matthias,

> I stumbled across two gnuradio-related projects [1] and [2]. [2] has last 
> change several years ago. [1] has last change 7 months ago and is written by 
> Andreas Müller (put in BCC) who also wrote a semester thesis  [3] about DAB - 
> Software Receiver Implementation which is quite good! Also stumbled across 
> references to [4] which is no longer available.

I did some work on Andreas' code 7 months ago to make it work with GNU Radio 
3.7.
 
> I tried to build an run the scripts in ./apps. I was not able to receive 
> successfully:
> 
> The execution of usrp_dab_rx.py returned several warnings:
> 
> gr::buffer::allocate_buffer: warning: tried to allocate
>    4 items of size 16000. Due to alignment requirements
>    32 were allocated.  If this isn't OK, consider padding
>    your structure to a power-of-two bytes.
>    On this platform, our allocation granularity is 4096 bytes.
> 
> This might be okay, but I did not allocate where this came from.
> 
> Afterwards I get several errors saying "FIB CRC error" coming from 
> ./lib/fib_sink_vb_impl.cc function gr::dab::fib_sink_vb_impl::process_fib. 
> ["FIB" standing for Fast Information Blocks that make up the Fast Information 
> Channel ("FIC")]

In order to receive something I had to add several arguments.

When I ran it like this:
 ./rtl_sdr_dab_rx.py -g 10 -c -f 229.072e6 -e -F

It worked. (just checked my shell history)

You need "fine frequency correction" and "equalization" at least, if I
don't remember wrong.

> Can anybody say that he or she is using gr-dab successfully at the moment? I 
> am not sure if this is an RF reception or software problem. From my point of 
> view the spectrum rather "looks good". If required I could also upload some 
> raw IQ data (old reference to [5] also seems to be outdated). Or maybe 
> somebody else could also provide samples to compare?
> 
> The hardware I was using: both an USRP N210 and a rtl-sdb dongle with 
> different antennas and antenna locations.
> 
> Just found a note right now: "the patch in 
> patches/not_applied_in_trunk/gr_peak_detector_XX.cc.t.diff must
>   be applied to the GNU Radio trunk before building" - is this still the 
> case? The problem is that I am currently using Gnuradio 3.7.2.1 Debian 
> packages in Linux Mint.

I've tried both with RTL-SDR and USRP B200. Both should work fine, N210 as well 
(although
I haven't tried).

However, there is still no support for audio reception with Andreas' code. It 
basically
just receives information messages on the FIC channel. But for that, the code 
works
fine.

If you just make sure you have a good DAB signal, tune into the correct 
frequency,
add the right arguments, you should be able to make it work.

Extending the code to support audio reception will be happily appreciated. I was
intending to do that, but I was a bit overwhelmed back them, and didn't get time
for it. It should not be very hard according to Andreas.

I'm not aware of any other GNU Radio code that supports audio reception. Anyone 
else?


Good luck!

Cheers,
Ruben

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