Bug decoding high-bitrate DAB services

[ryanginn]

Hi, just testing some stuff here, and have spotted a bug(?)

I have a 384kbps MP2 signal (within DAB spec) being sent, and AbracaDABra is not able to decode it, it just says "No service".

Decodes fine in DABlin:

[andimik]

https://opendigitalradio.github.io/cu_calc/

Well, it's within spec, this is true. But there are no services in mp2 using this highest allowed bitrate worldwide. It's only existing in your lab.

Hint: South Korea is using even higher bitrates for DMB, but I do not know any software supporting it. And I have never found a raw capture.

[KejPi]

I think this somehow duplicates issue #258.
I have limited maximum supported subchannel size to reduce memory footprint. I think that currently application supports MP2 bitrate up to 192kbps.

[andimik]

No, #258 was for sure violating the spec, as it had more than 144 CUs.

This one is in spec. However this configuration is not used anywhere, although it's possible.

I will again check Spanish Radio Classica which is 224 kBit in UEP 3. But I cannot remember I had problems with AbracaDABra.

[ryanginn]

Hmm. this is very weird. Do you guys need an IQ file? I haven't fully tested this on hardware, but the 384k service runs fine on welle-io and DABlin - the other services work fine in Abra, just not the 384k one.

[KejPi]

For sure, IQ would be fine for testing, thanks you!
As I wrote above, there is a limit in the library and for sure 384kbps audio is over. So this behavior is intended to limit memory usage. I have set the limit to cover "normal cases". Although memory usage may not be relevant on average computer, it may help on resource limited devices like RPi.

[ryanginn]

Ah yes, of course! This makes sense. It would be maybe better if it would be an option in the settings ;).

I will send on an IQ in a bit... 😄

[KejPi]

Any option means runtime handling, runtime handling means additional unnecessary CPU cycles.

[ryanginn]

Of course, that is the other side of it sadly.

Here's an IQ sample; https://www.swisstransfer.com/d/be8c05fd-1264-470d-8574-8f9f341bf444.

128kbps MP2 also included for comparisons.

[andimik]

224 kBit mp2 from Madrid is working.

(Hint: They don't have any PAD data, see https://digitalbitrate.com/dtv.php?mux=11B&cpid=3591307263&live=654&sec=0&lang=en )