Distorted audio on mono and 32 kHz sampled DAB stations

[orryverducci]

Describe the bug
Tuning in to DAB stations that broadcast either mono audio or audio using a 32 kHz sample rate results in distorted audio playback. Mono stations have stuttery audio, as if samples are regularly missing. 32 kHz stations play sped up and then drop out.

To Reproduce
Tune in to the frequency of a DAB multiplex containing a mono or 32 kHz samples station. Enable the DAB decoder, then select a mono or 32 kHz sampled station form the program list.

Expected behavior
Clean audio playback, as experienced when listening to a 48 kHz stereo DAB station.

Installation method
Docker image on a Raspberry Pi 4.

Versions
Latest tagged Docker image.

Log messages
None

Additional context
Mono and 32 kHz sampled stations are common in the UK, so many stations received from the UK DAB multiplexes are affected.

[jketterl]

Yeah this has been confirmed on the mailing list before. Basically, as of now the audio data coming out of dablin is unqualified, and the best (most common) option is to interpret them as 48kHz stereo. There has been work on dablin towards adding a header (Opendigitalradio/dablin#74) but this still needs to be integrated. See also #155 for some additional information.

At least we finally have an issue now ;)

[orryverducci]

Thanks for the additional context. I did search through the mailing list but somehow missed this, so that's useful to know.

It's good to see that the dablin team are making changes to provide this information.