Sorry for the delay, I was a little busy here, I ended up seeing the messages only now.
I enabled debugging for the suggested items and it didn't bring up many clues beyond what we already had, I ended up forgetting to comment, sorry.
I also did a new test using the URL suggested in Ron's last post and I still get the "No Data" message.
I tested the URL with some working IPTV channels I have on my server as well, I still get the "No Data" message.
As Ron commented, I can run ffmpeg smoothly via SSH, the audio is converted and works as expected, however the Pipe command always returns the message "No Data".
Given that, I can only think that it could be some bug in the ARM compilation, I believe that the development team would have to take a look.
If you have any more suggestions, I'd be very happy to try it out, if ffmpeg worked with Tvheadend it would be very useful for me.
Thanks a lot for the help guys!