Need Help with rtl_fm on the raspberry pi

[Matthew Simmons]

I've been using rtl_fm in conjunction with DSD on my Linux (Ubuntu 16.04 LTS) machine to decode P25 traffic from my local PD. They are not trunked so I have just been tuning to a single frequency and letting it decode.

I've since purchased a Raspberry Pi3b in the hopes of getting the same software working a in a semi-portable form factor.

The issue I have been having is that I cannot seem to get DSD to output sound on the pi. In Ubuntu I have been using | padsp dsd -i - -o pa:0 .  However raspian uses a system called aplay and I just cannot figure out how to format the command to use aplay instead of Pulse Audio.

I'm sure someone with the requisite Linux command line experience could shed a little light on this for me. Be gentle. I'm an idiot. 

[Adam Nielsen]

> The issue I have been having is that I cannot seem to get DSD to
> output sound on the pi. In Ubuntu I have been using | padsp dsd -i -
> -o pa:0 . However raspian uses a system called aplay and I just
> cannot figure out how to format the command to use aplay instead of
> Pulse Audio.

It looks like you might be trying to play a raw file, but I'm not
sure. You can look through the options for aplay online (it's part of
the standard Linux ALSA system) so from that list you could try:

- Using "-t raw" if there is no .wav header and you get an error about
the file format being unknown.
- Using /dev/stdin as the filename, so that it reads from the pipe.


Cheers,
Adam.