I have the DietPi BruteFIR package installed using a Raspberry Pi 3 and USB sound card.
BruteFIR plays sound fine if a .wav file is the input, but if I try to play anything through the loopback by for example using aplay to play a wav file it crashes with the following error:
ALSA I/O: Could not read audio: File descriptor in bad state.
I/O module failed to read, aborting.
I have had BruteFIR working on the same Raspberry Pi with a regular Raspian installation and I can't figure out what is causing the problem in this case...
I found that it doesn't crash as long as I just use the default sound output - i.e. don't specify which playback hardware aplay uses with the -D parameter. Even though the playback hardware I was specifying IS the default playback device.