alsa

For alsa backend, device passed through the --device option should be written exactly as output by aplay -L.

For instance, with

pi@raspberrypi2:~ $ aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
default:CARD=BossDAC
    BossDAC,
    Default Audio Device
sysdefault:CARD=BossDAC
    BossDAC,
    Default Audio Device
dmix:CARD=BossDAC,DEV=0
    BossDAC,
    Direct sample mixing device
dsnoop:CARD=BossDAC,DEV=0
    BossDAC,
    Direct sample snooping device
hw:CARD=BossDAC,DEV=0
    BossDAC,
    Direct hardware device without any conversions
plughw:CARD=BossDAC,DEV=0
    BossDAC,
    Hardware device with all software conversions

Then device should be specified through

--device "default:CARD=BossDAC"

Source: issue #161