I have a program which uses FIFO files for interacting with the user. An audio call can be made directing the output of
arecord to one of the program's FIFO files:
arecord -r 48000 -c 1 -f S16_LE > call_in
An audio call can be answered by directing the output of one of the program's FIFO files to
aplay -r 48000 -c 1 -f S16_LE - < call_out
How could an audio file be used in place of the first command, the one used to make a call? Let's say I want to play "sound.wav" into that
call_in file, how could it be done?