Airplay and hardware volume

[Tim Curtis]

I forgot to mention that you can set the output bit depth in Airplay Config. The values are 16, 24, 243LE, 243BE, 32 but IIRC volume is computed in 16 bit then zero padded to the specified output bit depth.

You would need to look at the shairport-sync sources or post a question in the shairport-sync repo.