Re-sampling and volume control issues on Android

[dragonman225]

On Android, all audio data are re-sampled automatically to maximum bit-depth and frequency that the USB soundcard supports, i.e. 24-bit / 96 kHz.

Besides, volume control on Android is done in software, that is, directly applied on audio samples, instead of sending commands to the USB soundcard. This means the maximum volume overall is the default volume hard-coded in the USB soundcard's firmware.

If we want to solve the above issues, one way I found is to set up a chroot environment with full ALSA stack installed, edit ~/.asoundrc to force ALSA use external USB soundcard, and play audio files with mocp.