Add support of internal sample rate to ALSA driver

[sadko4u]

Summary

Not all audio devices provide all sample rates that can be useful. For example, for analog radio broadcasting the 32 kHz sample rate is the preferred one. But trying to set up radio broadcasting chain with 44100 Hz sample rate gives several drawbacks:

• extra unnecessary frequencies above 16 kHz when trying to maximize loudness;
• removing these frequencies yields the audio to go out of 0 dbFS dure to gibbs phenomenon and overdrive the radio transceiver.

Instead of this, the best solution looks like just tune the whole audio processing chain in 32 kHz sample rate but not all audio devices support such sample rate. And finally we have different picture as it is on the radio receiver side.

If the audio device does not support 32 kHz sample rate, then the 44100 Hz sample rate is selected.

Instead of this, it is a good option to add on-the-fly resampling to force JACK to internally use 32 kHz sample rate but interact with the device using 44100 kHz. For example, it can be an additional option to ALSA driver:

jackdmp -d alsa --force-sample-rate 32000

This may introduce additional latency but for broadcasting it is pretty OK.