Roc can't play with PulseAudio when Resampler is enabled on Raspberry Pi A

[gavv]

If Resampler is enabled, and SoX is used for audio output (pulseaudio or ALSA), playback is discontinuous.

If we:

• disable Resampler (--resampling=no), or
• use direct ALSA backend (from alsa branch) instead of SoX,

everything becomes OK. This means that we have problems with CPU usage.

[gavv]

Related to #68.

[gavv]

Note that it's reproduced only when:

• pulseaudio is installed (because Roc doesn't work on non-44100 ALSA cards #61 breaks playback without pulseaudio)
• resampling is enabled (default)
• sox is used (default in develop branch)

At first, we need to determine the bottleneck.

Resampler and SoX are separate threads, so we can start with just monitoring their CPU usage. Then we can profile them with tools like pprof.

[gavv]

The problem is that Resampler eats up to ~85% CPU, and PulseAudio eats ~20% CPU, and thus we are out of CPU and hear glitches.

[gavv]

This is likely to be fixed by #85.

[gavv]

Needs testing.

[gavv]

Unable to test it, but I hope it's fixed. Closing for now.