[pulseaudio-discuss] 61ms delay in pa_simple_write()

pl bossart bossart.nospam at gmail.com
Fri Sep 24 09:11:56 PDT 2010

> For normal alsa playback, their typical values are 1024.  Pulseaudio
> sets them to large values and maybe is not entirely depending on the
> poll. It may be setting some timer to wake up itself when the DMA
> buffer runs low on data.
> Anyway the pulseaudio's large buffer scheme makes possible the 61ms
> pa_simple_write(). Qemu is not expecting such a large latency. Its
> QEMU_PA_SAMPLES defaults to 1024, which can only hold up to
> 1024/48=21ms samples. So the 61ms delay will obviously overflow the
> "data push" based USB audio model..

The default PulseAudio configuration is 4 periods of 25 ms each. You
can reduce this if you want by changing the relevant fields in

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