[...]

>I know only one way at the moment: routing Pulseaudio through JACK,
>equivalent to how Pd is routed through JACK. If this is called
>'Pulseaudio on top of JACK', then 'yes'. The extra latency is because
>I need to set 2 periods of 512 samples (23 ms) for JACK's buffering to
>get audio without dropouts in this setup. In Pd I have it fixed at 15
>ms. In practice there are more causes for latency, so I measure
>roundtrip latency in Pd with a sample-precise routine (see attached
>patch 'latency-tester2.pd'). Pd's 15 nominal ms is in practice 18 ms
>when routed directly via ALSA. Via the JACK + Pulseaudio setup it is a
>total of 50 ms in practice.

There's no other combination of frames/period and period/buffer you
can use to get ca. 17-20ms latency without dropouts?

>By the way this does of course not say anything about latency in
>Pulseaudio. Maybe there is a way to test that with a 'pulsified'
>application, for example Audacity.

That would be interesting to see.

-Jonathan