On Thu, September 19, 2013 6:42 pm, Tanu Kaskinen wrote: > On Wed, 2013-09-18 at 04:28 +1000, Patrick Shirkey wrote: >> Hi, >> >> Can someone shed some light on the best case and typical latency that >> Pulse provides for standard operations? > > What do you mean by standard operations? I'd estimate volume changes > etc. normally (on an ALSA sink) have a few millisecond latency (best > case 0.5 ms audio buffer + scheduling latency). > Just a "normal" round trip signal flow, for example : PA (in) -> audacity (in) -> audacity (out) -> pa (out) >> Also how that is affected by using jack-sink assuming jack is set to the >> lowest possible latency that a device can handle? > > When jackd asks for N frames from PulseAudio, pulseaudio will render N > frames. There's no extra buffering done in the Jack sink, so volume > changes etc. will have latency that is roughly the same as the normal > Jack client latency. > Do you have an suggestions on how to get an accurate measurement? > If by "standard operations" you meant the stream latency that PulseAudio > clients see (in which case "standard operations" is a strange way to say > it, IMO), then that depends on what the clients request. If they let > PulseAudio choose, the latency is typically 2 seconds. If they want > minimal latency, with infinite CPU power I think the lower bound is > maybe a couple of milliseconds, but since computers don't have infinite > CPU power, the practical limit is some tens of milliseconds based on > what I've heard (the exact limit naturally depends on how beefy the CPU > is). I would like to accurately measure the lower bounds. Do you know of any tools for that? I know PA provides latency measurements as part of the API but is there an app the already provides this data in an accessible format? -- Patrick Shirkey Boost Hardware Ltd
