[pulseaudio-discuss] ALSA or PulseAudio for low-latency voice?

[David Henningsson]

On 2011-03-19 17:45, Philip Jägenstedt wrote:
> Hi PulseAudionauts,
>
> I've been meaning to experiment a bit with low-latency voice codecs
> and naturally want to add as little latency as possible to what is
> imposed by the codec on both capture and playback. (My guess is that
> the latency added would be between min(capture_latency,
> playback_latency) and capture_latency+playback_latency, depending on
> how well capture end and playback begin are synchronized.)
>
> Q: Does it matters for latency if I program against ALSA or PulseAudio?

Well, that kind of depends on what scale you're on. If you need 
latencies under say - and this is just a qualified guess - ~ 10-20 ms, 
you'll need to program against ALSA or Jack. Above that and you'll be 
good with PulseAudio.

> This is assuming a setup like on Ubuntu, where the default ALSA device
> is using a PulseAudio backend. (Portability and code complexity may
> favor one solution or the other, but that's not what I'm asking.)

When I say program against ALSA above, I mean directly against an ALSA 
sound card, i e bypassing Pulseaudio. As for if ALSA plugin -> 
PulseAudio -> ALSA -> HW gives worse latency than PulseAudio -> ALSA -> 
HW, I don't think that matters much.

-- 
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic