[pulseaudio-discuss] a question about audio synchronization between local sink and tunnel sink

[Daniël Sonck]

I'll add some of my findings. I have some special system that connects 
several tunnels to computers. When I start some music, the local sound 
card actually is the one behind the network sink. I do remember that 
sometimes the network sink stops to get in sync with the local 
soundcard.

But you'll always have some noticeable delay, simply because you'll 
probably have two different sound cards.

On a side note, when I had a bug in my system which allowed two tunnels 
from my server to the same client it actually caused a flange effect. 
That indicates that it always has a different delay and apparently it 
doesn't wait for the exact moment to play it back. I think this is the 
most significant indication that you won't be able to have an exactly 
synchronized playback. I currently use this to have music in different 
rooms where you can close a door, or you don't hear the music from 
other rooms.

Daniel

On Sun 14 Oct 2012 07:19:41 PM CEST, Tanu Kaskinen wrote:
> On Wed, 2012-10-10 at 20:45 +0000, Sun, Xiaodong wrote:
>> Hi,
>>
>> I have a pulseaudio daemon running on one PC (with my music songs
>> stored and played on this PC, let's call it PC-1). And then I setup
>> another PC (let's call it PC-2) running pulseaudio daemon on it and
>> enabled native TCP protocol. Then I configured (by using pacmd) PC-1
>> pulseaudio to load a tunnel sink pointing to PC-2, and then loaded a
>> combine sink which combines PC-2 tunnel sink and PC-1 local analog
>> audio sink. Now I can hear audio from both PC-1 and PC-2 at the same
>> time. But the audio playing are not synchronized between PC-1 and
>> PC-2. There is a delay on PC-2 comparing with PC-1.
>>
>> Now my question is, is pulseaudio designed for synchronized playback
>> between local sink and tunnel sink? If yes, what kinds of parameters
>> should I tune?
>
> I had a look, and it seems like module-tunnel is tries to report pretty
> accurate latency, and module-combine-sink in turn is supposed to
> synchronize the outputs if they provide valid latency information. So it
> looks like this should work, without any parameter tuning.
> Unfortunately, if it doesn't work, I don't have much ideas for making it
> work. How big is the delay between the two outputs? If you let it play
> for a while, does it get better?
>

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