[pulseaudio-discuss] rtp question

CJ van den Berg cj at vdbonline.com
Wed Feb 20 03:00:22 PST 2008

On Tue, Feb 19, 2008 at 10:10:39PM -0500, Paul Fox wrote:
> i'm curious about the rtp capability -- is there anything in the
> protocol to guarantee synchronization all the way to the sound hardware?
> i understand that since the stream is multicast, all network receivers
> will get it at the same time, but different servers may have different
> latencies.  i suppose these latencies will tend to be constant, and
> not drift, but i'm worried that if the sound hardware is driving systems
> that can be heard from one another (e.g., one in the kitchen, one in
> the livingroom two rooms away) that the delay may be annoying.

RTP doesn't provide any kind of synchronisation, so the different
machines will definitely drift. This is a much bigger problem that the
different latencies. At least the latencies are constant. And yes, it
will be very annoying. 

> any experience with this?

I've tried it once between two rooms at opposite ends of my house.  It
started out with a slight reverb effect, which was pretty acceptable.
But after about 3-5 minutes it was far enough out of sync that turned
into an annoying echo effect.

Now I use module-tunnel + module-combine, which works just fine. It's
good enough that you can't really tell whether the slight reverb effect
you get in the hallway is network induced or just the acoustics of the
house. I haven't yet tried running an audio cable across the house to
find out.  :-)

CJ van den Berg

mailto:cj at vdbonline.com
  xmpp:cj at vdbonline.com
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