[LAU] Tuning icecast/ices for low latency

Hans Wilmers hanswil at notam02.no
Wed Sep 8 00:18:40 UTC 2010

On 09/07/2010 01:39 PM, Julien Claassen wrote:
> 'Owdo again!
>   Now that I've icecast running with ices as a feeder, I wonder, if I 
> can turn down latency. In icecast I set the burst-size to 0 and in ices 
> I set realtime. Still the delay is considereable. Is there any chance of 
> tuning this setup further to reduce latency?

The setup of the receiving client matters also. I have used the 
combination ices->icecast->ogg123 for streaming over the internet with a 
latency of ca. 3-4seconds, which is worse than what you get. But the 
three processes were on three machines with the internet in between, and 
the receiving side was connected using CDMA.

The crude tweaks I used to get latency down, were:

In ices.conf:
- use a high bandwidth, so any buffers along the way are filled up 
faster. I used 320kbit/s.

In icecast.xml:
- set burst-size to 0, just as you did

With ogg123:
- chose a small input buffer. I used:
$ ogg123 -b 8 http://users.notam02.no:8000/bells.ogg
and got dropouts, and then I used
$ ogg123 -b 16 http://users.notam02.no:8000/bells.ogg
and run without dropouts for 30minutes.

One problem I saw, was that drifting of the clocks caused the buffers 
either to be emptied or to be overfilled after a while - depending on 
which soundcard was the faster one.

/ Hans

Hans Wilmers
Nedre Gate 5
N-0551 Oslo Norway
tlf.: +47 22358065

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