[Icecast] Keeping icecast + ices 2.X running on a strict schedule?

"Thomas B. Rücker" thomas at ruecker.fi
Sun May 25 13:23:09 UTC 2014

On 05/25/2014 01:13 PM, Jordan Verner wrote:
> Icecast and Ices are running on the same machine and it is a dedicated
> server.
> It is a Xeon 1270 V2 CPU with 16 GB ram running Centos 64-bit.
> Any thoughts on which settings I could try next? I have tried
> everything that appears to relate to the speed at which the stream
> occurs to no avail.
> One point I forgot to mention is that some tracks bring on more
> deviation than others. Shorter tracks, like spots, through it off more
> than longer tracks (I think). There are definitely tracks that inflict
> this effect more than others.

I'm going to revise my guess. It's probably inaccuracies in how you
account for track length in your system. But ultimately it's irrelevant.
I'd suggest to explore the idea of a filler jingle, as pointed out
earlier. If you want to get fancy, you can even have several to
dynamically chose to adjust for the offset more accurately. Although,
I'm going to say that this is overkill and a 10s jingle/sound file
should be just fine, also most listener software will have a buffer of
10-60s anyway, so being "on the dot" doesn't really come out right
anyway. If you want silence, then please note that you should use very
low level noise instead of digital silence. For the listener it will be
indistinguishable, as the noise will probably be below the noise floor
of their sound card, but for the vorbis encoder this makes a crucial
difference. Digital silence compresses down to single bits per second
and will lead to source timeouts and ill effects in listener software
and should be avoided at all cost when streaming.

> I haven't experienced any other timing oddities on the machine.

If you can live with the above, then I'd suggest to take that route.



> > Date: Sun, 25 May 2014 07:05:42 +0000
> > From: thomas at ruecker.fi
> > To: icecast at xiph.org
> > Subject: Re: [Icecast] Keeping icecast + ices 2.X running on a
> strict schedule?
> >
> > Hi,
> >
> > On 05/24/2014 11:29 PM, Jordan Verner wrote:
> > > I'm using Icecast, Ices, and the script module configuration to serve
> > > the playlist to the server. Playlists are scheduled once per day with
> > > regularely placed events (like spots) which run at specific times.
> > > Unfortunately it's being served too fast, so it's always getting ahead
> > > of schedule (gaining about 10 seconds on every hour).
> >
> > Sounds like the clocking is faster for some reason.
> >
> > > I have tried adjusting the flush-samples setting in ices.xml and the
> > > queue size in the icecast.xml file to no avail.
> > > I've had to resort to implementing a forced delay into the php script
> > > which feeds the filenames to ices, so that if ices calls it
> > > significantly early it'll wait to issue the next filename until it's
> > > closer to it's scheduled start time. This was causing disconnects
> > > whenever it became deviated beyond 10 seconds. Disabling source
> > > timeout fixed this, but still it tries to get as far ahead as
> > > physically possible and takes as much wiggle room as I give it
> plus more.
> >
> > That won't fix it. You're inserting gaps into the stream and that's a
> > bad thing for your listeners too.
> >
> > > Is there any fix for this? Streaming for 24 hours would have it
> > > calling the script as much as 4 minutes ahead of schedule, forcing my
> > > script to hang for all that time before issuing each and every
> filename.
> > > This is way too much deviation for streams which stick to a schedule.
> > > Two weeks of streaming would have everything an hour early.
> >
> > So for some reason on your system Ices is running 0.28% faster. I'm not
> > sure what causes this and where those samples go. Is it by chance a
> > virtual machine?
> >
> > You can try to fiddle further with ices settings. If that doesn't fix it
> > then you could always have your script insert a 10s filler jingle if it
> > detects that you're out of the timeframe.
> >
> > Other options would be to explore different automation solutions, but
> > they might suffer the same problem if it's some underlying clock oddity
> > on your system.
> >
> > Cheers
> >
> > Thomas
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> > Icecast at xiph.org
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