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

Brad Isbell brad at musatcha.com
Sun May 25 20:48:49 PDT 2014


The server doesn't control the rate, the source does.  Provided you aren't
getting corrupt stream data (and it doesn't sound like you are), you don't
have a server bug in this case.  At a basic level, the server level takes
the data that comes in from the source, buffers it, and sends it right back
out the door at the rate at which it came in.

It isn't entirely clear to me where you're seeing the timing issue and what
your setup is, but there are a couple other things to think about:

   - Clock drift happens.  It's pretty severe but not unheard of for a
   sound card to play back +/- 1% or so of the rate.  In your case, you're
   looking at a 0.28% difference.  Perhaps there is a problem on the playback
   end?  Are you sure your users are having this trouble?  Even if they all
   aren't, some inevitably will on any station.
   - Measurement in time of lossy audio files is usually not very exact.
    MP3 files in particular have no track length header.
   - Timing tracks down to the second will throw you off by 10 seconds at
   the end of a playlist anyway, due to rounding up/down to the nearest second.
   - If you can, don't plan out your perfect playlist by time.  You need
   something that will automatically adjust things for you as you go.  It's
   unrealistic to assume that you will be able to come up with a playlist
   timed perfectly when dealing with a variety of formats and codecs with an
   encoder that has an artificial clock sending audio to remotes that have
   completely separate clocks.

I don't know what the core of the problem is that you're having, so
hopefully this is helpful.

Brad Isbell
brad at musatcha.com
http://www.musatcha.com


On Sun, May 25, 2014 at 9:23 PM, Jordan Verner <jv_erner at hotmail.com> wrote:

> Hello,
> In conclusion I'm pretty sure this issue is the symptom of a bug, either
> within Ices or Icecast itself. I decided to try running the same setup on
> Shoutcast today, and it's working perfectly. An hour of streaming at the
> time of this message, and absolutely no schedule deviation.
> It appears as though Shoutcast has better rate control than Icecast does
> at the moment or something.
> Thanks,
>
> Jordan.
>
> ------------------------------
> From: jv_erner at hotmail.com
> To: icecast at xiph.org
> Date: Sun, 25 May 2014 10:03:10 -0400
>
> Subject: Re: [Icecast] Keeping icecast + ices 2.X running on a strict
> schedule?
>
> Hello,
> Regarding accounting for track lengths, could sox (soxi) be getting it
> wrong?
> Here's my approach atm:
> $lengths = array();
> foreach($files as $val)
> {
> //Note that $files has already been populated by glob()
> $temp = explode(":", shell_exec('soxi -d "'.$val.'"'));
> $length = $temp[0] * 60 * 60;//convert the hours to seconds.
> $length += ($temp[1] * 60);//convert minutes to seconds
> $length += $temp[2];//add the seconds
> $length *= 1000;//convert to milliseconds.
>
> $lengths[$val] = $length;
> }
> With that done, I can retrieve lengths like this:
> $test = $lengths["/home/caturria/songs/etc.ogg"];
> I'm going to try subtracting a tenth of a second or so from these values
> just to see if I can get slightly more sane results.
> Thanks,
>
> Jordan.
>
> ------------------------------
> Date: Sun, 25 May 2014 13:23:09 +0000
> From: thomas at ruecker.fi
> To: icecast at xiph.org
> Subject: Re: [Icecast] Keeping icecast + ices 2.X running on a strict
> schedule?
>
> 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.
>
> Cheers
>
> TBR
>
>
>
> > 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
> > _______________________________________________
> > Icecast mailing list
> > Icecast at xiph.org
> > http://lists.xiph.org/mailman/listinfo/icecast
>
>
> _______________________________________________
> Icecast mailing listIcecast at xiph.orghttp://lists.xiph.org/mailman/listinfo/icecast
>
>
>
> _______________________________________________ Icecast mailing list
> Icecast at xiph.org http://lists.xiph.org/mailman/listinfo/icecast
>
> _______________________________________________ Icecast mailing list
> Icecast at xiph.org http://lists.xiph.org/mailman/listinfo/icecast
>
> _______________________________________________
> Icecast mailing list
> Icecast at xiph.org
> http://lists.xiph.org/mailman/listinfo/icecast
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.xiph.org/pipermail/icecast/attachments/20140525/89e61583/attachment.htm 


More information about the Icecast mailing list