[Icecast] Odd icecast hiccup problem with low-bandwidth cellular client

Karl Heyes karl at xiph.org
Mon Mar 28 18:21:13 UTC 2005

On Mon, 2005-03-28 at 04:39, Nick Dunklee wrote:
> Here's a very odd question - I don't know if anybody can even begin to
> answer.
> I am attempting something very odd and geeky. I set up an icecast Win32
> server streaming a 96kbps mp3 stream (using all the latest as of today
> software, winamp, icecast2 and oddcast v3) so I can listen to it on my cell
> phone while at work.
> My phone does GPRS EDGE data at 131kbps-ish, just barely fast enough to keep
> up.
> I know 96kbps SHOULD work with this because Di.FM trance streams at 96kbps
> and I can listen to that hours on end off my cell phone connection and it
> plays smooth....my own connection however isn't working so good.

make sure that that the TCP settings on your win32 allow for that
bitrate. You could be throttling the connection.

> When my phone connects all it does is hiccup and skip and then some,
> occasionally reconnecting altogether, and just not playing smoothly.
> I noticed di.fm uses shoutcast, so I tried a shoutcast server instead, but
> it hiccups the same.

this would confirm a starvation issue, either at the TCP level or just
that you cannot maintain an upload rate of 96kbit + overhead from your
icecast server.

> I am convinced my problem somehow has to do with the way icecast is
> prebuffering. The current limits section of my config looks like this:

burst will max out the link to the client but glitches in the playback
would indicate a failure to maintain bitrate.

> I'm tearing my hair out here, I've tried everything, researched all over
> several icecast config docs, mailing lists, google, etc., etc., etc. nobody
> seems to have any problem even remotely close to mine and I really don't
> know what to do...are there any undocumented configuration options for the
> icecast server like tweaking how often metadata gets muxed into the mp3
> stream?
> I'm willing to try anything!
> Oh, and it does stream to computers both within my LAN and externally across
> the internet just fine, its just my cellular packet data connection giving
> me issues. I'll connect to di.fm trance, it works fine, then mine, and it
> hiccups, so i know it's not network congestion issues on the cellular end.

Don't forget DI have setup their systems to have listeners connecting,
whereas I guess you have done some tweaks in icecast only. I would check
the TCP settings for your windows version, ie TCP windows scaling or TCP
send window, something like that. I can't say how exactly the phone is
configured but default win32 usually has fixed size TCP windows which
may be getting maxed out with the high latency.


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