[Icecast] IceCast KH - question

[Ross Levis]

If this occurs with multiple listeners on different computers then I would
also suspect the problem is with the playback speed of the soundcard, which
in your case dictates the encoding speed.

Each soundcard often utilizes a crystal to obtain a frequency for
determining playback speed, and no crystal can be cut exactly the same so
there will be slight variances in speeds, usually undetectable to the human
ear.

Your tracks are likely playing slightly slower on your automation PC,
perhaps losing 200ms every minute for example.  But your listeners are
playing back at normal speed or whatever there soundcard determines.  

The listeners playback buffer in their player will be slowly depleting at
200ms per minute until after some time the buffer is empty and it needs to
pre-buffer more audio which usually causes a pause in playback.

The reverse can also be true where the encoding PC is encoding slightly
faster than 44100 samples per second and the playback PC buffer will
over-fill causing it to discard some audio every so often.

Ideally the stream playback software should detect where the buffer is
depleting or increasing steadily and resample the audio to playback at a
slower or faster speed.  I'm not aware of any that do that.

We have done something similar in our radio broadcasting software when
sending the audio to 2 soundcards, as we found the same issue with 2
soundcards playing at different speeds.

Regards,

Ross Levis
StationPlaylist.com

-----Original Message-----
From: icecast-bounces at xiph.org [mailto:icecast-bounces at xiph.org] On Behalf
Of Live Mix - Arvy
Sent: Tuesday, 11 June 2013 4:43 AM
To: Karl Heyes
Cc: icecast at xiph.org
Subject: Re: [Icecast] IceCast KH - question

Hello Thomas and Karl, thank you for your answer and time.

We've tested with several listeners and different connections, using WinAmp
and JW Player. For about 15 minutes, everything is ok. After
15-18 minutes, WinAmp starts do blink that "red square" (packet loss or
instability), and after about 20 minutes sounds starts to "pop", with small
cuts, and then starts to cut a lot. I think the problem is
progressive: more time, more cuts.

We use SAM Broadcaster to encode AAC+ HE 48k. We're using the latest IceCast
KH version, Win32.

Other datail: all users have always "Lag: 0" on Admin interface

If you want to listen what happens, if you can and have time (very
appreciated) the stream is http://mp4.livemix.com.br/livemix - if possible
using WinAmp. Wait about 15-20 minutes to see the problem.

Any ideas I really appreciate, because we have about 100-200 listeners at
same time we really don't know what to do :(

Thanks a lot,
Rogerio



> On 06/06/13 17:13, Live Mix - Arvy wrote:
>> Hi there,
>>
>> we use IceCast KH on our webradio, no commercial. We have an issue 
>> that we dont know where to look. When listening using WinAmp (but in 
>> other players too like JW Player), after 70 or 90 minutes, we realize 
>> that the "green square" on top of WinAmp becomes a "red square". 
>> About 60 minutes after start, sometimes the "red square" blinks, and 
>> then more frequently. It happens with different internet connections 
>> and providers. Until 60 minutes, the broadcast is perfect.
>>
>> Can you give me an idea where to look or solve this issue? It's 
>> related to Icecast, or encoder, or internet connection, etc?
>
> My initial guess would be the encoder sending rate being mismatched 
> with the samplerate.  When a player reports an issue it needs to be 
> clear on what it is relating to, but I suspect it will be down to a 
> starvation of the incoming data.
>
> Any issue within icecst here would should as an increased lag value 
> for that listener on the admin page, icecast will send a lot faster 
> than the source but is still subject to certain limits like CPU or may 
> be a per-mount limit (limit-rate is set).
>
> If it is affecting multiple listeners at different locations at a 
> consistent offset into the stream then the sending rate from the 
> source is suspect. May be a 44k/48k mismatch or a bad clock on the 
> source client.
>
> karl.
>
>

Live Mix
www.livemix.com.br

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