[Icecast] Best way to handle multiple (6+) streams

Andy Baxter andy at earthsong.free-online.co.uk
Sat May 21 12:08:08 PDT 2005

On Thursday 19 May 2005 04:02, Seth McTigh wrote:
> I have a need to stream 6 or 8 different audio sources (radios), and am
> seeking suggestions on the best way to do it.  Although I'd like to stream
> each separately, I could combine them to stereo streams and do 2 on each.

Sounds like a bad idea - you'd get cross-talk between the two channels.

> I'd like to know what the best hardware configuration would be to
> accomplish this?  Are there any multiple input sound cards that have been
> successfully tested, or will I need to run 6 or 8 separate boxes to stream
> into a main server?
> Is it possible to configure 4 sound cards in a single computer?

Yes if you have the slots, but a single multi-input card would be better.

> Any suggestions/pointers would be greatly appreciated.

One point is if you want to encode 6-8 streams on a single machine, you'll 
probably need a pretty fast machine, as encoding is quite 
processor-intensive. As an example, I just encoded a 4 minute, 34 second 
track in 40 seconds using oggenc at 64 kbps on a 1.4 GHz athlon, which means 
that streaming live audio the encoder would use around 100*40/(4*60+34)=14.5% 
of the CPU. I.e. you'd run out of CPU trying to encode more than 5-6 streams 
at that bitrate on this machine.

You can do this test yourself on the machine you'll be using like this:

$ oggenc -b 64 track.wav -o track.ogg
Opening with wav module: WAV file reader
Encoding "track.wav" to
at approximate bitrate 64 kbps (VBR encoding enabled)
        [ 99.9%] [ 0m00s remaining] /

Done encoding file "track.ogg"

        File length:  4m 34.0s
        Elapsed time: 0m 40.3s
        Rate:         6.8263
        Average bitrate: 66.7 kb/s

Then look for the 'rate' parameter in the results - this is the number of 
times faster than real time the track encoded in, which should roughly 
translate to the maximum number of live streams you can encode at once.

andy baxter.

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Thanks, andy.

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