[icecast] Many sources into one stream

Geoff Shang gshang at pacific.net.au
Sat Apr 24 11:44:22 PDT 2004



Hi:

This is going to be difficult to do digitally.  Firstly, there is latency.
MP3 and Vorbis both have latency, and more is introduced by players
buffering. At least in Linux, the latter can be minimised by tweaking
buffer settings in programs like mpg123/321 and ogg123.

Assuming you get the latency to where it is acceptable, you will also have
to provide a way for each person to hear the other without hearing
themself echo back.  If one party is actually where the computer is then
there might be ways to do this, but it's a bit tricky.

Ultimately, the streams will need to be decoded, probably to a soundcard,
then mixed, re-encoded and sent out.  This is not trivial.

On the few occasions I've done something like this, I've used a VOIP
program to do the comms with the remote party and just treated the
program's output like any other source.  I have the advantage though of
using 2 PC's when I broadcast, so I can get my first one to record just me
and not the remote party when recording the sound to send back to them.
The same could be achieved if you had two soundcards however, with the mic
plugged into the first and the VOIP program also using that, and the output
of that card wired to the input of the second which is used for the
broadcast feed.

Unfortunately, I've not found anything for the Linux console that wil allow
me to use sampling rates above 11khz.  Something that could use Speex
wideband or ultra wideband would be great.

Geoff.

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