[vorbis] Realtime encoding at 44.1khz

Geoff Shang gshang at uq.net.au
Fri Sep 7 07:03:02 PDT 2001


I've been experimenting with streaming vorbis across my network from the
windows box to an icecast2 server on my linux machine (the server I usually
use is having some network issues at present).  I've tested both ostream
0.7.1 and oddcast beta26.   It seems that neither can encode on the fly on
my P2-266 at 44100 fast enough to be able to stream it.  Ostream looked the
more promising of the two, with breaks in the audio but otherwise coping OK
... until it crashed, presumably because it filled some buffer somewhere.
It can maintain a 44.1khz mono stream at lowest bitrate (aprox. 40kbps) but
only just.  I only tried oddcast once, at 64kbps stereo.  It sounded very
weird, as if it was only recording half the data in a given time period.
It sounded as if it was playing at about double speed but wasn't pitch

What I want to know is this.  Am I expecting too much of my P2-266 to do
44.1khz 64kbps stereo in real-time?  Assuming I'm not, is this an
optimisation issue or should I be able to do it already?

BTW: I don't know if anyone's fiddled with it or not, but I think results
at lower sampling rates could be improved if the lowpass wasn't so severe.
Of course, I don't know if this will introduce artifacts, but I can easily
hear the roll-off and it's noticeably lower than the uncompressed audio
would be at that rate.  For example, the difference between vorbis at
44.1khz and 32khz is more noticeable, particularly in stereo, than it is
for uncompressed samples.


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