On Thu, Oct 17, 2002 at 03:31:36PM -0400, Taybin Rutkin wrote:
On Thu, 17 Oct 2002, David Arney wrote:
I work with a small community radio station, and
since we're continually
strapped for cash we implement our studio-transmitter link by streaming
audio over a network. We use a variety of players and formats (mainly xmms
and realplayer), but all of them share a common problem. Despite our
process monitoring software, the stream occasionally goes silent. We would
like to find a way to detect when the output of the playback computer's
soundcard is silent- or at least quiet enough to count as such.
Were you planning on using a noisegate algorithm? I think you would have
to. One common mistake people make is thinking that silence is going to
be all zeros. But that's almost never the case when doing real work with
analog equipment.
I'm not sure where to find an algorithm for that, but Steve Harris has
many many open plugins at plugin.org.uk .
we've got some bits of code for doing that at CSIRO:
* MPEG Maaate has an analysis plugin for detecting loudness
levels in the MPEG compressed domain:
http://www.cmis.csiro.au/maaate/
* we did a "select by energy" plugin for Sweep that works on
PCM data by a similar algorithm; have a look at
plugins/byenergy/byenergy.c in the Sweep source distribution:
http://sweep.sourceforge.net/
(both are GPL)
Conrad.