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.
