[MPlayer-users] high-pitched sound during mencoder recordings

[Todd Lyons]

> > > I believe it is interference, but I can't be sure.
> ... I plugged the cable coming from my TV-card
> line-out into my sound card's mic-in instead of
> regular line-in. Now the interference has gone, guess
> it has something to do with some additional
> pre-amplifier - please don't ask me for details, it
> just works. :)

Yeah, the signal coming out of a microphone has to be amplified tremendously
to reach standard analog audio levels.  You were pushing a signal that was
already that strong into the mic input, which means you were overdriving the
mic pre-amps, resulting in clipped output from the pre-amps to the circuitry
for standard levels.  The filters in the pre-amp (and probably also in the
standard circuitry) filter out some of the higher levels of harmonics (i.e.
the high odd numbers that make square waves "more square"), which you then
hear as a continuous ringing noise as the removed components leave lots of
high frequency remnants.

If anybody wants to reply and make my response more technically correct,
feel free to.  If you can correct my understanding of the goings on
described above, I won't be offended.

Glad you found this one cause I was curious what the heck could happen in
software to do this.  Glad it wasn't the software.

Blue skies...			Todd