Parametric equalizer demonstration
Welcome to the prototype parametric equaliser control panel! This is a
single-band stereo equaliser, which we are using to get the parametric
controls set up right. Once that's done, we'll probably just make this
into a four-band parametric, and try and add some sensible
dynamic range limiting as well.
General information
As for the other audio IO demos, this application controls
the Sun Audio device. By default, the Ptolemy universe that created it
configures the device to run stereo at 44.1 kHz with 16-bit linear
encoding.
There is a single band of parametric equalisation, with control over
the band frequency, band width, and band gain. The frequency range is
settable; in the future, it will also be possible to select low-pass,
band-pass, or high-pass filtering as well.
Controls
- Input and output selectors
- The input and output selectors do the obvious thing. Or, at least,
they would if they worked.
- Rec
- Controls the gain on the input. For CD source, this should really
be down quite low to avoid clipping.
- Bal
- Controls the balance of the output signal. Negative numbers are
left, positive are right.
- Gain
- Controls the output gain. Again, if it's too high or there's too
much gain in a filter, you'll get nasty
noises. This is why we need dynamic range control :-)
- Freq
- Controls the center frequency of the filter, in Hz. The two entry
boxes at the top left of the filter set the range of adjustment. You
may notice a couple of funnies of you use this -- we re working on
logarithmic scaling for the slider, which should fix things.
- BW
- Controls the band-width of the filter, in octaves. This is
measured at the half-gain (in dB) point. A typical ten-band
graphic equaliser, for example, has a band-width of one active.
- Gain
- Controls the peak gain of the filter, in dB. At maximum gain, the
filter sometimes craps out, which is a mystery. (Bill?)
Shortcuts
- Start -- Control-g
- Pause -- Control-p
- Resume -- Control-r
- Stop -- Control-s
- Close -- Control-x k
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