ref: 687cf020c1602161b61c4eaf904651cb73bbb2c7
parent: 3956d17e66a7b0251b55fcefa2dc29e1eca22351
author: robs <robs>
date: Mon Nov 27 14:01:39 EST 2006
Filled in the man-page entries for the butterworth filters and gave more precise info on highp and lowp filters.
--- a/sox.1
+++ b/sox.1
@@ -816,22 +816,22 @@
i.e. peaking at the
.I center
frequency and settling around it.
-See \fBfilter\fR for a bandpass effect with steeper shoulders.
This effect supports the \fI-o\fR option (see above).
+See \fBfilter\fR for a bandpass filter with steeper shoulders.
.TP 10
-bandpass \fIfrequency bandwidth\fB
-Butterworth bandpass filter. Description coming soon!
+bandpass|bandreject \fIfrequency bandwidth\fR
+Apply a two-pole Butterworth band-pass or band-reject filter with
+central frequency (in Hz) \fIfrequency\fR,
+and bandwidth (in Hz, and as determined by the 3dB points)
+\fIbandwidth\fR.
+The filter rolls off at 6dB per octave (20dB per decade).
-This effect supports the \fI-o\fR option (see above).
-
+These effects support the \fI-o\fR option (see above).
.TP 10
-bandreject \fIfrequency bandwidth\fB
-Butterworth bandreject filter. Description coming soon!
-
-This effect supports the \fI-o\fR option (see above).
-
+bandreject \fIfrequency bandwidth\fR
+See \fI bandpass\fR.
.TP 10
bass|treble \fIgain\fR [\fIfrequency\fR] [\fIslope\fR]
Boost or cut the bass (lower) or treble (upper) frequencies of
@@ -1009,39 +1009,27 @@
The modulation is either sinusoidal (-s) or triangular
(-t). Gain-out is the volume of the output.
.TP 10
-highp \fIfrequency\fR
-Apply a single pole recursive high-pass filter.
-The frequency response drops logarithmically with
-I frequency
-in the middle of the drop.
-The slope of the filter is quite gentle.
-See \fBfilter\fR for a highpass effect with sharper cutoff.
+highp|lowp \fIfrequency\fR
+Apply a single-pole recursive high-pass or low-pass filter with
+3dB point \fIfrequency\fR.
+The filter rolls off at 6dB per octave (20dB per decade).
-This effect supports the \fI-o\fR option (see above).
+These effects support the \fI-o\fR option (see above).
+See \fBfilter\fR for filters with a sharper cutoff.
.TP 10
-highpass \fIfrequency\fB
-Butterworth highpass filter. Description coming soon!
+highpass|lowpass \fIfrequency\fR
+Apply a two-pole Butterworth high-pass or low-pass filter with
+3dB point \fIfrequency\fR.
+The filter rolls off at 12dB per octave (40dB per decade).
-This effect supports the \fI-o\fR option (see above).
-
+These effects support the \fI-o\fR option (see above).
.TP 10
lowp \fIfrequency\fR
-Apply a single pole recursive low-pass filter.
-The frequency response drops logarithmically with
-.I frequency
-in the middle of the drop.
-The slope of the filter is quite gentle.
-See \fBfilter\fR for a lowpass effect with sharper cutoff.
-
-This effect supports the \fI-o\fR option (see above).
-
+See \fIhighp\fR.
.TP 10
lowpass \fIfrequency\fB
-Butterworth lowpass filter. Description coming soon!
-
-This effect supports the \fI-o\fR option (see above).
-
+See \fIhighpass\fR.
.TP 10
mask
Add "masking noise" to signal.