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Diffstat (limited to 'usr.sbin/virtual_oss/virtual_equalizer/virtual_equalizer.8')
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diff --git a/usr.sbin/virtual_oss/virtual_equalizer/virtual_equalizer.8 b/usr.sbin/virtual_oss/virtual_equalizer/virtual_equalizer.8 new file mode 100644 index 000000000000..db47db84305e --- /dev/null +++ b/usr.sbin/virtual_oss/virtual_equalizer/virtual_equalizer.8 @@ -0,0 +1,127 @@ +.\" +.\" Copyright (c) 2019 Google LLC, written by Richard Kralovic <riso@google.com> +.\" +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" +.Dd February 12, 2025 +.Dt VIRTUAL_EQUALIZER 8 +.Os +.Sh NAME +.Nm virtual_equalizer +.Nd audio equalizer +.Sh SYNOPSIS +.Nm +.Op Fl h +.Op Fl o +.Op Fl q +.Op Fl d Ar devname +.Op Fl w Ar what +.Op Fl p Ar part +.Op Fl c Ar channels +.Op Fl f Ar file +.Sh DESCRIPTION +.Nm +sets the given frequency response for the given +.Xr virtual_oss 8 +instance via the control character device given by the -d option. +The design goal of this equalizer is to provide precise equalization +for arbitrary requested frequency response at the expense of higher +latency, utilizing a so-called finite impulse response, FIR, filter. +.Pp +The requested frequency response is configured via standard input or +the file specified by the -f option. +There is one control point in per line. +Each line consists of two numbers, frequency in Hz and requested +amplification. +Amplification between two consecutive control points is a linear +interpolation of the given control point values. +.Pp +To make the filter finite, it is windowed in time domain using a Hann +window. +The windowing actually modifies the frequency response - the actual +response is a convolution of the requested response and spectrum of +the window. +This is, however, very close to the requested response. +.Pp +The following options are available: +.Bl -tag -width indent +.It Fl q +Be quiet and don't print anything to standard output. +.It Fl d Ar device +The +.Xr virtual_oss 8 +control character device. +.It Fl w Ar what +Select what part the FIR filter should apply to. +Valid values are: rx_dev, tx_dev, rx_loop and tx_loop. +The default value is tx_dev. +.It Fl p Ar part +Select the index of the part given by the -w option to apply the filter to. +Default is zero. +.It Fl c Ar channels +Select number of channels to apply filter to, starting at channel zero. +By default all channels of the given part are updated. +.It Fl f Ar file +Read filter coefficients from the given file instead of standard input. +.It Fl o +Turn equalizer off. +.It Fl h +Show usage. +.El +.Sh EXAMPLES +To pass only frequencies between 200Hz and 400Hz: +.Bd -literal -offset indent +# Note that the -F and -G options enable FIR filtering. +virtual_oss -B -C 2 -c 2 -S -Q 0 -b 32 -r 48000 -s 8ms -F 80ms -G 80ms \\ + -f /dev/dsp -d dsp.virtual -t vdsp.ctl + +# For simplex operation use this: +virtual_oss -B -C 2 -c 2 -S -Q 0 -b 32 -r 48000 -s 8ms -F 80ms -G 80ms \\ + -R /dev/null -O /dev/dsp -d dsp.virtual -t vdsp.ctl + +# Load normalized filter points to avoid sample value overflow +cat << EOF | virtual_equalizer -d /dev/vdsp.ctl -w tx_dev -p 0 -c 2 +NORMALIZE +199 0.0 +200 1.0 +400 1.0 +401 0.0 +EOF + +# Load FIR filter based on sine frequency points +cat << EOF | virtual_equalizer -d /dev/vdsp.ctl -w tx_dev -p 0 -c 2 +199 0.0 +200 1.0 +400 1.0 +401 0.0 +EOF + +.Ed +.Sh SEE ALSO +.Xr virtual_oss 8 +.Sh AUTHORS +.Nm +was written by +.An Richard Kralovic riso@google.com . |