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Christos Margiolis
9cab9fde5e
This patch diverges quite a bit from the current upstream [1] in a few ways: 1. virtual_oss(8), virtual_bt_speaker(8) and virtual_oss_cmd(8) are actually separate programs. 2. Backends (lib/virtual_oss) are built as separate shared libraries and we dlopen() them in virtual_oss(8) and virtual_bt_speaker(8) on demand. 3. virtual_equalizer(8) and the sndio and bluetooth backends are built as ports, because they depend on third-party libraries. 4. Use newer libav API in bluetooth backend (see HAVE_LIBAV ifdefs) to address compiler errors. [1] https://github.com/freebsd/virtual_oss Sponsored by: The FreeBSD Foundation MFC after: 1 week Reviewed by: emaste Differential Revision: https://reviews.freebsd.org/D52308
128 lines
4.2 KiB
Plaintext
128 lines
4.2 KiB
Plaintext
.\"
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.\" Copyright (c) 2019 Google LLC, written by Richard Kralovic <[email protected]>
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.\"
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\"
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.Dd February 12, 2025
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.Dt VIRTUAL_EQUALIZER 8
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.Os
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.Sh NAME
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.Nm virtual_equalizer
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.Nd audio equalizer
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.Sh SYNOPSIS
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.Nm
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.Op Fl h
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.Op Fl o
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.Op Fl q
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.Op Fl d Ar devname
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.Op Fl w Ar what
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.Op Fl p Ar part
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.Op Fl c Ar channels
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.Op Fl f Ar file
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.Sh DESCRIPTION
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.Nm
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sets the given frequency response for the given
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.Xr virtual_oss 8
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instance via the control character device given by the -d option.
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The design goal of this equalizer is to provide precise equalization
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for arbitrary requested frequency response at the expense of higher
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latency, utilizing a so-called finite impulse response, FIR, filter.
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.Pp
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The requested frequency response is configured via standard input or
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the file specified by the -f option.
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There is one control point in per line.
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Each line consists of two numbers, frequency in Hz and requested
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amplification.
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Amplification between two consecutive control points is a linear
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interpolation of the given control point values.
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.Pp
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To make the filter finite, it is windowed in time domain using a Hann
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window.
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The windowing actually modifies the frequency response - the actual
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response is a convolution of the requested response and spectrum of
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the window.
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This is, however, very close to the requested response.
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.Pp
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The following options are available:
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.Bl -tag -width indent
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.It Fl q
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Be quiet and don't print anything to standard output.
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.It Fl d Ar device
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The
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.Xr virtual_oss 8
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control character device.
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.It Fl w Ar what
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Select what part the FIR filter should apply to.
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Valid values are: rx_dev, tx_dev, rx_loop and tx_loop.
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The default value is tx_dev.
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.It Fl p Ar part
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Select the index of the part given by the -w option to apply the filter to.
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Default is zero.
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.It Fl c Ar channels
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Select number of channels to apply filter to, starting at channel zero.
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By default all channels of the given part are updated.
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.It Fl f Ar file
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Read filter coefficients from the given file instead of standard input.
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.It Fl o
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Turn equalizer off.
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.It Fl h
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Show usage.
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.El
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.Sh EXAMPLES
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To pass only frequencies between 200Hz and 400Hz:
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.Bd -literal -offset indent
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# Note that the -F and -G options enable FIR filtering.
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virtual_oss -B -C 2 -c 2 -S -Q 0 -b 32 -r 48000 -s 8ms -F 80ms -G 80ms \\
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-f /dev/dsp -d dsp.virtual -t vdsp.ctl
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# For simplex operation use this:
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virtual_oss -B -C 2 -c 2 -S -Q 0 -b 32 -r 48000 -s 8ms -F 80ms -G 80ms \\
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-R /dev/null -O /dev/dsp -d dsp.virtual -t vdsp.ctl
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# Load normalized filter points to avoid sample value overflow
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cat << EOF | virtual_equalizer -d /dev/vdsp.ctl -w tx_dev -p 0 -c 2
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NORMALIZE
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199 0.0
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200 1.0
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400 1.0
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401 0.0
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EOF
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# Load FIR filter based on sine frequency points
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cat << EOF | virtual_equalizer -d /dev/vdsp.ctl -w tx_dev -p 0 -c 2
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199 0.0
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200 1.0
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400 1.0
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401 0.0
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EOF
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.Ed
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.Sh SEE ALSO
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.Xr virtual_oss 8
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.Sh AUTHORS
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.Nm
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was written by
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.An Richard Kralovic [email protected] .
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