doc/filters: sort audio filters by name

1 files changed, 464 insertions, 458 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 17c54c5e6c..af9dfcd0bf 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -347,282 +347,6 @@ aconvert=u8:auto
 @end example
 @end itemize
 
-@section allpass
-
-Apply a two-pole all-pass filter with central frequency (in Hz)
-@var{frequency}, and filter-width @var{width}.
-An all-pass filter changes the audio's frequency to phase relationship
-without changing its frequency to amplitude relationship.
-
-The filter accepts the following options:
-
-@table @option
-@item frequency, f
-Set frequency in Hz.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Specify the band-width of a filter in width_type units.
-@end table
-
-@section highpass
-
-Apply a high-pass filter with 3dB point frequency.
-The filter can be either single-pole, or double-pole (the default).
-The filter roll off at 6dB per pole per octave (20dB per pole per decade).
-
-The filter accepts the following options:
-
-@table @option
-@item frequency, f
-Set frequency in Hz. Default is 3000.
-
-@item poles, p
-Set number of poles. Default is 2.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Specify the band-width of a filter in width_type units.
-Applies only to double-pole filter.
-The default is 0.707q and gives a Butterworth response.
-@end table
-
-@section lowpass
-
-Apply a low-pass filter with 3dB point frequency.
-The filter can be either single-pole or double-pole (the default).
-The filter roll off at 6dB per pole per octave (20dB per pole per decade).
-
-The filter accepts the following options:
-
-@table @option
-@item frequency, f
-Set frequency in Hz. Default is 500.
-
-@item poles, p
-Set number of poles. Default is 2.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Specify the band-width of a filter in width_type units.
-Applies only to double-pole filter.
-The default is 0.707q and gives a Butterworth response.
-@end table
-
-@section bass
-
-Boost or cut the bass (lower) frequencies of the audio using a two-pole
-shelving filter with a response similar to that of a standard
-hi-fi's tone-controls. This is also known as shelving equalisation (EQ).
-
-The filter accepts the following options:
-
-@table @option
-@item gain, g
-Give the gain at 0 Hz. Its useful range is about -20
-(for a large cut) to +20 (for a large boost).
-Beware of clipping when using a positive gain.
-
-@item frequency, f
-Set the filter's central frequency and so can be used
-to extend or reduce the frequency range to be boosted or cut.
-The default value is @code{100} Hz.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Determine how steep is the filter's shelf transition.
-@end table
-
-@section treble
-
-Boost or cut treble (upper) frequencies of the audio using a two-pole
-shelving filter with a response similar to that of a standard
-hi-fi's tone-controls. This is also known as shelving equalisation (EQ).
-
-The filter accepts the following options:
-
-@table @option
-@item gain, g
-Give the gain at whichever is the lower of ~22 kHz and the
-Nyquist frequency. Its useful range is about -20 (for a large cut)
-to +20 (for a large boost). Beware of clipping when using a positive gain.
-
-@item frequency, f
-Set the filter's central frequency and so can be used
-to extend or reduce the frequency range to be boosted or cut.
-The default value is @code{3000} Hz.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Determine how steep is the filter's shelf transition.
-@end table
-
-@section bandpass
-
-Apply a two-pole Butterworth band-pass filter with central
-frequency @var{frequency}, and (3dB-point) band-width width.
-The @var{csg} option selects a constant skirt gain (peak gain = Q)
-instead of the default: constant 0dB peak gain.
-The filter roll off at 6dB per octave (20dB per decade).
-
-The filter accepts the following options:
-
-@table @option
-@item frequency, f
-Set the filter's central frequency. Default is @code{3000}.
-
-@item csg
-Constant skirt gain if set to 1. Defaults to 0.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Specify the band-width of a filter in width_type units.
-@end table
-
-@section bandreject
-
-Apply a two-pole Butterworth band-reject filter with central
-frequency @var{frequency}, and (3dB-point) band-width @var{width}.
-The filter roll off at 6dB per octave (20dB per decade).
-
-The filter accepts the following options:
-
-@table @option
-@item frequency, f
-Set the filter's central frequency. Default is @code{3000}.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Specify the band-width of a filter in width_type units.
-@end table
-
-@section biquad
-
-Apply a biquad IIR filter with the given coefficients.
-Where @var{b0}, @var{b1}, @var{b2} and @var{a0}, @var{a1}, @var{a2}
-are the numerator and denominator coefficients respectively.
-
-@section equalizer
-
-Apply a two-pole peaking equalisation (EQ) filter. With this
-filter, the signal-level at and around a selected frequency can
-be increased or decreased, whilst (unlike bandpass and bandreject
-filters) that at all other frequencies is unchanged.
-
-In order to produce complex equalisation curves, this filter can
-be given several times, each with a different central frequency.
-
-The filter accepts the following options:
-
-@table @option
-@item frequency, f
-Set the filter's central frequency in Hz.
-
-@item width_type
-Set method to specify band-width of filter.
-@table @option
-@item h
-Hz
-@item q
-Q-Factor
-@item o
-octave
-@item s
-slope
-@end table
-
-@item width, w
-Specify the band-width of a filter in width_type units.
-
-@item gain, g
-Set the required gain or attenuation in dB.
-Beware of clipping when using a positive gain.
-@end table
-
 @section afade
 
 Apply fade-in/out effect to input audio.
@@ -738,6 +462,36 @@ For example to force the output to either unsigned 8-bit or signed 16-bit stereo
 aformat=sample_fmts=u8|s16:channel_layouts=stereo
 @end example
 
+@section allpass
+
+Apply a two-pole all-pass filter with central frequency (in Hz)
+@var{frequency}, and filter-width @var{width}.
+An all-pass filter changes the audio's frequency to phase relationship
+without changing its frequency to amplitude relationship.
+
+The filter accepts the following options:
+
+@table @option
+@item frequency, f
+Set frequency in Hz.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Specify the band-width of a filter in width_type units.
+@end table
+
 @section amerge
 
 Merge two or more audio streams into a single multi-channel stream.
@@ -1071,170 +825,8 @@ amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
 [a2] [b2] amerge
 @end example
 
-@section atempo
-
-Adjust audio tempo.
-
-The filter accepts exactly one parameter, the audio tempo. If not
-specified then the filter will assume nominal 1.0 tempo. Tempo must
-be in the [0.5, 2.0] range.
-
-@subsection Examples
-
-@itemize
-@item
-Slow down audio to 80% tempo:
-@example
-atempo=0.8
-@end example
-
-@item
-To speed up audio to 125% tempo:
-@example
-atempo=1.25
-@end example
-@end itemize
-
-@section earwax
-
-Make audio easier to listen to on headphones.
-
-This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
-so that when listened to on headphones the stereo image is moved from
-inside your head (standard for headphones) to outside and in front of
-the listener (standard for speakers).
-
-Ported from SoX.
-
-@section pan
-
-Mix channels with specific gain levels. The filter accepts the output
-channel layout followed by a set of channels definitions.
-
-This filter is also designed to remap efficiently the channels of an audio
-stream.
-
-The filter accepts parameters of the form:
-"@var{l}:@var{outdef}:@var{outdef}:..."
-
-@table @option
-@item l
-output channel layout or number of channels
-
-@item outdef
-output channel specification, of the form:
-"@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
-
-@item out_name
-output channel to define, either a channel name (FL, FR, etc.) or a channel
-number (c0, c1, etc.)
-
-@item gain
-multiplicative coefficient for the channel, 1 leaving the volume unchanged
-
-@item in_name
-input channel to use, see out_name for details; it is not possible to mix
-named and numbered input channels
-@end table
-
-If the `=' in a channel specification is replaced by `<', then the gains for
-that specification will be renormalized so that the total is 1, thus
-avoiding clipping noise.
-
-@subsection Mixing examples
-
-For example, if you want to down-mix from stereo to mono, but with a bigger
-factor for the left channel:
-@example
-pan=1:c0=0.9*c0+0.1*c1
-@end example
-
-A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
-7-channels surround:
-@example
-pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
-@end example
-
-Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
-that should be preferred (see "-ac" option) unless you have very specific
-needs.
-
-@subsection Remapping examples
-
-The channel remapping will be effective if, and only if:
-
-@itemize
-@item gain coefficients are zeroes or ones,
-@item only one input per channel output,
-@end itemize
-
-If all these conditions are satisfied, the filter will notify the user ("Pure
-channel mapping detected"), and use an optimized and lossless method to do the
-remapping.
-
-For example, if you have a 5.1 source and want a stereo audio stream by
-dropping the extra channels:
-@example
-pan="stereo: c0=FL : c1=FR"
-@end example
-
-Given the same source, you can also switch front left and front right channels
-and keep the input channel layout:
-@example
-pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
-@end example
-
-If the input is a stereo audio stream, you can mute the front left channel (and
-still keep the stereo channel layout) with:
-@example
-pan="stereo:c1=c1"
-@end example
-
-Still with a stereo audio stream input, you can copy the right channel in both
-front left and right:
-@example
-pan="stereo: c0=FR : c1=FR"
-@end example
-
-@section silencedetect
-
-Detect silence in an audio stream.
-
-This filter logs a message when it detects that the input audio volume is less
-or equal to a noise tolerance value for a duration greater or equal to the
-minimum detected noise duration.
-
-The printed times and duration are expressed in seconds.
-
-The filter accepts the following options:
-
-@table @option
-@item duration, d
-Set silence duration until notification (default is 2 seconds).
-
-@item noise, n
-Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
-specified value) or amplitude ratio. Default is -60dB, or 0.001.
-@end table
-
-@subsection Examples
-
-@itemize
-@item
-Detect 5 seconds of silence with -50dB noise tolerance:
-@example
-silencedetect=n=-50dB:d=5
-@end example
-
-@item
-Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
-tolerance in @file{silence.mp3}:
-@example
-ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -
-@end example
-@end itemize
-
 @section asyncts
+
 Synchronize audio data with timestamps by squeezing/stretching it and/or
 dropping samples/adding silence when needed.
 
@@ -1266,7 +858,32 @@ with a negative pts due to encoder delay.
 
 @end table
 
+@section atempo
+
+Adjust audio tempo.
+
+The filter accepts exactly one parameter, the audio tempo. If not
+specified then the filter will assume nominal 1.0 tempo. Tempo must
+be in the [0.5, 2.0] range.
+
+@subsection Examples
+
+@itemize
+@item
+Slow down audio to 80% tempo:
+@example
+atempo=0.8
+@end example
+
+@item
+To speed up audio to 125% tempo:
+@example
+atempo=1.25
+@end example
+@end itemize
+
 @section atrim
+
 Trim the input so that the output contains one continuous subpart of the input.
 
 This filter accepts the following options:
@@ -1330,32 +947,113 @@ ffmpeg -i INPUT -af atrim=end_sample=1000
 
 @end itemize
 
-@section channelsplit
-Split each channel in input audio stream into a separate output stream.
+@section bandpass
+
+Apply a two-pole Butterworth band-pass filter with central
+frequency @var{frequency}, and (3dB-point) band-width width.
+The @var{csg} option selects a constant skirt gain (peak gain = Q)
+instead of the default: constant 0dB peak gain.
+The filter roll off at 6dB per octave (20dB per decade).
+
+The filter accepts the following options:
 
-This filter accepts the following named parameters:
 @table @option
-@item channel_layout
-Channel layout of the input stream. Default is "stereo".
+@item frequency, f
+Set the filter's central frequency. Default is @code{3000}.
+
+@item csg
+Constant skirt gain if set to 1. Defaults to 0.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
 @end table
 
-For example, assuming a stereo input MP3 file
-@example
-ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
-@end example
-will create an output Matroska file with two audio streams, one containing only
-the left channel and the other the right channel.
+@item width, w
+Specify the band-width of a filter in width_type units.
+@end table
 
-To split a 5.1 WAV file into per-channel files
-@example
-ffmpeg -i in.wav -filter_complex
-'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
--map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
-front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
-side_right.wav
-@end example
+@section bandreject
+
+Apply a two-pole Butterworth band-reject filter with central
+frequency @var{frequency}, and (3dB-point) band-width @var{width}.
+The filter roll off at 6dB per octave (20dB per decade).
+
+The filter accepts the following options:
+
+@table @option
+@item frequency, f
+Set the filter's central frequency. Default is @code{3000}.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Specify the band-width of a filter in width_type units.
+@end table
+
+@section bass
+
+Boost or cut the bass (lower) frequencies of the audio using a two-pole
+shelving filter with a response similar to that of a standard
+hi-fi's tone-controls. This is also known as shelving equalisation (EQ).
+
+The filter accepts the following options:
+
+@table @option
+@item gain, g
+Give the gain at 0 Hz. Its useful range is about -20
+(for a large cut) to +20 (for a large boost).
+Beware of clipping when using a positive gain.
+
+@item frequency, f
+Set the filter's central frequency and so can be used
+to extend or reduce the frequency range to be boosted or cut.
+The default value is @code{100} Hz.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Determine how steep is the filter's shelf transition.
+@end table
+
+@section biquad
+
+Apply a biquad IIR filter with the given coefficients.
+Where @var{b0}, @var{b1}, @var{b2} and @var{a0}, @var{a1}, @var{a2}
+are the numerator and denominator coefficients respectively.
 
 @section channelmap
+
 Remap input channels to new locations.
 
 This filter accepts the following named parameters:
@@ -1388,7 +1086,116 @@ To fix a 5.1 WAV improperly encoded in AAC's native channel order
 ffmpeg -i in.wav -filter 'channelmap=1|2|0|5|3|4:channel_layout=5.1' out.wav
 @end example
 
+@section channelsplit
+
+Split each channel in input audio stream into a separate output stream.
+
+This filter accepts the following named parameters:
+@table @option
+@item channel_layout
+Channel layout of the input stream. Default is "stereo".
+@end table
+
+For example, assuming a stereo input MP3 file
+@example
+ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
+@end example
+will create an output Matroska file with two audio streams, one containing only
+the left channel and the other the right channel.
+
+To split a 5.1 WAV file into per-channel files
+@example
+ffmpeg -i in.wav -filter_complex
+'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
+-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
+front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
+side_right.wav
+@end example
+
+@section earwax
+
+Make audio easier to listen to on headphones.
+
+This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
+so that when listened to on headphones the stereo image is moved from
+inside your head (standard for headphones) to outside and in front of
+the listener (standard for speakers).
+
+Ported from SoX.
+
+@section equalizer
+
+Apply a two-pole peaking equalisation (EQ) filter. With this
+filter, the signal-level at and around a selected frequency can
+be increased or decreased, whilst (unlike bandpass and bandreject
+filters) that at all other frequencies is unchanged.
+
+In order to produce complex equalisation curves, this filter can
+be given several times, each with a different central frequency.
+
+The filter accepts the following options:
+
+@table @option
+@item frequency, f
+Set the filter's central frequency in Hz.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Specify the band-width of a filter in width_type units.
+
+@item gain, g
+Set the required gain or attenuation in dB.
+Beware of clipping when using a positive gain.
+@end table
+
+@section highpass
+
+Apply a high-pass filter with 3dB point frequency.
+The filter can be either single-pole, or double-pole (the default).
+The filter roll off at 6dB per pole per octave (20dB per pole per decade).
+
+The filter accepts the following options:
+
+@table @option
+@item frequency, f
+Set frequency in Hz. Default is 3000.
+
+@item poles, p
+Set number of poles. Default is 2.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Specify the band-width of a filter in width_type units.
+Applies only to double-pole filter.
+The default is 0.707q and gives a Butterworth response.
+@end table
+
 @section join
+
 Join multiple input streams into one multi-channel stream.
 
 The filter accepts the following named parameters:
@@ -1425,10 +1232,209 @@ ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
 out
 @end example
 
+@section lowpass
+
+Apply a low-pass filter with 3dB point frequency.
+The filter can be either single-pole or double-pole (the default).
+The filter roll off at 6dB per pole per octave (20dB per pole per decade).
+
+The filter accepts the following options:
+
+@table @option
+@item frequency, f
+Set frequency in Hz. Default is 500.
+
+@item poles, p
+Set number of poles. Default is 2.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Specify the band-width of a filter in width_type units.
+Applies only to double-pole filter.
+The default is 0.707q and gives a Butterworth response.
+@end table
+
+@section pan
+
+Mix channels with specific gain levels. The filter accepts the output
+channel layout followed by a set of channels definitions.
+
+This filter is also designed to remap efficiently the channels of an audio
+stream.
+
+The filter accepts parameters of the form:
+"@var{l}:@var{outdef}:@var{outdef}:..."
+
+@table @option
+@item l
+output channel layout or number of channels
+
+@item outdef
+output channel specification, of the form:
+"@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
+
+@item out_name
+output channel to define, either a channel name (FL, FR, etc.) or a channel
+number (c0, c1, etc.)
+
+@item gain
+multiplicative coefficient for the channel, 1 leaving the volume unchanged
+
+@item in_name
+input channel to use, see out_name for details; it is not possible to mix
+named and numbered input channels
+@end table
+
+If the `=' in a channel specification is replaced by `<', then the gains for
+that specification will be renormalized so that the total is 1, thus
+avoiding clipping noise.
+
+@subsection Mixing examples
+
+For example, if you want to down-mix from stereo to mono, but with a bigger
+factor for the left channel:
+@example
+pan=1:c0=0.9*c0+0.1*c1
+@end example
+
+A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
+7-channels surround:
+@example
+pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
+@end example
+
+Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
+that should be preferred (see "-ac" option) unless you have very specific
+needs.
+
+@subsection Remapping examples
+
+The channel remapping will be effective if, and only if:
+
+@itemize
+@item gain coefficients are zeroes or ones,
+@item only one input per channel output,
+@end itemize
+
+If all these conditions are satisfied, the filter will notify the user ("Pure
+channel mapping detected"), and use an optimized and lossless method to do the
+remapping.
+
+For example, if you have a 5.1 source and want a stereo audio stream by
+dropping the extra channels:
+@example
+pan="stereo: c0=FL : c1=FR"
+@end example
+
+Given the same source, you can also switch front left and front right channels
+and keep the input channel layout:
+@example
+pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
+@end example
+
+If the input is a stereo audio stream, you can mute the front left channel (and
+still keep the stereo channel layout) with:
+@example
+pan="stereo:c1=c1"
+@end example
+
+Still with a stereo audio stream input, you can copy the right channel in both
+front left and right:
+@example
+pan="stereo: c0=FR : c1=FR"
+@end example
+
 @section resample
+
 Convert the audio sample format, sample rate and channel layout. This filter is
 not meant to be used directly.
 
+@section silencedetect
+
+Detect silence in an audio stream.
+
+This filter logs a message when it detects that the input audio volume is less
+or equal to a noise tolerance value for a duration greater or equal to the
+minimum detected noise duration.
+
+The printed times and duration are expressed in seconds.
+
+The filter accepts the following options:
+
+@table @option
+@item duration, d
+Set silence duration until notification (default is 2 seconds).
+
+@item noise, n
+Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
+specified value) or amplitude ratio. Default is -60dB, or 0.001.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Detect 5 seconds of silence with -50dB noise tolerance:
+@example
+silencedetect=n=-50dB:d=5
+@end example
+
+@item
+Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
+tolerance in @file{silence.mp3}:
+@example
+ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -
+@end example
+@end itemize
+
+@section treble
+
+Boost or cut treble (upper) frequencies of the audio using a two-pole
+shelving filter with a response similar to that of a standard
+hi-fi's tone-controls. This is also known as shelving equalisation (EQ).
+
+The filter accepts the following options:
+
+@table @option
+@item gain, g
+Give the gain at whichever is the lower of ~22 kHz and the
+Nyquist frequency. Its useful range is about -20 (for a large cut)
+to +20 (for a large boost). Beware of clipping when using a positive gain.
+
+@item frequency, f
+Set the filter's central frequency and so can be used
+to extend or reduce the frequency range to be boosted or cut.
+The default value is @code{3000} Hz.
+
+@item width_type
+Set method to specify band-width of filter.
+@table @option
+@item h
+Hz
+@item q
+Q-Factor
+@item o
+octave
+@item s
+slope
+@end table
+
+@item width, w
+Determine how steep is the filter's shelf transition.
+@end table
+
 @section volume
 
 Adjust the input audio volume.