@end example
@section compand
-
Compress or expand audio dynamic range.
A description of the accepted options follows.
@table @option
+
@item attacks
@item decays
-Set list of times in seconds for each channel over which the instantaneous
-level of the input signal is averaged to determine its volume.
-@option{attacks} refers to increase of volume and @option{decays} refers
-to decrease of volume.
-For most situations, the attack time (response to the audio getting louder)
-should be shorter than the decay time because the human ear is more sensitive
-to sudden loud audio than sudden soft audio.
-Typical value for attack is @code{0.3} seconds and for decay @code{0.8}
-seconds.
+Set list of times in seconds for each channel over which the instantaneous level
+of the input signal is averaged to determine its volume. @var{attacks} refers to
+increase of volume and @var{decays} refers to decrease of volume. For most
+situations, the attack time (response to the audio getting louder) should be
+shorter than the decay time because the human ear is more sensitive to sudden
+loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and
+a typical value for decay is 0.8 seconds.
@item points
-Set list of points for transfer function, specified in dB relative to maximum
-possible signal amplitude.
-Each key points list need to be defined using the following syntax:
-@code{x0/y0 x1/y1 x2/y2 ...}.
+Set list of points for the transfer function, specified in dB relative to the
+maximum possible signal amplitude. Each key points list must be defined using
+the following syntax: @code{x0/y0|x1/y1|x2/y2|....} or
+@code{x0/y0 x1/y1 x2/y2 ....}
-The input values must be in strictly increasing order but the transfer
-function does not have to be monotonically rising.
-The point @code{0/0} is assumed but may be overridden (by @code{0/out-dBn}).
-Typical values for the transfer function are @code{-70/-70 -60/-20}.
+The input values must be in strictly increasing order but the transfer function
+does not have to be monotonically rising. The point @code{0/0} is assumed but
+may be overridden (by @code{0/out-dBn}). Typical values for the transfer
+function are @code{-70/-70|-60/-20}.
@item soft-knee
-Set amount for which the points at where adjacent line segments on the
-transfer function meet will be rounded. Defaults is @code{0.01}.
+Set the curve radius in dB for all joints. Defaults to 0.01.
@item gain
-Set additional gain in dB to be applied at all points on the transfer function
-and allows easy adjustment of the overall gain.
-Default is @code{0}.
+Set additional gain in dB to be applied at all points on the transfer function.
+This allows easy adjustment of the overall gain. Defaults to 0.
@item volume
Set initial volume in dB to be assumed for each channel when filtering starts.
-This permits the user to supply a nominal level initially, so that,
-for example, a very large gain is not applied to initial signal levels before
-the companding has begun to operate. A typical value for audio which is
-initially quiet is -90 dB. Default is @code{0}.
+This permits the user to supply a nominal level initially, so that, for
+example, a very large gain is not applied to initial signal levels before the
+companding has begun to operate. A typical value for audio which is initially
+quiet is -90 dB. Defaults to 0.
@item delay
-Set delay in seconds. Default is @code{0}. The input audio
-is analysed immediately, but audio is delayed before being fed to the
-volume adjuster. Specifying a delay approximately equal to the attack/decay
-times allows the filter to effectively operate in predictive rather than
-reactive mode.
+Set delay in seconds. The input audio is analyzed immediately, but audio is
+delayed before being fed to the volume adjuster. Specifying a delay
+approximately equal to the attack/decay times allows the filter to effectively
+operate in predictive rather than reactive mode. Defaults to 0.
+
@end table
@subsection Examples
+
@itemize
@item
-Make music with both quiet and loud passages suitable for listening
-in a noisy environment:
+Make music with both quiet and loud passages suitable for listening in a noisy
+environment:
@example
-compand=.3 .3:1 1:-90/-60 -60/-40 -40/-30 -20/-20:6:0:-90:0.2
+compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2
@end example
@item
-Noise-gate for when the noise is at a lower level than the signal:
+Noise gate for when the noise is at a lower level than the signal:
@example
-compand=.1 .1:.2 .2:-900/-900 -50.1/-900 -50/-50:.01:0:-90:.1
+compand=.1|.1:.2|.2:-900/-900|-50.1/-900|-50/-50:.01:0:-90:.1
@end example
@item
-Here is another noise-gate, this time for when the noise is at a higher level
+Here is another noise gate, this time for when the noise is at a higher level
than the signal (making it, in some ways, similar to squelch):
@example
-compand=.1 .1:.1 .1:-45.1/-45.1 -45/-900 0/-900:.01:45:-90:.1
+compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
@end example
@end itemize
Simple interlacing filter from progressive contents. This interleaves upper (or
lower) lines from odd frames with lower (or upper) lines from even frames,
halving the frame rate and preserving image height. A vertical lowpass filter
-is always applied in order to avoid twitter effects and reduce moire patterns.
+is always applied in order to avoid twitter effects and reduce moiré patterns.
@example
Original Original New Frame
projects / ffmpeg / blobdiff