avfilter: add tremolo filter

Signed-off-by: Kyle Swanson <k@ylo.ph>

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 88cb3ce863..5bbbaf0b78 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2568,6 +2568,25 @@ slope
 Determine how steep is the filter's shelf transition.
 @end table
 
+@section tremolo
+
+Sinusoidal amplitude modulation.
+
+The filter accepts the following options:
+
+@table @option
+@item f
+Modulation frequency in Hertz. Modulation frequencies in the subharmonic range
+(20 Hz or lower) will result in a tremolo effect.
+This filter may also be used as a ring modulator by specifying
+a modulation frequency higher than 20 Hz.
+Range is 0.1 - 20000.0. Default value is 5.0 Hz.
+
+@item d
+Depth of modulation as a percentage. Range is 0.0 - 1.0.
+Default value is 0.5.
+@end table
+
 @section volume
 
 Adjust the input audio volume.