add silenceremove filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index d13278ef71..627f112724 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1875,6 +1875,75 @@ ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -
 @end example
 @end itemize
 
+@section silenceremove
+
+Remove silence from the beginning, middle or end of the audio.
+
+The filter accepts the following options:
+
+@table @option
+@item start_periods
+This value is used to indicate if audio should be trimmed at beginning of
+the audio. A value of zero indicates no silence should be trimmed from the
+beginning. When specifying a non-zero value, it trims audio up until it
+finds non-silence. Normally, when trimming silence from beginning of audio
+the @var{start_periods} will be @code{1} but it can be increased to higher
+values to trim all audio up to specific count of non-silence periods.
+Default value is @code{0}.
+
+@item start_duration
+Specify the amount of time that non-silence must be detected before it stops
+trimming audio. By increasing the duration, bursts of noises can be treated
+as silence and trimmed off. Default value is @code{0}.
+
+@item start_threshold
+This indicates what sample value should be treated as silence. For digital
+audio, a value of @code{0} may be fine but for audio recorded from analog,
+you may wish to increase the value to account for background noise.
+Can be specified in dB (in case "dB" is appended to the specified value)
+or amplitude ratio. Default value is @code{0}.
+
+@item stop_periods
+Set the count for trimming silence from the end of audio.
+To remove silence from the middle of a file, specify a @var{stop_periods}
+that is negative. This value is then threated as a positive value and is
+used to indicate the effect should restart processing as specified by
+@var{start_periods}, making it suitable for removing periods of silence
+in the middle of the audio.
+Default value is @code{0}.
+
+@item stop_duration
+Specify a duration of silence that must exist before audio is not copied any
+more. By specifying a higher duration, silence that is wanted can be left in
+the audio.
+Default value is @code{0}.
+
+@item stop_threshold
+This is the same as @option{start_threshold} but for trimming silence from
+the end of audio.
+Can be specified in dB (in case "dB" is appended to the specified value)
+or amplitude ratio. Default value is @code{0}.
+
+@item leave_silence
+This indicate that @var{stop_duration} length of audio should be left intact
+at the beginning of each period of silence.
+For example, if you want to remove long pauses between words but do not want
+to remove the pauses completely. Default value is @code{0}.
+
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+The following example shows how this filter can be used to start a recording
+that does not contain the delay at the start which usually occurs between
+pressing the record button and the start of the performance:
+@example
+silenceremove=1:5:0.02
+@end example
+@end itemize
+
 @section treble
 
 Boost or cut treble (upper) frequencies of the audio using a two-pole