avfilter: add dcshift filter

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

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 2f29c46f9c..8069554eb4 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -917,6 +917,7 @@ audio, the data is treated as if all the planes were concatenated.
 A list of Adler-32 checksums for each data plane.
 @end table
 
+@anchor{astats}
 @section astats
 
 Display time domain statistical information about the audio channels.
@@ -1394,6 +1395,24 @@ compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
 @end example
 @end itemize
 
+@section dcshift
+Apply a DC shift to the audio.
+
+This can be useful to remove a DC offset (caused perhaps by a hardware problem
+in the recording chain) from the audio. The effect of a DC offset is reduced
+headroom and hence volume. The @ref{astats} filter can be used to determine if
+a signal has a DC offset.
+
+@table @option
+@item shift
+Set the DC shift, allowed range is [-1, 1]. It indicates the amount to shift
+the audio.
+
+@item limitergain
+Optional. It should have a value much less than 1 (e.g. 0.05 or 0.02) and is
+used to prevent clipping.
+@end table
+
 @section earwax
 
 Make audio easier to listen to on headphones.