avfilter: add feedback video filter

1 files changed, 38 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 5fae4424e6..71a04baee5 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -12181,6 +12181,44 @@ fade=t=in:st=5.5:d=0.5
 
 @end itemize
 
+@section feedback
+Apply feedback video filter.
+
+This filter pass cropped input frames to 2nd output.
+From there it can be filtered with other video filters.
+After filter receives frame from 2nd input, that frame
+is combined on top of original frame from 1st input and passed
+to 1st output.
+
+The typical usage is filter only part of frame.
+
+The filter accepts the following options:
+@table @option
+@item x
+@item y
+Set the top left crop position.
+
+@item w
+@item h
+Set the crop size.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Blur only top left rectangular part of video frame size 100x100 with gblur filter.
+@example
+[in][blurin]feedback=x=0:y=0:w=100:h=100[out][blurout];[blurout]gblur=8[blurin]
+@end example
+
+@item
+Draw black box on top left part of video frame of size 100x100 with drawbox filter.
+@example
+[in][blurin]feedback=x=0:y=0:w=100:h=100[out][blurout];[blurout]drawbox=x=0:y=0:w=100:h=100:t=100[blurin]
+@end example
+@end itemize
+
 @section fftdnoiz
 Denoise frames using 3D FFT (frequency domain filtering).