avfilter: add vif filter

This is Visual Information Fidelity (VIF) filter and one of the component
filters of VMAF. It outputs the average VIF score over all frames.

Signed-off-by: Ashish Singh <ashk43712@gmail.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 9dfc0ec67f..426cb158da 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -21266,6 +21266,27 @@ otherwise colors will be less saturated, more towards gray.
 
 This filter supports the all above options as @ref{commands}.
 
+@section vif
+
+Obtain the average VIF (Visual Information Fidelity) between two input videos.
+
+This filter takes two input videos.
+
+Both input videos must have the same resolution and pixel format for
+this filter to work correctly. Also it assumes that both inputs
+have the same number of frames, which are compared one by one.
+
+The obtained average VIF score is printed through the logging system.
+
+The filter stores the calculated VIF score of each frame.
+
+In the below example the input file @file{main.mpg} being processed is compared
+with the reference file @file{ref.mpg}.
+
+@example
+ffmpeg -i main.mpg -i ref.mpg -lavfi vif -f null -
+@end example
+
 @anchor{vignette}
 @section vignette