doc/cropdetect: update boxblur options description.

doc/filters.texi

@@ -2329,12 +2329,7 @@ Calculate necessary cropping parameters and prints the recommended
 parameters through the logging system. The detected dimensions
 correspond to the non-black area of the input video.
 
-The filter accepts parameters as a list of @var{key}=@var{value}
-pairs, separated by ":". If the key of the first options is omitted,
-the arguments are interpreted according to the syntax
-[@option{limit}[:@option{round}[:@option{reset}]]].
-
-A description of the accepted options follows.
+The filter accepts the following options:
 
 @table @option
 
@@ -2349,7 +2344,7 @@ offset is automatically adjusted to center the video. Use 2 to get
 only even dimensions (needed for 4:2:2 video). 16 is best when
 encoding to most video codecs. Default value is 16.
 
-@item reset
+@item reset_count, reset
 Set the counter that determines after how many frames cropdetect will
 reset the previously detected largest video area and start over to
 detect the current optimal crop area. Default value is 0.