lavfi/blend: switch to AVOption-based system

doc/filters.texi

@@ -1904,8 +1904,7 @@ It takes two input streams and outputs one stream, the first input is the
 "top" layer and second input is "bottom" layer.
 Output terminates when shortest input terminates.
 
-This filter accepts a list of options in the form of @var{key}=@var{value}
-pairs separated by ":". A description of the accepted options follows.
+A description of the accepted options follows.
 
 @table @option
 @item c0_mode

libavfilter/avfilter.c

@@ -659,6 +659,7 @@ int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque
         !strcmp(filter->filter->name,  "aformat") ||
         !strcmp(filter->filter->name,  "ass")     ||
         !strcmp(filter->filter->name,  "blackframe") ||
+        !strcmp(filter->filter->name,  "blend"     ) ||
         !strcmp(filter->filter->name,  "boxblur"   ) ||
         !strcmp(filter->filter->name,  "cellauto") ||
         !strcmp(filter->filter->name,  "colormatrix") ||

libavfilter/vf_blend.c

@@ -453,8 +453,6 @@ static const AVFilterPad blend_outputs[] = {
     { NULL }
 };
 
-static const char *const shorthand[] = { NULL };
-
 AVFilter avfilter_vf_blend = {
     .name          = "blend",
     .description   = NULL_IF_CONFIG_SMALL("Blend two video frames into each other."),
@@ -465,5 +463,4 @@ AVFilter avfilter_vf_blend = {
     .inputs        = blend_inputs,
     .outputs       = blend_outputs,
     .priv_class    = &blend_class,
-    .shorthand     = shorthand,
 };