lavfi/thumbnail: switch to an AVOptions-based system.

doc/filters.texi

@@ -5392,10 +5392,7 @@ Swap U & V plane.
 @section thumbnail
 Select the most representative frame in a given sequence of consecutive frames.
 
-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
-thumbnail[=@var{n}].
+The filter accepts the following options:
 
 @table @option
 @item n

libavfilter/avfilter.c

@@ -681,6 +681,7 @@ int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque
         !strcmp(filter->filter->name,   "format") ||
         !strcmp(filter->filter->name, "noformat") ||
         !strcmp(filter->filter->name, "resample") ||
+        !strcmp(filter->filter->name, "thumbnail") ||
 //         !strcmp(filter->filter->name, "scale"      ) ||
         0
         ;

libavfilter/vf_thumbnail.c

@@ -227,8 +227,6 @@ static const AVFilterPad thumbnail_outputs[] = {
     { NULL }
 };
 
-static const char *const shorthand[] = { "n", NULL };
-
 AVFilter avfilter_vf_thumbnail = {
     .name          = "thumbnail",
     .description   = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."),
@@ -239,5 +237,4 @@ AVFilter avfilter_vf_thumbnail = {
     .inputs        = thumbnail_inputs,
     .outputs       = thumbnail_outputs,
     .priv_class    = &thumbnail_class,
-    .shorthand     = shorthand,
 };