@@ -1613,6 +1613,28 @@ static void show_help_muxer(const char *name)

         show_help_children(fmt->priv_class, AV_OPT_FLAG_ENCODING_PARAM);

 }

+static void show_help_filter(const char *name)

+{

+    const AVFilter *filter;

+

+    if (!name) {

+        av_log(NULL, AV_LOG_ERROR, "No filter name specified.\n");

+        return;

+    }

+    filter = avfilter_get_by_name(name);

+    if (!filter) {

+        av_log(NULL, AV_LOG_ERROR, "Filter '%s' not found.\n", name);

+        return;

+    }

+    printf("Filter %s\n", filter->name);

+    if (filter->description)

+        printf("  %s\n", filter->description);

+    if (filter->priv_class)

+        show_help_children(filter->priv_class, AV_OPT_FLAG_FILTERING_PARAM);

+    else

+        printf("No AVOption available\n");

+}

+

 int show_help(void *optctx, const char *opt, const char *arg)

 {

     char *topic, *par;

@@ -1633,6 +1655,8 @@ int show_help(void *optctx, const char *opt, const char *arg)

         show_help_demuxer(par);

     } else if (!strcmp(topic, "muxer")) {

         show_help_muxer(par);

+    } else if (!strcmp(topic, "filter")) {

+        show_help_filter(par);

     } else {

         show_help_default(topic, par);

     }