avfilter: add nb_threads to AVFilterContext

To be used in following commits.

libavfilter/avfilter.c

@@ -616,6 +616,8 @@ static const AVOption avfilter_options[] = {
         { .i64 = AVFILTER_THREAD_SLICE }, 0, INT_MAX, FLAGS, "thread_type" },
         { "slice", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = AVFILTER_THREAD_SLICE }, .unit = "thread_type" },
     { "enable", "set enable expression", OFFSET(enable_str), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "threads", "Allowed number of threads", OFFSET(nb_threads), AV_OPT_TYPE_INT,
+        { .i64 = 0 }, 0, INT_MAX, FLAGS },
     { NULL },
 };
 

libavfilter/avfilter.h

@@ -361,6 +361,13 @@ struct AVFilterContext {
      * hardware context information.
      */
     AVBufferRef *hw_device_ctx;
+
+    /**
+     * Max number of threads allowed in this filter instance.
+     * If <= 0, its value is ignored.
+     * Overrides global number of threads set per filter graph.
+     */
+    int nb_threads;
 };
 
 /**

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  57
+#define LIBAVFILTER_VERSION_MINOR  58
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \