lavfi/zscale: enable runtime change flag

enable runtime change flag
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavfilter/vf_zscale.c

@@ -738,12 +738,13 @@ static int process_command(AVFilterContext *ctx, const char *cmd, const char *ar
 
 #define OFFSET(x) offsetof(ZScaleContext, x)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+#define TFLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
 
 static const AVOption zscale_options[] = {
-    { "w",      "Output video width",  OFFSET(w_expr),    AV_OPT_TYPE_STRING, .flags = FLAGS },
-    { "width",  "Output video width",  OFFSET(w_expr),    AV_OPT_TYPE_STRING, .flags = FLAGS },
-    { "h",      "Output video height", OFFSET(h_expr),    AV_OPT_TYPE_STRING, .flags = FLAGS },
-    { "height", "Output video height", OFFSET(h_expr),    AV_OPT_TYPE_STRING, .flags = FLAGS },
+    { "w",      "Output video width",  OFFSET(w_expr),    AV_OPT_TYPE_STRING, .flags = TFLAGS },
+    { "width",  "Output video width",  OFFSET(w_expr),    AV_OPT_TYPE_STRING, .flags = TFLAGS },
+    { "h",      "Output video height", OFFSET(h_expr),    AV_OPT_TYPE_STRING, .flags = TFLAGS },
+    { "height", "Output video height", OFFSET(h_expr),    AV_OPT_TYPE_STRING, .flags = TFLAGS },
     { "size",   "set video size",      OFFSET(size_str),  AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, FLAGS },
     { "s",      "set video size",      OFFSET(size_str),  AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, FLAGS },
     { "dither", "set dither type",     OFFSET(dither),    AV_OPT_TYPE_INT, {.i64 = 0}, 0, ZIMG_DITHER_ERROR_DIFFUSION, FLAGS, "dither" },