ffmpeg_opt: add OPT_INPUT to -fix_sub_duration and -canvas_size.

ffmpeg_opt.c

@@ -2733,9 +2733,9 @@ const OptionDef options[] = {
         "force subtitle codec ('copy' to copy stream)", "codec" },
     { "stag",   OPT_SUBTITLE | HAS_ARG  | OPT_EXPERT  | OPT_PERFILE | OPT_OUTPUT, { .func_arg = opt_old2new }
         , "force subtitle tag/fourcc", "fourcc/tag" },
-    { "fix_sub_duration", OPT_BOOL | OPT_EXPERT | OPT_SUBTITLE | OPT_SPEC, { .off = OFFSET(fix_sub_duration) },
+    { "fix_sub_duration", OPT_BOOL | OPT_EXPERT | OPT_SUBTITLE | OPT_SPEC | OPT_INPUT, { .off = OFFSET(fix_sub_duration) },
         "fix subtitles duration" },
-    { "canvas_size", OPT_SUBTITLE | HAS_ARG | OPT_STRING | OPT_SPEC, { .off = OFFSET(canvas_sizes) },
+    { "canvas_size", OPT_SUBTITLE | HAS_ARG | OPT_STRING | OPT_SPEC | OPT_INPUT, { .off = OFFSET(canvas_sizes) },
         "set canvas size (WxH or abbreviation)", "size" },
 
     /* grab options */