fftools/cmdutils: drop redundant code

It allocates a dummy sws/swr context and tries setting options on it,
apparently to check if they are valid. This is redundant, since the
options will be checked if/when they are later applied on a context that
is actually used for conversion.

fftools/cmdutils.c

@@ -540,20 +540,12 @@ int opt_default(void *optctx, const char *opt, const char *arg)
 #if CONFIG_SWSCALE
     if (!consumed && (o = opt_find(&sc, opt, NULL, 0,
                          AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ))) {
-        struct SwsContext *sws = sws_alloc_context();
-        int ret = av_opt_set(sws, opt, arg, 0);
-        sws_freeContext(sws);
         if (!strcmp(opt, "srcw") || !strcmp(opt, "srch") ||
             !strcmp(opt, "dstw") || !strcmp(opt, "dsth") ||
             !strcmp(opt, "src_format") || !strcmp(opt, "dst_format")) {
             av_log(NULL, AV_LOG_ERROR, "Directly using swscale dimensions/format options is not supported, please use the -s or -pix_fmt options\n");
             return AVERROR(EINVAL);
         }
-        if (ret < 0) {
-            av_log(NULL, AV_LOG_ERROR, "Error setting option %s.\n", opt);
-            return ret;
-        }
-
         av_dict_set(&sws_dict, opt, arg, FLAGS);
 
         consumed = 1;
@@ -567,13 +559,6 @@ int opt_default(void *optctx, const char *opt, const char *arg)
 #if CONFIG_SWRESAMPLE
     if (!consumed && (o=opt_find(&swr_class, opt, NULL, 0,
                                     AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ))) {
-        struct SwrContext *swr = swr_alloc();
-        int ret = av_opt_set(swr, opt, arg, 0);
-        swr_free(&swr);
-        if (ret < 0) {
-            av_log(NULL, AV_LOG_ERROR, "Error setting option %s.\n", opt);
-            return ret;
-        }
         av_dict_set(&swr_opts, opt, arg, FLAGS);
         consumed = 1;
     }