static int opt_metadata(const char *opt, const char *arg)
{
    char *mid= strchr(arg, '=');
    if(!mid){
        fprintf(stderr, "Missing =\n");
        exit_program(1);
    }
    *mid++= 0;
    av_dict_set(&metadata, arg, mid, 0);
    return 0;
}
['static int opt_metadata(const char *opt, const char *arg)\n{\n    char *mid= strchr(arg, \'=\');\n    if(!mid){\n        fprintf(stderr, "Missing =\\n");\n        exit_program(1);\n    }\n    *mid++= 0;\n    av_dict_set(&metadata, arg, mid, 0);\n    return 0;\n}']