@defgroup opt_eval_funcs Evaluating option strings
@{
This group of functions can be used to evaluate option strings
and get numbers out of them. They do the same thing as av_opt_set(),
except the result is written into the caller-supplied pointer.
@param obj a struct whose first element is a pointer to AVClass.
@param o an option for which the string is to be evaluated.
@param val string to be evaluated.
@param *_out value of the string will be written here.
@return 0 on success, a negative number on failure.
@defgroup opt_eval_funcs Evaluating option strings @{ This group of functions can be used to evaluate option strings and get numbers out of them. They do the same thing as av_opt_set(), except the result is written into the caller-supplied pointer.
@param obj a struct whose first element is a pointer to AVClass. @param o an option for which the string is to be evaluated. @param val string to be evaluated. @param *_out value of the string will be written here.
@return 0 on success, a negative number on failure.