Iterate over the AVClasses corresponding to potential AVOptions-enabled
children.
@param iter pointer to opaque iteration state. The caller must initialize
*iter to NULL before the first call.
@return AVClass for the next AVOptions-enabled child or NULL if there are
no more such children.
@note The difference between child_next and this is that child_next
iterates over _already existing_ objects, while child_class_iterate
iterates over _all possible_ children.
Iterate over the AVClasses corresponding to potential AVOptions-enabled children.
@param iter pointer to opaque iteration state. The caller must initialize *iter to NULL before the first call. @return AVClass for the next AVOptions-enabled child or NULL if there are no more such children.
@note The difference between child_next and this is that child_next iterates over _already existing_ objects, while child_class_iterate iterates over _all possible_ children.