Allocate a new message queue.
@param mq pointer to the message queue @param nelem maximum number of elements in the queue @param elsize size of each element in the queue @return >=0 for success; <0 for error, in particular AVERROR(ENOSYS) if lavu was built without thread support
See Implementation
Allocate a new message queue.
@param mq pointer to the message queue @param nelem maximum number of elements in the queue @param elsize size of each element in the queue @return >=0 for success; <0 for error, in particular AVERROR(ENOSYS) if lavu was built without thread support