Interface BufferListDoFunction

A function for accessing the last buffer returned by gst_buffer_list_iterator_next(). The function can leave buffer in the list, replace buffer in the list or remove buffer from the list, depending on the return value. If the function returns NULL, buffer will be removed from the list, otherwise buffer will be replaced with the returned buffer. The last buffer returned by gst_buffer_list_iterator_next() will be replaced with the buffer returned from the function. The function takes ownership of unreffed. If NULL is returned, the buffer will be removed from the list. The list must be writable. from the list