Function av_fifo_write_from_cb 

pub unsafe extern "C" fn av_fifo_write_from_cb(
    f: *mut AVFifo,
    read_cb: AVFifoCB,
    opaque: *mut c_void,
    nb_elems: *mut usize,
) -> c_int

Write data from a user-provided callback into a FIFO.

@param f the FIFO buffer @param read_cb Callback supplying the data to the FIFO. May be called multiple times. @param opaque opaque user data to be provided to read_cb @param nb_elems Should point to the maximum number of elements that can be written. Will be updated to contain the number of elements actually written.

@return non-negative number on success, a negative error code on failure