Function vmeta_frame_to_csv 

pub unsafe extern "C" fn vmeta_frame_to_csv(
    meta: *const vmeta_frame,
    str_: *mut c_char,
    maxlen: usize,
) -> isize

Write frame metadata as a CSV string. The str string must have been previously allocated. The function writes up to maxlen characters. The CSV separator is a space character. @param meta: pointer to a frame metadata structure @param str: pointer to the string to write to (output) @param maxlen: maximum length of the string @return the number of characters written on success, negative errno value in case of error