函数 sws_test_format 

pub unsafe extern "C" fn sws_test_format(
    format: AVPixelFormat,
    output: c_int,
) -> c_int

Test if a given (software) pixel format is supported.

@param output If 0, test if compatible with the source/input frame; otherwise, with the destination/output frame. @param format The format to check.

@return A positive integer if supported, 0 otherwise.