Function unpack 

pub fn unpack(
    src: &[u8],
    layout: PackedLayout,
    dst: &mut [u16],
    dst_stride: usize,
    parallel: bool,
    simd: bool,
    lenient: bool,
) -> Result<()>

Unpack src into dst rows of dst_stride samples. A source too short for every row is an error unless lenient (recovering truncated data): then complete rows and the complete samples of a partial final row are unpacked, and the remaining samples are left untouched (callers pass zeroed buffers).