Function fill_band_map 

fn fill_band_map(
    map: &mut Vec<i8>,
    codec: Codec,
    width: u32,
    height: u32,
    (from, to): (f64, f64),
    delta: i32,
) -> usize

Fill map, the QP delta map of a width x height picture of codec (one entry a 16x16 macroblock for H.264, a 32x32 coding tree block for HEVC, a 64x64 superblock for AV1, in raster order), with delta over the blocks the share of the picture from..to covers, rounded outward, and 0 elsewhere; returns the band’s first block.