Function dct8x8_blocks_then_dwt53_float 

pub fn dct8x8_blocks_then_dwt53_float(
    blocks: &[[[f64; 8]; 8]],
    block_cols: usize,
    block_rows: usize,
    width: usize,
    height: usize,
) -> Result<Dwt53TwoDimensional<f64>, Dct53GridError>

Reference path for a DCT block grid: DCT coefficients -> float IDCT samples -> separable linearized 5/3.