A video data encoding apparatus operable to encode an array of input video data values includes: a differential pulse code modulation (DPCM) coder configured to apply a differential pulse code modulation operation to the array of input video data values to generate an array of DPCM data values; a quantizer operable to quantize data derived from the DPCM data values; and controller circuitry controlling selection of a rounding operation by the quantizer from two or more candidate rounding operations.