Methods and apparatus for improved quantization rounding offset adjustment for video encoding and decoding

An apparatus, comprising:

• a video decoder for decoding a coding unit by receiving at least one quantized coefficient corresponding to a transformed and quantized residual between an original version of the coding unit and a reference coding unit, de-quantizing the at least one quantized coefficient to obtain at least one de-quantized coefficient by determining a quantization step size and a rounding offset, and applying an inverse transform to the at least one de-quantized coefficient to obtain a reconstructed residual,
• wherein said video decoder receives information describing the selected rounding offset from a bitstream that includes the at least one quantized coefficient wherein the rounding offset is selected and applied only for smooth classified macroblocks while a default rounding offset typically used by said encoder is applied to textured classified macroblocks.

A nontransitory computer readable storage media having video signal data encoded thereupon, comprising:

• an input coding unit encoded by determining a residual for the input coding unit corresponding to a difference between the input coding unit and a reference coding unit, applying a transform to the residual to obtain at least one transform coefficient, and quantizing the at least one transform coefficient by selecting a quantization step size and a rounding offset wherein the rounding offset is selected and applied only for smooth classified macroblocks while a default rounding offset typically used by said encoder is applied to textured classified macroblocks.