1. An encoder for encoding video signal data for an image block, comprising: a quantizer for receiving transform coefficients for the image block, and for adaptively performing dead-zone quantization based on coefficient positions and coefficient distributions of the transform coefficients to form quantization levels, wherein said quantizer adaptively performs the dead-zone quantization by determining a preliminary quantization level using a fixed dead-zone/rounding control, and repeating the dead-zone quantization based on the preliminary quantization level and using a coefficient quantization level dependent dead-zone/rounding control; and an inverse quantizer for de-quantizing the quantization levels to generate reconstructed levels, wherein a rounding parameter used for de-quantizing a quantization level of a transform coefficient is determined by the quantization level.