Method and apparatus for error compensation using a non-linear digital-to-analog converter

Apparatus for digital-to-analog conversion of an n-bit input, said apparatus comprising:

• means for producing a linear analog output responsive to all n bits of said n-bit input;
• decoder circuitry coupled to at least one of the n bits of said n-bit input, said decoder circuitry having a decoder output;
• and
• means for altering said linear analog output responsive to said decoder output;
• wherein said decoder circuitry is capable of decoding for at least first and second states;
• and
• wherein said means for altering said analog output comprises circuitry for selectively adding a first compensation value to said analog output when said first state is decoded and adding a second compensation value to said analog output when said second state is decoded.

A method for processing a color intensity value in a computer graphics system that uses a digital-to-analog converter to drive a display device, said computer graphics system of the type in which the dynamic range of color intensity values is reduced during pre-processing such that the reduced dynamic range is less than the full range of inputs required to drive the digital-to-analog converter over its full output range, said method comprising the steps of:

• generating a digital integer output value that represents the integer portion of the result of scaling said color intensity value by a non-integer greater than 1;
• generating a first analog output that is proportional to said digital integer output value;
• decoding at least one bit of said digital integer output value;
• generating, responsive to said decoding step, a second analog output that is approximately proportional to the fractional portion of the result of scaling said color intensity value by said non-integer greater than 1;
• combining said first and second analog outputs to produce a combined analog output;
• and
• communicating said combined analog output to the display device.

Apparatus for producing an analog output with correction for quantization error introduced during digital data processing, said apparatus comprising:

• first and second digital to analog converter circuitries;
• a data path for communicating a digital value to the input of said first digital to analog converter circuitry;
• and
• decoder circuitry having a decoder circuitry input coupled to at least one of the bits of said data path, and having a decoder circuitry output;
• wherein the input of said second digital to analog converter circuitry is coupled to said decoder circuitry output, and wherein the analog output is proportional to the sum of the outputs of said first and second digital to analog converter circuitries, the output of said second digital to analog conversion circuitry representing correction for the quantization error.

A method for producing an analog output with correction for quantization error introduced during digital data processing, said method comprising the steps of:

• communicating a digital value having quantization error to the input of first digital to analog converter circuitry;
• communicating at least one of the bits of said digital value having quantization error to the input of decoder circuitry;
• communicating the output of said decoder circuitry to the input of second digital to analog converter circuitry;
• and
• summing the outputs of said first and second digital to analog converter circuitries, the output of said second digital to analog converter circuitry representing correction for the quantization error.