Adaptive Loop Filtering Coefficient Coding

The patent applies parameter changes by using exponential Golomb coding to represent ALF filter coefficients, transforming the representation method of coefficient values. This coding scheme efficiently represents a wide range of coefficient values with variable bit-length, reducing the bitrate required to signal filter parameters while maintaining filtering effectiveness, thus improving compression efficiency without proportionally increasing computational complexity

The patent segments the ALF parameter signaling by dividing coefficients into different groups (e.g., luma and chroma components, different coefficient positions) and applying differential coding or constrained ranges to each segment. This segmentation allows the encoder to signal only necessary parameter variations rather than full parameter sets, reducing computational overhead while maintaining visual quality

The patent uses copying by deriving certain ALF coefficients from previously coded coefficients or from template filter sets. Instead of signaling all coefficients independently, the encoder copies reference coefficient values and signals only differences or selection indices, maintaining filtering accuracy while significantly reducing transmission overhead through redundant information elimination

The patent applies partial action by signaling ALF parameters at selective locations (e.g., only at block boundaries or for significant coefficients) rather than for every coefficient. This partial signaling approach maintains sufficient filtering accuracy for visual quality while reducing the total amount of parameter information that must be transmitted