1. A video-encoder-device-implemented method for encoding a set of impairments-compensation-filter coefficient values for an encoded video frame, the method comprising: by the video encoder device, obtaining an unencoded frame of video; by the video encoder device, encoding the unencoded frame of video into an encoded bitstream by differencing a block of unencoded video in the unencoded frame with a first impairments-compensated predication signal block from a motion compensation process to determine a residual block, transforming the residual block into a block of coefficients, quantizing the block of coefficients into a block of quantized coefficients, and encoding the block of quantized coefficients into the encoded bitstream by an entropy coder; by the video encoder device, reverse quantizing and reverse transforming the block of quantized coefficients into a locally decoded block, assembling the locally decoded block into a locally assembled frame and deblock filtering the locally assembled frame into a deblocked frame; by the video encoder device, obtaining a codebook including a plurality of sets of impairments-compensation-filter coefficient values suitable for configuring an impairments compensation filter of a video decoder to process frames of encoded videos having a variety of characteristics; by the video encoder device, computing a target set of impairments-compensation-filter coefficient values according to the deblocked frame; by the video encoder device, adaptively selecting from the codebook a set of impairments-compensation-filter coefficient values and forming an impairments-compensated reconstructed frame, which impairments-compensated reconstructed frame is used as a reference frame by the motion compensation process to prepare a second impairments-compensated prediction signal block; and including in the encoded bitstream generated by the video encoder device an indicator enabling the video decoder to select the selected set of impairments-compensation-filter coefficient values from the video decoder's copy of the codebook.