1. A method, comprising: by apparatus comprising one or more data processors configured by software, one or more programmable logic devices, one or more logic circuits or a combination thereof: selecting a candidate set of function parameter values for a mapping function from a plurality of candidate sets of function parameter values for the mapping function; dividing each input image, in a sequence of input images, into image blocks; determining, for each image block, a standard deviation of pixel values in that block; constructing a set of image blocks, from among said image blocks, having non-zero standard deviation in pixel values for at least one input image in the sequence of input images; generating mapped image blocks by applying the mapping function with the candidate set of function parameter values to the pixel values in the set of image blocks in the at least one input image; determining, for each mapped image block, a standard deviation of the pixel values in that block; constructing a subset of mapped image blocks from among the mapped image blocks, each mapped image block of said subset having a standard deviation larger than a predefined threshold value; determining a total number of mapped image blocks with non-zero standard deviations in said subset of mapped image blocks; using the total number of mapped image blocks with non-zero standard deviations to determine whether the candidate set of function parameter values is optimal for the mapping function to map the at least one input image; generating a plurality of mapped images that correspond to the plurality of input images by applying the mapping function with an overall optimal set of function parameter values, optimally selected from among the plurality of candidate sets of function parameter values for the mapping function, to the plurality of images; compressing the plurality of mapped images as base-layer (BL) image data into an output multi-layer video signal.