1. A method of encoding an input video frame into an encoded video frame, the method comprising disassembling the input video frame into a plurality of blocks of pixels, and, for a current block of pixels: determining a subset of intra-frame prediction modes from a pre-determined set of possible intra-frame prediction modes based on comparing pixel values between different predicted blocks associated with different intra-frame prediction modes in the pre-determined set, the number of modes in the subset being fewer than the number of modes in the pre-determined set; selecting an intra-frame prediction mode from the subset; generating a predicted block as an intra-frame prediction of the current block, based on applying the selected intra-frame prediction mode to a partially reconstructed frame comprising an assembly of one or more previous blocks that have been reconstructed as if decoded; generating a residual block by subtracting the predicted block from the current block; encoding the residual block and an indication of the selected intra-frame prediction mode to generate the encoded video frame, the encoding of said indication being based on the number of intra-frame prediction modes in the subset; and refraining from signaling the determined subset to a decoding apparatus that independently determines that subset.