Patent ID: 8670485
Filing Date: 2014-03-11
Classification: H04N

Abstract:
1. A method of coding using a coding apparatus, the method comprising: accepting an ordered series of quantized transform coefficients of a block of image data, the quantized transform coefficients of the series having a most likely-to-occur amplitude, and one or more other amplitudes including a next-to-most likely-to-occur amplitude; position encoding positions of quantized coefficients that are in the series and that have respective amplitudes other than the most likely-to-occur amplitude, the position encoding including recognizing and encoding position events to form position codewords using a plurality of position code mappings that map position events to position codewords, the position encoding including switching between the code mappings of the plurality based on a position context; the position context being defined by one or more position-context parameters that, when encoding a current position event, are known or derivable from one or more previously encoded position events; encoding of amplitudes of quantized coefficients that are in the series and that have respective amplitudes other than the most likely-to-occur amplitude, the encoding of amplitudes including encoding amplitude events using more than one amplitude code mapping, which amplitude code mapping dependent on at least whether or not the amplitude event includes a coefficient having other than the most likely-to-occur amplitude that is adjacent to at least one coefficient having the most likely-to-occur amplitude, the encoding of amplitudes being in the reverse order of the original ordering of the series and forming amplitude codewords; and concatenating the position and amplitude codewords, such that on average, sequences of quantized coefficients that are more likely-to-occur are encoded by shorter sets of codewords than are sequences of quantized coefficients that are less likely-to-occur.