Bit-plane encoder and decoder

A method for encoding transform coefficients into a data stream, the transform coefficients being grouped into coefficient groups, the coefficient groups being grouped into group sets, the method comprising

• signaling in the data stream a coding mode to be a first mode or a second mode,
• inserting into the data stream information which identifies a first subset of group sets for which the coding mode is not to be used, and a second subset of group sets for which the coding mode is to be used;
• for each group set out of the first subset, for each coefficient group of the respective group set,
• identifying a first set of coded bit planes in the data stream by
• deriving a first prediction for the first set of coded bit planes based on a first previously coded coefficient group,
• inserting into the data stream a first prediction residual for correcting the first prediction so as to acquire a corrected prediction for the first set of coded bit planes,
• inserting bits of the respective coefficient group within the first set of coded bit planes into the data stream;
• each group set out of the second subset,
• depending on the coding mode
• if the coding mode is the first mode,
• for each coefficient group of the respective group set,
• identifying a second set of coded bit planes by deriving a second prediction for the second set of coded bit planes based on a second previously coded coefficient group, wherein a prediction residual for the second prediction is to be assumed to be zero, and
• inserting bits within the second set of coded bit planes into the data stream;
• and
• wherein, if the coding mode is the second mode, for each group set of the second subset, for each coefficient group of respective group set, coefficients of the respective coefficient group are to be set to zero or to pseudo noise.

A digital storage medium storing a picture by means of a data stream which has transform coefficients of a spectral decomposition of the picture encoded thereinto, the transform coefficients being grouped into coefficient groups, the coefficient groups being grouped into group sets, the data stream comprising

• an indication whether a coding mode is a first mode or a second mode,
• information which identifies a first subset of group sets for which the coding mode is not to be used, and a second subset of group sets for which the coding mode is to be used;
• wherein, for each group set out of the first subset, for each coefficient group of the respective group set,
• a first set of coded bit planes is indicated in the data stream
• relative to a first prediction for the first set of coded bit planes derived based on a first previously coded coefficient group,
• by way of a first prediction residual which corrects the first prediction so as to acquire a corrected prediction for the first set of coded bit planes,
• the data stream comprises bits of the respective coefficient group within the first set of coded bit planes;
• for each group set out of the second subset,
• depending on the coding mode
• if the coding mode is the first mode,
• for each coefficient group of the respective group set, a second set of coded bit planes is defined to be derivable by a second prediction for the second set of coded bit planes based on a second previously coded coefficient group, wherein a prediction residual for the second prediction is to be assumed to be zero, and the data stream comprises bits within the second set of coded bit planes into the data stream;
• and
• wherein, if the coding mode is the second mode, for each group set of the second subset, for each coefficient group of respective group set, coefficients of the respective coefficient group are to be set to zero or to pseudo noise.

A method for decoding transform coefficients from a data stream,

• the transform coefficients being spectral coefficients of a spectral decomposition of a picture and the transform coefficients being grouped into coefficient groups, the coefficient groups being grouped into group sets, the method comprising deriving from the data stream an indication of a coding mode;
• deriving from the data stream information which identifies a first subset of group sets for which the coding mode is not to be used, and a second subset of group sets for which the coding mode is to be used;
• for each group set out of the first subset, for each coefficient group of the respective group set,
• identifying a first set of coded bit planes by
• deriving a first prediction for the first set of coded bit planes based on a first previously decoded coefficient group,
• correcting the first prediction using a first prediction residual derived from the data stream so as to acquire a corrected prediction for the first set of coded bit planes,
• deriving bits of the respective coefficient group within the first set of coded bit planes from the data stream;
• for each group set out of the second subset,
• depending on the coding mode
• if the coding mode is the first mode,
• for each coefficient group of the respective group set,
• identifying a second set of coded bit planes by deriving a second prediction for the second set of coded bit planes based on a second previously decoded coefficient group, and assuming a prediction residual for the second prediction to be zero and
• deriving bits of the respective coefficient group within the second set of coded bit planes from the data stream;
• and
• if the coding mode is a second mode, for each group set of the second subset,
• inheriting that for each coefficient group of respective group set, coefficients of the respective coefficient group are zero or to be set to pseudo noise.