Image data compression using switching between a set of transforms

An apparatus for predictively encoding a picture that is subdivided into a set of segments into a data stream, the apparatus comprising:

• a processor;
• and
• a memory having instructions which, when executed by the processor, cause the apparatus to:
• select at least one transform from a set of transforms and an intra-coding mode from a set of intra-coding modes for encoding a segment from the set of segments, wherein the set of transforms is comprised of concatenations of a first one of a set of one-dimensional spatial-to-spectral transforms applied horizontally and a second one of the set of one-dimensional spatial-to-spectral transforms applied vertically;
• signal the intra-coding mode in the data stream using an intra-coding mode signalization;
• use a transform class signalization signal for indicating the selected transform in the data stream, wherein the transform class signalization comprises a number of bins, and wherein the transform class signalization indicates the selected at least one transform using a prefix portion indicating a first state or a second state, the first state indicating that the selected at least one transform is a previous transform selection of a neighboring segment, the second state indicating a switching to at least one different transform specified by a suffix portion of the transform class signalization;
• context-adaptively encode the transform class signalization using a context based on the intra-coding mode;
• and
• use a first plurality of the bins to index the first one of the set of one-dimensional spatial-to-spectral transforms applied horizontally and a second plurality of the bins, that is different than the first plurality of the bins, to index the second one of the set of one-dimensional spatial-to-spectral transforms applied vertically;
• wherein the intra-coding mode is used to encode a first bin of the first plurality of the bins and the intra-coding mode is used to encode a first bin of the second plurality of the bins, and wherein the first bin of the first plurality of the bins is used to encode a second bin of the first plurality of bins and the first bin of the second plurality of the bins is used to encode a second bin of the second plurality of bins.

A method for predictively decoding a picture from a data stream, wherein the picture is subdivided into a set of segments, the method comprising:

• decoding, from the data stream, an intra-coding mode signalization for a segment from the set of segments;
• selecting an intra-coding mode for the segment using the intra-coding mode signalization;
• decoding, from the data stream, a transform class signalization corresponding to the segment based on a context dependent on the intra-coding mode, wherein the transform class signalization comprises a number of bins;
• determining that a prefix portion of the transform class signalization indicates a first state or a second state;
• in response to the prefix portion indicating the first state, selecting, for the segment, a transform from a set of transforms based on a previous transform selection of a neighboring segment without decoding a suffix portion of the transform class signalization decoding, from the data stream, a transform class signalization corresponding to the segment based on a context dependent on the intra-coding mode, wherein the set of transforms is comprised of concatenations of a first one of a set of one-dimensional spectral-to-spatial transforms applied horizontally and a second one of the set of one-dimensional spectral-to-spatial transforms applied vertically;
• in response to the prefix portion indicating the second state, decoding the suffix portion from the data stream and selecting, for the segment, a transform from the set of transforms identified by the suffix portion, the suffix portion corresponding to a fixed-length binarization;
• continue parsing the data stream for decoding subsequent segments from the set of segments;
• and
• using a first plurality of the bins to index the first one of the set of one-dimensional spectral-to-spatial transforms applied horizontally and a second plurality of the bins, that is different than the first plurality of the bins, to index the second one of the set of one-dimensional spectral-to-spatial transforms applied vertically;
• wherein the intra-coding mode is used to read a first bin of the first plurality of the bins and the intra-coding mode is used to read a first bin of the second plurality of the bins, and wherein the first bin of the first plurality of the bins is used to read a second bin of the first plurality of bins and the first bin of the second plurality of the bins is used to read a second bin of the second plurality of bins.

A method for predictively encoding a picture that is subdivided into a set of segments, the method comprising:

• selecting at least one transform from a set of transforms and an intra-coding mode from a set of intra-coding modes for encoding a segment from the set of segments, wherein the set of transforms is comprised of concatenations of a first one of a set of one-dimensional spatial-to-spectral transforms applied horizontally and a second one of the set of one-dimensional spatial-to- spectral transforms applied vertically;
• signaling the intra-coding mode in the data stream using an intra-coding mode signalization;
• using a transform class signalization signal for indicating the selected transform in the data stream, wherein the transform class signalization comprises a number of bins, and wherein the transform class signalization indicates the selected at least one transform using a prefix portion indicating a first state or a second state, the first state indicating that the selected at least one transform is a previous transform selection of a neighboring segment, the second state indicating a switching to at least one different transform specified by a suffix portion of the transform class signalization;
• context-adaptively encoding the transform class signalization using a context based on the intra-coding mode;
• and
• using a first plurality of the bins to index the first one of the set of one-dimensional spatial-to-spectral transforms applied horizontally and a second plurality of the bins, that is different than the first plurality of the bins, to index the second one of the set of one-dimensional spatial-to-spectral transforms applied vertically;
• wherein the intra-coding mode is used to encode a first bin of the first plurality of the bins and the intra-coding mode is used to encode a first bin of the second plurality of the bins, and wherein the first bin of the first plurality of the bins is used to encode a second bin of the first plurality of bins and the first bin of the second plurality of the bins is used to encode a second bin of the second plurality of bins.

A non-transitory computer readable medium encoded with a computer program that, when executed by a computer, causes the computer to implement a method for predictively decoding a picture that is subdivided into a set of segments from a data stream, the method comprising:

• decoding, from the data stream, an intra-coding mode signalization for a segment from the set of segments;
• selecting an intra-coding mode for the segment using the intra-coding mode signalization;
• decoding, from the data stream, a transform class signalization corresponding to the segment based on a context dependent on the intra-coding mode, the transform class signalization comprising a number of bins;
• determining that a prefix portion of the transform class signalization indicates a first state or a second state;
• in response to the prefix portion indicating the first state, selecting for the segment, a transform from a set of transforms based on a previous transform selection of a neighboring segment without decoding a suffix portion of the transform class signalization, wherein the set of transforms is comprised of concatenations of a first one of a set of one-dimensional spectral-to-spatial transforms applied horizontally and a second one of the set of one-dimensional spectral-to-spatial transforms applied vertically;
• in response to the prefix portion indicating the second state, decoding the suffix portion from the data stream and select, for the segment, a transform from the set of transforms identified by the suffix portion, the suffix portion corresponding to a fixed-length binarization;
• continue to parse the data stream for decoding subsequent segments from the set of segments;
• and
• using a first plurality of the bins to index the first one of the set of one-dimensional spectral-to-spatial transforms applied horizontally and a second plurality of the bins, that is different than the first plurality of the bins, to index the second one of the set of one-dimensional spectral-to-spatial transforms applied vertically;
• wherein the intra-coding mode is used to read a first bin of the first plurality of the bins and the intra-coding mode is used to read a first bin of the second plurality of the bins. and wherein the first bin of the first plurality of the bins is used to read a second bin of the first plurality of bins and the first bin of the second plurality of the bins is used to read a second bin of the second plurality of bins.

A non-transitory computer readable medium encoded with a computer program that, when executed by a computer, causes the computer to implement a method for predictively encoding a picture that is subdivided into a set of segments into a data stream, the method comprising:

• selecting at least one transform from a set of transforms and an intra-coding mode from a set of intra-coding modes for encoding a segment from the set of segments, wherein the set of transforms is comprised of concatenations of a first one of a set of one-dimensional spatial-to-spectral transforms applied horizontally and a second one of the set of one-dimensional spatial-to-spectral transforms applied vertically;
• signaling the intra-coding mode in the data stream using an intra-coding mode signalization ;
• using a transform class signalization signal for indicating the selected transform in the data stream, wherein the transform class signalization comprises a number of bins, and wherein the transform class signalization indicates the selected at least one transform using a prefix portion indicating a first state or a second state, the first state indicating that the selected at least one transform is a previous transform selection of a neighboring segment, the second state indicating a switching to at least one different transform specified by a suffix portion of the transform class signalization;
• context-adaptively encode the transform class signalization using a context based on the intra-coding mode;
• and
• using a first plurality of the bins to index the first one of the set of one-dimensional spatial-to-spectral transforms applied horizontally and a second plurality of the bins, that is different than the first plurality of the bins, to index the second one of the set of one-dimensional spatial-to-spectral transforms applied vertically;
• wherein the intra-coding mode is used to encode a first bin of the first plurality of the bins and the intra-coding mode is used to encode a first bin of the second plurality of the bins, and wherein the first bin of the first plurality of the bins is used to encode a second bin of the first plurality of bins and the first bin of the second plurality of the bins is used to encode a second bin of the second plurality of bins.