Method, apparatus and system for encoding and decoding the significance map for residual coefficients of a transform unit

A method of encoding a significance map in a digital signal coding system, said method comprising:

• identifying a scan pattern by which the significance map can be scanned to form a list of significant coefficient flags;
• subject to the scan pattern, identifying a group of significant coefficient flags including a last significant coefficient flag and referencing the identified group with a scan index value;
• scanning the significance map in accordance with the scan pattern up to and including an entirety of the identified group;
• and
• encoding the scanned flag values.

A method of encoding a significant flag boundary for a significance map of a transform unit, the transform unit encoding residual coefficients of video data, the method comprising:

• providing a scan direction that determines the encoding order for significance flags of the transform unit;
• identifying a location of a last significant flag to encode in the transform unit;
• selecting, based on the scan direction, a set from a plurality of predetermined sets that contains the identified location of the last significant flag, each of the predetermined sets containing a plurality of transform unit locations;
• and
• storing an index of the selected set as a reference to a plurality of the transform locations to encode the significant flag boundary.

A computer readable storage medium having a program recorded thereon, the program being executable by computerized apparatus to encode a significance map in a digital signal coding system, said program comprising:

• code for identifying a scan pattern by which the significance map can be scanned to form a list of significant coefficient flags;
• code operative subject to the scan pattern, for identifying a group of significant coefficient flags including a last significant coefficient flag and referencing the identified group with a scan index value;
• code for scanning the significance map in accordance with the scan pattern up to and including an entirety of the identified group;
• and
• code for encoding the scanned flag values.

A computer readable storage medium having a program recorded thereon, the program being executable by computerized apparatus to decode a significance map from an encoded bitstream, the program comprising:

• code for identifying a scan pattern by which the bitstream can be decoded;
• code for decoding a set index value from the bitstream that specifies a set of flags according to the scan pattern that contains a last significant coefficient flag of the significance map;
• and
• code for decoding individual significance flags and writing the decoded values into the significance map according to the scan pattern and including an entirety of the specified set of flags.

A video decoding apparatus comprising:

• an entropy decoder for receiving an encoded video bitstream and operative to decode a significance map by:
• identifying a scan pattern by which the bitstream can be decoded;
• decoding a set index value from the bitstream that specifies a set of flags according to the scan pattern that contains a last significant coefficient flag of the significance map;
• and
• decoding individual significance flags and writing the decoded values into the significance map according to the scan pattern and including an entirety of the specified set of flags.