Scalable video coding using subblock-based coding of transform coefficient blocks in the enhancement layer

A scalable video decoding method comprising:

• decoding a base layer residual signal of a base layer signal from a coded data stream;
• and
• reconstructing an enhancement layer signal comprising decoding a transform coefficient block of transform coefficients representing an enhancement layer signal from the coded data stream, by:
• selecting, for the transform coefficient block representing the enhancement layer signal, a subblock subdivision among a set of possible subblock subdivisions based on information including a spectral decomposition of a portion of the base layer residual signal or the base layer signal, wherein the transform coefficient block is subdivided into subblocks according to the selected subblock subdivision such that a dimension of at least one of the subblocks is longer along a first axis direction that is transverse to a second axis direction along which a spectral energy distribution of the spectral decomposition is narrower, and
• traversing positions of the transform coefficients in units of the subblocks such that all positions within one subblock are traversed before proceeding to a next subblock in a subblock order defined among the subblocks,
• wherein for a current-subblock being traversed, wherein the traversing a current subblock comprises:
• decoding from the data stream a syntax element indicating as to whether the current subblock comprises any significant transform coefficient,
• if the syntax element indicates that the current subblock does not comprise any significant transform coefficient, setting the transform coefficients within the current-subblock equal to zero, and
• if the syntax element indicates that the current subblock comprises any significant transform coefficient, decoding from the data stream syntax elements indicating levels of the transform coefficients within the current subblock.

A scalable video encoder comprising:

• a first block-based encoding unit configured to encode, using a processor, a base layer residual signal of a base layer signal into a coded data stream;
• and
• a second block-based encoding unit configured to encode, using the processor, an enhancement layer signal, the second block-based encoding unit configured for encoding, using the processor, a transform coefficient block of transform coefficients representing the enhancement layer signal from the coded data stream, by:
• selecting, for the transform coefficient block representing the enhancement layer signal, a subblock subdivision among a set of possible subblock subdivisions based on information including a spectral decomposition of a portion of the base layer residual signal or the base layer signal, wherein the transform coefficient block is subdivided into subblocks according to the selected subblock subdivision such that a dimension of at least one of the subblocks is longer along a first axis direction that is transverse to a second axis direction along which a spectral energy distribution of the spectral decomposition is narrower, and
• traversing positions of the transform coefficients in units of the subblocks such that all positions within one subblock are traversed before proceeding to a next subblock in a subblock order defined among the subblocks,
• wherein for a current-subblock being traversed, the second block-based encoding unit is configured for:
• encoding into the data stream a syntax element indicating as to whether the current subblock comprises any significant transform coefficient or not, and
• if the syntax element indicates that the current subblock comprises any significant transform coefficient, encoding into the data stream syntax elements indicating levels of the transform coefficients within the current subblock.

A scalable video encoding method comprising:

• encoding a base layer residual signal of a base layer signal into a coded data stream;
• and
• encoding an enhancement layer signal comprising encoding a transform coefficient block of transform coefficients representing the enhancement layer signal from the coded data stream, by:
• selecting, for the transform coefficient block representing the enhancement layer signal, a subblock subdivision among a set of possible subblock subdivisions based on information including a spectral decomposition of a portion of the base layer residual signal or the base layer signal, wherein the transform coefficient block is subdivided into subblocks according to the selected subblock subdivision such that a dimension of at least one of the subblocks is longer along a first axis direction that is transverse to a second axis direction along which a spectral energy distribution of the spectral decomposition is narrower, and
• traversing positions of the transform coefficients in units of the subblocks such that all positions within one subblock are traversed before proceeding to a next subblock in a subblock order defined among the subblocks, wherein for a current-subblock being traversed, wherein the traversing a current subblock comprises:
• encoding into the data stream a syntax element indicating as to whether the current subblock comprises any significant transform coefficient, and
• if the syntax element indicates that the current subblock comprises any significant transform coefficient, encoding into the data stream syntax elements indicating levels of the transform coefficients within the current subblock.