Coding and decoding of transform skipped blocks

摘要

Video encoder and decoder and methods therein for transform skipped encoding and decoding of blocks of pixels. The methods comprises a modified use of an existing context model associated with transform coefficients, for deriving contexts for a bitmask indicating which residual values (i.e. not transform coefficients), in a transform skipped residual block, that are greater than one. The methods are applicable to video coding schemes such as HEVC.

主权项

1. A method performed by a video decoder operable according to a video decoding scheme applying residual decoding comprising use of a context model for deriving contexts to be used for decoding flags, in a bitmask, which flags indicate, respectively, whether an absolute value of a non-zero transform coefficients in a transformed residual block is greater than one, where the context model comprises a plurality of states, each state corresponding to a context and a probability, where a procedure for deriving contexts for a number of flags related to transform coefficients is started in a first state, A, and where, after decoding a flag which corresponds to an absolute value of a transform coefficient that is greater than one, the context model goes to a second state, D, which is used for decoding remaining flags in said bitmask, the method comprising:
for a transform-skipped residual block comprising residual values and not transform coefficients, deriving contexts to be used for decoding flags, in a bitmask, that indicate, respectively, whether an absolute value of a non-zero residual value in the transform-skipped block is greater than one, by use of the context model, starting in the second state D.