Image decoding apparatus and method for handling intra-image predictive decoding with various color spaces and color signal resolutions

摘要

The present invention is directed to an image information decoding apparatus adapted for performing intra-image decoding based on resolution of color components and color space of an input image signal. An intra prediction unit serves to adaptively change block size in generating a prediction image based on a chroma format signal indicating whether resolution of color components is one of 4:2:0 format, 4:2:2 format, and 4:4:4 format, and a color space signal indicating whether color space is one of YCbCr, RGB, and XYZ. An inverse orthogonal transform unit and an inverse quantization unit serve to also change orthogonal transform technique and quantization technique in accordance with the chroma format signal and the color space signal. A decoding unit decodes the chroma format signal and the color space signal to generate a prediction image corresponding to the chroma format signal and the color space signal.

主权项

1. An image information decoding apparatus comprising:
a processor; an inverse quantization unit configured by the processor to:
perform, when a chroma format signal has a 4:4:4 format, an inverse quantization of quantized transform coefficients of an encoded image in accordance with an inverse quantization scale factor, the encoded image corresponding to the chroma signal; andgenerate inverse quantized coefficients corresponding to the chroma signal; and an inverse transformation unit configured by the processor to perform an inverse transformation on 4×4 pixel blocks of the inverse quantized coefficients in accordance with a corresponding normalization coefficient, and generate a decoded image corresponding to the chroma signal based on an output of the inverse transformation, the pixel blocks being associated with inverse transformation scaling factors, and the normalization coefficient being a product of at least two of the inverse transformation scaling factors, wherein the inverse quantization unit is further configured by the processor to:
identify one or more of the inverse transformation scaling factors, the identified inverse transformation scaling factors being associated with an application of the inverse transformation to corresponding ones of the pixel blocks; andcalculate the inverse quantization scaling factor based on the identified transformation scaling factors and a block size of the inverse transformation applied to the corresponding pixel blocks.