Apparatus for Encoding an Image

摘要

Provided is an apparatus for encoding an image that adaptively filters reference pixels according to an intra prediction mode and a size of a prediction block, and generates the prediction block using reference pixels determined by the intra prediction mode. The reference pixels are adaptively filtered according to the size of the prediction block for intra prediction modes existing between a horizontal mode and an intra prediction mode having a direction of 45° with reference to the horizontal mode. When the reference pixels for a second directional intra prediction mode are filtered, the reference pixels for a first directional intra prediction mode, that is closer to the intra prediction mode having the direction of 45° with reference to the horizontal mode than the second directional intra prediction mode is, are also filtered. The plurality of sub-blocks and non-zero coefficients of each sub-block are scanned according to a scan pattern and the scan pattern for scanning the plurality of sub-blocks and for scanning the non-zero coefficients of each sub-block is determined by the intra prediction mode of the prediction block. Accordingly, an image compression ratio can be improved.

主权项

1. An apparatus for encoding an image, the apparatus comprising:
an intra prediction unit configured to generate reference pixels when one or more unavailable reference pixels exist and generate a prediction block according to an intra prediction mode; a transform/quantization unit configured to transform and quantize a residual block to generate a quantized block; and an entropy coding unit configured to entropy-code the quantized block, wherein the intra prediction unit adaptively filters the reference pixels according to the size of a prediction block for intra prediction modes existing between a horizontal mode and an intra prediction mode having a direction of 45° with reference to the horizontal mode, wherein, when the intra prediction unit filters the reference pixels for a second directional intra prediction mode, the intra prediction unit also filters the reference pixels for a first directional intra prediction mode that is closer to the intra prediction mode having the direction of 45° with reference to the horizontal mode than the second directional intra prediction mode is, wherein the second and the first directional intra prediction modes exist between the horizontal mode and the intra prediction mode having the direction of 45° with reference to the horizontal mode, wherein the number of intra prediction modes in which the filter is applied increases as the size of the prediction unit increases, wherein coefficients of the quantized block are divided into a plurality of sub-blocks if it is determined that a size of a transform block is equal to 8×8 in an intra prediction, wherein the plurality of sub-blocks and non-zero coefficients of each sub-block are scanned according to a scan pattern, wherein said scan pattern for scanning the plurality of sub-blocks and for scanning the non-zero coefficients of each sub-block is determined by the intra prediction mode of the prediction block, and wherein, when the intra prediction mode is a horizontal mode, the scan pattern is a vertical scan pattern.