Apparatus for encoding and decoding image using adaptive DCT coefficient scanning based on pixel similarity and method therefor
The present invention discloses an encoding apparatus using a Discrete Cosine Transform (DCT) scanning, which includes a mode selection means for selecting an optimal mode for intra prediction; an intra prediction means for performing intra prediction onto video inputted based on the mode selected in the mode selection means; a DCT and quantization means for performing DCT and quantization onto residual coefficients of a block outputted from the intra prediction means; and an entropy encoding means for performing entropy encoding onto DCT coefficients acquired from the DCT and quantization by using a scanning mode decided based on pixel similarity of the residual coefficients.
1. An encoding apparatus comprising:
a mode selection unit configured to select an intra prediction mode;
an intra prediction unit configured to perform intra prediction using the selected intra prediction mode to obtain predicted pixel values;
a transformation and quantization unit configured to perform transformation and quantization to obtain transform coefficients; and
an entropy encoding unit configured to perform entropy encoding of the transform coefficients scanned according to a scanning mode selected based on the selected intra prediction mode, wherein the scanning mode is selected to be a horizontal scanning mode when the selected intra prediction mode is a vertical intra prediction mode, and the scanning mode is selected to be a vertical scanning mode when the selected intra prediction mode is a horizontal intra prediction mode.
2. The encoding apparatus of claim 1 , wherein the entropy encoding unit is further configured to:
perform entropy encoding of the transform coefficients scanned according to a horizontal scanning mode when the selected intra prediction mode is a vertical intra prediction mode and a vertical pixel similarity of difference values between pixel values and the predicted pixel values is high;
perform entropy encoding of the transform coefficients scanned according to a vertical scanning mode when the selected intra prediction mode is a horizontal intra prediction mode and a horizontal pixel similarity of the difference values is high; and
perform entropy encoding of the transform coefficients scanned according to a zigzag scanning mode when the vertical pixel similarity of the difference values and the horizontal pixel similarity of the difference values are similar to each other.
3. The encoding apparatus of claim 2 , wherein the entropy encoding unit is further configured to decide that the vertical pixel similarity of the difference values is high when a vertical pixel similarity value of the difference values is greater than a value obtained by multiplying a horizontal pixel similarity value of the difference values by a first multiplication factor.
4. The encoding apparatus of claim 3 , wherein the entropy encoding unit is further configured to calculate the vertical pixel similarity of the difference values by calculating a dispersion of pixels adjacent to a left part of a block of pixels of a current block that is currently being encoded.
5. The encoding apparatus of claim 3 , wherein the first multiplication factor is a natural number 2 .
6. The encoding apparatus of claim 2 , wherein the entropy encoding unit is further configured to decide that the horizontal pixel similarity is high when a horizontal pixel similarity value of the difference values is greater than a value obtained by multiplying a vertical pixel similarity value of the difference values by a second multiplication factor.
7. The encoding apparatus of claim 6 , wherein the entropy encoding unit is further configured to calculate the horizontal pixel similarity of the difference values by calculating a dispersion of pixels adjacent to an upper part of a block of pixels of a current block that is currently being encoded.
8. The encoding apparatus of claim 6 , wherein the second multiplication factor is a natural number 2 .