Encoding device, decoding device, and encoding method and decoding method thereof
An encoding apparatus encoding a bitstream including an image frame is disclosed. The encoding apparatus comprises a selection unit for selecting a plurality of pixels including non-zero transform coefficients in a transform coefficient block constituting an image frame, an inverse transform unit for generating a plurality of groups of code candidates including combinations of codes assignable to the non-zero transform coefficients of the selected plurality of pixels and generating candidate reconstruction blocks by performing an inverse transform on each of the transform coefficient blocks in which the sign is assigned to the non-zero transform coefficients according to the generated plurality of groups of code candidates, a cost calculation unit for calculating a cost on the basis of a pixel value difference between pixel values of a plurality of pixels selected from among the generated candidate reconstruction blocks and pixel values of other pixels adjacent to the selected plurality of pixels and an encoding unit for assigning different predetermined codewords to a plurality of groups of code candidates on the basis of the calculated cost and encoding one codeword of the codewords into encoding information of non-zero transform coefficients of the selected plurality of pixels.
1. An encoding apparatus for encoding a bitstream including an image frame, the encoding apparatus comprising:
a selection unit configured to select a plurality of pixels including non-zero transform coefficients in a transform coefficient block constituting an image frame;
an inverse transformation unit configured to assign a sign to the non-zero transform coefficients, and generate candidate reconstruction blocks by performing an inverse transform on each of the transform coefficient blocks in which the sign is assigned;
a cost calculation unit configured to calculate a cost corresponding to each of the candidate reconstruction blocks based on pixel values of the selected plurality of pixels and pixel values of other pixels adjacent to the selected plurality of pixels; and
an encoding unit configured to assign predetermined codewords to the plurality of candidate reconstruction blocks based on the calculated cost, and encode one codeword among the assigned codewords based on a bit size of the assigned codewords.
2. The encoding apparatus of claim 1 , wherein the selection unit selects a predetermined number of pixels in a decreasing order of a transform coefficient value from among the transform coefficient block constituting the image frame.
3. The encoding apparatus of claim 1 , wherein the encoding unit allocates a codeword constituting a smallest bits from among the predetermined codeword for a code group having a small cost, and encodes a codeword composed of the smallest bits to encoding information of non-zero transform coefficients included in each pixel.
4. The encoding apparatus of claim 3 , wherein the encoding unit allocates codeword ‘0’ to a candidate group having the smallest cost.
5. The encoding apparatus of claim 1 , wherein the inverse transformation unit generates a restoration block in which an inverse transform is performed for each block where transform coefficients included in remaining pixels other than each of the selected pixel from among the transform coefficient blocks are replaced with zero and a restoration block in which inverse transform is performed on a block where all the selected pixels from among the transformed coefficient block are replaced with zero, and generates a candidate reconstruction block through the sum or difference of the restoration blocks generated.
6. The encoding apparatus of claim 1 , wherein the cost calculation unit calculates boundary matching cost based on a difference between pixel values of a plurality of pixels selected from the candidate reconstruction blocks and pixel values of other pixels in pre-restored another block adjacent to the selected plurality of pixels.
7. The encoding apparatus of claim 1 , wherein the cost calculation unit calculates a variance cost based on the pixel value difference between adjacent pixels within the candidate reconstruction block.
8. An encoding method comprising:
selecting a plurality of pixels including non-zero transform coefficients in a transform coefficient block constituting an image frame;
assigning a sign to the non-zero transform coefficients;
generating candidate reconstruction blocks by performing an inverse transform on each of the transform coefficient blocks in which the sign is assigned to;
calculating a cost corresponding to each of the candidate reconstruction blocks pixel values of the selected plurality of pixels and pixel values of other pixels adjacent to the selected plurality of pixels; and
assigning predetermined codewords to the plurality of candidate reconstruction blocks based on the calculated cost and encoding one codeword among the codewords based on a bit size of the assigned codewords.
9. The method of claim 8 , wherein the selecting comprises selecting a predetermined number of pixels in a decreasing order of a transform coefficient value from among the transform coefficient block constituting the image frame.
10. The method of claim 8 , wherein the encoding comprises allocating a codeword constituting a smallest bits from among the predetermined codeword for a code group having a small cost, and encoding a codeword composed of the smallest bits to encoding information of non-zero transform coefficients included in each pixel.
11. The method of claim 10 , wherein the encoding comprises allocating codeword ‘0’ to a candidate group having the smallest cost.
12. The method of claim 8 , wherein the generating comprises:
generating a restoration block in which inverse transform is performed for each block where transform coefficients included in remaining pixels other than each of the selected pixel from among the transform coefficient blocks are replaced with zero and a restoration block in which inverse transform is performed on a block where all the selected pixels from among the transformed coefficient block are replaced with zero; and
generating a candidate reconstruction block through the sum or difference of the reconstructed blocks generated.
13. The method of claim 8 , wherein the calculating comprises calculating boundary matching cost based on a difference between pixel values of a plurality of pixels selected from the candidate reconstruction blocks and pixel values of other pixels in pre-restored another block adjacent to the selected plurality of pixels.
14. The method of claim 8 , wherein the calculating comprises calculating a variance cost based on the pixel value difference between adjacent pixels within the candidate reconstruction block.
15. A decoding apparatus for decoding a bitstream including an image frame, the decoding apparatus comprising:
a parsing unit configured to parse a codeword encoded with sign information of non-zero transform coefficients included in a plurality of pixels selected from a transform coefficient block constituting an image frame;
a selection unit configured to select a plurality of pixels to be decoded in a transform coefficient block constituting an image frame;
an inverse transformation unit configured to assign a sign to the non-zero transform coefficients, and generate candidate reconstruction blocks by performing an inverse transform on each of the transform coefficient blocks in which the sign is assigned;
a cost calculation unit configured to calculate a cost corresponding to each of the generated candidate reconstruction blocks based on pixel values of the selected plurality of pixels and pixel values of other pixels adjacent to the selected plurality of pixels; and
a decoding unit configured to allocate predetermined codewords to the plurality of candidate reconstruction blocks based on the calculated cost, and determine a sign of the non-zero transform coefficients of the selected plurality of pixels according to a sign to which a codeword corresponding to the parsed codeword is allocated.