Method and apparatus for interpolating a reference pixel in an annular image and encoding/decoding an annular image

1. A computer-implemented method for interpolating an object reference pixel in an annular image, the method comprising using a computer to carry out the steps of:

selecting a plurality of reference pixels located in a direction of a distortion of the annular image;

interpolating the object reference pixel to be interpolated based on the selected plurality of reference pixels;

wherein the plurality of reference pixels are exclusively located on one single circumference of a circle having a radius between a center of the annular image and the object reference pixel and are located within a predetermined distance from the object reference pixel.

2. The method of claim 1 , wherein the selection of the plurality of reference pixels comprises selecting the plurality of reference pixels using positions of the plurality of reference pixels, which are determined using a predetermined equation.

3. The method of claim 1 , wherein the selection of the plurality of reference pixels comprises selecting the plurality of reference pixels using a table that stores positions of the plurality of reference pixels located on the circumference of the circle.

4. The method of claim 1 , wherein the object reference pixel is a ½ pixel or a ¼pixel.

5. The method of claim 1 , wherein the interpolation of the object reference pixel comprises:

applying different predetermined weights to the plurality of reference pixels; and

obtaining the object reference pixel by adding the reference pixels to which the different predetermined weights are applied.

6. An apparatus for interpolating an object reference pixel in an annular image, the apparatus comprising:

a reference pixel selecting unit for selecting a plurality of reference pixels located in a direction of a distortion of the annular image; and

an interpolating unit for interpolating the object reference pixel to be interpolated based on the selected plurality of reference pixels;

wherein the plurality of reference pixels are exclusively located on one single circumference of a circle having a radius between a center of the annular image and the object reference pixel and are located within a predetermined distance from the object reference pixel.

7. The apparatus of claim 6 , wherein the reference pixel selecting unit selects the plurality of reference pixels using positions of the plurality of reference pixels, which are determined using a predetermined equation.

8. The apparatus of claim 6 , wherein the reference pixel selecting unit selects the plurality of reference pixels using a table that stores positions of the plurality of reference pixels located on the circumference of the circle.

9. The apparatus of claim 6 , wherein the object reference pixel is a ½ pixel or a ¼ pixel.

10. The apparatus of claim 6 , wherein the interpolating unit applies different predetermined weights to the plurality of reference pixels and obtains the object reference pixel by adding the reference pixels to which the predetermined different weights are applied.

11. A method of encoding an annular image, the method comprising:

interpolating an object reference pixel to be interpolated based on a plurality of reference pixels exclusively located on one single circumference of a circle having a radius between a center of the annular image and a position of the object reference pixel to perform motion estimation on the annular image, thereby determining a prediction macroblock for a current macroblock; and

performing a discrete cosine transform (DCT) on a difference between the prediction macroblock and the current macroblock, quantizing DCT coefficients, reordering the quantized DCT coefficients, and entropy-encoding the reordered DCT coefficients.

12. An apparatus for encoding an annular image, the apparatus comprising:

a motion estimation and compensation unit for interpolating an object reference pixel to be interpolated based on a plurality of reference pixels exclusively located on one single circumference of a circle having a radius between a center of the annular image and a position of the object reference pixel to perform motion estimation on the annular image, thereby determining a prediction macroblock for a current macroblock;

a discrete cosine transform (DCT) unit for performing a DCT on a difference between the prediction macroblock and the current macroblock;

a quantization unit for quantizing DCT coefficients;

a reordering unit for reordering the quantized DCT coefficients; and

an entropy encoding unit for entropy-encoding the reordered DCT coefficients.

13. A method of decoding an annular image, the method comprising:

entropy-decoding a received encoded bitstream, reordering entropy-decoded data samples, inversely quantizing the reordered data samples, and performing an inverse discrete cosine transform (DCT) on the inversely quantized data samples, thereby generating inverse DCT coefficients;

interpolating an object reference pixel to be interpolated based on a plurality of reference pixels exclusively located on one single circumference of a circle having a radius between a center of the annular image and a position of the object reference pixel, thereby determining a prediction macroblock for a current macroblock; and

adding a macroblock comprising the inverse DCT coefficients and the prediction macroblock.

14. An apparatus for decoding an annular image, the apparatus comprising:

an entropy decoding unit for entropy-decoding a received encoded bitstream;

a reordering unit for reordering entropy-decoded data samples;

an inverse quantization unit for inversely quantizing the reordered data samples;

an inverse discrete cosine transform (DCT) unit for generating inverse DCT coefficients by performing an inverse DCT on the inversely quantized data samples;

a motion compensation unit for interpolating an object reference pixel to be interpolated based on a plurality of reference pixels exclusively located on one single circumference of a circle having a radius between a center of the annular image and a position of the object reference pixel, thereby determining a prediction macroblock for a current macroblock; and

an adder for adding a macroblock comprising the inverse DCT coefficients and the prediction macroblock.