Partial sample interpolation for reference image resampling

Abstract

This invention provides an encoding and decoding method that improves interpolation filters for motion compensation. [Solution] In the video decoder 410, the interpolation filter is selected from two interpolation filter versions 431 and 432 that have different edge preservation characteristics, and the selection is made based on whether the current image has the same image resolution as the reference sample array in the horizontal and / or vertical dimensions and / or constraint information 425 in the data stream 420.

Claims

1. A method for decoding an image from a data stream, The value of the first syntax element is determined, at least partially, based on the flag and index values, If the value of the first syntax element is 3, then it is determined that the half-sample interpolation index value is 1. To derive a scaling ratio that shows the current image and the reference image are the same size, Based on the half-sample interpolation index value and the scaling ratio, an interpolation filter (431) having six non-zero coefficients is selected to obtain the half-sample value in the reference image. Predicting the current image using the interpolation filter and the reference image, Methods that include...

2. The method according to claim 1, wherein the six non-zero coefficients of the interpolation filter (431) are 3, 9, 20, 20, 9, and 3, and the scaling ratio is represented by a value of 16384.

3. The interpolation filter (431) is a first interpolation filter, The aforementioned method, To determine whether the horizontal dimension of the current image (421) and the horizontal dimension of the reference image are the same, In response to determining that the horizontal dimension of the current image (421) and the horizontal dimension of the reference image are the same, the first interpolation filters (431, 432) are selected. In response to determining that the horizontal dimension of the current image (421) and the horizontal dimension of the reference image are different, a second interpolation filter (431, 432) having eight non-zero coefficients is selected. The method according to claim 1, further comprising:

4. The interpolation filter (431) is a first interpolation filter, The aforementioned method, To determine whether the vertical dimension of the current image (421) and the vertical dimension of the reference image are the same, In response to determining that the vertical dimension of the current image (421) and the vertical dimension of the reference image are the same, the first interpolation filters (431, 432) are selected. In response to determining that the vertical dimension of the current image (421) and the vertical dimension of the reference image are different, a second interpolation filter (431, 432) having eight non-zero coefficients is selected. The method according to claim 1, further comprising:

5. The eight non-zero coefficients of the second interpolation filter (431, 432) are -1, 4, -11, 40, 40, -11, 4, and -1. The method according to claim 3.

6. A device comprising at least one processor configured to carry out the method described in any one of claims 1 to 5, A video decoder (410) for decoding an image from a data stream.

7. A computer-readable medium storing a computer program, wherein the computer program includes a software code portion configured to perform each step of the method according to any one of claims 1 to 5 when the computer program is executed on a processing device. Computer-readable media.

8. A method for encoding an image into a data stream, Identify a scaling ratio that indicates the current image and the reference image are the same size, Setting the value of the first syntax element based at least partially on the flag and index values, If the value of the first syntax element is 3, then it is determined that the half-sample interpolation index value is 1. Based on the half-sample interpolation index value and the scaling ratio, an interpolation filter (431) having six non-zero coefficients is selected to obtain the half-sample value in the reference image. To predict the current image using the selected interpolation filter and the reference image, the first syntax element, the flag and the index value are encoded, Methods that include...

9. The method according to claim 8, wherein the six non-zero coefficients of the interpolation filter (431) are 3, 9, 20, 20, 9, and 3, and the scaling ratio is represented by a value of 16384.

10. The interpolation filter (431) is a first interpolation filter, The aforementioned method, To determine whether the horizontal dimension of the current image (421) and the horizontal dimension of the reference image are the same, In response to determining that the horizontal dimension of the current image (421) and the horizontal dimension of the reference image are the same, the first interpolation filters (431, 432) are selected. In response to determining that the horizontal dimension of the current image (421) and the horizontal dimension of the reference image are different, a second interpolation filter (431, 432) having eight non-zero coefficients is selected. The method according to claim 8, further comprising:

11. The interpolation filter (431) is a first interpolation filter, The aforementioned method, To determine whether the vertical dimension of the current image (421) and the vertical dimension of the reference image are the same, In response to determining that the vertical dimension of the current image (421) and the vertical dimension of the reference image are the same, the first interpolation filters (431, 432) are selected. In response to determining that the vertical dimension of the current image (421) and the vertical dimension of the reference image are different, a second interpolation filter (431, 432) having eight non-zero coefficients is selected. The method according to claim 8, further comprising:

12. The eight non-zero coefficients of the second interpolation filter (431, 432) are -1, 4, -11, 40, 40, -11, 4, and -1. The method according to claim 10.

13. A device comprising at least one processor configured to carry out the method described in any one of claims 8 to 12, A video encoder (410) for encoding an image into a data stream.

14. A computer-readable medium storing a computer program, wherein the computer program includes a software code portion configured to perform each step of the method according to any one of claims 8 to 12 when the computer program is executed on a processing device. Computer-readable media.

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