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JP-2026075504-A - Image decoding device, image decoding method, and program

JP2026075504AJP 2026075504 AJP2026075504 AJP 2026075504AJP-2026075504-A

Abstract

[Problem] To provide an image decoding device, an image decoding method, and a program that improve coding efficiency. [Solution] The image decoding device 200 includes an intra prediction unit 204 that replaces part or all of the intra prediction with PDP (Position-Dependent Prediction) in TIMD (Template-based intra Mode Diversion), and applies PDP based on a template cost calculated using a prediction method that requires less computation than PDP. [Selection Diagram] Figure 1

Inventors

  • 加藤 晴久
  • 木谷 佳隆
  • 河村 圭

Assignees

  • ＫＤＤＩ株式会社

Dates

Publication Date
20260508
Application Date
20241022

Claims (17)

  1. An image decoding device, An image decoding device characterized by comprising an intra-prediction unit in which part or all of the intra-prediction in TIMD is replaced with PDP, and the PDP is applied based on a template cost calculated using a prediction method that requires less computation than the PDP.
  2. The image decoding apparatus according to claim 1, characterized in that the intra-prediction unit calculates the template cost in the intra-prediction, regardless of whether or not the PDP is replaced.
  3. The image decoding apparatus according to claim 1, characterized in that the intra-prediction unit calculates the template cost using the PDP only for modes with costs within a first threshold.
  4. The image decoding apparatus according to claim 3, characterized in that the intra-prediction unit sets the first threshold based on the minimum cost.
  5. The image decoding apparatus according to claim 1, characterized in that the intra-prediction unit calculates the template cost using the PDP only for a predetermined number of modes surrounding the mode with the minimum cost.
  6. The image decoding apparatus according to claim 1, characterized in that the intra-prediction unit obtains the template cost of the PDP by multiplying the template cost calculated by the intra-prediction by a second threshold.
  7. The image decoding apparatus according to claim 3, characterized in that the intra-prediction unit sets the first threshold based on control information.
  8. The image decoding device according to claim 5, characterized in that the intra-prediction unit sets the predetermined number based on control information.
  9. The image decoding apparatus according to claim 6, characterized in that the intra-prediction unit sets the second threshold based on control information.
  10. The image decoding apparatus according to claim 3, characterized in that the intra-prediction unit sets the first threshold based on the mode in which the template cost is minimized.
  11. The image decoding apparatus according to claim 5, characterized in that the intra-prediction unit sets the predetermined number based on the mode in which the template cost is minimized.
  12. The image decoding apparatus according to claim 6, characterized in that the intra-prediction unit sets the second threshold based on the mode in which the template cost is minimized.
  13. The image decoding apparatus according to claim 1, characterized in that the intra-prediction unit calculates the template cost using the PDP only for the Planar mode and DC mode of the PDP, with the template cost of the Planar mode and DC mode of the PDP being smaller.
  14. The image decoding apparatus according to claim 1, characterized in that, if the intra-prediction unit omits calculating the template cost of the corresponding PDP in Planar mode or DC mode when the template cost of the intra-prediction in Planar mode or DC mode exceeds the third threshold multiple of the minimum cost.
  15. The image decoding apparatus according to claim 14, characterized in that the intra-prediction unit sets the third threshold based on the minimum value of the template cost calculated by the intra-prediction.
  16. An image decoding method, An image decoding method characterized by having a step in which part or all of the intra prediction in TIMD is replaced with a PDP, and the PDP is applied based on a template cost calculated using a prediction method that requires less computation than the PDP.
  17. A program that makes a computer function as an image decoding device, The aforementioned image decoding device is A program characterized by comprising an intra-prediction unit that replaces part or all of an intra-prediction with a PDP, and applies the PDP based on a template cost calculated using a prediction method that requires less computation than the PDP.

Description

This invention relates to an image decoding device, an image decoding method, and a program. Non-Patent Document 1 discloses an intra-prediction method. Non-Patent Documents 2-4 disclose an extended method of the intra-prediction method disclosed in Non-Patent Document 1. Furthermore, Non-Patent Documents 1 and 2 disclose TIMD (Template-based intra-Mode Derivation). Furthermore, Non-Patent Documents 1 and 3 disclose a Position-Dependent Prediction (PDP) method that uses weights obtained through prior learning as a matrix table and predicts pixels by performing sum-of-products operations with neighboring pixels of the block to be decoded. Furthermore, Non-Patent Document 4 discloses the application of PDP to TIMD. M. Coban, et al., “Algorithm description of Enhanced Compression Model 13 (ECM 13),” JVET-AH2025, 2024.K. Cao et al., “JVET-W0123: Fusion for template-based intra mode derivation,” JVET-W0123, 2021.B. Ray, et al., "EE2-2.13: Matrix based intra prediction replacing conventional intra modes," JVET-AH0209, 2024.Y. Kidani, et al., “Non-EE2: Matrix-based position dependent intra prediction for TIMD,” JVET-AI0085, 2024. Figure 1 shows an example of the functional block of the image decoding device 200 according to the first embodiment.Figure 2 shows an example of a template cost calculated by the intra-prediction unit 204 of the image decoding device 200 according to the first embodiment.Figure 3 shows an example of the scope of data for calculating template costs using PDP.Figure 4 shows an example of the scope of data used to calculate template costs using PDP. The embodiments of the present invention will be described below with reference to the drawings. Note that the components in the following embodiments can be replaced with existing components as appropriate, and various variations are possible, including combinations with other existing components. Therefore, the description of the following embodiments does not limit the content of the invention as described in the claims. <First Embodiment> The image decoding device 200 according to this embodiment will be described below with reference to Figures 1 to 4. The image decoding device 200 according to the first embodiment of the present invention is designed for a variety of image signals (hereinafter referred to as "images"). For example, the image decoding device 200 according to this embodiment is designed for YUV (YCbCr) images composed of luminance pixels and chrominance pixels, RGB images composed of RGB pixels, and monochrome images. Here, each pixel constituting an image has discrete values (pixel values) with a predetermined bit width. Furthermore, in the following descriptions of the functions of each part, the term "pixel" may refer to a block (unit) composed of pixels, a tree block (the largest block size), or a slice, tile, or image (picture) larger than a tree block. Figure 1 shows an example of the functional block of the image decoding device 200 according to this embodiment. As shown in Figure 1, the image decoding device 200 includes a decoding unit 201, an inverse quantization unit 202, an inverse transformation unit 203, an intra-prediction unit 204, a motion compensation unit 205, an adder 206, and an accumulation unit 207. The decoding unit 201 is configured to decode control information and quantization values from the coded information encoded by the image encoding device. For example, the decoding unit 201 is configured to output control information and quantization values by performing variable-length decoding on such coded information. Here, the quantized values are sent to the inverse quantization unit 202, and the control information is sent to the intra-prediction unit 204 and the motion compensation unit 205. This control information includes information necessary for controlling the inverse quantization unit 202, the intra-prediction unit 204, and the motion compensation unit 205, and may also include header information such as sequence parameter sets, picture parameter sets, picture headers, and slice headers. The inverse quantization unit 202 is configured to inverse quantize the quantized values sent from the decoding unit 201 to obtain conversion coefficients. These conversion coefficients are then sent to the inverse conversion unit 203. The inverse transformation unit 203 is configured to inversely transform the transformation coefficients sent from the inverse quantization unit 202 to obtain the predicted residual. This predicted residual is then sent to the adder 207. The intra-prediction unit 204 is configured to generate a first prediction pixel for addition with the prediction residual in the adder 206, based on the decoded pixels obtained via the adder 206 and the control information decoded by the decoding unit 201. This first prediction pixel is then sent to the adder 206. The motion compensation unit 205 is configured to generate a second predicted pixel for addition with the predicted residual in the