JP-7855748-B2 - Decoding device and program

Inventors

• 市ヶ谷 敦郎
• 岩村 俊輔

Assignees

• 日本放送協会

Dates

Publication Date

20260508

Application Date

20250219

Priority Date

20161128

Claims (2)

1. A decoding device, The system includes an acquisition means for obtaining a bitstream that includes quantization coefficients obtained by quantizing the transformation coefficients of blocks obtained by dividing an image, and a sequence parameter set which is a high-level syntax. The decoding device uses the sequence parameter set acquired by the acquisition means to set one or more thresholds to be used for deblocking filtering of the block. The decoding device generates a reconstructed image using the quantization coefficient acquired by the acquisition means. The decoding device identifies the luminance signal level range to which the luminance signal level belongs by setting one or more thresholds using the sequence parameter set acquired by the acquisition means, and determines parameters for controlling the deblocking filter process using adjustment values associated with the identified luminance signal level range.
2. A program that causes a computer to function as the decoding device described in claim 1.

Description

This invention relates to an encoding device, a decoding device, and a program that perform deblocking filter processing. In mainstream video encoding schemes, such as MPEG, real-time processing is easily achieved by dividing video units, called frames (or pictures), into small block-like regions. Encoding (compression) is performed on a block-by-block basis using techniques such as transformation and prediction. In such encoding schemes, differences in encoding control between adjacent blocks can lead to perceived quality differences and distortion at block boundaries. Recent encoding schemes, such as H.264/AVC and H.265/HEVC, employ a process called deblocking filtering to reduce this encoding distortion. Block distortion occurs due to signal degradation caused by the quantization of orthogonal transformation coefficients at the boundary between two adjacent blocks, resulting in sharp signal fluctuations in adjacent regions that should ideally be smooth. Deblocking filters designed to mitigate this distortion are generally designed as low-pass filters that smooth out signal fluctuations. Since the amount of signal degradation varies depending on the coarseness of quantization, the filter strength is controlled by quantization parameters that define the coarseness of quantization (see, for example, Non-Patent Document 1). Recommendation ITU-T H. 265, (04/2013) “, High efficiency video coding”, International Telecommunication Union, April 2013 An encoding device according to one embodiment is an encoding device for encoding an input image, comprising: a transformation unit that performs an orthogonal transformation on a residual image showing the difference between the input image and a predicted image of the input image to calculate orthogonal transformation coefficients; a quantization unit that generates quantization coefficients by quantizing the orthogonal transformation coefficients based on quantization parameters; an entropy encoding unit that generates encoded data by encoding the quantization coefficients; an image decoding unit that restores the orthogonal transformation coefficients from the quantization coefficients based on the quantization parameters, performs an inverse orthogonal transformation on the orthogonal transformation coefficients to restore the residual image, and adds the predicted image to generate a reconstructed image; and a deblocking filter unit that performs a filter operation on the reconstructed image. The deblocking filter unit is characterized by controlling the filter intensity according to the luminance signal level of the reconstructed image and the quantization parameters. A decoding device according to one embodiment is a decoding device for decoding encoded data of an input image, comprising: an entropy decoding unit that decodes the encoded data and obtains quantization coefficients obtained by quantizing the orthogonal transformation coefficients; an image decoding unit that reconstructs the orthogonal transformation coefficients from the quantization coefficients based on quantization parameters, performs an inverse orthogonal transformation on the orthogonal transformation coefficients, and generates a reconstructed image by adding a predicted image to the reconstructed residual image; and a deblocking filter unit that performs filtering on the reconstructed image. The deblocking filter unit is characterized by controlling the filter intensity according to the luminance signal level of the reconstructed image and the quantization parameters. This diagram shows the correspondence between signal level and brightness level.This is a block diagram showing an example configuration of an encoding device according to one embodiment of the present invention.This figure shows the block boundaries that undergo deblocking filtering.This is a block diagram showing an example configuration of a decoding device according to one embodiment of the present invention. A key feature of this new video medium is the standardization of HDR (high dynamic range) signals, which expand the range of black and white that cannot be represented by conventional video signals. Compared to conventional SDR (Standard Dynamic Range) signals, HDR signals record a wide range of light intensity (from low to high, i.e., from dark to bright) within a limited bit depth, requiring a more extreme signal suppression process called gamma correction. Currently, HDR methods include the HLG (Hybrid-Log Gamma) method, defined in ARIB STD-B67, and the PQ (Perceptual Quantize) method, defined in SMPTE ST.2084. These methods are internationally standardized as Recommendation ITU-R BT.2100 by the ITU-R. It is possible that other methods may be standardized in the future. Figure 1 shows the correspondence (inverse gamma correction) between the image luminance signal level and the display luminance level shown on the display device for SDR signals and HDR signals using the HLG and PQ methods. Note that the HLG met