JP2012175615A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further compress a code amount required for defining a quantization matrix.SOLUTION: Provided is an image processing apparatus comprising: an acquisition unit that acquires a first parameter for specifying a scan pattern to be used in generating a quantization matrix among a plurality of scan patterns; a generation unit that generates a quantization matrix using a scan pattern specified by the first parameter acquired by the acquisition unit; and an inverse quantization unit that performs inverse quantization on transform coefficient data of an image to be decoded using the quantization matrix generated by the generation unit.

Description

  The present invention relates to an image processing apparatus and an image processing method.

  H. is one of the standard specifications of the video coding system. In H.264 / AVC, in a profile higher than High Profile, different quantization steps can be used for each component of the orthogonal transform coefficient when image data is quantized. The quantization step for each component of the orthogonal transform coefficient can be set based on a quantization matrix (also referred to as a scaling list) defined with a size equivalent to the unit of the orthogonal transform and a reference step value.

  H. In H.264 / AVC, a user can use a predetermined quantization matrix prepared in advance for each combination of size, prediction method (intra prediction / inter prediction), and signal component (Y / Cb / Cr component). The user can also define a unique quantization matrix separately from the predetermined quantization matrix. The user-specific quantization matrix is defined in the sequence parameter set or the picture parameter set. The definition of a quantization matrix is given by transforming a two-dimensional array of quantization matrices into a one-dimensional array by zigzag scanning and encoding the values of each element of the one-dimensional array using a DPCM (Differential Pulse Code Modulation) method. (See FIGS. 19 and 20). FIG. 19 shows a scan pattern of an existing zigzag scan. FIG. 20 conceptually shows a state of encoding by the zigzag scan and the DPCM method.

  H. In High Efficiency Video Coding (HEVC), which is being standardized as a next-generation video coding scheme following H.264 / AVC, the concept of a coding unit (CU: Coding Unit) corresponding to a conventional macroblock has been introduced. (See Non-Patent Document 1 below). The range of the size of the coding unit is specified by a set of powers of two such as an LCU (Largest Coding Unit) and an SCU (Smallest Coding Unit) in the sequence parameter set. Then, using split_flag, the size of a specific coding unit within the range specified by the LCU and the SCU is specified.

  In HEVC, one coding unit may be divided into one or more orthogonal transform units, ie, one or more transform units (TUs). As the size of the conversion unit, any of 4 × 4, 8 × 8, 16 × 16, and 32 × 32 can be used. Thus, a quantization matrix can also be specified for each available transform unit size. Non-Patent Document 2 below defines a plurality of quantization matrix candidates for the size of one transform unit in one picture, and adaptively applies a quantization matrix for each block from the viewpoint of optimization of RD (Rate-Distortion). Suggest to choose.

JCTVC-B205, “Test Model under Consideration”, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11 2nd Meeting: Geneva, CH, 21-28 July, 2010 VCEG-AD06, “Adaptive Quantization Matrix Selection on KTA Software”, ITU-Telecommunications Standardization Sector STUDY GROUP 16 Question 6 Video Coding Experts Group (VCEG) 30th Meeting: Hangzhou, China, 23-24 October, 2006

  However, the quantization matrix suitable for quantization and inverse quantization differs depending on the characteristics of each image included in the video. Therefore, H.H. In coding by zigzag scanning used in H.264 / AVC, the correlation between adjacent components in the one-dimensional array converted from the quantization matrix is not necessarily high, and as a result, the amount of code required for defining the quantization matrix is reduced. In some cases, it could not be compressed sufficiently. Furthermore, if more transform unit sizes are available, such as HEVC, the number of quantization matrices defined accordingly increases. Therefore, it is expected that the need to further compress the code amount required for defining the quantization matrix will increase.

  Therefore, the present invention is intended to provide an image processing apparatus and an image processing method that can further compress the amount of code required for defining a quantization matrix.

  According to an embodiment of the present invention, an acquisition unit that acquires a first parameter that specifies a scan pattern used in generating a quantization matrix among a plurality of scan patterns, and the acquisition unit acquires the first parameter. A generation unit that generates a quantization matrix using the scan pattern specified by the first parameter, and a dequantization of transform coefficient data of an image to be decoded using the quantization matrix generated by the generation unit An image processing apparatus is provided.

  The image processing apparatus can typically be realized as an image decoding apparatus that decodes an image.

  In addition, the acquisition unit acquires a second parameter indicating whether the first parameter exists, and the second parameter indicates that the first parameter exists when the second parameter indicates that the first parameter exists. One parameter may be acquired.

  The acquisition unit may acquire one second parameter for a plurality of types of quantization matrices defined within the same parameter set.

  Further, the generation unit generates a quantization matrix by decoding the predictive-coded one-dimensional array and reconstructing the decoded one-dimensional array into a matrix according to the scan pattern specified by the first parameter. May be.

  The generation unit may predict at least one element of the one-dimensional array from an element different from the immediately preceding element when the scan pattern specified by the first parameter is a predetermined scan pattern. You may decode based on.

  In addition, one of the plurality of scan patterns may be a scan pattern in which the uppermost row and the leftmost column of the quantization matrix are scanned straight.

  According to another embodiment of the present invention, a step of acquiring a first parameter that specifies a scan pattern used in generating a quantization matrix among a plurality of scan patterns, and the acquired first parameter An image including a step of generating a quantization matrix using a scan pattern specified by a parameter of 1, and a step of inversely quantizing transform coefficient data of an image to be decoded using the generated quantization matrix A processing method is provided.

  Further, according to another embodiment of the present invention, a quantization unit that quantizes transform coefficient data of an image to be encoded using a quantization matrix, and the quantization unit among a plurality of scan patterns are used. There is provided an image processing apparatus comprising: an insertion unit that inserts a first parameter that specifies a scan pattern used when generating a quantization matrix into a parameter set.

  The image processing apparatus can typically be realized as an image encoding apparatus that encodes an image.

  The image processing apparatus may further include a setting unit that sets a scan pattern that optimizes a code amount required for defining the quantization matrix among the plurality of scan patterns.

  The setting unit may select the scan pattern for optimizing the code amount offline.

  The image processing apparatus may further include a transmission unit that transmits the parameter set in which the first parameter is inserted to the apparatus that decodes the image.

  According to another embodiment of the present invention, the step of inserting a first parameter for specifying a scan pattern used in generating a quantization matrix among a plurality of scan patterns into the parameter set, and encoding Quantizing the conversion coefficient data of the image to be processed using the quantization matrix.

  As described above, according to the image processing apparatus and the image processing method according to the present invention, it is possible to further compress the code amount required for defining the quantization matrix.

It is a block diagram which shows an example of a structure of the image coding apparatus which concerns on one Embodiment. FIG. 2 is a block diagram illustrating an example of a detailed configuration of a syntax processing unit illustrated in FIG. 1. It is explanatory drawing which shows an example of the parameter for the definition of the quantization matrix which concerns on one Embodiment. It is explanatory drawing for demonstrating the 1st example of a new scan pattern. It is explanatory drawing for demonstrating the 2nd example of a new scan pattern. It is explanatory drawing for demonstrating the 3rd example of a new scan pattern. It is explanatory drawing for demonstrating the 4th example of a new scan pattern. It is explanatory drawing for demonstrating the 5th example of a new scan pattern. It is a flowchart which shows an example of the flow of the parameter generation process which concerns on one Embodiment. It is a 1st explanatory view for explaining compression of the amount of codes in one embodiment. It is the 2nd explanatory view for explaining compression of the amount of codes in one embodiment. It is a block diagram which shows an example of a structure of the image decoding apparatus which concerns on one Embodiment. It is a block diagram which shows an example of a detailed structure of the syntax process part shown in FIG. It is a flowchart which shows an example of the flow of the quantization matrix production | generation process which concerns on one Embodiment. It is a flowchart which shows an example of the detailed flow of the quantization matrix reconstruction process which concerns on one Embodiment. It is a block diagram which shows an example of a schematic structure of a television apparatus. It is a block diagram which shows an example of a schematic structure of a mobile telephone. It is a block diagram which shows an example of a schematic structure of a recording / reproducing apparatus. It is a block diagram which shows an example of a schematic structure of an imaging device. H. 2 is an explanatory diagram illustrating a scan pattern of a zigzag scan in H.264 / AVC. It is explanatory drawing which shows notionally the mode of the encoding by a zigzag scan and a DPCM system.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be given in the following order.
1. 1. Configuration example of image encoding device according to embodiment 1-1. Overall configuration example 1-2. Configuration example of syntax processing unit 1-3. Examples of scan patterns 2. Process flow during encoding according to one embodiment 2-1. Parameter generation process 2-2. 2. Example of code amount reduction 3. Configuration example of image decoding apparatus according to one embodiment 3-1. Overall configuration example 3-2. 3. Configuration example of syntax processing unit Flow of processing during decoding according to one embodiment 4-1. Quantization matrix generation process 4-2. 4. Quantization matrix reconstruction process Application example 6. Summary

<1. Configuration Example of Image Encoding Device According to One Embodiment>
In this section, a configuration example of an image encoding device according to an embodiment will be described.

[1-1. Overall configuration example]
FIG. 1 is a block diagram showing an example of the configuration of an image encoding device 10 according to an embodiment of the present invention. Referring to FIG. 1, an image encoding device 10 includes an A / D (Analogue to Digital) conversion unit 11, a rearrangement buffer 12, a syntax processing unit 13, a subtraction unit 14, an orthogonal transformation unit 15, a quantization unit 16, Lossless encoding unit 17, accumulation buffer 18, rate control unit 19, inverse quantization unit 21, inverse orthogonal transformation unit 22, addition unit 23, deblock filter 24, frame memory 25, selector 26, intra prediction unit 30, motion search Unit 40 and mode selection unit 50.

  The A / D conversion unit 11 converts an image signal input in an analog format into image data in a digital format, and outputs a series of digital image data to the rearrangement buffer 12.

  The rearrangement buffer 12 rearranges the images included in the series of image data input from the A / D conversion unit 11. The rearrangement buffer 12 rearranges the images according to the GOP (Group of Pictures) structure related to the encoding process, and then outputs the rearranged image data to the syntax processing unit 13.

  The syntax processing unit 13 sequentially recognizes NAL (Network Abstraction Layer) units in the stream of image data input from the rearrangement buffer 12, and inserts a non-VCL NAL unit that stores header information into the stream. To do. The non-VCL NAL unit inserted in the stream by the syntax processing unit 13 includes a sequence parameter set (SPS) and a picture parameter set (PPS). The syntax processing unit 13 adds a slice header to the head of the slice. Then, the syntax processing unit 13 outputs a stream of image data including the VCL NAL unit and the non-VCL NAL unit to the subtraction unit 14, the intra prediction unit 30, and the motion search unit 40. The detailed configuration of the syntax processing unit 13 will be further described later.

  The subtraction unit 14 is supplied with image data input from the syntax processing unit 13 and predicted image data selected by a mode selection unit 50 described later. The subtraction unit 14 calculates prediction error data that is a difference between the image data input from the syntax processing unit 13 and the predicted image data input from the mode selection unit 50, and the calculated prediction error data is orthogonally converted unit 15. Output to.

  The orthogonal transform unit 15 performs orthogonal transform on the prediction error data input from the subtraction unit 13. The orthogonal transform executed by the orthogonal transform unit 15 may be, for example, a discrete cosine transform (DCT) or a Karhunen-Loeve transform. The orthogonal transform unit 15 outputs transform coefficient data acquired by the orthogonal transform process to the quantization unit 16.

  The quantization unit 16 quantizes the transform coefficient data input from the orthogonal transform unit 15 using a quantization matrix, and transforms the quantized transform coefficient data (hereinafter referred to as quantized data) to the lossless encoding unit 17 and the inverse. The data is output to the quantization unit 21. The bit rate of the quantized data is controlled based on a rate control signal from the rate control unit 19. The quantization matrix used by the quantization unit 16 is defined in SPS or PPS, and can be specified in the slice header for each slice. If no quantization matrix is specified, a flat quantization matrix with equal quantization steps for all components is used.

  The lossless encoding unit 17 generates an encoded stream by performing a lossless encoding process on the quantized data input from the quantization unit 16. The lossless encoding by the lossless encoding unit 17 may be, for example, variable length encoding or arithmetic encoding. Further, the lossless encoding unit 17 multiplexes information related to intra prediction or information related to inter prediction input from the mode selection unit 50 in the header of the encoded stream. Then, the lossless encoding unit 17 outputs the generated encoded stream to the accumulation buffer 18.

  The accumulation buffer 18 temporarily accumulates the encoded stream input from the lossless encoding unit 17 using a storage medium such as a semiconductor memory. Then, the accumulation buffer 18 outputs the accumulated encoded stream to a transmission unit (not shown) (for example, a communication interface or a connection interface with peripheral devices) at a rate corresponding to the bandwidth of the transmission path.

  The rate control unit 19 monitors the free capacity of the accumulation buffer 18. Then, the rate control unit 19 generates a rate control signal according to the free capacity of the accumulation buffer 18 and outputs the generated rate control signal to the quantization unit 16. For example, the rate control unit 19 generates a rate control signal for reducing the bit rate of the quantized data when the free capacity of the storage buffer 18 is small. For example, when the free capacity of the storage buffer 18 is sufficiently large, the rate control unit 19 generates a rate control signal for increasing the bit rate of the quantized data.

  The inverse quantization unit 21 performs inverse quantization processing on the quantized data input from the quantization unit 16 using a quantization matrix. Then, the inverse quantization unit 21 outputs transform coefficient data acquired by the inverse quantization process to the inverse orthogonal transform unit 22.

  The inverse orthogonal transform unit 22 restores the prediction error data by performing an inverse orthogonal transform process on the transform coefficient data input from the inverse quantization unit 21. Then, the inverse orthogonal transform unit 22 outputs the restored prediction error data to the addition unit 23.

  The adding unit 23 generates decoded image data by adding the restored prediction error data input from the inverse orthogonal transform unit 22 and the predicted image data input from the mode selection unit 50. Then, the addition unit 23 outputs the generated decoded image data to the deblock filter 24 and the frame memory 25.

  The deblocking filter 24 performs a filtering process for reducing block distortion that occurs when an image is encoded. The deblocking filter 24 removes block distortion by filtering the decoded image data input from the adding unit 23, and outputs the decoded image data after filtering to the frame memory 25.

  The frame memory 25 stores the decoded image data input from the adder 23 and the decoded image data after filtering input from the deblock filter 24 using a storage medium.

  The selector 26 reads decoded image data before filtering used for intra prediction from the frame memory 25 and supplies the read decoded image data to the intra prediction unit 30 as reference image data. Further, the selector 26 reads out the filtered decoded image data used for inter prediction from the frame memory 25 and supplies the read decoded image data to the motion search unit 40 as reference image data.

  The intra prediction unit 30 performs intra prediction processing in each intra prediction mode based on the image data to be encoded input from the syntax processing unit 13 and the decoded image data supplied via the selector 26. For example, the intra prediction unit 30 evaluates the prediction result in each intra prediction mode using a predetermined cost function. Then, the intra prediction unit 30 selects an intra prediction mode in which the cost function value is minimum, that is, an intra prediction mode in which the compression rate is the highest as the optimal intra prediction mode. Further, the intra prediction unit 30 outputs information related to intra prediction, such as prediction mode information indicating the optimal intra prediction mode, predicted image data, and cost function value, to the mode selection unit 50.

  The motion search unit 40 performs inter prediction processing (interframe prediction processing) based on the image data to be encoded input from the syntax processing unit 13 and the decoded image data supplied via the selector 26. For example, the motion search unit 40 evaluates the prediction result in each prediction mode using a predetermined cost function. Next, the motion search unit 40 selects a prediction mode with the smallest cost function value, that is, a prediction mode with the highest compression rate, as the optimum prediction mode. Further, the motion search unit 40 generates predicted image data according to the optimal prediction mode. Then, the motion search unit 40 outputs information related to inter prediction such as prediction mode information, prediction image data, and cost function values to the mode selection unit 50.

  The mode selection unit 50 compares the cost function value related to intra prediction input from the intra prediction unit 30 with the cost function value related to inter prediction input from the motion search unit 40. And the mode selection part 50 selects the prediction method with few cost function values among intra prediction and inter prediction. When selecting the intra prediction, the mode selection unit 50 outputs information on the intra prediction to the lossless encoding unit 17 and outputs the predicted image data to the subtraction unit 14 and the addition unit 23. In addition, when the inter prediction is selected, the mode selection unit 50 outputs the above-described information regarding inter prediction to the lossless encoding unit 17 and outputs the predicted image data to the subtraction unit 14 and the addition unit 23.

[1-2. Configuration example of syntax processing unit]
FIG. 2 is a block diagram illustrating an example of a detailed configuration of the syntax processing unit 13 of the image encoding device 10 illustrated in FIG. 1. Referring to FIG. 2, the syntax processing unit 13 includes a setting unit 110, a parameter generation unit 120, and an insertion unit 130.

(1) Setting Unit The setting unit 110 holds various settings used for encoding processing by the image encoding device 10. For example, the setting unit 110 holds data relating to a profile of each sequence of image data, a coding mode of each picture, a GOP structure, and the like. In addition, the setting unit 110 holds settings for the quantization matrix used by the quantization unit 16 (and the inverse quantization unit 21).

  More specifically, the setting unit 110 determines in advance for each slice, which quantization matrix the quantization unit 16 should use based on the analysis of the image. The quantization matrix suitable for quantization and inverse quantization differs depending on the characteristics of each image included in the video.

  For example, in an application example such as a digital video camera, since there is no compression distortion in an input image, a quantization matrix having a smaller quantization step can be used even in a high frequency range. The quantization matrix changes in picture units or frame units. When the complexity of the input image is low, the image quality perceived by the user can be improved by using a flat quantization matrix having a smaller quantization step. On the other hand, when the complexity of the input image is high, it is desirable to use a larger quantization step in order to suppress an increase in the code amount. In this case, if a flat quantization matrix is used, the distortion of the low-frequency signal may be recognized as block noise. Therefore, it is beneficial to reduce noise by using a quantization matrix in which the quantization step increases from the low range to the high range.

  In an application example such as a recorder that recompresses broadcast content encoded in MPEG2, MPEG2 compression distortion such as mosquito noise exists in the input image itself. Mosquito noise is noise generated as a result of quantizing a high-frequency signal with a larger quantization step, and the frequency component of the noise itself has a very high frequency. For such an input image, it is desirable to use a quantization matrix having a large quantization step in the high band when recompressing. Further, compared to the progressive signal, the interlace signal has a higher correlation between the signals in the horizontal direction than the correlation between the signals in the vertical direction due to the influence of interlaced scanning. Therefore, it is also beneficial to use a different quantization matrix depending on whether the image signal is a progressive signal or an interlace signal.

  Thus, depending on the characteristics of the image, various user-specific quantization matrices may be defined. When transforming each quantization matrix into a one-dimensional array for encoding, there are often cases in which the correlation between adjacent components in the one-dimensional array does not increase in the zigzag scan as illustrated in FIG. Therefore, in the present embodiment, a plurality of scan patterns including scan patterns other than the zigzag scan are prepared in advance. For each quantization matrix, the setting unit 110 evaluates the code amount generated when the quantization matrix is encoded for each scan pattern, and selects an optimal scan pattern that minimizes the code amount.

  The determination of the quantization matrix and selection of the optimum scan pattern by the setting unit 110 are typically performed offline prior to image encoding. By selecting the optimum scan pattern offline, even when there are many scan pattern candidates, it is possible to appropriately find the optimum scan pattern using, for example, the brute force method. Then, the setting unit 110 holds, as the setting for the quantization matrix, the identifier of the optimum scan pattern selected offline for each quantization matrix defined in the parameter set.

(2) Parameter Generation Unit The parameter generation unit 120 generates a parameter that defines the setting for the encoding process held by the setting unit 110, and outputs the generated parameter to the insertion unit 130. For example, in the present embodiment, the parameter generation unit 120 generates a parameter for defining a quantization matrix used by the quantization unit 16. FIG. 3 shows an example of parameters for defining the quantization matrix generated by the parameter generation unit 120.

  In the example of FIG. 3, the “pattern ID presence flag” is a flag indicating whether or not a pattern ID that is a parameter for specifying a scan pattern exists in the parameter set. When the pattern ID presence flag indicates “0: does not exist”, there is no pattern ID in the parameter set. In this case, the user-specific quantization matrix may be defined using zigzag scanning according to existing techniques. On the other hand, when the pattern ID presence flag indicates “1: exists”, the pattern ID exists in the parameter set.

  “Pattern ID” is an ID (identifier) that identifies an optimal scan pattern for defining a quantization matrix. In one parameter set, a plurality of pattern IDs respectively associated with individual types of quantization matrices can be included. The type of quantization matrix is typically identified by a combination of size, prediction scheme (intra prediction / inter prediction) and signal component (Y / Cb / Cr component). In the example of FIG. 3, the pattern ID1 is associated with the Y component of size 4 × 4 intra prediction, the pattern ID2 is associated with the Cb component of size 4 × 4 intra prediction, and the pattern IDn is associated with the Y component of size 32 × 32 inter prediction. It has been.

  “Array data” is data of a one-dimensional array that is predictively encoded by the DPCM method and defines the values of the elements of the quantization matrix. In the example of FIG. 3, array data 1 is a Y component for intra prediction of size 4 × 4, array data 2 is a Cb component of intra prediction of size 4 × 4, and array data n is a Y component of inter prediction of size 32 × 32. The data associated with each.

(3) Insertion Unit The insertion unit 130 inserts header information such as SPS, PPS, and a slice header, each including a parameter group generated by the parameter generation unit 120, into a stream of image data input from the rearrangement buffer 12. . The SPS and the PPS may include parameters for defining the quantization matrix as illustrated in FIG. In addition, the slice header may include a parameter that specifies a quantization matrix to be used for quantization and inverse quantization for the slice among quantization matrices defined by SPS or PPS. Then, the insertion unit 130 outputs the stream of image data in which the header information is inserted to the subtraction unit 14, the intra prediction unit 30, and the motion search unit 40.

[1-3. Example of scan pattern]
Scan pattern candidates that can be set by the setting unit 110 of the syntax processing unit 13 include new scan patterns exemplified in FIGS. 4 to 8 in addition to the zigzag scan (see FIG. 19) that is an existing scan pattern. It's okay.

(1) First Example FIG. 4 is an explanatory diagram for describing a first example of a new scan pattern. The scan pattern shown in FIG. 4 is referred to as “mixed scan” in this specification. In the mixed scan, the uppermost row and the leftmost column of the quantization matrix are scanned straight (S1, S2), and the remaining square elements are scanned zigzag (S3). Is a combined scan pattern.

  For the sake of explanation, the element in the i-th row and j-th column of the quantization matrix is expressed as (i, j). In the mixed scan, first, the eight elements (1, 1) to (1, 8) in the upper end row are scanned straight in the horizontal direction. Next, the seven elements (2, 1) to (8, 1) in the left end row are scanned straight in the vertical direction. Thereafter, the remaining lower right square elements (2, 2) to (8, 8) are scanned in a zigzag manner.

  One of the features of the mixed scan is that the scan pattern is not a so-called one-stroke drawing like the existing zigzag scan, but has a branch in the middle of the scan pattern. The meaning of this branch is that the value of the element located in each branch is determined from the value of the element (two or more previous elements in the one-dimensional array) different from the previous element when encoding in the DPCM method. That is to be predicted. In the mixed scan example of FIG. 4, the element immediately before the first element (2, 1) of the straight scan in the leftmost column is the last element (1, 8) of the straight scan in the uppermost row. However, when encoding the element (2, 1), the element (1, 1) is used as a reference element instead of the element (1, 8). Then, the difference between the value of the element (2, 1) and the value of the reference element (1, 1) is encoded. Similarly, the element immediately before the first element (2, 2) of the lower right square zigzag scan is the last element (8, 1) of the straight scan of the left end column. However, when encoding the element (2, 2), the element (2, 1) is used as the reference element instead of the element (8, 1). Then, the difference between the value of the element (2, 2) and the value of the reference element (2, 1) is encoded. In this specification, an element encoded with reference to an element different from the immediately preceding element is referred to as a discontinuous reference element. In the mixed scan shown in FIG. 4, the elements (2, 1) and (2, 2) are discontinuous reference elements.

  Note that the discontinuous reference element typically uses, as a reference element (an element serving as a basis for prediction), an element located closer to the two-dimensional quantization matrix instead of the immediately preceding element. This is because in a normally used quantization matrix, there is a high correlation of values between elements located near each other.

(2) Second Example FIG. 5 is an explanatory diagram for describing a second example of a new scan pattern. The scan pattern shown in FIG. 5 is referred to as “divided mixed scan” in this specification. In the divided mixed scan, first, the eight elements (1, 1) to (1, 8) in the upper end row are scanned straight in the horizontal direction (S1). Next, the seven elements (2, 1) to (8, 1) in the left end row are scanned straight in the vertical direction (S2). Next, the upper right triangular element groups (2, 2) to (8, 8) divided by diagonal lines in the remaining quadrangular regions are scanned zigzag (S3). Next, the remaining lower left triangular element groups (3, 2) to (8, 7) are scanned zigzag (S4).

  Similarly to the mixed scan illustrated in FIG. 4, the divided mixed scan also has a branch in the middle of the scan pattern. Specifically, the elements (2, 1), (2, 2), and (3, 2) are discontinuous reference elements. When encoding the element (2, 1), the difference from the value of the reference element (1, 1) is encoded instead of the immediately preceding element (1, 8). When encoding the element (2, 2), the difference from the value of the reference element (2, 1) is encoded instead of the immediately preceding element (8, 1). When encoding the element (3, 2), the difference from the value of the reference element (2, 2) is encoded instead of the immediately preceding element (8, 8).

  Both the first example and the second example of the new scan pattern are scan patterns obtained by combining a straight scan and a zigzag scan. The straight scan is performed particularly on the uppermost row and the leftmost column of the quantization matrix. Such a scan pattern is useful when orthogonal transform coefficients are concentrated on the elements in the uppermost row and the leftmost column of the transform unit, and the correlation of the quantization step between these elements is high (in fact, Such quantization matrices can be used frequently). The second example is useful when the correlation between the upper right half element group and the lower left half element group is low, and it is better to scan these separately.

(3) Third Example FIG. 6 is an explanatory diagram for describing a third example of a new scan pattern. The scan pattern shown in FIG. 6 is a so-called field scan. As in the zigzag scan, the field scan has no branch in the middle of the scan pattern. Therefore, there is no discontinuous reference element in the field scan. The third example is useful when the correlation between quantization steps along the scan direction of the field scan is high.

(4) Fourth Example FIG. 7 is an explanatory diagram for describing a fourth example of a new scan pattern. The scan pattern shown in FIG. 7 is referred to as “vertical stripe scan” in this specification. In the vertical stripe scan, first, the eight elements (1, 1) to (8, 1) in the left end row are scanned straight in the vertical direction (S1). Next, the eight elements (1, 2) to (8, 2) in the second column from the left are scanned straight in the vertical direction (S2). Thereafter, vertical scanning in the vertical direction is sequentially repeated from the third column to the eighth column (S3 to S8).

  The vertical stripe scan has a branch in the middle of the scan pattern. Specifically, the elements (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (1, 7) and (1, 8) are discontinuous. Reference element. When the element (1, 2) is encoded, the difference from the value of the reference element (1, 1) is encoded instead of the immediately preceding element (8, 1). When encoding the element (1, 3), the difference from the value of the reference element (1, 2) is encoded instead of the immediately preceding element (8, 2). Also for other discontinuous reference elements, not the immediately preceding element in the one-dimensional array after scanning, but the difference from the values of two or more previous elements is encoded.

(5) Fifth Example FIG. 8 is an explanatory diagram for describing a fifth example of a new scan pattern. The scan pattern shown in FIG. 8 is referred to as “horizontal stripe scan” in this specification. In the horizontal stripe scan, first, the eight elements (1, 1) to (1, 8) in the upper end row are scanned straight in the horizontal direction (S1). Next, the eight elements (2, 1) to (2, 8) in the second row from the top are scanned straight in the horizontal direction (S2). Thereafter, the horizontal straight scan is sequentially repeated from the third row to the eighth row (S3 to S8).

  The horizontal stripe scan has a branch in the middle of the scan pattern. Specifically, elements (2,1), (3,1), (4,1), (5,1), (6,1), (7,1) and (8,1) are discontinuous Reference element. When encoding the element (2, 1), the difference from the value of the reference element (1, 1) is encoded instead of the immediately preceding element (1, 8). When encoding the element (3, 1), the difference from the value of the reference element (2, 1) is encoded instead of the immediately preceding element (2, 8). Also for other discontinuous reference elements, not the immediately preceding element in the one-dimensional array after scanning, but the difference from the values of two or more previous elements is encoded.

  The fourth and fifth examples of the new scan pattern are both scan patterns configured only by straight scan. Such a scan pattern is when the correlation of quantization steps between elements along one of the vertical and horizontal directions is high and the correlation of quantization steps between elements along the other is low. Useful.

  Although an 8 × 8 quantization matrix has been described as an example here, similar scan patterns may be set for quantization matrices of other sizes. The scan pattern shown here is only an example. Any of the scan patterns described above may be omitted from the scan pattern candidates, and another scan pattern may be added to the scan pattern candidates.

<2. Flow of processing during encoding according to one embodiment>
[2-1. Parameter generation process]
FIG. 9 is a flowchart showing an example of the flow of parameter generation processing by the parameter generation unit 120 of the syntax processing unit 13 according to the present embodiment. The parameter generation process shown in FIG. 9 is a process that can be executed for a quantization matrix to be defined when there is a quantization matrix to be newly defined.

  First, the parameter generation unit 120 recognizes the optimum scan pattern selected offline by the setting unit 110 corresponding to the quantization matrix to be newly defined (step S100). The subsequent steps S104 to S110 are repeated for each element of the quantization matrix (step S102). The order of the elements to be processed follows the scan pattern recognized in step S100.

  First, the parameter generation unit 120 acquires the value of an element to be processed (hereinafter referred to as an element of interest) in the quantization matrix according to the scan pattern (step S104). Next, the parameter generation unit 120 determines whether or not the element of interest is a discontinuous reference element (step S106). If the target element is not a discontinuous reference element, the parameter generation unit 120 determines the difference value between the immediately preceding element (the previous target element) and the target element (for the first target element, the target element Is stored in a one-dimensional array (step S108). On the other hand, if the element of interest is a discontinuous reference element, the parameter generation unit 120 stores the difference value between the predetermined reference element before the immediately preceding element and the element of interest in a one-dimensional array (step) S110).

  As a result of such processing, a set of pattern IDk and array data k (k is any one of 1 to n) among the parameters for defining the quantization matrix illustrated in FIG. 3 is generated. The parameter generation unit 120 performs the above-described parameter generation processing on a quantization matrix (one or more types) to be newly defined, for example, at the timing when SPS or PPS is inserted into a stream of image data. The parameters generated by the parameter generation unit 120 are included in the SPS or PPS by the insertion unit 130. At this time, the pattern ID presence flag indicates “1: exists”.

[2-2. Example of code reduction]
10A and 10B are explanatory diagrams for explaining compression of the code amount in the present embodiment.

At the top left of FIG. 10A, there is shown a quantization matrix QM _A as an example, which may be defined by the user. If 1-dimensional array of quantization matrix QM _A in zigzag scan (pattern ID = "0"), the sequence shown in the upper center of FIG. (6,10,10,13, ..., 255) is derived. In FIG. 10A, a one-dimensional array having 64 elements is divided into eight stages for convenience. Further, when the one-dimensional array generated by the zigzag scan is encoded according to the DPCM method, the one-dimensional array (6, 4, 0, 3,..., 0) of the difference values shown on the upper right of the figure is derived. The sum of the absolute values of the elements of the one-dimensional array of difference values generated in this way is 391.

On the other hand, when one-dimensional array by a mixed quantization matrix QM _A-scan (pattern ID = "1"), the sequence shown in the middle center of the diagram (6,10,13,16, ..., 255) is derived. Further, when the one-dimensional array generated by the mixed scan is encoded according to the DPCM method, the one-dimensional array (6, 4, 3, 3,..., 0) of the difference values shown in the middle right of the figure is derived. The sum of the absolute values of the elements of the one-dimensional array of difference values generated in this way is 293. Therefore, those who quantization matrix QM _A deformed to a one-dimensional array with a mixed scan rather than zigzag scan, code amount after variable length coding is can be seen that less.

Further, when one-dimensional array of at quantization matrix QM _A division mixed scanning (pattern ID = "2"), the sequence shown in the lower center of FIG. (6,10,13,16, ..., 255) is derived . Further, when the one-dimensional array generated by the divided and mixed scan is encoded according to the DPCM method, the one-dimensional array (6, 4, 3, 3,..., 127) of difference values shown on the lower right of the figure is derived. The sum of the absolute values of the elements of the one-dimensional array of difference values generated in this way is 528. Therefore, if the scan pattern candidate zigzag scanning, if the three mixing scan and split mixing scan, the smallest optimum scan pattern for code amount when encoding quantization matrix QM _A, mixed scanning (pattern ID = “1”).

In the upper left of FIG. 10B, there is shown a quantization matrix QM _B as another example that may be defined by the user. If 1-dimensional array of quantization matrices QM _B in zigzag scan (pattern ID = "0"), the sequence shown in the upper center of FIG. (6,6,10,13, ..., 27) is derived. Further, when the one-dimensional array generated by the zigzag scan is encoded according to the DPCM method, the one-dimensional array (6, 0, 4, 3,..., 0) of the difference values shown on the upper right of the figure is derived. The total sum of absolute values of the elements of the one-dimensional array of difference values generated in this way is 167.

On the other hand, when one-dimensional array of quantization matrices QM _B in vertical stripe scan (pattern ID = "4"), the sequence shown in the middle center of the diagram (6,10,13,16, ..., 27) is guided . Further, when the one-dimensional array generated by the vertical stripe scan is encoded according to the DPCM method, the one-dimensional array (6, 4, 3, 3,..., 2) of the difference values shown on the right in the middle of the figure is derived. The sum of the absolute values of the elements of the one-dimensional array of difference values generated in this way is 174.

Further, when one-dimensional array of quantization matrices QM _B in horizontal stripe scan (pattern ID = "5"), the sequence shown in the lower center of FIG. (6,6,6,6, ..., 27) is guided . Further, when the one-dimensional array generated by the horizontal stripe scan is encoded according to the DPCM method, the one-dimensional array (6, 0, 0, 0,..., 0) of difference values shown on the lower right of the figure is derived. The sum of the absolute values of the elements of the one-dimensional array of difference values generated in this way is 27. Therefore, if the scan candidate pattern zigzag scan, if the three vertical stripe scanning and horizontal stripe scan, the smallest optimum scan pattern of the code amount in encoding the quantization matrix QM _B, horizontal stripe scan (Pattern ID = “5”).

  The setting unit 110 may evaluate the code amount for each scan pattern in this way for each quantization matrix, and may select the optimum scan pattern with the smallest code amount. Thereby, compared with the case where a quantization matrix is uniformly arranged in a one-dimensional array by zigzag scanning, the amount of code required for defining the quantization matrix can be further compressed.

  In FIGS. 10A and 10B, elements surrounded by a dotted frame are discontinuous reference elements. For example, the value of the discontinuous reference element E1 before DPCM in the divided mixed scan of FIG. The value of the element immediately before the element E1 is 255. Therefore, if the element E1 is encoded according to the normal DPCM method, the value of the element E1 after DPCM is 22-255 = −233. However, in the present embodiment, the reference element of the discontinuous reference element E1 is the element R1. Therefore, the value of the element E1 after DPCM in this embodiment is 22-20 = 2. In this way, by introducing discontinuous reference elements, it is possible to further compress the code amount required for defining the quantization matrix.

<3. Configuration Example of Image Decoding Device According to One Embodiment>
In this section, a configuration example of an image decoding apparatus according to an embodiment of the present invention will be described.

[3-1. Overall configuration example]
FIG. 11 is a block diagram showing an example of the configuration of the image decoding device 60 according to an embodiment of the present invention. Referring to FIG. 11, the image decoding device 60 includes a syntax processing unit 61, a lossless decoding unit 62, an inverse quantization unit 63, an inverse orthogonal transform unit 64, an addition unit 65, a deblocking filter 66, a rearrangement buffer 67, a D / A (Digital to Analogue) conversion unit 68, frame memory 69, selectors 70 and 71, intra prediction unit 80, and motion compensation unit 90.

  The syntax processing unit 61 acquires header information such as SPS, PPS, and slice header from the encoded stream input via the transmission path, and performs decoding processing by the image decoding device 60 based on the acquired header information. Recognize various settings. For example, in the present embodiment, the syntax processing unit 61 generates a quantization matrix used in the inverse quantization process by the inverse quantization unit 63 based on the parameters included in the SPS or PPS. The detailed configuration of the syntax processing unit 61 will be further described later.

  The lossless decoding unit 62 decodes the encoded stream input from the syntax processing unit 61 according to the encoding method used at the time of encoding. Then, the lossless decoding unit 62 outputs the decoded quantized data to the inverse quantization unit 62. Further, the lossless decoding unit 62 outputs information related to intra prediction included in the header information to the intra prediction unit 80, and outputs information related to inter prediction to the motion compensation unit 90.

  The inverse quantization unit 63 uses the quantization matrix generated by the syntax processing unit 61 to inversely quantize the quantized data (that is, quantized transform coefficient data) after being decoded by the lossless decoding unit 62. . Of the quantization matrices generated by the syntax processing unit 61, which quantization matrix should be used for each block in a certain slice can be specified in the slice header.

  The inverse orthogonal transform unit 64 generates prediction error data by performing inverse orthogonal transform on the transform coefficient data input from the inverse quantization unit 63 according to the orthogonal transform method used at the time of encoding. Then, the inverse orthogonal transform unit 64 outputs the generated prediction error data to the addition unit 65.

  The adding unit 65 adds the prediction error data input from the inverse orthogonal transform unit 64 and the predicted image data input from the selector 71 to generate decoded image data. Then, the addition unit 65 outputs the generated decoded image data to the deblock filter 66 and the frame memory 69.

  The deblock filter 66 removes block distortion by filtering the decoded image data input from the adder 65 and outputs the decoded image data after filtering to the rearrangement buffer 67 and the frame memory 69.

  The rearrangement buffer 67 generates a series of time-series image data by rearranging the images input from the deblocking filter 66. Then, the rearrangement buffer 67 outputs the generated image data to the D / A conversion unit 68.

  The D / A converter 68 converts the digital image data input from the rearrangement buffer 67 into an analog image signal. Then, the D / A conversion unit 68 displays an image by outputting an analog image signal to a display (not shown) connected to the image decoding device 60, for example.

  The frame memory 69 stores the decoded image data before filtering input from the adding unit 65 and the decoded image data after filtering input from the deblocking filter 66 using a storage medium.

  The selector 70 switches the output destination of the image data from the frame memory 70 between the intra prediction unit 80 and the motion compensation unit 90 for each block in the image according to the mode information acquired by the lossless decoding unit 62. . For example, when the intra prediction mode is designated, the selector 70 outputs the decoded image data before filtering supplied from the frame memory 70 to the intra prediction unit 80 as reference image data. Further, when the inter prediction mode is designated, the selector 70 outputs the decoded image data after filtering supplied from the frame memory 70 as reference image data to the motion compensation unit 90.

  The selector 71 sets the output source of the predicted image data to be supplied to the adding unit 65 for each block in the image according to the mode information acquired by the lossless decoding unit 62 between the intra prediction unit 80 and the motion compensation unit 90. Switch between. For example, the selector 71 supplies the prediction image data output from the intra prediction unit 80 to the adding unit 65 when the intra prediction mode is designated. The selector 71 supplies the predicted image data output from the motion compensation unit 90 to the adding unit 65 when the inter prediction mode is designated.

  The intra prediction unit 80 performs in-screen prediction of pixel values based on information related to intra prediction input from the lossless decoding unit 62 and reference image data from the frame memory 69, and generates predicted image data. Then, the intra prediction unit 80 outputs the generated predicted image data to the selector 71.

  The motion compensation unit 90 performs motion compensation processing based on the information related to inter prediction input from the lossless decoding unit 62 and the reference image data from the frame memory 69, and generates predicted image data. Then, the motion compensation unit 90 outputs the generated predicted image data to the selector 71.

[3-2. Configuration example of syntax processing unit]
FIG. 12 is a block diagram illustrating an example of a detailed configuration of the syntax processing unit 61 of the image decoding device 60 illustrated in FIG. 11. Referring to FIG. 12, the syntax processing unit 61 includes a parameter acquisition unit 160 and a generation unit 170.

(1) Parameter Acquisition Unit The parameter acquisition unit 160 recognizes header information such as SPS, PPS, and slice header from the image data stream, and acquires parameters included in the header information. For example, in this embodiment, the parameter acquisition unit 160 acquires a parameter that defines a quantization matrix from SPS or PPS. The parameters that define the quantization matrix may include a pattern ID presence flag as exemplified in FIG. 3, and a pattern ID and array data for each type of quantization matrix. Then, the parameter acquisition unit 160 outputs the acquired parameters to the generation unit 170. Also, the parameter acquisition unit 160 outputs a stream of image data to the lossless decoding unit 62.

(2) Generation Unit The generation unit 170 generates various data used in the processing by each unit illustrated in FIG. 11 based on the parameters acquired by the parameter acquisition unit 160. For example, the generation unit 170 recognizes the range of the size of the encoding unit from the set of LCU and SCU values, and sets the size of the encoding unit according to the value of split_flag. Image data is decoded using the encoding unit set here as a unit of processing. In addition, the generation unit 170 further sets the size of the conversion unit. The inverse quantization performed by the inverse quantization unit 63 and the inverse orthogonal transform performed by the inverse orthogonal transform unit 64 are performed using the transform unit set here as a processing unit.

  In the present embodiment, the generation unit 170 generates a quantization matrix based on parameters acquired from the SPS or PPS by the parameter acquisition unit 160. More specifically, the generation unit 170 decodes array data that is a predictive-coded one-dimensional array according to the DPCM method, and reconstructs the decoded one-dimensional array into a two-dimensional quantization matrix. When a pattern ID that specifies one of a plurality of scan patterns is acquired from the parameter set, the reconstruction of the quantization matrix from the one-dimensional array is performed using the scan pattern specified by the pattern ID. Is called. When the scan pattern specified by the pattern ID is a predetermined scan pattern, the generation unit 170 determines at least one discontinuous reference element of the one-dimensional array based on a prediction from a reference element different from the immediately preceding element. To decrypt. The predetermined scan pattern can include, for example, the above-described mixed scan, divided mixed scan, vertical stripe scan, and horizontal stripe scan.

  When no pattern ID is present in the parameter set, reconstruction of the quantization matrix is performed with a scan pattern of zigzag scanning. The generation unit 170 can determine whether a pattern ID exists in the parameter set from the value indicated by the pattern ID presence flag. Only one pattern ID presence flag may be provided in common for a plurality of types of quantization matrices defined in the same parameter set. As a result, when a quantization matrix is to be defined according to an existing method, it can be simply indicated by a small code amount that there is no pattern ID.

<4. Flow of processing at the time of decoding according to an embodiment>
[4-1. Quantization matrix generation process]
FIG. 13 is a flowchart showing an exemplary flow of a quantization matrix generation process by the syntax processing unit 61 according to this embodiment. The quantization matrix generation process of FIG. 13 is a process that can be performed every time SPS or PPS is detected in a stream of image data.

  Referring to FIG. 13, the parameter acquisition unit 160 first acquires a pattern ID presence flag from the SPS or PPS (step S200). The subsequent steps S204 to S212 are repeated for each type of quantization matrix (step S202).

  In step S204, the parameter acquisition unit 160 determines whether a pattern ID exists in the parameter set from the value indicated by the pattern ID presence flag (step S204). If it is determined that there is a pattern ID, the parameter acquisition unit 160 further acquires a pattern ID and array data for the type of quantization matrix to be processed (step S206). Then, the generation unit 170 performs a quantization matrix reconstruction process illustrated in FIG. 14 (Step S208). On the other hand, when it is determined that the pattern ID does not exist, the parameter acquisition unit 160 further acquires only the array data regarding the type of the quantization matrix to be processed (step S210). Then, the generation unit 170 performs a quantization matrix reconstruction process using a zigzag scan as in the existing method (step S212).

[4-2. Quantization matrix reconstruction process]
FIG. 14 is a flowchart showing an example of a detailed flow of the quantization matrix reconstruction process in step S208 of FIG.

  Referring to FIG. 14, first, the generation unit 170 recognizes a scan pattern corresponding to the pattern ID acquired by the parameter acquisition unit 160 (step S220). The subsequent steps S224 to S230 are repeated for each element of the one-dimensional array included in the array data (step S222).

  In step S224, the generation unit 170 determines whether the element of interest is a discontinuous reference element (step S224). If the target element is not a discontinuous reference element, the generation unit 170 adds the difference value of the target element included in the array data to the decoded value of the immediately preceding element (the previous target element), The decoded value of the element of interest is calculated (step S226). On the other hand, when the target element is a discontinuous reference element, the generation unit 170 adds the difference value of the target element to the decoded value of the predetermined reference element before the previous element, thereby generating the target element. Is calculated (step S228). Next, the generation unit 170 sets the value of the element corresponding to the element of interest in the quantization matrix to the value calculated in step S226 or S228 (step S230).

  When such processing is completed for all elements of the one-dimensional array included in the array data, one quantization matrix defined by the user is completed.

<5. Application example>
The image encoding device 10 and the image decoding device 60 according to the above-described embodiments are a transmitter or a receiver in satellite broadcasting, cable broadcasting such as cable TV, distribution on the Internet, and distribution to terminals by cellular communication, The present invention can be applied to various electronic devices such as a recording device that records an image on a medium such as an optical disk, a magnetic disk, and a flash memory, or a playback device that reproduces an image from these storage media. Hereinafter, four application examples will be described.

[5-1. First application example]
FIG. 15 shows an example of a schematic configuration of a television apparatus to which the above-described embodiment is applied. The television apparatus 900 includes an antenna 901, a tuner 902, a demultiplexer 903, a decoder 904, a video signal processing unit 905, a display unit 906, an audio signal processing unit 907, a speaker 908, an external interface 909, a control unit 910, a user interface 911, And a bus 912.

  The tuner 902 extracts a signal of a desired channel from a broadcast signal received via the antenna 901, and demodulates the extracted signal. Then, the tuner 902 outputs the encoded bit stream obtained by the demodulation to the demultiplexer 903. In other words, the tuner 902 serves as a transmission unit in the television apparatus 900 that receives an encoded stream in which an image is encoded.

  The demultiplexer 903 separates the video stream and audio stream of the viewing target program from the encoded bit stream, and outputs each separated stream to the decoder 904. Further, the demultiplexer 903 extracts auxiliary data such as EPG (Electronic Program Guide) from the encoded bit stream, and supplies the extracted data to the control unit 910. Note that the demultiplexer 903 may perform descrambling when the encoded bit stream is scrambled.

  The decoder 904 decodes the video stream and audio stream input from the demultiplexer 903. Then, the decoder 904 outputs the video data generated by the decoding process to the video signal processing unit 905. In addition, the decoder 904 outputs audio data generated by the decoding process to the audio signal processing unit 907.

  The video signal processing unit 905 reproduces the video data input from the decoder 904 and causes the display unit 906 to display the video. In addition, the video signal processing unit 905 may cause the display unit 906 to display an application screen supplied via a network. Further, the video signal processing unit 905 may perform additional processing such as noise removal on the video data according to the setting. Furthermore, the video signal processing unit 905 may generate a GUI (Graphical User Interface) image such as a menu, a button, or a cursor, and superimpose the generated image on the output image.

  The display unit 906 is driven by a drive signal supplied from the video signal processing unit 905, and displays a video or an image on a video screen of a display device (for example, a liquid crystal display, a plasma display, or an OLED).

  The audio signal processing unit 907 performs reproduction processing such as D / A conversion and amplification on the audio data input from the decoder 904 and outputs audio from the speaker 908. The audio signal processing unit 907 may perform additional processing such as noise removal on the audio data.

  The external interface 909 is an interface for connecting the television device 900 to an external device or a network. For example, a video stream or an audio stream received via the external interface 909 may be decoded by the decoder 904. That is, the external interface 909 also has a role as a transmission unit in the television apparatus 900 that receives an encoded stream in which an image is encoded.

  The control unit 910 includes a processor such as a CPU (Central Processing Unit) and a memory such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The memory stores a program executed by the CPU, program data, EPG data, data acquired via a network, and the like. The program stored in the memory is read and executed by the CPU when the television device 900 is activated, for example. The CPU controls the operation of the television device 900 according to an operation signal input from the user interface 911, for example, by executing the program.

  The user interface 911 is connected to the control unit 910. The user interface 911 includes, for example, buttons and switches for the user to operate the television device 900, a remote control signal receiving unit, and the like. The user interface 911 detects an operation by the user via these components, generates an operation signal, and outputs the generated operation signal to the control unit 910.

  The bus 912 connects the tuner 902, the demultiplexer 903, the decoder 904, the video signal processing unit 905, the audio signal processing unit 907, the external interface 909, and the control unit 910 to each other.

  In the television device 900 configured as described above, the decoder 904 has the function of the image decoding device 60 according to the above-described embodiment. Therefore, it is possible to compress the code amount required for defining the quantization matrix for the video decoded by the television apparatus 900.

[5-2. Second application example]
FIG. 16 shows an example of a schematic configuration of a mobile phone to which the above-described embodiment is applied. A cellular phone 920 includes an antenna 921, a communication unit 922, an audio codec 923, a speaker 924, a microphone 925, a camera unit 926, an image processing unit 927, a demultiplexing unit 928, a recording / reproducing unit 929, a display unit 930, a control unit 931, an operation A portion 932 and a bus 933.

  The antenna 921 is connected to the communication unit 922. The speaker 924 and the microphone 925 are connected to the audio codec 923. The operation unit 932 is connected to the control unit 931. The bus 933 connects the communication unit 922, the audio codec 923, the camera unit 926, the image processing unit 927, the demultiplexing unit 928, the recording / reproducing unit 929, the display unit 930, and the control unit 931 to each other.

  The mobile phone 920 has various operation modes including a voice call mode, a data communication mode, a shooting mode, and a videophone mode, and is used for sending and receiving voice signals, sending and receiving e-mail or image data, taking images, and recording data. Perform the action.

  In the voice call mode, an analog voice signal generated by the microphone 925 is supplied to the voice codec 923. The audio codec 923 converts an analog audio signal into audio data, A / D converts the compressed audio data, and compresses it. Then, the audio codec 923 outputs the compressed audio data to the communication unit 922. The communication unit 922 encodes and modulates the audio data and generates a transmission signal. Then, the communication unit 922 transmits the generated transmission signal to a base station (not shown) via the antenna 921. In addition, the communication unit 922 amplifies a radio signal received via the antenna 921 and performs frequency conversion to acquire a received signal. Then, the communication unit 922 demodulates and decodes the received signal to generate audio data, and outputs the generated audio data to the audio codec 923. The audio codec 923 expands the audio data and performs D / A conversion to generate an analog audio signal. Then, the audio codec 923 supplies the generated audio signal to the speaker 924 to output audio.

  Further, in the data communication mode, for example, the control unit 931 generates character data that constitutes an e-mail in response to an operation by the user via the operation unit 932. In addition, the control unit 931 causes the display unit 930 to display characters. In addition, the control unit 931 generates e-mail data in response to a transmission instruction from the user via the operation unit 932, and outputs the generated e-mail data to the communication unit 922. The communication unit 922 encodes and modulates email data and generates a transmission signal. Then, the communication unit 922 transmits the generated transmission signal to a base station (not shown) via the antenna 921. In addition, the communication unit 922 amplifies a radio signal received via the antenna 921 and performs frequency conversion to acquire a received signal. Then, the communication unit 922 demodulates and decodes the received signal to restore the email data, and outputs the restored email data to the control unit 931. The control unit 931 displays the content of the electronic mail on the display unit 930 and stores the electronic mail data in the storage medium of the recording / reproducing unit 929.

  The recording / reproducing unit 929 has an arbitrary readable / writable storage medium. For example, the storage medium may be a built-in storage medium such as a RAM or a flash memory, or an externally mounted storage medium such as a hard disk, a magnetic disk, a magneto-optical disk, an optical disk, a USB memory, or a memory card. May be.

  In the shooting mode, for example, the camera unit 926 captures an image of a subject, generates image data, and outputs the generated image data to the image processing unit 927. The image processing unit 927 encodes the image data input from the camera unit 926 and stores the encoded stream in the storage medium of the storage / playback unit 929.

  Further, in the videophone mode, for example, the demultiplexing unit 928 multiplexes the video stream encoded by the image processing unit 927 and the audio stream input from the audio codec 923, and the multiplexed stream is the communication unit 922. Output to. The communication unit 922 encodes and modulates the stream and generates a transmission signal. Then, the communication unit 922 transmits the generated transmission signal to a base station (not shown) via the antenna 921. In addition, the communication unit 922 amplifies a radio signal received via the antenna 921 and performs frequency conversion to acquire a received signal. These transmission signal and reception signal may include an encoded bit stream. Then, the communication unit 922 demodulates and decodes the received signal to restore the stream, and outputs the restored stream to the demultiplexing unit 928. The demultiplexing unit 928 separates the video stream and the audio stream from the input stream, and outputs the video stream to the image processing unit 927 and the audio stream to the audio codec 923. The image processing unit 927 decodes the video stream and generates video data. The video data is supplied to the display unit 930, and a series of images is displayed on the display unit 930. The audio codec 923 decompresses the audio stream and performs D / A conversion to generate an analog audio signal. Then, the audio codec 923 supplies the generated audio signal to the speaker 924 to output audio.

  In the mobile phone 920 configured as described above, the image processing unit 927 has the functions of the image encoding device 10 and the image decoding device 60 according to the above-described embodiment. Therefore, the amount of code required to define the quantization matrix can be compressed for video encoded and decoded by the mobile phone 920.

[5-3. Third application example]
FIG. 17 shows an example of a schematic configuration of a recording / reproducing apparatus to which the above-described embodiment is applied. For example, the recording / reproducing device 940 encodes audio data and video data of a received broadcast program and records the encoded data on a recording medium. In addition, the recording / reproducing device 940 may encode audio data and video data acquired from another device and record them on a recording medium, for example. In addition, the recording / reproducing device 940 reproduces data recorded on the recording medium on a monitor and a speaker, for example, in accordance with a user instruction. At this time, the recording / reproducing device 940 decodes the audio data and the video data.

  The recording / reproducing apparatus 940 includes a tuner 941, an external interface 942, an encoder 943, an HDD (Hard Disk Drive) 944, a disk drive 945, a selector 946, a decoder 947, an OSD (On-Screen Display) 948, a control unit 949, and a user interface. 950.

  The tuner 941 extracts a signal of a desired channel from a broadcast signal received via an antenna (not shown), and demodulates the extracted signal. Then, the tuner 941 outputs the encoded bit stream obtained by the demodulation to the selector 946. That is, the tuner 941 has a role as a transmission unit in the recording / reproducing apparatus 940.

  The external interface 942 is an interface for connecting the recording / reproducing apparatus 940 to an external device or a network. The external interface 942 may be, for example, an IEEE 1394 interface, a network interface, a USB interface, or a flash memory interface. For example, video data and audio data received via the external interface 942 are input to the encoder 943. That is, the external interface 942 serves as a transmission unit in the recording / reproducing device 940.

  The encoder 943 encodes video data and audio data when the video data and audio data input from the external interface 942 are not encoded. Then, the encoder 943 outputs the encoded bit stream to the selector 946.

  The HDD 944 records an encoded bit stream in which content data such as video and audio is compressed, various programs, and other data on an internal hard disk. Also, the HDD 944 reads out these data from the hard disk when playing back video and audio.

  The disk drive 945 performs recording and reading of data with respect to the mounted recording medium. The recording medium mounted on the disk drive 945 may be, for example, a DVD disk (DVD-Video, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, etc.) or a Blu-ray (registered trademark) disk. .

  The selector 946 selects an encoded bit stream input from the tuner 941 or the encoder 943 when recording video and audio, and outputs the selected encoded bit stream to the HDD 944 or the disk drive 945. In addition, the selector 946 outputs the encoded bit stream input from the HDD 944 or the disk drive 945 to the decoder 947 during video and audio reproduction.

  The decoder 947 decodes the encoded bit stream and generates video data and audio data. Then, the decoder 947 outputs the generated video data to the OSD 948. The decoder 904 outputs the generated audio data to an external speaker.

  The OSD 948 reproduces the video data input from the decoder 947 and displays the video. Further, the OSD 948 may superimpose a GUI image such as a menu, a button, or a cursor on the video to be displayed.

  The control unit 949 includes a processor such as a CPU and memories such as a RAM and a ROM. The memory stores a program executed by the CPU, program data, and the like. The program stored in the memory is read and executed by the CPU when the recording / reproducing apparatus 940 is activated, for example. The CPU controls the operation of the recording / reproducing device 940 according to an operation signal input from the user interface 950, for example, by executing the program.

  The user interface 950 is connected to the control unit 949. The user interface 950 includes, for example, buttons and switches for the user to operate the recording / reproducing device 940, a remote control signal receiving unit, and the like. The user interface 950 detects an operation by the user via these components, generates an operation signal, and outputs the generated operation signal to the control unit 949.

  In the recording / reproducing apparatus 940 configured as described above, the encoder 943 has the function of the image encoding apparatus 10 according to the above-described embodiment. The decoder 947 has the function of the image decoding device 60 according to the above-described embodiment. Therefore, the amount of code required for defining the quantization matrix can be compressed for the video encoded and decoded by the recording / reproducing apparatus 940.

[5-4. Fourth application example]
FIG. 18 illustrates an example of a schematic configuration of an imaging apparatus to which the above-described embodiment is applied. The imaging device 960 images a subject to generate an image, encodes the image data, and records it on a recording medium.

  The imaging device 960 includes an optical block 961, an imaging unit 962, a signal processing unit 963, an image processing unit 964, a display unit 965, an external interface 966, a memory 967, a media drive 968, an OSD 969, a control unit 970, a user interface 971, and a bus. 972.

  The optical block 961 is connected to the imaging unit 962. The imaging unit 962 is connected to the signal processing unit 963. The display unit 965 is connected to the image processing unit 964. The user interface 971 is connected to the control unit 970. The bus 972 connects the image processing unit 964, the external interface 966, the memory 967, the media drive 968, the OSD 969, and the control unit 970 to each other.

  The optical block 961 includes a focus lens and a diaphragm mechanism. The optical block 961 forms an optical image of the subject on the imaging surface of the imaging unit 962. The imaging unit 962 includes an image sensor such as a CCD or a CMOS, and converts an optical image formed on the imaging surface into an image signal as an electrical signal by photoelectric conversion. Then, the imaging unit 962 outputs the image signal to the signal processing unit 963.

  The signal processing unit 963 performs various camera signal processes such as knee correction, gamma correction, and color correction on the image signal input from the imaging unit 962. The signal processing unit 963 outputs the image data after the camera signal processing to the image processing unit 964.

  The image processing unit 964 encodes the image data input from the signal processing unit 963, and generates encoded data. Then, the image processing unit 964 outputs the generated encoded data to the external interface 966 or the media drive 968. The image processing unit 964 also decodes encoded data input from the external interface 966 or the media drive 968 to generate image data. Then, the image processing unit 964 outputs the generated image data to the display unit 965. In addition, the image processing unit 964 may display the image by outputting the image data input from the signal processing unit 963 to the display unit 965. Further, the image processing unit 964 may superimpose display data acquired from the OSD 969 on an image output to the display unit 965.

  The OSD 969 generates a GUI image such as a menu, a button, or a cursor, and outputs the generated image to the image processing unit 964.

  The external interface 966 is configured as a USB input / output terminal, for example. The external interface 966 connects the imaging device 960 and a printer, for example, when printing an image. Further, a drive is connected to the external interface 966 as necessary. For example, a removable medium such as a magnetic disk or an optical disk is attached to the drive, and a program read from the removable medium can be installed in the imaging device 960. Further, the external interface 966 may be configured as a network interface connected to a network such as a LAN or the Internet. That is, the external interface 966 has a role as a transmission unit in the imaging device 960.

  The recording medium mounted on the media drive 968 may be any readable / writable removable medium such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory. Further, a recording medium may be fixedly attached to the media drive 968, and a non-portable storage unit such as a built-in hard disk drive or an SSD (Solid State Drive) may be configured.

  The control unit 970 includes a processor such as a CPU and memories such as a RAM and a ROM. The memory stores a program executed by the CPU, program data, and the like. The program stored in the memory is read and executed by the CPU when the imaging device 960 is activated, for example. The CPU controls the operation of the imaging device 960 according to an operation signal input from the user interface 971, for example, by executing the program.

  The user interface 971 is connected to the control unit 970. The user interface 971 includes, for example, buttons and switches for the user to operate the imaging device 960. The user interface 971 detects an operation by the user via these components, generates an operation signal, and outputs the generated operation signal to the control unit 970.

  In the imaging device 960 configured as described above, the image processing unit 964 has the functions of the image encoding device 10 and the image decoding device 60 according to the above-described embodiment. Therefore, it is possible to compress the amount of code required to define the quantization matrix for the video encoded and decoded by the imaging device 960.

<6. Summary>
So far, the image encoding device 10 and the image decoding device 60 according to an embodiment of the present invention have been described with reference to FIGS. According to the present embodiment, the quantization matrix used in the quantization or inverse quantization of the transform coefficient data of the image is encoded using a scan pattern that is adaptively selected from a plurality of scan patterns. Or decrypted. Thereby, compared with the case where a zigzag scan is used uniformly, the code amount required for the definition of a quantization matrix can be compressed more.

  Further, according to the present embodiment, a flag indicating whether or not a pattern ID for specifying a scan pattern exists in the parameter set is inserted in the parameter set. One flag may be provided for a plurality of types of quantization matrices defined in the same parameter set. Therefore, when a quantization matrix is to be defined according to an existing method, it can be simply indicated that a pattern ID does not exist with a small code amount. As a result, the above-described adaptive scan pattern selection mechanism can be introduced without significantly affecting the existing apparatus.

  Further, according to the present embodiment, a discontinuous reference element can be adopted for a predetermined scan pattern. The encoding or decoding of the discontinuous reference element in the DPCM method is performed based on prediction from a reference element different from the element immediately before the one-dimensional array to be scanned. Thereby, it is possible to flexibly perform prediction between elements whose values are highly correlated with each other as compared with a case where a matrix is scanned by a so-called one-stroke drawing. Therefore, it becomes easy to use various scan patterns useful for reducing the code amount.

  In the present specification, an example in which parameters for defining a quantization matrix are multiplexed on the header of an encoded stream and transmitted from the encoding side to the decoding side has been described. However, the method of transmitting these parameters is not limited to such an example. For example, the parameters may be transmitted or recorded as separate data associated with the encoded bitstream without being multiplexed into the encoded bitstream. Here, the term “associate” means that an image (which may be a part of an image such as a slice or a block) included in the bitstream and information corresponding to the image can be linked at the time of decoding. Means. That is, information may be transmitted on a transmission path different from that of the image (or bit stream). Information may be recorded on a recording medium (or another recording area of the same recording medium) different from the image (or bit stream). Furthermore, the information and the image (or bit stream) may be associated with each other in an arbitrary unit such as a plurality of frames, one frame, or a part of the frame.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

10 Image processing device (image encoding device)
16 quantization unit 110 setting unit 120 parameter generation unit 130 insertion unit 60 image processing device (image decoding device)
63 Inverse quantization unit 160 Parameter acquisition unit 170 Generation unit

Claims (12)

An acquisition unit for acquiring a first parameter for specifying a scan pattern used in generating a quantization matrix among a plurality of scan patterns;
A generating unit that generates a quantization matrix using a scan pattern specified by the first parameter acquired by the acquiring unit;
An inverse quantization unit that inversely quantizes transform coefficient data of an image to be decoded using the quantization matrix generated by the generation unit;
An image processing apparatus comprising: The acquisition unit
Obtaining a second parameter indicating whether the first parameter exists;
Obtaining the first parameter when the second parameter indicates that the first parameter exists;
The image processing apparatus according to claim 1.   The image processing apparatus according to claim 2, wherein the acquisition unit acquires one second parameter for a plurality of types of quantization matrices defined in the same parameter set.   The generation unit generates a quantization matrix by decoding a predictively encoded one-dimensional array and reconstructing the decoded one-dimensional array into a matrix according to a scan pattern specified by the first parameter. The image processing apparatus according to claim 1.   When the scan pattern specified by the first parameter is a predetermined scan pattern, the generator generates at least one element of the one-dimensional array based on prediction from an element different from the immediately preceding element. The image processing apparatus according to claim 4, wherein decoding is performed.   2. The image processing apparatus according to claim 1, wherein one of the plurality of scan patterns is a scan pattern in which an uppermost row and a leftmost column of a quantization matrix are scanned straight. Obtaining a first parameter for specifying a scan pattern used when generating a quantization matrix among a plurality of scan patterns;
Generating a quantization matrix using a scan pattern specified by the acquired first parameter;
Using the generated quantization matrix, inversely quantizing transform coefficient data of an image to be decoded;
An image processing method including: A quantization unit that quantizes transform coefficient data of an image to be encoded using a quantization matrix;
An insertion unit that inserts a first parameter that specifies a scan pattern used in generating a quantization matrix used by the quantization unit among a plurality of scan patterns into a parameter set;
An image processing apparatus comprising:   The image processing apparatus according to claim 8, further comprising: a setting unit that sets a scan pattern that optimizes a code amount required for defining the quantization matrix among the plurality of scan patterns.   The image processing apparatus according to claim 9, wherein the setting unit selects the scan pattern for optimizing the code amount offline.   The image processing apparatus according to claim 8, further comprising: a transmission unit that transmits a parameter set in which the first parameter is inserted to an apparatus that decodes the image. Inserting a first parameter identifying a scan pattern used in generating a quantization matrix among a plurality of scan patterns into the parameter set;
Quantizing transform coefficient data of an image to be encoded using the quantization matrix;
An image processing method including:

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