JP2010009624A - Image signal conversion method, image signal reverse conversion method, image encoding device, image decoding device, image encoding method, image decoding method, image encoding program, and image decoding program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently express signals to be converted by concentrating the energy of the signals even when the correlation of the signals to be converted is not high. <P>SOLUTION: An image signal conversion method includes an intermediate value generation step and a conversion coefficient generation step to generate a 2<SP>N</SP>(N is a natural number) conversion samples from 2<SP>N</SP>input samples. In the intermediate value generation step, one input sample out of n-th pair (n=1 to 2<SP>N-1</SP>) of input samples determined in accordance with a conversion rule is weighted by the n-th weight coefficient and the weighted input sample is converted to generate the n-th pair of intermediate values. In the conversion coefficient generation step, generated 2<SP>N</SP>intermediate values are inputted, one intermediate value out of the m-th pair (m=1 to 2<SP>N-1</SP>) of intermediate values determined in accordance with the conversion rule is weighted by the m-th weight coefficient and the weighted intermediate value is converted to generate the m-th pair of conversion samples. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image encoding technique using an image signal conversion method and an image decoding technique using an image signal inverse conversion method.

  Conventionally, compression coding techniques have been used in order to efficiently transmit and store still images and moving image data. In particular, in the case of moving images, MPEG (Moving Picture Experts Group) 1, 2, 4 or H.264 is used. 261-H. In the case of H.264, still images, JPEG (Joint Photographic Experts Group) or JPEG2000 is used.

  In most of these encoding methods, an image to be encoded is divided into a plurality of blocks, and then each block itself or these blocks are divided using discrete cosine transform (hereinafter referred to as “DCT”). The difference signal between the prediction signal for the block and the block is converted into the frequency domain. Then, the data amount of the signal of the original image is compressed by quantizing the converted transform coefficient. At the time of reproduction, the signal of each block is inversely quantized from the compressed data and then subjected to inverse discrete cosine transform (hereinafter referred to as “IDCT”) to restore the signal in the pixel region or the differential signal. Coding using DCT is described in Patent Document 1, for example.

  FIG. 1 is a diagram for explaining DCT processing in the prior art. The example shown corresponds to the case where four pixels are converted into the frequency domain. The four pixels a0, a1, a2, and a3 are input from input terminals 101 to 104, respectively. The adder 113 adds a0 and a3, and the subtractor 114 calculates the difference between a0 and a3. Similarly, a 1 and a 2 are processed by the adder 115 and the subtractor 116. These results are sent to the next stage via terminals 105 to 108, respectively. Signals from terminals 105 and 106 are processed by adder 117 and subtractor 118, and signals from terminals 107 and 108 are processed by adder 119, subtractor 120, and multipliers 121 and 122. . The result thus obtained is a frequency domain coefficient and is output via terminals 109-112.

  FIG. 2 is a diagram for explaining IDCT processing in the prior art. The frequency domain coefficients are input from input terminals 201-204, respectively. The coefficients from the terminals 201 and 202 are processed by the adder 213 and the subtracter 214, and the coefficients from the terminals 203 and 204 are processed by the subtractor 215, the adder 216, and the multipliers 221 and 222. . The obtained signal is sent to the next stage via terminals 205-208. Signals from terminals 205 and 208 are processed by adder 217 and subtractor 218, and signals from terminals 206 and 207 are processed by adder 219 and subtractor 220. The frequency domain coefficients are inversely transformed into the original pixels a0, a1, a2, and a3, and then output from terminals 209 to 212, respectively. As described above, the encoding device realizes efficient encoding by converting an image into a frequency domain and expressing an input signal in a compact manner.

US Patent No. 5,1969,946

  However, in the conventional conversion method described above, since a signal to be converted is converted by one type of conversion method, it is difficult to increase the degree of energy concentration. In other words, when the correlation between the signals of interest is high, the energy concentration is increased and encoding can be performed efficiently. However, when the correlation of the signals is low, the coefficient by DCT is in the frequency band. Widely spread. As a result, efficient encoding becomes difficult.

  In general, since a captured still image or moving image signal has a high correlation, high-efficiency encoding using DCT is possible. On the other hand, when the difference between the prediction signal obtained by intra prediction or inter prediction and the image signal to be encoded is taken, the correlation between the difference signals is not high. Therefore, even if DCT is used, it is difficult to represent the difference signal in a compact manner.

  Therefore, an object of the present invention is to efficiently represent a signal by concentrating the energy of the signal even when the correlation of the signal to be converted is not high.

In order to solve the above problems, an image signal conversion method according to the present invention, according to a predetermined conversion rule, in ^the 2 ^N (N is a natural number) image signal conversion method for generating the 2 ^N transform samples from input samples Then, after weighting one input sample of the n-th pair (n = 1 to 2 ^N-1 ) input samples determined according to the conversion rule with the n-th weighting factor, the first conversion operation is performed. An intermediate value generation step for generating an n-th pair of intermediate values, and 2 ^N intermediate values generated in the intermediate value generation step as inputs, and an m-th pair (m = 1) determined according to the conversion rule A conversion coefficient generation step of performing a second conversion operation and generating an m-th pair of conversion samples after weighting one of the intermediate values of ~ ^2N-1 ) with the mth weighting coefficient; including.

  According to the present invention, a predetermined weighting process is performed on a target signal, so that the signal is converted with a conversion basis suitable for the original characteristics. For this reason, the concentration degree of energy can be raised and a signal can be encoded efficiently.

Image signal inverse conversion method according to the present invention, according to a predetermined conversion rule, a 2 ^N (N is a natural number) image signal inverse conversion method for generating a 2 ^N output samples than the conversion sample, the conversion rule The first conversion operation is performed after weighting one conversion sample of the nth conversion samples (n = 1 to 2 ^N-1 ) determined by the nth weighting factor, An intermediate value generating step for generating an intermediate value, and the ^2N intermediate values generated in the intermediate value generating step as inputs, and the m-th pair (m = 1 to 2 ^N−1 ) determined according to the conversion rule. And an output value generation step of generating an m-th pair of output samples by performing a second conversion operation after weighting one of the intermediate values by the m-th weighting factor.

  The image signal conversion method according to the present invention can also be applied to conversion processing in an image encoding device. That is, the image encoding device includes an input unit that inputs an input image to be encoded, an area dividing unit that divides the input image input by the input unit into a plurality of encoding regions, and the area dividing unit. Using the prediction means for performing the intra-screen prediction or the inter-screen prediction to obtain the difference signal, and generating the difference signal as a conversion target signal, and the above-described image signal conversion method. A conversion unit that converts the conversion target signal into the conversion coefficient by generating a conversion sample using the conversion target signal generated by the prediction unit as an input sample, and using the generated conversion sample as a conversion coefficient; Coding means for coding the transform coefficient transformed by the transform means.

  Preferably, in the image encoding device, the conversion unit is configured to perform energy concentration of the conversion target signal from among a plurality of weight coefficients in the intermediate value generation step and the conversion coefficient generation step in the image signal conversion method. The weighting coefficient that has the highest degree is selected, and the identification information of the weighting coefficient is further encoded.

  An image encoding method according to the present invention includes an input step for inputting an input image to be encoded, and an area dividing step for dividing the input image input in the input step into a plurality of encoding regions. A prediction step for obtaining a difference signal by performing either intra prediction or inter prediction for the coding region divided in the region division step, and generating the difference signal as a conversion target signal, as described above. Using the image signal conversion method, a conversion sample is generated using the conversion target signal generated in the prediction step as an input sample, and the generated conversion sample is used as a conversion coefficient, thereby converting the conversion target signal into the conversion coefficient. And a conversion step for encoding the conversion coefficient converted in the conversion step.

  Similarly, the image signal inverse transformation method according to the present invention can be applied to inverse transformation processing in an image decoding apparatus. That is, the image decoding apparatus includes an input unit that inputs compressed data generated by performing transform coding after performing either intra prediction or inter prediction on an image divided into a plurality of regions. Using the decoding means for restoring the transform coefficient corresponding to each region from the compressed data input by the input means, and generating the obtained transform coefficient as the restored transform coefficient, and the image signal inverse transform method described above, An inverse conversion unit configured to generate an output sample using the restored transform coefficient generated by the decoding unit as a transform sample, and converting the restored transform coefficient into the inverse transform data by using the output sample as an inverse transform data; .

  Preferably, in the image decoding device, the compressed data includes identification information of a weighting coefficient used in the intermediate value generation step or the output value generation step in the image signal inverse conversion method, and the decoding unit includes: The identification information is decoded, and the intermediate value generation step or the output value generation step is performed using a weighting factor corresponding to the identification information.

  In addition, the image decoding method according to the present invention inputs compressed data generated by performing transform coding after performing either intra prediction or inter prediction on an image divided into a plurality of regions. An input step, a decoding step for restoring the transform coefficient corresponding to each region from the compressed data input in the input step, and generating the obtained transform coefficient as a restored transform coefficient, and the above-described inverse image signal transform Using the method, an output sample is generated using the restored transform coefficient generated in the decoding step as a transform sample, and the output sample is used as inverse transform data, thereby transforming the decompression transform coefficient into the inverse transform data. An inverse transformation step.

  Furthermore, the encoding technique according to the present invention can be applied to a program. That is, the encoding program includes a process for inputting an input image to be encoded, a process for dividing the input image to be input into a plurality of encoding areas, and a screen for the divided encoding areas. A process for obtaining a difference signal by performing either intra prediction or inter-screen prediction, generating the difference signal as a conversion target signal, and using the image signal conversion method described above, the generated conversion target signal is input sampled As a conversion sample is generated, and the conversion sample is used as a conversion coefficient, the computer executes the process of converting the conversion target signal into the conversion coefficient and the process of encoding the converted conversion coefficient.

  Similarly, the decoding program according to the present invention inputs compressed data generated by performing transform coding after performing either intra prediction or inter prediction on an image divided into a plurality of regions. Using the above-described image signal inverse transform method, the process of restoring the transform coefficient corresponding to each region from the input compressed data, generating the transform coefficient obtained as a restored transform coefficient, An output sample is generated using the restored transform coefficient as a transform sample, and the output sample is used as inverse transform data, thereby causing the computer to execute processing for transforming the decompression transform coefficient into the inverse transform data.

  According to these inventions, by applying predetermined weighting to the target signal, the signal can be converted with a conversion basis suitable for the original characteristics. Thereby, the degree of energy concentration is increased, and the signal can be efficiently encoded. In particular, by applying a predetermined weight to a signal having a low correlation between signals such as a differential signal, the correlation of the signal is increased, and as a result, the coding efficiency is improved.

It is a figure for demonstrating the discrete cosine transformation process in a prior art. It is a figure for demonstrating the inverse discrete cosine transformation process in a prior art. It is a figure which shows the structure of the image signal converter in one Embodiment of this invention. It is a figure which shows notionally an example of the image signal used as the object of a conversion process. It is a figure which shows the structure of the image signal reverse conversion apparatus in one Embodiment of this invention. It is a figure which shows an example of the conventional matrix for performing conversion and reverse conversion. It is a figure which shows an example of the matrix which concerns on this invention for performing conversion and reverse conversion. It is a figure which shows the structure of the image coding apparatus in one Embodiment of this invention. It is a flowchart for demonstrating operation | movement of an image coding apparatus. It is a figure which shows the structure of the image decoding apparatus in one Embodiment of this invention. It is a flowchart for demonstrating operation | movement of an image decoding apparatus. It is a figure which shows notionally the structure of an image coding program. It is a figure which shows notionally the structure of an image decoding program. It is a figure which shows schematic structure of the computer which performs an image encoding / decoding program. And FIG. 20 is an external perspective view of a computer that executes an image encoding / decoding program.

  Hereinafter, an image signal converter according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 3 is a diagram showing the configuration of the image signal conversion apparatus according to the present invention. The image signal conversion apparatus 300 according to this embodiment includes input terminals 301 to 304, connection terminals 305 to 308, output terminals 309 to 312, subtracters 317, 322, 327, and 334, and adders 321 and 326. 333, 338, weighters 318, 323, 329, 335, and multipliers 320, 325, 328, 332, 337. These components are connected to each other through a bus so that signals can be input and output.

  The image signal converter 300 receives an image signal 501 composed of 4 × 4 pixels shown in FIG. In FIG. 4, each cell corresponds to one pixel. Hereinafter, one-dimensional conversion using a signal of four pixels, that is, the pixels 502 to 505 in FIG. 4 as an input will be described. However, the same processing may be performed on each row in FIG. Furthermore, the conversion process described later may be performed on each column, and the result may be processed in units of rows.

The pixels “a0” (502) to “a3” (505) in FIG. 4 are input to the input terminals 301 to 304, respectively. The pixel “a3” input from the input terminal 304 is weighted by w ₁ (318), and the result is subtracted from the pixel “a0” input to the input terminal 301. The intermediate value thus obtained is output to the connection terminal 305 and simultaneously to the adder 321.

  The adder 321 adds the intermediate value and the pixel “a3” doubled by the multiplier 320. The added intermediate value is output to the connection terminal 308. That is, the image signal conversion apparatus 300 converts the input signal by using the module including the weighting unit 318, the arithmetic unit 317, and the arithmetic units 320 and 321 as the basic conversion module 313.

  When the target signal to be converted is composed of two pixels, the above processing is completed. However, since four pixels are to be converted in this embodiment, the same applies to the pixels “a1” and “a2”. The data is converted by a conversion module 314 including a weighting device 323, a computing device 322, and computing devices (325 and 326). In this embodiment, the weighting unit 323 performs processing using a weighting factor different from that of the weighting unit 318, but the same weighting factor may be used.

  The intermediate values obtained from the conversion modules 313 and 314 are output to the conversion module 315 and the conversion module 316, and similar processing is performed. The weighting unit 329, the computing units (328, 327), and the computing units (332, 333) in the conversion module 315 are different from those of the conversion modules 313, 314. However, one input (input from the connection terminal 306) is weighted and then subtracted from the other input (input from the connection terminal 305), and the result of the subtraction is converted to the input signal from the connection terminal 306. The basic process of adding again is similar.

Similarly, for the intermediate value signals input from the connection terminals 307 and 308, the coefficients of the frequency components converted from the terminals 309 to 312 are output. The weighting factors w _{1 to} w ₄ shown in FIG. 3 are the same as the conversion shown in FIG. 1 when all take the value “1”. That is, the image signal conversion method according to the present invention is a conversion basis suitable for a signal to be converted by changing the weighting factors w _{1 to} w ₄ while performing processing according to the conversion rule in the conventional conversion method. Signal conversion can be performed.

In the conversion module 313 of FIG. 3, the weighting factor w ₁ in the weighting unit 318 corresponds to the “nth weighting factor” according to claim 1, and the subtraction processing by the subtractor 317 and the multiplier 320 and the addition processing by the adder 321 correspond to the “first conversion operation” according to claim 1. Further, the conversion module 314, the weight coefficient w ₂ by weighting 323 corresponds to the "n-th weighting factor" according to claim 1, the subtraction processing by a subtracter 322, and a multiplier 325, an adder The addition processing by 326 corresponds to the “first conversion operation” according to claim 1.

In the conversion module 315, the weighting factor w ₃ in the weighting unit 329 corresponds to the “mth weighting factor” according to claim 1, and the subtraction processing by the multiplier 328 and the subtracter 327, and the multiplier 320 The addition processing by the adder 321 corresponds to the “second conversion operation” according to claim 1. In the conversion module 316, the weighting factor w ₄ by the weighting unit 335 corresponds to the “mth weighting factor” according to claim 1, and the subtraction processing by the subtracter 334, the multiplier 337, the adder The addition processing by 338 corresponds to the “second conversion operation” according to claim 1.

  Next, image signal inverse conversion processing will be described with reference to FIG. FIG. 5 is a block diagram illustrating a configuration of an image signal inverse conversion apparatus that performs an inverse conversion process corresponding to the signal conversion process performed by the image signal conversion apparatus 300. The image signal inverse conversion apparatus 400 in this embodiment includes input terminals 401 to 404, connection terminals 405 to 408, output terminals 409 to 412, subtracters 419, 423, 428, 433, and adders 437, 440. , 430, 435, weighters 420, 426, 429, 434, and multipliers 421, 425, 431, 436. These components are connected to each other through a bus so that signals can be input and output.

  The image signal inverse conversion device 400 performs processing reverse to that of the image signal conversion device 300. The image signal inverse transform device 400 is a device that inversely transforms a frequency domain coefficient into a pixel domain signal, and includes four basic transform modules 413 to 416. As shown in FIG. 5, the image signal inverse conversion device 400 inputs the conversion coefficients obtained by the above-described signal conversion processing from the input terminals 401 to 404. The coefficient input from the input terminal 401 is calculated (subtracted) by the subtractor 419 with the coefficient input from the input terminal 402.

The calculation result is multiplied by ½ (439) and then output to the connection terminal 406 as an intermediate value. At the same time, the subtraction result is weighted by the coefficient of w _{3 in} the weighter 420 and then calculated as an input signal from the input terminal 401. This arithmetic processing is executed by the multipliers 421 and 422 and the adder 437. Similarly, conversion coefficients input from the input terminals 403 and 404 are processed by the conversion module 414. The obtained intermediate value is output to the connection terminals 405 to 408 and then inversely converted into a pixel region signal by the conversion modules 415 and 416. Multipliers 422, 425, 431, and 436 in FIG. 5 determine the multiplication coefficient so that the same magnitude as the input signal shown in FIG. 3 is obtained. Also, the weighters 421, 426, 429, and 434 in FIG. 5 correspond to the weighters in the conversion modules 313 to 316 shown in FIG. 3, so that the result of inverse conversion is the same as the signal before conversion. Each weighting factor is determined. Note that when all of the weighting factors w _{1 to} w ₄ in FIG. 5 have a value of “1”, the processing is the same as the inverse conversion processing described with reference to FIG.

  In the present embodiment, the conversion module adds the subtraction results, but conversely, a method of subtracting the addition results may be adopted. In this case, the image signal inverse conversion device may set the coefficient of the multiplier so that the input energy of the converter and the output energy of the inverse converter are held. Further, although the input signal of 4 pixels has been described, the input signal of N pixels (N is an arbitrary natural number) is prior to arithmetic processing (addition / subtraction) in a conventional N × N DCT conversion device or IDCT conversion device. Thus, data may be processed by providing corresponding weights.

Here, the weights used for image signal conversion and inverse conversion will be described. In the present embodiment, the highest energy concentration of the signal to be processed is obtained from a total of 16 coefficients of 19/16, 18/16, 17/16,..., 5/16, 4/16. To be elected. Each coefficient of w _{1 to} w ₄ takes the same value, but different coefficients may be used. Also, w ₃ may be fixed to “1” depending on the signal, and any of the above values may be used as other coefficients. Alternatively, w _{1 to} w ₃ may be fixed to “1” and only w ₄ may be variable. Furthermore, coefficients other than the 16 coefficients described above may be used.

The image signal inverse conversion device 400 substantially changes the conversion base by weighting the input signal with the weighting factors of w _{1 to} w ₄ . Such processing will be described with reference to FIGS. FIG. 6 is a diagram showing a matrix for performing conversion / inverse conversion in the prior art. The matrix 601 is a transformation matrix, the matrix 602 is an inverse transformation matrix, and the matrix 603 is a normalization matrix for conserving energy. On the other hand, FIG. 7 is a diagram showing a matrix for performing the conversion / inverse conversion according to the present invention. The matrix 701 is a transformation matrix, the matrix 702 is an inverse transformation matrix, and the matrix 703 is a normalization matrix for conserving energy.

Comparing the two figures, the w ₁ to w _4, but so that the base of a conventional transform and inverse transform matrix is changed, if the values of w ₁ to w ₄ is 1, the conventional conversion and It becomes an inverse transformation matrix. In other words, the image signal inverse conversion device 400 can adjust the conversion base by changing the values of w _{1 to} w ₄ , and thus can perform conversion suitable for the signal to be converted.

  Subsequently, an image encoding apparatus, method, and program using the above-described image signal conversion process will be described. FIG. 8 is a diagram showing the configuration of the image coding apparatus according to the present embodiment. As shown in FIG. 8, the image coding apparatus 800 includes an input terminal 801, a block divider 802, an intra-screen predictor 803, an inter-screen predictor 804, and connection terminals 805, 806, 807, 808, and 810. A changeover switch 809, an adder 811, a frame memory 812, a converter 813, a quantizer 814, an inverse quantizer 815, an inverse transformer 816, an adder 817, and a weight determiner 818. An entropy encoder 819 and an output terminal 820. These components are connected to each other through a bus so that signals can be input and output. Hereinafter, the components including the intra-screen predictor 803 and the inter-screen predictor 804 are collectively referred to as a predicted signal generator 821.

  When a plurality of images constituting a moving image are input from the input terminal 801, these images are divided by the block divider 802 into blocks composed of N × M pixels. In this embodiment, N = M = 8, but N ≠ M may be used, and division other than 8 pixels may be used. The block to be encoded is input to the intra-screen predictor 803 and the inter-screen predictor 804 via the line L820a.

  The intra-screen predictor 803 receives the block signal to be encoded and the image signal that has been reproduced and forms the same screen stored in the frame memory 812. A screen prediction signal similar to H.264 is generated. The inter-screen prediction 804 is input with a block to be encoded and a signal of a different screen that has been reproduced and stored in the frame memory 812. An inter-screen prediction signal is generated using motion detection prediction similar to H.264.

  The image encoding apparatus 800 assumes a case where nothing is input from the terminal 805, that is, a case where the original signal is directly subjected to encoding. The changeover switch 809 selects the mode with the smallest code amount from among the three modes of the prediction signal from the intra-screen predictor 803, the prediction signal from the inter-screen predictor 804, and no prediction signal. After the determined prediction signal is output to the adder 811, the difference from the block to be encoded is calculated. When the changeover switch 809 is connected to the terminal 808, since the input from the terminal 805 is “0”, the output of the adder 811 is the encoding target block itself. The difference signal is output to the weight determiner 818.

  The weight determiner 818 estimates the code amount of the conversion coefficient after performing the above-described image signal conversion processing on the difference signal using a plurality of weight coefficients. In the present embodiment, weight determiner 818 determines the weight with the smallest code amount after entropy encoding the transform coefficient, and outputs an identifier (corresponding to the identification information) for identifying the weight to converter 813. . The converter 813 performs conversion using the weight determined by the weight determiner 818. The converter 813 further divides the 8 × 8 pixel block in units of 4 × 4 pixels, and performs weighting conversion on each 4 × 4 block.

  Note that the processing executed by the weight determiner 818 may be incorporated into the converter 813 so that the converter 813 determines the optimum weighting conversion while performing a plurality of weighting conversions and at the same time generates the conversion coefficient. In this embodiment, four 4 × 4 blocks included in the 8 × 8 block are all processed by the same weighting conversion. However, the converter 813 is different for each 4 × 4 block. Weighting conversion may be performed.

  The transform coefficient obtained in this way is output to the quantizer 814 and quantized. The quantized coefficient is sent to the entropy encoder 819, subjected to variable length encoding, and then output from the output terminal 820. On the other hand, the quantized coefficient is inversely quantized by the inverse quantizer 815 and then inversely transformed by the inverse transformer 816 using the weight determined by the weight determiner 818. The result is added to the prediction signal via the line L811 in the adder 817 to generate a reproduction signal. The generated reproduction signal is stored in the frame memory 812. The identifier related to the weight coefficient determined by the weight determiner 818 is input to the entropy encoder 819 via the line L814 and then output from the output terminal 820 together with other data.

  Hereinafter, with reference to FIG. 9, the operation of the image coding apparatus according to the present invention and each step constituting the image coding method will be described. FIG. 9 is a flowchart for explaining an image encoding process performed by the image encoding apparatus 800. When an image to be encoded is input (S1), the image is divided into blocks of 8 × 8 pixels (S2). In S3, a prediction signal for a block to be encoded is generated. In the present embodiment, three modes of “intra-screen prediction”, “inter-screen prediction”, and “no prediction” are selected as the prediction signal generation method. Of the prediction signal candidates generated by these methods, the signal with the smallest error is determined as the prediction signal.

In S4, a difference signal is generated from the difference between the prediction signal and the block to be encoded. In S5, the differential signal divided in units of 4 × 4 samples is subjected to conversion processing by the above-described method using a plurality of weighting factors, and the weighting factor that can collect the signals in the most compact manner is determined. For example, when the code amount or the image quality is increased, the image coding apparatus 800 sets the weighting factors w _{1 to} w ₃ to “1” and the weighting factor w ₄ is any of the 16 values described above. Is used. On the other hand, when the code amount or the image quality is lowered, the weight coefficient w _{3 is set} to “1”, and the weight coefficients w ₁ , w ₂ , and w ₄ are set to any one of the 16 values described above.

  In S6, a conversion process according to the weighting factor determined in S5 is executed. Thereafter, each transform coefficient is quantized, and a quantized transform coefficient is generated (S7). The quantized transform coefficient is inversely quantized (S8) and then inversely transformed using the weighting coefficient determined in S5. As a result, a reproduction coefficient is generated (S9). In S10, the generated reproduction coefficient is added to the prediction signal determined in S3. As a result, a reproduction block is generated. The playback block is temporarily stored in the frame memory 812. At the same time, the quantized transform coefficient and the weight coefficient identifier are entropy-coded and output (S11).

  A series of processes from S3 to S11 is executed for all areas generated by the division process in S2 (S12; NO), and the image encoding process ends when the processes are completed for all the areas. If the image encoding apparatus 800 outputs the transform coefficient obtained when determining the weighting coefficient at the time of conversion in S5, it is not necessary to perform the conversion process again, and the process of S6 can be omitted. .

  An image decoding apparatus, method, and program using the above-described image signal inverse transform processing will be described. FIG. 10 is a diagram illustrating the configuration of the image decoding apparatus according to the present embodiment. As shown in FIG. 10, the image decoding apparatus 900 includes an input terminal 910, a data analyzer 911, an inverse quantizer 912, an inverse transformer 913, an adder 914, a prediction signal generator 915, a frame A memory 916 and an output terminal 917 are provided. These components are connected to each other through a bus so that signals can be input and output.

  The input terminal 910 inputs compressed data generated by performing transform coding after performing intra-screen prediction or inter-screen prediction on an image divided into a plurality of regions. The data analyzer 911 analyzes the compressed data and performs entropy decoding processing. In addition, a quantized transform coefficient, information regarding quantization, mode information regarding generation of a prediction signal, and an identifier (corresponding to identification information) of a weight coefficient used for inverse transform processing are extracted.

  The inverse quantizer 912 receives the quantized transform coefficient and information related to the quantization via the line L912, and generates a dequantized transform coefficient. The inverse transformer 913 inputs the inverse-quantized transform coefficient via the line L915 and also inputs the identifier of the weighting coefficient used for the inverse transform process via the line L914. Then, inverse transformation is performed using the designated weighting factor to generate an inverse transformation signal.

  When the prediction signal generator 915 inputs mode information related to generation of a prediction signal via the line L913, the prediction signal generator 915 selects an optimal mode from among intra prediction, inter prediction, and no prediction by referring to the information. Generate a signal. The adder 914 adds the inverse transform signal input via the line L916 and the prediction signal input via the line L917. The frame memory 916 stores the result of the addition, and the output terminal 917 displays this.

  Hereinafter, with reference to FIG. 11, the operation of the image decoding apparatus according to the present invention and the steps constituting the image decoding method will be described. FIG. 11 is a flowchart for explaining image decoding processing executed by the image decoding apparatus 900. When compressed data is input (T1), entropy decoding is performed, and quantized transform coefficients, quantization information, prediction signal generation mode information, and weight coefficient identifiers are extracted from the compressed data ( T2). In T3, a prediction signal is generated based on the mode information related to the prediction signal generation.

  At T4, the quantized transform coefficient is inversely quantized, and at T5, an inverse transform process is performed according to the weighting factor specified by the weighting factor identifier. As a result, an inverse conversion signal is generated. At T6, the prediction signal generated at T3 and the inverse transform signal generated at T5 are added to generate a reproduction block signal. This reproduction block signal is temporarily stored in the frame memory 916 at T7. A series of processing from T2 to T7 is executed for all the compressed data input at T1 (T8; NO), and the image decoding processing ends when the processing for all the data is completed.

  Here, the image encoding technique according to the present invention can also be realized as an image encoding program for causing a computer to operate as the image encoding apparatus 800. FIG. 12 is a diagram showing a configuration of an image encoding program 1000 according to the present invention. The image encoding program 1000 is recorded on the recording medium 1000a. The recording medium 1000a is, for example, a floppy (registered trademark) disk, a CD-ROM, a DVD (Digital Versatile Disc), or a semiconductor memory.

  As shown in FIG. 12, the image encoding program 1000 includes an image input module 1001, an image blocking module 1002, a prediction signal generation module 1003, a difference signal generation module 1004, a conversion weight determination module 1005, a conversion The module 1006, the quantization module 1007, the inverse quantization module 1008, the inverse transform module 1009, the addition module 1010, and the entropy encoding module 1012 are included as structural units. Functions realized by executing these modules include the input terminal 801, the block divider 802, the prediction signal generator 821, the adder 811, the weight determiner 818, and the image encoding device 800 (see FIG. 8) described above. The functions of the converter 813, the quantizer 814, the inverse quantizer 815, the inverse transformer 816, the adder 817, and the entropy encoder 819 are the same. Data stored by executing the storage module 1011 is the same as the data stored in the frame memory 812.

  The image decoding technique according to the present invention can also be realized as an image decoding program for causing a computer to operate as the image decoding apparatus 900. The image decoding program 1100 according to the present invention can adopt, for example, a configuration as shown in FIG. The image decoding program 1100 is recorded on the recording medium 1100a. The recording medium 1100a is, for example, a floppy (registered trademark) disk, a CD-ROM, a DVD, or a semiconductor memory.

  As shown in FIG. 13, the image decoding program 1100 includes a compressed data input module 1101, an entropy decoding module 1102, a prediction signal generation module 1103, an inverse quantization module 1104, an inverse transform module 1105, and an addition module 1106. As a structural unit. The functions realized by executing these modules include the input terminal 910, the data analyzer 911, the prediction signal generator 915, the inverse quantizer 912, the inverse transformer 913, and the adder 914 of the image decoding apparatus 900 described above. Each function is the same. Data stored by executing the storage module 1107 is the same as the data stored in the frame memory 916.

  FIG. 14 is a diagram illustrating a hardware configuration of a computer for executing a program recorded in the recording media 1000a and 1100a. As shown in FIG. 14, the computer 10 includes a data reader 11 including an FDD (Flexible Disk Drive), a CD-ROM drive device, and a DVD drive device, and a working memory (RAM: Random) for resident OS. Access Memory) 12, a memory 13 for storing programs read from the recording media 1000a and 1100a, a display 14 as a display device, a mouse 15 and a keyboard 16 as input devices, and data transmission / reception A communication device 17 and a CPU 18 that controls the overall execution of the program are provided.

  When the recording media 1000a and 1100a are inserted into the reading device 11, the computer 10 can access the image encoding program 1000 and the image decoding program 1100 recorded on the recording media 1000a and 1100a via the reading device 11, respectively. Become. The computer 10 operates as the image encoding device 800 described above by executing the image encoding program 1000 by the CPU 18. Similarly, the computer 10 can operate as the image decoding apparatus 900 described above by executing the image decoding program 1100 by the CPU 18.

  FIG. 15 is an external perspective view of the computer 10 for executing the programs recorded in the recording media 1000a and 1100a. The computer 10 is not limited to a PC (Personal Computer), and includes a DVD player, a set top box, a mobile phone, and the like that have a CPU and perform software information processing and control.

  As shown in FIG. 15, the image encoding program 1000 or the image decoding program 1100 may be provided (downloaded) via a network as the data signal 20 superimposed on a carrier wave. In this case, the computer 10 receives the image encoding program 1000 or the image decoding program 1100 by the communication device 17 and stores them in the memory 13 and then executes these programs.

  As described above, according to the image coding / decoding technique (apparatus, method, program) according to the present invention, weight conversion processing is performed so that the correlation of input signals becomes high in signal conversion processing. Thereby, since the signal can be expressed more compactly, the image signal can be efficiently encoded.

DESCRIPTION OF SYMBOLS 300 ... Image signal conversion apparatus, 400 ... Image signal reverse conversion apparatus, 800 ... Image coding apparatus, 801 ... Input terminal, 802 ... Block divider, 803 ... In-screen predictor, 804 ... Inter-screen predictor, 805, 806 , 807, 808, 810 ... connection terminal, 809 ... changeover switch, 811 ... adder, 812 ... frame memory, 813 ... converter, 814 ... quantizer, 815 ... inverse quantizer, 816 ... inverse converter, 817 ... adder, 818 ... weight determiner, 819 ... entropy encoder, 820 ... output terminal, 900 ... image decoding device, 910 ... input terminal, 911 ... data analyzer, 912 ... inverse quantizer, 913 ... inverse transform 914 ... adder, 915 ... prediction signal generator, 916 ... frame memory, 917 ... output terminal, 1000 ... image encoding program, 1001 ... image input Joule, 1002 ... Image blocking module, 1003 ... Prediction signal generation module, 1004 ... Difference signal generation module, 1005 ... Conversion weight determination module, 1006 ... Transformation module, 1007 ... Quantization module, 1008 ... Inverse quantization module, 1009 ... Inverse transform module, 1010 ... Addition module, 1011 ... Storage module, 1012 ... Entropy encoding module, 1100 ... Image decoding program, 1101 ... Compressed data input module, 1102 ... Entropy decoding module, 1103 ... Prediction signal generation module, 1104 ... Inverse quantization module, 1105, inverse transform module, 1106, addition module, 1107, storage module 1107.

Claims (10)

According to a predetermined conversion rule, (N is a natural number) 2 ^N pieces An image signal converting method of generating the 2 ^N transform samples from input samples,
A first conversion operation is performed after weighting one input sample of n-th (n = 1 to 2 ^N-1 ) input samples determined according to the conversion rule with an n-th weighting factor, an intermediate value generating step for generating n pairs of intermediate values;
^2N intermediate values generated in the intermediate value generation step are input, and one intermediate value of m-th pairs (m = 1 to 2 ^N−1 ) intermediate values determined according to the conversion rule is A conversion coefficient generating step of performing a second conversion operation after weighting with the m-th weighting coefficient and generating an m-th pair of conversion samples;
An image signal conversion method comprising: According to a predetermined conversion rule, a 2 ^N (N is a natural number) image signal inverse conversion method for generating a 2 ^N output samples than the conversion sample,
The first conversion operation is performed after weighting one conversion sample of the n-th pair (n = 1 to 2 ^N-1 ) conversion samples determined according to the conversion rule with the n-th weighting coefficient, an intermediate value generating step for generating n pairs of intermediate values;
^2N intermediate values generated in the intermediate value generation step are input, and one intermediate value of m-th pairs (m = 1 to 2 ^N−1 ) intermediate values determined according to the conversion rule is An output value generation step of performing a second conversion operation after weighting with the m-th weighting factor and generating an m-th pair of output samples;
An image signal inverse transform method comprising: An input means for inputting an input image to be encoded;
Area dividing means for dividing the input image input by the input means into a plurality of encoding areas;
A prediction unit that performs either intra-screen prediction or inter-screen prediction on the coding region divided by the region dividing unit to obtain a difference signal, and generates the difference signal as a conversion target signal;
The image signal conversion method according to claim 1, wherein a conversion sample is generated using the conversion target signal generated by the prediction unit as an input sample, and the generated conversion sample is used as a conversion coefficient. Conversion means for converting a signal into the conversion coefficient;
Encoding means for encoding the transform coefficient transformed by the transform means;
An image encoding device comprising:   In the intermediate value generation step and the conversion coefficient generation step in the image signal conversion method according to claim 1, the conversion means is configured such that the energy concentration of the conversion target signal is the highest among a plurality of weight coefficients. 4. The image coding apparatus according to claim 3, wherein a weighting factor is selected, and identification information of the weighting factor is further coded. Input means for inputting compressed data generated by transform coding after performing either intra prediction or inter prediction on an image divided into a plurality of regions;
Decoding means for restoring the transform coefficient corresponding to each region from the compressed data input by the input means, and generating the obtained transform coefficient as a restored transform coefficient;
An image signal inverse transform method according to claim 2, wherein an output sample is generated using the restored transform coefficient generated by the decoding means as a transform sample, and the output sample is used as inverse transform data, whereby the decompression transform is performed. Inverse transform means for transforming the coefficient into the inverse transform data;
An image decoding apparatus comprising: The compressed data includes identification information of weighting factors used in the intermediate value generation step or the output value generation step in the image signal inverse transformation method according to claim 2,
The said decoding means decodes the said identification information, and performs the process of the said intermediate value generation step or the said output value generation step using the weighting coefficient corresponding to the said identification information, The said output value generation step is characterized by the above-mentioned. Image decoding device. An input step for inputting an input image to be encoded;
A region dividing step for dividing the input image input in the input step into a plurality of coding regions;
A prediction step for obtaining a difference signal by performing either intra prediction or inter prediction for the coding region divided in the region dividing step, and generating the difference signal as a conversion target signal;
The image signal conversion method according to claim 1, wherein a conversion sample is generated using the conversion target signal generated in the prediction step as an input sample, and the generated conversion sample is used as a conversion coefficient. A conversion step of converting a target signal into the conversion coefficient;
An encoding step for encoding the conversion coefficient converted in the conversion step;
An image encoding method comprising: An input step for inputting compressed data generated by performing transform coding after performing either intra prediction or inter prediction on an image divided into a plurality of regions;
A decoding step of restoring the transform coefficient corresponding to each region from the compressed data input in the input step, and generating the obtained transform coefficient as a restored transform coefficient;
The image signal inverse transform method according to claim 2, wherein an output sample is generated using the restored transform coefficient generated in the decoding step as a transformed sample, and the output sample is used as an inverse transformed data, so that the restoration is performed. An inverse transformation step of transforming a transformation coefficient into the inverse transformation data;
An image decoding method comprising: A process of inputting an input image to be encoded;
Processing to divide the inputted input image into a plurality of coding regions;
A process for obtaining a difference signal by performing either intra prediction or inter prediction for the divided coding region, and generating the difference signal as a conversion target signal;
The image signal conversion method according to claim 1, wherein a conversion sample is generated using the generated conversion target signal as an input sample, and the conversion sample is used as a conversion coefficient, thereby converting the conversion target signal into the conversion coefficient. The process of converting to
A process of encoding the transformed transform coefficient;
An image encoding program that causes a computer to execute the above. A process of inputting compressed data generated by transform coding after performing either intra prediction or inter prediction on an image divided into a plurality of regions;
A process of restoring the transform coefficient corresponding to each region from the input compressed data, and generating the obtained transform coefficient as a restored transform coefficient;
An output signal is generated using the restored transform coefficient as a transform sample using the image signal inverse transform method according to claim 2, and the output sample is used as inverse transform data, whereby the restored transform coefficient is used as the inverse transform data. The process of converting to
An image decoding program that causes a computer to execute the above.

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