WO2013001717A1 - Appareil de codage d'images, appareil de décodage d'images, procédé de codage d'images et procédé de décodage d'images - Google Patents

Appareil de codage d'images, appareil de décodage d'images, procédé de codage d'images et procédé de décodage d'images Download PDF

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WO2013001717A1
WO2013001717A1 PCT/JP2012/003556 JP2012003556W WO2013001717A1 WO 2013001717 A1 WO2013001717 A1 WO 2013001717A1 JP 2012003556 W JP2012003556 W JP 2012003556W WO 2013001717 A1 WO2013001717 A1 WO 2013001717A1
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quantization parameter
image
quantization
difference
entropy
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PCT/JP2012/003556
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English (en)
Japanese (ja)
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憲道 日和佐
関口　俊一
杉本　和夫
彰 峯澤
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三菱電機株式会社
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/46—Embedding additional information in the video signal during the compression process
    • H04N19/463—Embedding additional information in the video signal during the compression process by compressing encoding parameters before transmission

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  • the present invention relates to an image encoding device and an image encoding method for encoding an image, and an image decoding device and an image decoding method for decoding an image encoded by the image encoding device.
  • FIG. 13 is an explanatory diagram showing the state of the quantization process described in Non-Patent Document 1 below, for example.
  • H. is an international standard for image coding.
  • MPEG-4AVC MPEG-4AVC
  • a frame or a field to be encoded is divided into blocks called “macroblocks” made up of pixels of 16 pixels ⁇ 16 lines, and an intra prediction mode or an inter prediction is performed for each macroblock.
  • Encode in mode In the encoding, quantization is performed using a quantization parameter QP that can be changed for each macroblock. At this time, the difference between the quantization parameter QP and the quantization parameter of the left macroblock adjacent to the encoding target macroblock is transmitted to the decoding side.
  • a block of an arbitrary size not limited to 16 pixels ⁇ 16 lines is used as a macro block, and encoding is performed in the intra prediction mode or the inter prediction mode for each encoded block obtained by sequentially dividing the macro block into four.
  • encoding a case where quantization is performed with a quantization parameter QP that can be changed for each encoding block will be described.
  • the macro block is divided into four, and the number of repetitions of the four divisions for the four divided blocks is arbitrary.
  • a block that is not further divided into four is defined as an encoded block.
  • the quantization parameter in this case also transmits a difference, but the quantization parameter of the left coding block adjacent to the current coding block or the quantization parameter of the upper coding block is set as a target for the difference. You can choose. Information indicating which coding block quantization parameter is selected is also transmitted to the decoding side.
  • H. is an international standard for image coding.
  • H.264 MPEG-4AVC
  • Recommendation ITU-T Rec. H.264
  • the conventional image coding apparatus is configured as described above, if a limitation is imposed on the fluctuation range of the quantization parameter, the image quality difference between adjacent blocks due to a sudden change in the quantization parameter is reduced. Occurrence can be suppressed.
  • the quantization parameter variation range is limited, the difference from the quantization parameter of the adjacent block is transmitted to the decoding side with the same amount of bits as when the variation range is not limited. ing. For this reason, there is a problem that a large amount of bits must be transmitted and the encoding efficiency is not improved.
  • the encoding characteristics differ between a block (intra block) that is encoded in the intra prediction mode and a block (inter block) that is encoded in the inter prediction mode
  • quantization may be performed with different quantization parameters between the intra block and the inter block, but the difference from the quantization parameter of the previous coding block, or the left or upper side Since the difference with the quantization parameter of the coding block is transmitted, there is a problem that the bit amount increases when the block to be obtained with the difference is the inter block in the quantization parameter of the intra block.
  • the present invention has been made to solve the above-described problems, and provides an image encoding apparatus and an image encoding method capable of reducing the amount of transmission bits of information related to quantization parameters and increasing encoding efficiency.
  • the purpose is to obtain.
  • Another object of the present invention is to provide an image decoding apparatus and an image decoding method that can decode an image even if the transmission bit amount of information related to a quantization parameter is reduced.
  • the image coding apparatus generates a prediction image by performing a prediction process on the coding block for each coding block constituting the input image, and a difference image between the coding block and the prediction image
  • a difference image generation means for generating a quantization parameter, and a quantization parameter fluctuation range is set in advance, and within a range in which a difference between quantization parameters in the encoded block and the encoded block falls within the fluctuation range
  • the coding block Quantization parameter determination means for determining a quantization parameter, and a difference image generated by the difference image generation means are orthogonally transformed, and using the quantization parameter determined by the quantization parameter determination means, a conversion coefficient of the difference image Quantization means for quantizing the quantization parameter, and the entropy coding means is a quantization parameter set by the quantization parameter determination means.
  • the bit stream is generated by entropy encoding the difference between the conversion parameters.
  • a difference for generating a prediction image by performing a prediction process on the coding block and generating a difference image between the coding block and the prediction image is set in advance with the image generation means, and the quantization parameter of the coding block is set within a range in which the difference between the quantization parameters of the encoded block and the encoded block falls within the variation width.
  • the quantization parameter determining means to determine and the difference image generated by the difference image generating means are orthogonally transformed, and the transform parameter of the difference image is quantized using the quantization parameter determined by the quantization parameter determining means.
  • Quantization means and the entropy encoding means has a quantization parameter fluctuation range set by the quantization parameter determination means.
  • the entropy includes the transform coefficient quantized by the quantization means, the prediction image generation information used when the prediction image is generated by the difference image generation means, and the difference between the quantization parameters in the coded block and the coded block. Since the bit stream is generated by encoding, there is an effect that the transmission bit amount of information on the quantization parameter can be reduced and the encoding efficiency can be improved.
  • FIG. 1 is a block diagram showing an image coding apparatus according to Embodiment 1 of the present invention.
  • H.264 which is an international standard for image coding systems.
  • An example of an image encoding device applied to H.264 (MPEG-4AVC) is shown, but an image encoding device applied to another image encoding method may be used.
  • the encoding unit 1 under the instruction of the encoding control unit 2, the encoding unit 1 performs encoding processing in units of macroblocks constituting an input image or in units of blocks smaller in size than macroblocks.
  • a macro block and a block smaller in size than the macro block are referred to as an encoded block.
  • the coding control unit 2 determines the variation width of the quantization parameter in advance, and within the range where the difference between the quantization parameter of the coding block and the quantization parameter of the encoded block falls within the variation width, Processing such as determining a quantization parameter is performed.
  • the intra prediction unit 11 of the encoding unit 1 selects an optimal intra prediction mode for each encoding block (macroblock or block into which the macroblock is further divided) constituting the input image, and the intra prediction. Using the local decoded image corresponding to the mode (local decoded image of the block around the encoded block that has already been encoded), an intra prediction process is performed on the encoded block to generate a predicted image Then, a process of generating a difference image between the encoded block and the predicted image is performed.
  • the motion search unit 12 performs a motion search by comparing the encoded block constituting the input image with the locally decoded image stored in the frame memory 23, and performs a process of calculating a motion vector.
  • the motion compensation prediction unit 13 performs a process for generating a predicted image by performing a motion compensation prediction process on the locally decoded image stored in the frame memory 23 using the motion vector calculated by the motion search unit 12. To do.
  • the differentiator 14 performs a process of generating a difference image by obtaining a difference between the encoded block constituting the input image and the predicted image generated by the motion compensated prediction unit 13.
  • the intra prediction unit 11, the motion search unit 12, the motion compensation prediction unit 13, and the differentiator 14 constitute a difference image generation unit.
  • the intra / inter determination unit 15 compares the prediction image generated by the intra prediction unit 11 and the prediction image generated by the motion compensation prediction unit 13 to determine an optimal prediction image, and the optimal prediction image is added to the adder 21. While outputting, the process which outputs the determination result which shows an optimal estimated image to the switch 16 and the entropy encoding part 24 is implemented. If the determination result output from the intra / inter determination unit 15 indicates that the prediction image generated by the intra prediction unit 11 is an optimal prediction image, the switch 16 generates a difference generated by the intra prediction unit 11. If an image is selected and output to the orthogonal transform unit 17 and the prediction image generated by the motion compensation prediction unit 13 indicates that it is an optimal prediction image, the difference image generated by the subtractor 14 is selected. The process of outputting to the orthogonal transform unit 17 is performed.
  • the orthogonal transform unit 17 performs orthogonal transform on the difference image output from the switch 16 and outputs a transform coefficient of the difference image to the quantization unit 18.
  • the quantization unit 18 quantizes the transform coefficient of the difference image output from the orthogonal transform unit 17 in units of orthogonal transform blocks using the quantization parameter output from the quantization control unit 32 of the encoding control unit 2. To implement. Note that the orthogonal transform unit 17 and the quantization unit 18 constitute quantization means.
  • the inverse quantization unit 19 performs a process of inversely quantizing the transform coefficient quantized by the quantization unit 18 and outputting the transform coefficient corresponding to the transform coefficient output from the orthogonal transform unit 17 to the inverse orthogonal transform unit 20.
  • the inverse orthogonal transform unit 20 performs a process of performing inverse orthogonal transform on the transform coefficient output from the inverse quantization unit 19 and outputting a difference image corresponding to the difference image output from the switch 16 to the adder 21.
  • the adder 21 adds the difference image output from the inverse orthogonal transform unit 20 and the prediction image selected by the intra / inter determination unit 15 to generate a local decoded image, and the local decoded image is converted into the intra prediction unit 11 and the demultiplexing unit 11.
  • the process which outputs to the blocking filter part 22 is implemented.
  • the deblocking filter unit 22 performs a deblocking filter process on the local decoded image generated by the adder 21, compensates for distortion due to compression, and stores the local decoded image after distortion compensation in the frame memory 23. To do.
  • the frame memory 23 is a recording medium for storing the locally decoded image after distortion compensation.
  • the entropy encoding unit 24 includes a variation width of the quantization parameter output from the quantization control unit 32 of the encoding control unit 2, a transform coefficient quantized by the quantization unit 18, an encoded block, and an encoded block , Quantization parameter difference, determination result output from the intra / inter determination unit 15, and prediction image generation information used for generating an optimal prediction image (determination result output from the intra / inter determination unit 15) Indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image, the intra prediction mode selected by the intra prediction unit 11 and the prediction image generated by the motion compensation prediction unit 13 are If it indicates that the image is an optimal prediction image, the motion vector calculated by the motion search unit 12 is entropy-encoded to generate a bit pattern.
  • the entropy encoding unit 24 constitutes entropy encoding means.
  • the variation width of the quantization parameter is also entropy-encoded, but the variation width of the quantization parameter may be multiplexed on the header of the bitstream or the like without being entropy-encoded.
  • the transmission buffer 25 is connected to an external transmission means such as a line or a storage medium, for example, and temporarily stores the bit stream generated by the entropy encoding unit 24 and then performs processing to output the bit stream. To do.
  • the quantization parameter variation range determination unit 31 of the encoding control unit 2 performs a process of determining the variation range of the quantization parameter based on, for example, the distribution of frequency components in the input image in units of frames.
  • the fluctuation range of the quantization parameter indicates the limit value of the shift amount that the quantization parameter of the coding block can be changed from the quantization parameter of the previous coded block.
  • a method of determining the fluctuation range for example, when similar frequency components are distributed over the entire frame, the fluctuation range is reduced, and when many different frequency components are scattered, the fluctuation range is increased. The method of doing etc. can be considered.
  • the quantization parameter variation range determination unit 31 determines the variation range of the quantization parameter from the input image. However, information indicating the variation range of the quantization parameter is input from the outside. Thus, the variation range of the quantization parameter may be set.
  • the quantization control unit 32 determines the quantization of the coding block from the buffer amount of the bit stream accumulated in the transmission buffer 25, the target code amount for each coding block, the code amount of the bit stream actually generated, and the like. A process for determining the activation parameter is performed. However, within the range in which the difference between the quantization parameter of the coding block and the quantization parameter of the previous coded block falls within the fluctuation range set by the quantization parameter fluctuation range determination unit 31, The quantization parameter is determined.
  • the quantization parameter variation width determination unit 31 and the quantization control unit 32 constitute a quantization parameter determination unit.
  • an intra prediction unit 11 a motion search unit 12, a motion compensation prediction unit 13, a differentiator 14, an intra / inter determination unit 15, a switch 16, an orthogonal transform unit 17, which are components of the image encoding device,
  • each of the quantization control units 32 is assumed to be configured with dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or a one-chip microcomputer), the image encoding device All or a part may be constituted by a computer.
  • FIG. 2 is a flowchart showing the processing contents (image coding method) of the image coding apparatus according to Embodiment 1 of the present invention.
  • FIG. 3 is a block diagram showing an image decoding apparatus according to Embodiment 1 of the present invention.
  • the reception buffer 51 performs a process of receiving the bit stream generated by the image encoding device in FIG. 1 and outputting the bit stream to the entropy decoding unit 52.
  • the entropy decoding unit 52 entropy-decodes the variation width of the quantization parameter from the bit stream output from the reception buffer 51, and the quantization parameter in the coded block and the previous coded block from the variation width of the quantization parameter. 1 is specified, the difference between the quantization parameters is entropy-decoded from the bit stream, and the transform coefficient quantized by the quantization unit 18 of the image encoding device in FIG.
  • the entropy decoding unit 52 outputs the difference between the quantization parameters of the encoded block and the previous encoded block to the inverse quantization parameter generation unit 53, and reverses the transform coefficient quantized by the quantization unit 18.
  • a process of outputting to the quantization unit 54 and outputting the determination result of the intra / inter determination unit 15 to the switch 58 is performed.
  • the intra prediction mode that is the prediction image generation information is set to intra prediction.
  • the entropy decoding unit 52 constitutes entropy decoding means.
  • the inverse quantization parameter generation unit 53 performs a process of determining the quantization parameter of the coding block from the difference between the quantization parameter in the coding block output from the entropy decoding unit 52 and the previous coded block.
  • the inverse quantization parameter generation unit 53 constitutes a quantization parameter determination unit.
  • the inverse quantization unit 54 uses the quantization parameter determined by the inverse quantization parameter generation unit 53 to inversely quantize the transform coefficient output from the entropy decoding unit 52 in units of orthogonal transform blocks, thereby performing the image coding in FIG.
  • a process of outputting a transform coefficient corresponding to the transform coefficient output from the orthogonal transform unit 17 in the apparatus to the inverse orthogonal transform unit 55 is performed.
  • the inverse orthogonal transform unit 55 performs inverse orthogonal transform on the transform coefficient output from the inverse quantization unit 54 and outputs a difference image corresponding to the difference image output from the switch 16 in the image encoding device of FIG. Perform the process.
  • the inverse quantization unit 54 and the inverse orthogonal transform unit 55 constitute an inverse quantization unit.
  • the intra predicted image generation unit 56 When the intra prediction mode is output from the entropy decoding unit 52, the intra predicted image generation unit 56 generates a decoded image generated by the adder 59 corresponding to the intra prediction mode (peripheral of a coded block that has already been decoded). Using the decoded image of the block), a process for generating a predicted image is performed by performing an intra prediction process on the encoded block.
  • the inter predicted image generation unit 57 performs motion compensation prediction processing on the decoded image stored in the frame memory 61 using the motion vector, so that FIG. The process which produces
  • the switch 58 If the determination result of the intra / inter determination unit 15 output from the entropy decoding unit 52 indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image, the switch 58 generates an intra prediction image.
  • the prediction image generated by the unit 56 is output to the adder 59, and the determination result of the intra / inter determination unit 15 indicates that the prediction image generated by the motion compensation prediction unit 13 is the optimal prediction image.
  • generation part 57 to the adder 59 is implemented.
  • the intra predicted image generation unit 56, the inter predicted image generation unit 57, and the switch 58 constitute a predicted image generation unit.
  • the adder 59 adds the predicted image output from the switch 58 and the difference image output from the inverse orthogonal transform unit 55 to generate a decoded image, and the decoded image is used as the intra predicted image generation unit 56 and the deblocking filter unit 60. Execute the process to output to.
  • the adder 59 constitutes a decoded image generating means.
  • the deblocking filter unit 60 performs a deblocking filter process on the decoded image generated by the adder 59 to compensate for distortion due to compression, and stores the decoded image after distortion compensation in the frame memory 61.
  • the frame memory 61 is a recording medium for storing the decoded image after distortion compensation.
  • the switch 62 selects the decoded image after distortion compensation by the deblocking filter unit 60 or the decoded image stored in the frame memory 61 in the display order, and performs the process of outputting the selected decoded image.
  • Each of the inter prediction image generation unit 57, the switch 58, the adder 59, the deblocking filter unit 60, the frame memory 61, and the switch 62 has dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or one chip However, all or part of the image decoding apparatus may be configured by a computer.
  • FIG. 4 is a flowchart showing the processing contents (image decoding method) of the image decoding apparatus according to Embodiment 1 of the present invention.
  • the intra prediction unit 11 of the encoding unit 1 selects an optimal intra prediction mode for each encoding block (macroblock or block obtained by further dividing the macroblock) constituting the input image, and the intra prediction mode is selected.
  • the prediction image is generated by performing the intra prediction process on the encoded block. (Step ST1 in FIG. 2).
  • a technique for generating a predicted image by selecting an optimal intra prediction mode is a known technique, a detailed description thereof is omitted (see, for example, H.264).
  • the intra prediction unit 11 When generating the prediction image, the intra prediction unit 11 generates a difference image between the encoded block constituting the input image and the prediction image, and outputs the difference image to the switch 16 (step ST2). Note that the intra prediction unit 11 needs to generate the same predicted image even in the image decoding apparatus, so that the intra prediction mode is transmitted to the entropy encoding unit 24 as the predicted image generation information used for generating the predicted image. Output.
  • the motion search unit 12 calculates a motion vector by performing a motion search by comparing the encoded block constituting the input image with the locally decoded image stored in the frame memory 23. Since the motion vector calculation process is also a known technique, a detailed description thereof will be omitted (see, for example, H.264). Since the motion search unit 12 needs to generate the same predicted image even in the image decoding apparatus, the motion vector is output to the entropy encoding unit 24 as predicted image generation information used for generating the predicted image. To do.
  • the motion compensation prediction unit 13 When the motion search unit 12 calculates a motion vector, the motion compensation prediction unit 13 performs a motion compensation prediction process on the locally decoded image stored in the frame memory 23 using the motion vector, thereby obtaining a predicted image. Generate (step ST3). Since the motion compensation prediction process is also a known technique, a detailed description thereof is omitted (for example, see H.264).
  • the difference unit 14 When the motion compensation prediction unit 13 generates a prediction image, the difference unit 14 generates a difference image by obtaining a difference between the encoded block constituting the input image and the prediction image, and sends the difference image to the switch 16. Output (step ST4).
  • the intra / inter determination unit 15 compares the two prediction images to determine an optimal prediction image (step ST5).
  • a generally widely used method for determining the optimum predicted image is to calculate the difference absolute value or the square difference value of the pixel at the same pixel position of the encoded block constituting the input image and the predicted image as a block. The calculated value is used as the evaluation value. In this case, the smaller evaluation value is selected.
  • the intra / inter determination unit 15 determines an optimal predicted image
  • the intra / inter determination unit 15 outputs the predicted image to the adder 21.
  • the determination result indicating the optimum predicted image is output to the switch 16 and the entropy encoding unit 24.
  • the switch 16 determines that the intra prediction unit 11 Is selected and output to the orthogonal transform unit 17 (step ST6).
  • the determination result indicates that the prediction image generated by the motion compensation prediction unit 13 is an optimal prediction image (step ST5)
  • the difference image generated by the differentiator 14 is selected and orthogonally transformed. It outputs to the part 17 (step ST7).
  • the orthogonal transform unit 17 Upon receiving the difference image from the switch 16, the orthogonal transform unit 17 performs orthogonal transform on the difference image in units of orthogonal transform blocks (4 ⁇ 4 blocks or 8 ⁇ 8 blocks), and transform coefficients of the difference image Is output to the quantization unit 18 (step ST8).
  • the quantization parameter variation range determination unit 31 of the encoding control unit 2 examines the distribution of frequency components in the input image for each frame, and determines the variation range of the quantization parameter according to the distribution of the frequency components (step). ST9).
  • the fluctuation range for example, when similar frequency components are distributed over the entire frame, the fluctuation range is reduced, and when many different frequency components are scattered, the fluctuation range is increased. Possible ways to do this. Note that if the distribution of the frequency component of the frame cannot be obtained before encoding the encoded frame, the fluctuation range obtained one frame before is used.
  • the quantization parameter fluctuation width determination unit 31 determines the fluctuation width of the quantization parameter according to the distribution of the frequency components, but the method of determining the fluctuation width is not limited to this, For example, there is a method of specifying the maximum fluctuation range when the quantization parameter is determined without limiting the quantization parameter fluctuation range, and determining the maximum fluctuation range as the quantization parameter fluctuation range. It is done.
  • the quantization control unit 32 of the encoding control unit 2 includes the buffer amount of the bit stream accumulated by the transmission buffer 25, the target code amount for each encoding block, the code amount of the bit stream actually generated, etc. From this, the quantization parameter QP of the coding block is determined.
  • TM5 used in the MPEG-2 verification test (for example, the Journal of the Television Society, April 1995, Vol 49, No. 4). See).
  • the quantization control unit 32 determines the quantization parameter QP of the coding block
  • the difference dQP (Delta QP) between the quantization parameter QP and the quantization parameter of the previous coded block is changed in the quantization parameter. It is determined whether or not the variation range determined by the width determination unit 31 is within the variation range, and if not, the quantization parameter QP is limited so as to be within the variation range (step ST10). For example, when the quantization parameter QP is “N”, the quantization parameter of the previous coded block is “N + 3”, and the difference dQP is “3”, the quantization parameter variation width determination unit 31 determines the quantization parameter QP.
  • the quantization parameter QP is changed to “N + 1” so as to be within the fluctuation range.
  • the quantization control unit 32 outputs the quantization parameter QP (quantization parameter in which the difference is within the fluctuation range) of the coding block to the quantization unit 18 and the entropy coding unit 24. Further, the fluctuation range determined by the quantization parameter fluctuation range determination unit 31 is output to the entropy encoding unit 24.
  • the quantization unit 18 When the quantization unit 18 receives the transform coefficient of the difference image from the orthogonal transform unit 17, the quantization unit 18 quantizes the transform coefficient of the difference image in units of orthogonal transform blocks using the quantization parameter QP output from the quantization control unit 32. (Step ST11).
  • the quantization unit 18 quantizes the transform coefficient of the difference image
  • the inverse quantization unit 19 inversely quantizes the transform coefficient so that the transform coefficient corresponding to the transform coefficient output from the orthogonal transform unit 17 is inverted.
  • Output to the orthogonal transform unit 20 When the inverse orthogonal transform unit 20 receives the transform coefficient from the inverse quantization unit 19, the inverse orthogonal transform is performed on the transform coefficient to output a difference image corresponding to the difference image output from the switch 16 to the adder 21. .
  • the adder 21 adds the difference image output from the inverse orthogonal transform unit 20 and the predicted image selected by the intra / inter determination unit 15 to generate a local decoded image.
  • the adder 21 outputs the local decoded image to the intra prediction unit 11 in preparation for the next intra prediction process. Further, the local decoded image is output to the deblocking filter unit 22.
  • the deblocking filter unit 22 performs a deblocking filter process on the locally decoded image to compensate for distortion due to compression, and the distortion-compensated local decoded image is stored in the frame memory 23. To store.
  • the entropy encoding unit 24 entropy encodes the following information to generate a bit stream (step ST12).
  • the transform coefficient quantized by the quantization unit 18 The determination result of the intra / inter determination unit 15
  • the prediction image generation information used for generating the optimal prediction image (the determination output from the intra / inter determination unit 15 If the result indicates that the prediction image generated by the intra prediction unit 11 is an optimal prediction image, the intra prediction mode selected by the intra prediction unit 11 and the prediction image generated by the motion compensation prediction unit 13 Is a motion vector calculated by the motion search unit 12)
  • a difference dQP between quantization parameters of the coded block and the previous coded block -Variation width of quantization parameter (the quantization parameter variation width is transmitted for each picture or slice, so entropy coding is performed only at the timing of transmitting the picture header or slice header)
  • the variation width of the quantization parameter is also entropy-encoded, but the quantization parameter variation width is transmitted for each picture or slice, and the quantization parameter variation width is transmitted. Since the amount of bits required for each frame is very small per frame, it may be multiplexed in the picture header or slice header without entropy coding, or by a Golomb code which is a general variable length code. You may make it multiplex by entropy encoding.
  • the quantization parameter difference dQP between the coded block and the previous coded block is transmitted as it is without entropy coding.
  • the range that the quantization parameter QP can take is 0 to 51
  • the range that the difference dQP can take is ⁇ 51 to +51.
  • the bit length necessary for transmitting this differential dQP is 7 bits.
  • the bit length necessary for transmitting the differential dQP is 7 bits.
  • the bit length necessary for transmitting the differential dQP is 7 bits.
  • the bit length necessary for transmitting the differential dQP is 3 bits. Since the reduction of the bit amount is applied to each coding block, the reduction amount per frame is very large. As shown in FIG. 6, even when entropy coding the difference dQP of the quantization parameter, if a variation width of the quantization parameter is transmitted, a short codeword can be assigned to the same difference dQP. Can be reduced.
  • the transmission buffer 25 temporarily holds the bit stream, and then transmits the bit stream to the image decoding device via an external transmission unit such as a line. Send.
  • the variation width of the quantization parameter is set in advance, and the difference between the quantization parameters of the coded block and the previous coded block is the variation width.
  • An orthogonal transform that orthogonally transforms the difference image generated by the intra prediction unit 11 or the difference image output from the differentiator 14 within a range that falls within the range of Unit 17 and a quantization unit 18 that quantizes transform coefficients of the difference image output from the orthogonal transform unit 17 using the quantization parameter determined by the encoding control unit 2, and an entropy encoding unit 24 Is the variation width of the quantization parameter set by the encoding control unit 2, the transform coefficient quantized by the quantization unit 18, the intra prediction unit 11 or the motion compensation prediction unit 1 Since the bit stream is generated by entropy encoding the prediction image generation information used when the prediction image is generated and the difference dQP of the quantization parameter between the encoded block and the encoded block. There is an effect that it is possible to reduce the transmission bit amount of the information related
  • the reception buffer 51 receives the bit stream transmitted from the image encoding device in FIG. 1 and outputs the bit stream to the entropy decoding unit 52.
  • the entropy decoding unit 52 performs entropy decoding on the bit stream (step ST21 in FIG. 4).
  • the entropy decoding unit 52 When entropy decoding is performed on the bit stream, the entropy decoding unit 52 entropy decodes the fluctuation range of the quantization parameter from the decoded data of the bit stream. However, since the fluctuation range of the quantization parameter is transmitted in units of pictures or slices as described above, entropy decoding is performed in units of pictures or slices.
  • the entropy decoding unit 52 specifies the bit length of the difference dQP of the quantization parameter between the coded block and the previous coded block from the variation width. For example, when the range of the difference dQP is limited to ⁇ 5 to +5, the bit length of the difference dQP is 4 bits, and when the range of the difference dQP is limited to ⁇ 2 to +2, the bit length of the difference dQP Is 3 bits.
  • the entropy decoding unit 52 entropy decodes the quantization parameter difference dQP included in the decoded data of the bitstream (step ST22).
  • the entropy decoding unit 52 also includes the transform coefficient quantized by the quantization unit 18 of the image encoding device in FIG. 1 included in the decoded data of the bitstream, the determination result of the intra / inter determination unit 15, and the predicted image Entropy decodes the generation information.
  • the entropy decoding unit 52 outputs the quantization parameter difference dQP to the inverse quantization parameter generation unit 53, and outputs the transform coefficient quantized by the quantization unit 18 to the inverse quantization unit 54.
  • the determination result of the / inter determination unit 15 is output to the switch 58.
  • the intra prediction mode that is the prediction image generation information is set to intra prediction. If it is output to the image generation unit 56 and the determination result of the intra / inter determination unit 15 indicates that the prediction image generated by the motion compensation prediction unit 13 is an optimal prediction image, the prediction image generation information is used.
  • a certain motion vector is output to the inter prediction image generation unit 57.
  • the inverse quantization parameter generation unit 53 receives the quantization parameter difference dQP and the previous quantization parameter difference dQP.
  • the quantization parameter QP of the coding block is determined by adding the quantization parameter in the coded block (this quantization parameter is stored in the inverse quantization parameter generation unit 53), and the coding block
  • the quantization parameter QP is output to the inverse quantization unit 54 (step ST23).
  • the inverse quantization unit 54 uses the quantization parameter QP to convert the transform coefficient output from the entropy decoding unit 52 into an orthogonal transform block.
  • transform coefficients corresponding to transform coefficients output from the orthogonal transform unit 17 in the image coding apparatus in FIG. 1 are output to the inverse orthogonal transform unit 55 (step ST24).
  • the inverse orthogonal transform unit 55 When receiving the transform coefficient from the inverse quantization unit 54, the inverse orthogonal transform unit 55 performs inverse orthogonal transform on the transform coefficient to thereby obtain a difference corresponding to the difference image output from the switch 16 in the image encoding device in FIG. The image is output to the adder 59 (step ST25).
  • the intra predicted image generation unit 56 When receiving the intra prediction mode as the prediction image generation information from the entropy decoding unit 52, the intra predicted image generation unit 56 receives the decoded image generated by the adder 59 corresponding to the intra prediction mode (decoding has already been completed). By performing the intra prediction process using the decoded image of the block around the encoding block), a prediction image corresponding to the prediction image generated by the intra prediction unit 11 in the image encoding device in FIG. 1 is generated. (Step ST26).
  • the inter predicted image generation unit 57 uses the motion vector to perform motion compensation prediction processing on the decoded image stored in the frame memory 61.
  • a predicted image corresponding to the predicted image generated by the motion compensated prediction unit 13 in the image encoding device of FIG. 1 is generated (step ST27).
  • the switch 58 (step ST28).
  • the prediction image generated by the intra prediction image generation unit 56 is output to the adder 59 (step ST29), and the determination result of the intra / inter determination unit 15 indicates that the prediction image generated by the motion compensation prediction unit 13 is optimal. If it shows that it is a prediction image (step ST28), the prediction image produced
  • the adder 59 adds the predicted image output from the switch 58 and the difference image output from the inverse orthogonal transform unit 55 to generate a decoded image, and uses the decoded image as the intra predicted image generation unit 56 and the deblocking unit. It outputs to the filter part 60 (step ST31).
  • the deblocking filter unit 60 performs a deblocking filter process on the decoded image, compensates for distortion due to compression, and stores the decoded image after distortion compensation in the frame memory 61.
  • the switch 62 selects the decoded image generated by the adder 59 or the decoded image stored in the frame memory 61 in the display order, and outputs the selected decoded image.
  • the variation width of the quantization parameter is entropy-decoded from the bitstream, and the quantization parameter in the encoded block and the encoded block is determined from the variation width of the quantization parameter.
  • the difference dQP bit length is specified, the difference dQP of the quantization parameter is entropy decoded from the bitstream, and the quantized transform coefficient and the prediction image used when the prediction image is generated from the bitstream
  • An entropy decoding unit 52 that entropy-decodes the generation information
  • an inverse quantization parameter generation unit 53 that determines a quantization parameter QP of the coding block from the quantization parameter difference dQP entropy-decoded by the entropy decoding unit 52, Determined by the quantization parameter generation unit 53
  • the inverse quantization unit 54 that inversely quantizes the transform coefficient entropy-decoded by the entropy decoding unit 52 and the inverse orthogonal transform of the
  • the quantization control unit 32 of the coding control unit 2 performs the coding block within the range in which the quantization parameter difference dQP falls within the variation range set by the quantization parameter variation range determination unit 31.
  • the quantization parameter QP is determined, but when the quantization parameter fluctuation range is not set by the quantization parameter fluctuation width determination unit 31, the coding block is set so that the quantization parameter difference dQP falls within the fluctuation width. The process of limiting the quantization parameter QP is not performed.
  • the entropy encoding unit 24 includes information indicating that the quantization parameter fluctuation range is not set in the bitstream. .
  • the entropy decoding unit 52 of the image decoding device when information indicating that the variation width of the quantization parameter is not set is included in the bitstream, the difference dQP between the quantization parameters of the encoded block and the encoded block Is recognized as a fixed bit length (for example, 7 bits), and the difference dQP of the quantization parameter is entropy-decoded from the bit stream. Accordingly, the present invention can also be applied to the case where there is no restriction on the fluctuation range of the quantization parameter difference.
  • the quantization parameter is determined from the quantization parameter of the previous or neighboring coding block or the quantization parameter of the neighboring coding block Any coding scheme that transmits a difference from the quantization parameter obtained by the calculation method can be applied.
  • the quantization control unit 32 of the coding control unit 2 performs the coding block within the range in which the quantization parameter difference dQP falls within the variation range set by the quantization parameter variation range determination unit 31.
  • the quantization parameter variation range determination unit 31 sets the maximum value MaxQP and the minimum value MinQP of the quantization parameter.
  • the quantization control unit 32 may determine the quantization parameter QP of the coding block that falls within the range of the maximum value MaxQP and the minimum value MinQP.
  • the entropy encoding unit 24 multiplexes and transmits the maximum value MaxQP and the minimum value MinQP in a header in units of pictures or slices (the maximum value MaxQP and the minimum value MinQP may be entropy-encoded, or the entropy code
  • the amount of bits required to transmit the maximum value MaxQP and the minimum value MinQP is very small per frame.
  • the quantization parameter initial value SliceQP which is the initial value of the quantization parameter in the slice
  • the maximum value MaxQP and the quantization parameter initial value SliceQP are The difference MaxQP-SliceQP is multiplexed as the maximum differential quantization value dMaxQP
  • the difference between the quantization parameter initial value SliceQP and the minimum value MinQP is multiplexed as the differential minimum quantization value dMinQP.
  • the maximum differential quantization value dMax and the minimum differential quantization value dMinQP may be entropy-encoded so that shorter codewords are assigned in ascending order of absolute values.
  • the entropy coding unit 24 entropy codes the quantization parameter difference dQP to generate a bitstream.
  • the quantization parameter of the previous coding block is PreQP
  • the minimum value of the difference dQP is MinQP-PreQP
  • the maximum of the difference dQP is The value is MaxQP-PreQP.
  • the maximum value MaxQP-PreQP of the difference dQP is “+1”, which is shown in FIG.
  • a short codeword can be assigned to the same difference dQP.
  • the difference dQP is “ ⁇ 4”
  • the code word of the difference dQP becomes 7 bits, but the maximum value MaxQP and the minimum value MinQP are set. Then, the code word of the difference dQP becomes 5 bits, and the bit amount is reduced by 2 bits.
  • the entropy decoding unit 52 of the image decoding device When entropy decoding the bitstream, the entropy decoding unit 52 of the image decoding device entropy decodes the maximum value MaxQP and the minimum value MinQP of the quantization parameter included in the decoded data of the bitstream. However, since the maximum value MaxQP and the minimum value MinQP of the quantization parameter are transmitted in units of pictures or slices as described above, they are multiplexed in the picture header or slice header, and the maximum value MaxQP in units of pictures or slices. The minimum value MinQP is entropy decoded.
  • the quantization parameter initial value SliceQP that is an initial value of the quantization parameter in the slice is multiplexed, and the maximum value MaxQP and the quantum value are quantized.
  • MaxQP-SliceQP which is a difference from the quantization parameter initial value SliceQP, is multiplexed as the differential maximum quantization value dMaxQP, and the difference QP between the quantization parameter initial value SliceQP and the minimum value MinQP is changed to the differential minimum quantization value.
  • the entropy decoding unit 52 When multiplexed as dMinQP and entropy-encoded so that a short codeword is assigned to the differential maximum quantized value dMax and differential minimum quantized value dMinQP in ascending order of absolute values, the entropy decoding unit 52 amount Entropy decoding the quantization parameter initial value SliceQP, the differential maximum quantization value dMax, and the differential minimum quantization value dMinQP, and decoding the maximum value MaxQP by adding the quantization parameter initial value SliceQP and the differential maximum quantization value dMax, The minimum value MinQP can be decoded by subtracting the minimum differential quantization value dMin from the quantization parameter initial value SliceQP.
  • the entropy decoding unit 52 When the entropy decoding unit 52 entropy-decodes the maximum value MaxQP and the minimum value MinQP of the quantization parameter, the difference dQP of the quantization parameter between the encoded block and the previous encoded block from the maximum value MaxQP and the minimum value MinQP. Specifies the bit length of.
  • the entropy decoding unit 52 specifies the bit length of the quantization parameter difference dQP
  • the entropy decoding unit 52 entropy decodes the quantization parameter difference dQP included in the decoded data of the bitstream. In this way, even by limiting the value of the quantization parameter QP itself, the encoding efficiency of the quantization parameter difference dQP can be improved as in the case of limiting the fluctuation range of the quantization parameter difference dQP. .
  • the quantization parameter fluctuation range determination unit 31 sets the maximum value MaxQP and the minimum value MinQP of the quantization parameter.
  • the quantization parameter fluctuation range determination unit 31 uses the quantization parameter.
  • the quantization parameter maximum value MaxQP and the minimum value MinQP are set, and the quantization control unit 32 is within a range where the quantization parameter difference dQP is within the above-described variation range, and the maximum value is set. You may make it determine the quantization parameter QP of the encoding block which fits in the range of MaxQP and minimum value MinQP.
  • the entropy encoding unit 24 multiplexes the quantization parameter variation range, the maximum value MaxQP, and the minimum value MinQP set by the quantization parameter variation range determination unit 31 in a picture or slice unit, and transmits the multiplexed value (header).
  • the fluctuation range, the maximum value MaxQP, and the minimum value MinQP may be entropy encoded or may not be entropy encoded).
  • the encoding efficiency of the quantization parameter difference dQP can be further improved.
  • the fluctuation range of the difference dQP is “ ⁇ 2” and the quantization parameter PreQP of the previous macroblock is smaller by 1 than the maximum quantization parameter value MaxQP, the absolute value of the difference dQP If a variable-length code is designed so that a short codeword is assigned in ascending order of the value, the difference dQP can be encoded with a smaller amount of bits.
  • Embodiment 3 a case will be described in which a coding block for performing intra coding and a coding block for performing inter coding coexist. Also in the third embodiment, it is assumed that the quantization parameter can be changed for each coding block. As described above, the macroblock is divided into four, and the block divided into four is further divided into four to generate an encoded block. Whether to divide the macroblock into four or not, it is arbitrary how far each of the four divided blocks is divided into four. The lowest layer block that is not divided into four is defined as an encoded block.
  • FIG. 9 is a block diagram showing an image coding apparatus according to Embodiment 3 of the present invention.
  • the intra / inter determination unit 41 compares the prediction image generated by the intra prediction unit 11 and the prediction image generated by the motion compensated prediction unit 13 to obtain an optimal prediction image. Is performed, and an optimal prediction image is output to the adder 21 and a determination result indicating the optimal prediction image is output to the switch 16, the quantization control unit 42, and the entropy encoding unit 43.
  • the quantization control unit 42 determines the quantization of the coding block from the buffer amount of the bit stream accumulated in the transmission buffer 25, the target code amount for each coding block, the code amount of the bit stream actually generated, and the like. If the quantization parameter QP is determined and the determination result output from the intra / inter determination unit 41 indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image, the quantization parameter QP is set.
  • the transition value QP_offset for the quantization parameter conversion (the transition value QP_offset is adaptive according to, for example, a fixed value determined in advance according to the encoding rate or the buffer amount of the transmission buffer 25). It is a variable value to be changed and is transmitted to the image decoding device in units of pictures or slices) Process to implement that.
  • the quantization control unit 42 adds a transition value.
  • the quantization parameter QP of the coding block that has not been output is output to the quantization unit 18 as the quantization parameter QP_inter for inter, and the determination result output from the intra / inter determination unit 41 is generated by the intra prediction unit 11 If it indicates that the predicted image is an optimal predicted image, the quantization parameter of the coding block after the addition of the transition value is output to the quantization unit 18 as an intra quantization parameter QP_intra.
  • the quantization control unit 42 outputs the quantization parameter conversion transition value QP_offset and the quantization parameter QP of the coding block to which the transition value is not added to the entropy coding unit 43.
  • the quantization control unit 42 constitutes a quantization parameter determining unit.
  • the determination result output from the intra / inter determination unit 15 and the prediction image generation information used for generating the optimal prediction image are displayed by the intra prediction unit 11. If the generated predicted image indicates that it is the optimal predicted image, the intra selected by the intra prediction unit 11 is selected.
  • the bitstream is generated by entropy encoding the motion vector calculated by the motion search unit 12). Perform the process.
  • the transition value QP_offset for quantization parameter conversion is also entropy encoded, but the transition value QP_offset for quantization parameter conversion may be multiplexed on the header of the bitstream without being entropy encoded.
  • the difference dQP between the quantization parameter QP of the coding block and the quantization parameter of the coded block is entropy coded, but the quantization parameter QP of the coding block is entropy coded. Also good.
  • the entropy encoding unit 43 constitutes entropy encoding means.
  • Each of the quantization unit 18, the inverse quantization unit 19, the inverse orthogonal transform unit 20, the adder 21, the deblocking filter unit 22, the frame memory 23, the entropy encoding unit 43, the transmission buffer 25, and the quantization control unit 42 is dedicated.
  • the hardware is configured by a hardware integrated circuit (for example, a semiconductor integrated circuit on which a CPU is mounted or a one-chip microcomputer). It may be.
  • an intra prediction unit 11 When all or part of the image coding apparatus is configured by a computer, an intra prediction unit 11, a motion search unit 12, a motion compensation prediction unit 13, a difference unit 14, an intra / inter determination unit 41, a switch 16, an orthogonal transform 17, quantization unit 18, inverse quantization unit 19, inverse orthogonal transform unit 20, adder 21, deblocking filter unit 22, frame memory 23, entropy encoding unit 43, transmission buffer 25, and quantization control unit 42.
  • a program describing all or part of the processing contents may be stored in the memory of a computer, and the CPU of the computer may execute the program stored in the memory.
  • the entropy decoding unit 71 includes a quantization parameter conversion transition value QP_offset included in the decoded data of the bitstream output from the reception buffer 51, the quantization parameter of the encoding block, and the quantization parameter of the encoded block. Difference dQP (including a flag indicating whether the encoded block is the left block or the upper block of the encoded block), the transform coefficient quantized by the quantizing unit 18, and the determination of the intra / inter determining unit 41 The result and the information for generating a predicted image are entropy decoded.
  • the entropy decoding unit 71 outputs the transition value QP_offset for the quantization parameter conversion, the difference between the quantization parameters, and the determination result of the intra / inter determination unit 15 to the inverse quantization parameter generation unit 72, and the quantization unit 18 performs the quantization.
  • the converted transform coefficient is output to the inverse quantization unit 54, and the determination result of the intra / inter determination unit 41 is output to the switch 58.
  • the intra prediction mode that is the prediction image generation information is set to intra prediction.
  • the entropy decoding unit 71 constitutes entropy decoding means.
  • the inverse quantization parameter generation unit 72 outputs the quantization parameter difference dQP output from the entropy decoding unit 71 and the quantization parameter in the previous encoded block (the quantization parameter is the inverse quantization parameter generation unit 72). Is stored) to determine the quantization parameter QP of the coding block.
  • the inverse quantization parameter generation unit 72 indicates that the determination result of the intra / inter determination unit 41 output from the entropy decoding unit 71 indicates that the prediction image generated by the motion compensation prediction unit 13 is the optimal prediction image.
  • the quantization parameter QP of the coding block is output to the inverse quantization unit 54 as the quantization parameter QP_inter for inter, and the determination result of the intra / inter determination unit 41 is the prediction generated by the intra prediction unit 11
  • the image indicates that it is an optimal predicted image
  • the quantization parameter conversion transition value QP_offset output from the entropy decoding unit 71 is added to the quantization parameter QP of the coding block, and the transition value addition is performed.
  • the inverse quantization unit 54 uses the subsequent quantization parameter as an intra quantization parameter QP_intra. And it carries out a process of outputting.
  • the inverse quantization parameter generation unit 72 constitutes a quantization parameter determination unit.
  • a reception buffer 51 an entropy decoding unit 71, an inverse quantization parameter generation unit 72, an inverse quantization unit 54, an inverse orthogonal transform unit 55, an intra-prediction image generation unit 56, which are components of the image decoding device,
  • Each of the inter prediction image generation unit 57, the switch 58, the adder 59, the deblocking filter unit 60, the frame memory 61, and the switch 62 has dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or one chip However, all or part of the image decoding apparatus may be configured by a computer.
  • an entropy decoding unit 71 When all or part of the image decoding apparatus is configured by a computer, an entropy decoding unit 71, an inverse quantization parameter generation unit 72, an inverse quantization unit 54, an inverse orthogonal transform unit 55, an intra predicted image generation unit 56, an inter prediction image generation unit 56,
  • a program describing all or part of the processing contents of the predicted image generation unit 57, the switch 58, the adder 59, the deblocking filter unit 60, and the switch 62 is stored in the memory of the computer, and the CPU of the computer stores the memory
  • the program stored in the program may be executed.
  • FIG. 11 is an explanatory diagram showing an example in which encoding is performed using an encoded block in a macroblock as an intra block.
  • the coding block that is shaded is a block (intra block) that performs intra coding.
  • a white coded block not shaded is a block (inter block) for performing inter coding.
  • the intra / inter determination unit 41 predicts the prediction image generated by the intra prediction unit 11 (prediction image of the intra block) and the prediction generated by the motion compensation prediction unit 13.
  • the image (inter-block prediction image) is compared to determine an optimal prediction image, and the optimal prediction image is output to the adder 21.
  • the intra / inter determination unit 41 displays a determination result indicating whether the optimal prediction image is an intra-block prediction image or an inter-block prediction image by using the switch 16, the quantization control unit 42, and the entropy encoding unit. Output to 43.
  • the quantization control unit 42 actually generates the buffer amount of the bit stream accumulated in the transmission buffer 25, the target code amount for each coding block, and the like.
  • the quantization parameter QP of the coding block is determined from the code amount of the bit stream and the like, and the quantization parameter QP is output to the entropy coding unit 43. Further, when the quantization control unit 42 receives the determination result from the intra / inter determination unit 41, the determination result indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image.
  • the quantization parameter conversion transition value QP_offset is added to the quantization parameter QP of the coding block, and the quantization parameter after the transition value addition is quantized for intra.
  • the parameter QP_intra is output to the quantization unit 18.
  • QP_intra QP + QP_offset (1)
  • the prescribed value is output to the quantization unit 18 as the intra quantization parameter QP_intra.
  • the quantization control unit 42 does not add the transition value.
  • the quantization parameter QP of the coding block is output to the quantization unit 18 as an inter quantization parameter QP_inter.
  • QP_inter QP (2)
  • the quantization unit 18 uses the intra quantization parameter QP_intra output from the quantization control unit 42 to output the orthogonal transform unit 17.
  • the output transform coefficient of the difference image is quantized in units of orthogonal transform blocks, and the quantized transform coefficient is output to the entropy encoding unit 43.
  • the prediction image generated by the motion compensation prediction unit 13 is an optimal prediction image, it is output from the orthogonal transform unit 17 using the inter quantization parameter QP_inter output from the quantization control unit 42.
  • the transform coefficient of the difference image is quantized in units of orthogonal transform blocks, and the quantized transform coefficient is output to the entropy encoding unit 43.
  • the entropy encoding unit 43 includes a transition value QP_offset for converting the quantization parameter output from the quantization control unit 42 of the encoding control unit 2, the transform coefficient quantized by the quantization unit 18, and the quantization control unit.
  • the difference dQP between the quantization parameter of the coding block output from 42 and the quantization parameter of the coded block and the quantization parameter of the coded block (whether the coded block is the left block of the coded block or the upper block Including a flag indicating whether or not there is), a determination result output from the intra / inter determination unit 41, and prediction image generation information used for generating an optimal prediction image (output from the intra / inter determination unit 41) If the determination result indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image, intra prediction If the intra prediction mode selected by 11 and the prediction image generated by the motion compensation prediction unit 13 indicate that the prediction image is an optimal prediction image, the motion vector calculated by the motion search unit 12) is entropy-encoded.
  • the quantization parameter conversion transition value QP_offset Since the quantization parameter conversion transition value QP_offset is transmitted for each picture or slice, it is entropy-encoded only at the timing of transmitting the picture header or slice header.
  • the transition value QP_offset for quantization parameter conversion is also entropy-encoded.
  • the difference dQP between the quantization parameter of the coding block and the quantization parameter of the coded block is entropy coded, but the quantization parameter QP of the coding block may be entropy coded. Good.
  • the entropy decoding unit 71 performs entropy decoding on the quantization parameter conversion transition value QP_offset included in the decoded data of the bit stream.
  • the transition value QP_offset for quantization parameter conversion is transmitted in units of pictures or slices as described above, it is multiplexed in the picture header or slice header, and entropy-decoded in units of pictures or slices.
  • the entropy decoding unit 71 includes a difference dQP of quantization parameters included in the decoded data of the bitstream (including a flag indicating whether the encoded block is the left block or the upper block of the encoded block), The transform coefficient quantized by the quantization unit 18, the determination result of the intra / inter determination unit 41, and the prediction image generation information are entropy decoded.
  • the entropy decoding unit 71 outputs the quantization parameter difference dQP and the quantization parameter conversion transition value QP_offset to the inverse quantization parameter generation unit 72 (the transition value QP_offset is transmitted in units of pictures or slices).
  • the transform coefficient quantized by the quantizing unit 18 is output to the dequantizing unit 54 and the determination result of the intra / inter determining unit 41 is output to the inverse quantization parameter generating unit 72 in units of pictures or slices. Is output to the switch 58 and the inverse quantization parameter generation unit 72.
  • the intra prediction mode that is the prediction image generation information is set to intra prediction. If it is output to the image generation unit 56 and the determination result of the intra / inter determination unit 41 indicates that the prediction image generated by the motion compensation prediction unit 13 is an optimal prediction image, the prediction image generation information is used. A certain motion vector is output to the inter prediction image generation unit 57.
  • the inverse quantization parameter generation unit 72 Upon receiving the quantization parameter difference dQP from the entropy decoding unit 71, the inverse quantization parameter generation unit 72 receives the quantization parameter difference dQP and the quantization parameter in the previous coded block (this quantization parameter). Is stored in the inverse quantization parameter generation unit 72) to determine the quantization parameter QP of the coding block. When receiving the quantization parameter QP of the coding block from the entropy decoding unit 71, the process of determining the quantization parameter QP is not performed.
  • the inverse quantization parameter generation unit 72 receives the determination result of the intra / inter determination unit 41 from the entropy decoding unit 71, the determination result indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image.
  • the quantization parameter conversion transition value QP_offset is added to the quantization parameter QP of the coding block, as in the quantization control unit 42 of FIG. 9 (see the above equation (1)).
  • the quantization parameter after the addition of the transition value is output to the inverse quantization unit 54 as an intra quantization parameter QP_intra.
  • the intra quantization parameter QP_intra exceeds the specified value determined by the standard, the specified value is output to the inverse quantization unit 54 as the intra quantization parameter QP_intra.
  • the inverse quantization parameter generation unit 72 performs the quantization of FIG. Similar to the control unit 42, the quantization parameter QP of the coding block to which the transition value is not added is output to the inverse quantization unit 54 as an inter quantization parameter QP_inter.
  • the inverse quantization unit 54 uses the intra quantization parameter QP_intra output from the inverse quantization parameter generation unit 72 to perform entropy decoding.
  • the inverse transform unit 55 converts the transform coefficient corresponding to the transform coefficient output from the orthogonal transform unit 17 in the image encoding device of FIG. 9 by inversely quantizing the transform coefficient output from the unit 71 in units of orthogonal transform blocks. Output to.
  • the predicted image generated by the motion compensated prediction unit 13 is an optimal predicted image, it is output from the entropy decoding unit 71 using the inter quantization parameter QP_inter output from the inverse quantization parameter generation unit 72.
  • the inverse transform is performed on the transform coefficients in units of orthogonal transform blocks, so that transform coefficients corresponding to the transform coefficients output from the orthogonal transform unit 17 in the image coding apparatus in FIG. 9 are output to the inverse orthogonal transform unit 55.
  • the coding block when a coding block for performing intra coding and a coding block for performing inter coding coexist, the coding block performs intra coding.
  • the difference dQP of the same quantization parameter is transmitted to the decoding side regardless of whether it is a block or a block that performs inter coding, but the transition value QP_offset for quantization parameter conversion is in units of pictures or slices.
  • the decoding side it is possible to inversely quantize the transform coefficient quantized by the quantization unit 18 using the intra quantization parameter QP_intra for a coding block that performs intra coding.
  • the quantization parameter QP_inter for inter is used for coding blocks that perform inter coding. Te, it is possible to inverse quantizing the transform coefficients quantized by the quantization unit 18. For this reason, it is possible to obtain an optimum image quality without increasing the bit amount to be transmitted.
  • Embodiment 4 FIG.
  • the quantization control unit 42 indicates that the determination result of the intra / inter determination unit 41 indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image
  • the code Although the quantization parameter QP_offset for quantization parameter conversion is added to the quantization parameter QP of the quantization block to generate the intra quantization parameter QP_intra, the prediction generated by the intra prediction unit 11 is shown.
  • the conversion table indicating the correspondence between the quantization parameter QP of the coding block and the quantization parameter QP_intra for intra is referred to and the quantum of the coding block is referred to.
  • the quantization parameter QP may be converted into an intra quantization parameter QP_intra.
  • the image encoding device and the image decoding device need to store the same conversion table.
  • FIG. 12 is an explanatory diagram showing an example of a conversion table showing the correspondence between the quantization parameter QP of the coding block and the quantization parameter QP_intra for intra.
  • the quantization control unit 42 of the image coding apparatus determines the quantization parameter QP of the coding block in the same manner as in the third embodiment, the determination result of the intra / inter determination unit 41 is obtained by the intra prediction unit 11. If the generated prediction image indicates that it is the optimal prediction image, the quantization parameter QP of the coding block is converted into the quantization parameter QP_intra for intra with reference to the conversion table of FIG.
  • the intra quantization parameter QP_intra is output to the quantization unit 18.
  • FIG. 12 is an explanatory diagram showing an example of a conversion table showing the correspondence between the quantization parameter QP of the coding block and the quantization parameter QP_intra for intra.
  • the quantization parameter QP of the coding block is “11”
  • the quantization parameter QP_intra for intra is determined to be “10”
  • the quantization parameter QP of the coding block is “28”. If there is, the intra quantization parameter QP_intra is determined to be “25”.
  • the quantization control unit 42 quantizes the encoded block.
  • the parameter QP is output to the quantization unit 18 as an inter quantization parameter QP_inter.
  • the inverse quantization parameter generation unit 72 of the image decoding apparatus indicates that the determination result of the intra / inter determination unit 41 output from the entropy decoding unit 71 indicates that the prediction image generated by the intra prediction unit 11 is the optimal prediction image. 12, the quantization parameter QP of the coding block is converted into the quantization parameter QP_intra for the intra with reference to the conversion table of FIG. 12, and the quantization parameter QP_intra for the intra is converted into the inverse quantization unit 54. Output to. If the determination result of the intra / inter determination unit 41 indicates that the prediction image generated by the motion compensation prediction unit 13 is an optimal prediction image, the quantization parameter QP of the coding block is quantized for inter. The parameter QP_inter is output to the inverse quantization unit 54.
  • the quantization control unit 42 and the inverse quantization parameter generation unit 72 refer to the same conversion table to convert the quantization parameter QP of the coding block into the quantization parameter QP_intra for intra.
  • the quantization control unit 42 and the inverse quantization parameter generation unit 72 refer to the same conversion table to convert the quantization parameter QP of the coding block into the quantization parameter QP_intra for intra.
  • the quantization control unit 42 and the inverse quantization parameter generation unit 72 refer to the same conversion table and convert the quantization parameter QP of the coding block into the quantization parameter QP_intra for intra.
  • the entropy encoding unit 43 updates the correspondence May be multiplexed on the header of the bitstream in picture units or frame units. For example, in the conversion table of FIG. 12, when the correspondence relationship between the quantization parameter QP of the coding block and the quantization parameter QP_intra for intra is shifted by M (in FIG.
  • the quantization parameter QP of the coding block “3” corresponds to “3” of the quantization parameter QP_intra for intra
  • “8” of the quantization parameter QP of the coding block corresponds to “7” of the quantization parameter QP_intra for intra
  • “3” of the quantization parameter QP of the coding block corresponds to “5” of the quantization parameter QP_intra for intra
  • the quantization control unit 42 and the inverse quantization parameter generation unit 72 refer to the same conversion table and convert the quantization parameter QP of the coding block into the quantization parameter QP_intra for intra.
  • the quantization parameter QP of the coding block is set.
  • the quantization parameter QP of the coding block may be output as the intra quantization parameter QP_intra without being converted into the intra quantization parameter QP_intra.
  • the entropy encoding unit 43 multiplexes a flag indicating that the conversion table of FIG. 12 is not used in the header of the bitstream in units of pictures or frames.
  • the inverse quantization parameter generation unit 72 When the entropy decoding unit 71 extracts a flag indicating that the conversion table of FIG. 12 is not used from the bitstream, the inverse quantization parameter generation unit 72 generates the determination result of the intra / inter determination unit 41 by the intra prediction unit 11. Even when the predicted image is an optimum predicted image, the quantization parameter QP of the coding block is not converted into the quantization parameter QP_intra for the intra without converting the quantization parameter QP of the coding block. The quantization parameter QP_intra for intra is output. Thus, the present invention can be applied even when the conversion table is not applied.
  • the contents of the third and fourth embodiments may be applied to the contents of the first and second embodiments.
  • the image encoding device, the image decoding device, the image encoding method, and the image decoding method according to the present invention perform a prediction process on the encoded block for each encoded block constituting the input image, and generate a predicted image.
  • a difference image generation means for generating a difference image between the encoded block and the predicted image, and a quantization parameter fluctuation range is set in advance, and the difference between the quantization parameters in the encoded block and the encoded block is
  • the quantization parameter determining means for determining the quantization parameter of the coding block and the difference image generated by the difference image generating means within the range that falls within the fluctuation range are orthogonally transformed and determined by the quantization parameter determining means.
  • a quantization means for quantizing the transform coefficient of the difference image using the quantization parameter, and the entropy coding means The fluctuation range of the quantization parameter set by the parameter determination means, the transform coefficient quantized by the quantization means, the prediction image generation information used when the prediction image is generated by the difference image generation means, and the above encoding It is configured to generate a bitstream by entropy encoding the difference between the quantization parameters of the block and the encoded block, thereby reducing the transmission bit amount of information related to the quantization parameter and improving the encoding efficiency. Therefore, it is suitable for use in quantization processing.

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Abstract

L'invention comprend notamment : une unité de commande du codage (2) qui définit à l'avance une plage de variation d'un paramètre de quantification et détermine un paramètre de quantification du bloc à coder de manière à ce que la différence de paramètres de quantification entre le bloc à coder et le bloc codé qui le précède immédiatement s'inscrive dans la plage de variation ; et une unité de codage entropique (24) qui inclut, dans un train de bits, la plage de variation du paramètre de quantification établie par ladite unité de commande du codage (2).
PCT/JP2012/003556 2011-06-30 2012-05-30 Appareil de codage d'images, appareil de décodage d'images, procédé de codage d'images et procédé de décodage d'images WO2013001717A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018033044A (ja) * 2016-08-25 2018-03-01 キヤノン株式会社 画像符号化装置及びその制御方法及びプログラム

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