WO2013002111A1 - Image processing device and method - Google Patents

Abstract

This technology relates to an image processing device and method that make it possible to improve the image quality of decoded images whilst minimizing the reduction in encoding efficiency. The image processing device is equipped with: a determination unit for determining whether there is a large disparity in image quality between an area of interest which is in the area to be processed, and the peripheral area in a decoded image; a differential quantization parameter generation unit for generating the differential quantization parameters for the area of interest via an operation that uses a prescribed offset, if the determination unit determines that the disparity in image quality between the area of interest and the peripheral area is large; and a transmission unit for transmitting the differential quantization parameters generated by the differential quantization parameter generation unit. The present disclosure is applicable to image processing devices.

Description

Image processing apparatus and method

The present disclosure relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method capable of suppressing a reduction in image quality due to encoding / decoding.

In recent years, image information is handled as digital data, and MPEG (compressed by orthogonal transform such as discrete cosine transform and motion compensation is used for the purpose of efficient transmission and storage of information. A device that conforms to a method such as Moving (Pictures Experts Group) has been widely used for both information distribution in broadcasting stations and information reception in general households.

In particular, MPEG2 (ISO (International Organization for Standardization) / IEC (International Electrotechnical Commission) 13818-2) is defined as a general-purpose image coding system, and includes both interlaced scanning images and sequential scanning images, as well as standard resolution images and This standard covers high-definition images and is currently widely used in a wide range of professional and consumer applications. By using the MPEG2 compression method, for example, a standard resolution interlaced scanning image having 720 × 480 pixels is 4 to 8 Mbps, and a high resolution interlaced scanning image having 1920 × 1088 pixels is 18 to 22 Mbps. (Bit rate) can be assigned to achieve a high compression rate and good image quality.

MPEG2 was mainly intended for high-quality encoding suitable for broadcasting, but it did not support encoding methods with a lower code amount (bit rate) than MPEG1, that is, a higher compression rate. With the widespread use of mobile terminals, the need for such an encoding system is expected to increase in the future, and the MPEG4 encoding system has been standardized accordingly. Regarding the image coding system, the standard was approved as an international standard in December 1998 as ISO / IEC 14496-2.

In recent years, the standardization of H.26L (ITU-T (International Telecommunication Union Telecommunication Standardization Sector) Q6 / 16 VCEG (Video Coding Expert Group)) has been progressing for the purpose of initial video coding for video conferences. Yes. H.26L is known to achieve higher encoding efficiency than the conventional encoding schemes such as MPEG2 and MPEG4, although a large amount of calculation is required for encoding and decoding. In addition, as part of MPEG4 activities, Joint 取 り 入 れ Model of Enhanced-Compression Video Coding has been implemented based on this H.26L and incorporating functions not supported by H.26L to achieve higher coding efficiency. It was broken.

The standardization schedule became an international standard in March 2003 under the names H.264 and MPEG-4 Part 10 (Advanced Video Coding, hereinafter referred to as AVC).

Furthermore, as an extension, RGB, 4: 2: 2, 4: 4: 4 encoding tools necessary for business use, 8x8DCT (Discrete Cosine Transform) and quantization matrix specified by MPEG-2 are added. FRExt (Fidelity Range Extension) standardization was completed in February 2005. This makes it possible to use AVC to properly express film noise in movies. It has been used for a wide range of applications such as Blu-Ray Disc.

However, in recent years, even higher compression ratios such as wanting to compress images of about 4000 x 2000 pixels, which is four times higher than high-definition images, or distributing high-definition images in a limited transmission capacity environment such as the Internet. There is a growing need for encoding. For this reason, in the VCEG (Video Coding Expert Group) under the ITU-T umbrella, studies on improving the coding efficiency are continuing.

By the way, the conventional macroblock size of 16 pixels × 16 pixels is a large image frame such as UHD (Ultra High Definition: 4000 pixels × 2000 pixels), which is the target of the next generation encoding method. There was a fear that it was not optimal.

Therefore, HEVC (High Efficiency Video Video Coding) is now being developed by JCTVC (Joint Collaboration Collaboration Team Video Coding), a joint standardization organization of ITU-T and ISO / IEC, with the aim of further improving coding efficiency over AVC. Is being standardized (for example, see Non-Patent Document 1).

In this HEVC encoding system, a coding unit (CU (Coding Unit)) is defined as a processing unit similar to a macroblock in AVC. The CU is not fixed to a size of 16 × 16 pixels like the AVC macroblock, and is specified in the image compression information in each sequence.

By the way, in the case of HEVC described above, intra prediction-predicted units (PU) and inter-predicted prediction units (PU) can be mixed in B slices and P slices.

However, in general, since the prediction accuracy of inter prediction is higher than that of intra prediction, the image quality of a PU that is intra predicted is often worse than that of an inter predicted PU. Therefore, a partial change in PSNR (PeakNRSignal-to-Noise Ratio) may be visually noticeable in the B slice and the P slice where both images are mixed.

The present disclosure has been made in view of such a situation, and aims to improve the image quality of a decoded image.

In one aspect of the present disclosure, in the decoded image, a determination unit that determines whether or not a difference between an image quality of a target region to be processed and an image quality of a surrounding region is large, and the image quality of the target region is determined by the determination unit. And a difference quantization parameter generation unit that generates a difference quantization parameter of the region of interest by a calculation using a predetermined offset when it is determined that there is a large difference between the image quality of the surrounding region and the surrounding region, and the difference quantization parameter And a transmission unit that transmits the differential quantization parameter generated by the generation unit.

The region-of-interest quantization parameter generating unit for generating the region-of-interest region quantization parameter is further provided, and the region-of-interest quantization parameter generation unit is configured to determine, by the determination unit, the difference between the image quality of the region of interest and the image quality of surrounding regions If it is determined that the quantization parameter is large, it is possible to generate the quantization parameter of the region of interest that is significantly different from the quantization parameter of the surrounding region.

The region-of-interest quantization parameter generation unit, when the determination unit determines that the image quality of the region of interest is particularly low compared to the image quality of the surrounding region, the value is particularly greater than the quantization parameter of the surrounding region A small quantization parameter for the region of interest can be generated.

The region-of-interest quantization parameter generation unit, when the determination unit determines that the image quality of the region of interest is particularly high compared to the image quality of the surrounding region, the value is particularly greater than the quantization parameter of the surrounding region. A large quantization parameter for the region of interest can be generated.

The offset value may be a value that reduces a difference in value between the quantization parameter of the region of interest and the quantization parameter of the surrounding region.

The differential quantization parameter generation unit, when the determination unit determines that the difference between the image quality of the attention area and the image quality of the surrounding area is large, the quantization parameter of the attention area is determined from the quantization parameter of the attention area. The difference quantization parameter can be generated by subtracting the prediction value of the quantization parameter and further subtracting the offset.

When the determination unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is not large, the difference quantization parameter generation unit determines the region of interest from the quantization parameter of the region of interest. The difference quantization parameter can be generated by subtracting the predicted value of the quantization parameter.

The difference between the image quality of the region of interest and the image quality of the surrounding region is due to a difference in prediction accuracy between inter prediction and intra prediction, and the condition determination unit determines a prediction method for each of the attention region and the surrounding region. By checking, it can be determined whether or not the difference between the image quality of the attention area and the image quality of the surrounding area is large.

The condition determination unit determines whether or not a difference between the image quality of the attention area and the image quality of the surrounding area is large by confirming a prediction method of the attention area and a type of a slice in which the attention area exists. can do.

One aspect of the present disclosure is also an image processing method of the image processing device, in which the determination unit determines whether or not a difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large in the decoded image. And when the difference quantization parameter generation unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization of the region of interest is performed by a calculation using a predetermined offset. In this image processing method, a parameter is generated, and a transmission unit transmits the generated differential quantization parameter.

In another aspect of the present disclosure, the reception unit that receives the differential quantization parameter of the attention area that is the processing target and whether or not the difference between the image quality of the attention area that is the processing target and the image quality of the surrounding area is large in the decoded image. When the determination unit and the determination unit determine that the difference between the image quality of the attention area and the image quality of the surrounding area is large, the determination unit receives the reception unit by a calculation using a predetermined offset. And an attention area quantization parameter reconstructing unit that reconstructs the quantization parameter of the attention area from the difference quantization parameter.

Another aspect of the present disclosure is also an image processing method of the image processing device, in which the reception unit receives a difference quantization parameter of a region of interest that is a processing target, and the determination unit is a processing target in the decoded image. It is determined whether or not the difference between the image quality of a certain region of interest and the image quality of the surrounding region is large, and the region of interest quantization parameter reconstruction unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large If determined, the image processing method reconstructs the quantization parameter of the region of interest from the received difference quantization parameter by an operation using a predetermined offset.

In one aspect of the present disclosure, in the decoded image, it is determined whether or not a difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large, and the image quality of the attention area and the image quality of the surrounding area are determined. When it is determined that the difference is large, a differential quantization parameter for the attention area is generated by calculation using a predetermined offset, and the generated differential quantization parameter is transmitted.

In another aspect of the present disclosure, the difference quantization parameter of the attention area to be processed is received, and whether or not the difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large in the decoded image. When the difference between the image quality of the attention area and the image quality of the surrounding area is determined to be large, the quantization parameter of the attention area is re-established from the received difference quantization parameter by an operation using a predetermined offset. Built.

According to the present disclosure, an image can be processed. In particular, it is possible to suppress degradation of the image quality of the decoded image.

It is a block diagram which shows the main structural examples of an image coding apparatus. It is a figure explaining the structural example of a coding unit. It is a figure explaining the example of PSNR. 3 is a block diagram illustrating a main configuration example of a quantization unit and a quantization parameter encoding unit 121. FIG. It is a figure which shows the example of selection of the difference quantization parameter calculation method according to conditions. It is a block diagram which shows the main structural examples of a difference quantization parameter production | generation part. It is a flowchart explaining the example of the flow of an encoding process. It is a flowchart explaining the example of the flow of a quantization process. It is a block diagram which shows the main structural examples of an image decoding apparatus. It is a block diagram which shows the main structural examples of an inverse quantization part and a quantization parameter decoding part. It is a figure which shows the selection example of the attention area quantization parameter reconstruction method according to conditions. It is a block diagram which shows the main structural examples of an attention area quantization parameter production | generation part. It is a flowchart explaining the example of the flow of a decoding process. It is a flowchart explaining the example of the flow of a dequantization process. FIG. 26 is a block diagram illustrating a main configuration example of a personal computer. It is a block diagram which shows an example of a schematic structure of a television apparatus. It is a block diagram which shows an example of a schematic structure of a mobile telephone. It is a block diagram which shows an example of a schematic structure of a recording / reproducing apparatus. It is a block diagram which shows an example of a schematic structure of an imaging device.

Hereinafter, modes for carrying out the present disclosure (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. First Embodiment (Image Encoding Device)
2. Second embodiment (image decoding apparatus)
3. Third embodiment (computer)
4). Fourth embodiment (television receiver)
5. Fifth embodiment (mobile phone)
6). Sixth embodiment (recording / reproducing apparatus)
7). Seventh embodiment (imaging device)

<1. First Embodiment>
[Image encoding device]
FIG. 1 is a block diagram illustrating a main configuration example of an image encoding device that is an image processing device.

The image encoding device 100 shown in FIG. Like the H.264 and MPEG (Moving Picture Experts Group) 4 Part 10 (AVC (Advanced Video Coding)) coding system, the image data is encoded using a prediction process.

As shown in FIG. 1, the image encoding device 100 includes an A / D conversion unit 101, a screen rearrangement buffer 102, a calculation unit 103, an orthogonal transformation unit 104, a quantization unit 105, a lossless encoding unit 106, and a storage buffer. 107. The image coding apparatus 100 also includes an inverse quantization unit 108, an inverse orthogonal transform unit 109, a calculation unit 110, a loop filter 111, a frame memory 112, a selection unit 113, an intra prediction unit 114, a motion prediction / compensation unit 115, and a prediction. An image selection unit 116 and a rate control unit 117 are included.

The image encoding device 100 further includes a quantization parameter encoding unit 121.

The A / D conversion unit 101 performs A / D conversion on the input image data, and supplies the converted image data (digital data) to the screen rearrangement buffer 102 for storage. The screen rearrangement buffer 102 rearranges the images of the frames in the stored display order in the order of frames for encoding in accordance with GOP (Group Of Picture), and the images in which the order of the frames is rearranged. This is supplied to the calculation unit 103. The screen rearrangement buffer 102 also supplies the image in which the order of the frames is rearranged to the intra prediction unit 114 and the motion prediction / compensation unit 115.

The calculation unit 103 subtracts the prediction image supplied from the intra prediction unit 114 or the motion prediction / compensation unit 115 via the prediction image selection unit 116 from the image read from the screen rearrangement buffer 102, and the difference information Is output to the orthogonal transform unit 104.

For example, in the case of an image on which intra coding is performed, the calculation unit 103 subtracts the prediction image supplied from the intra prediction unit 114 from the image read from the screen rearrangement buffer 102. For example, in the case of an image on which inter coding is performed, the arithmetic unit 103 subtracts the predicted image supplied from the motion prediction / compensation unit 115 from the image read from the screen rearrangement buffer 102.

The orthogonal transform unit 104 performs orthogonal transform such as discrete cosine transform and Karhunen-Loeve transform on the difference information supplied from the computation unit 103. Note that this orthogonal transformation method is arbitrary. The orthogonal transform unit 104 supplies the transform coefficient to the quantization unit 105.

The quantization unit 105 quantizes the transform coefficient supplied from the orthogonal transform unit 104. The quantization unit 105 sets a quantization parameter based on the information regarding the target value of the code amount supplied from the rate control unit 117, and performs the quantization. At that time, the quantization unit 105 sets the quantization parameter to a small value for an image with a low PSNR. Note that this quantization method is arbitrary. The quantization unit 105 supplies the quantized transform coefficient to the lossless encoding unit 106.

Further, the quantization unit 105 causes the quantization parameter encoding unit 121 to obtain a difference between the quantization parameter of the attention region (attention region quantization parameter) that is the current processing target and the predicted value (predicted quantization parameter). A value (differential quantization parameter) is generated, acquired, and supplied to the lossless encoding unit 106.

The lossless encoding unit 106 encodes the transform coefficient quantized by the quantization unit 105 using an arbitrary encoding method. Since the coefficient data is quantized under the control of the rate control unit 117, the code amount becomes a target value set by the rate control unit 117 (or approximates the target value).

Also, the lossless encoding unit 106 acquires the differential quantization parameter supplied from the quantization unit 105. Further, the lossless encoding unit 106 acquires the offset value supplied from the quantization parameter encoding unit 121.

Further, the lossless encoding unit 106 acquires intra prediction information including information indicating an intra prediction mode from the intra prediction unit 114, and moves inter prediction information including information indicating an inter prediction mode, motion vector information, and the like. Obtained from the prediction / compensation unit 115. Further, the lossless encoding unit 106 acquires filter coefficients used in the loop filter 111 and the like.

The lossless encoding unit 106 encodes these various types of information using an arbitrary encoding method, and makes it a part of the header information of the encoded data (multiplexes). The lossless encoding unit 106 supplies the encoded data obtained by encoding to the accumulation buffer 107 for accumulation.

Examples of the encoding method of the lossless encoding unit 106 include variable length encoding or arithmetic encoding. Examples of variable length coding include H.264. CAVLC (Context-Adaptive Variable Length Coding) defined in the H.264 / AVC format. Examples of arithmetic coding include CABAC (Context-Adaptive Binary Arithmetic Coding).

The accumulation buffer 107 temporarily holds the encoded data supplied from the lossless encoding unit 106. The accumulation buffer 107 outputs the stored encoded data as a bit stream at a predetermined timing, for example, to a recording device (recording medium) or a transmission path (not shown) in the subsequent stage. That is, various encoded information is supplied to the decoding side.

Also, the transform coefficient quantized by the quantization unit 105 is also supplied to the inverse quantization unit 108. Further, the quantization unit 105 supplies the attention area quantization parameter to the inverse quantization unit 108.

The inverse quantization unit 108 uses the attention area quantization parameter supplied from the quantization unit 105 to quantize the transform coefficient supplied from the quantization unit 105 to the quantization by the quantization unit 105. Inverse quantization using the method The inverse quantization method may be any method as long as it is a method corresponding to the quantization processing by the quantization unit 105. The inverse quantization unit 108 supplies the obtained transform coefficient to the inverse orthogonal transform unit 109.

The inverse orthogonal transform unit 109 performs inverse orthogonal transform on the transform coefficient supplied from the inverse quantization unit 108 by a method corresponding to the orthogonal transform process by the orthogonal transform unit 104. The inverse orthogonal transform method may be any method as long as it corresponds to the orthogonal transform processing by the orthogonal transform unit 104. The inversely orthogonally transformed output (difference information restored locally) is supplied to the calculation unit 110.

The calculation unit 110 converts the inverse orthogonal transform result supplied from the inverse orthogonal transform unit 109, that is, locally restored difference information, into the intra prediction unit 114 or the motion prediction / compensation unit 115 via the predicted image selection unit 116. Are added to the predicted image to obtain a locally reconstructed image (hereinafter referred to as a reconstructed image). The reconstructed image is supplied to the loop filter 111 or the frame memory 112.

The loop filter 111 includes a deblock filter, an adaptive loop filter, and the like, and appropriately performs a filtering process on the decoded image supplied from the calculation unit 110. For example, the loop filter 111 removes block distortion of the decoded image by performing a deblocking filter process on the decoded image. In addition, for example, the loop filter 111 performs image quality improvement by performing loop filter processing using a Wiener filter on the deblock filter processing result (decoded image from which block distortion has been removed). Do.

Note that the loop filter 111 may perform arbitrary filter processing on the decoded image. Further, the loop filter 111 can supply information such as filter coefficients used for the filter processing to the lossless encoding unit 106 and encode it as necessary.

The loop filter 111 supplies a filter processing result (hereinafter referred to as a decoded image) to the frame memory 112.

The frame memory 112 stores the reconstructed image supplied from the calculation unit 110 and the decoded image supplied from the loop filter 111, respectively. The frame memory 112 supplies the stored reconstructed image to the intra prediction unit 114 via the selection unit 113 at a predetermined timing or based on a request from the outside such as the intra prediction unit 114. The frame memory 112 also stores the decoded image stored at a predetermined timing or based on a request from the outside such as the motion prediction / compensation unit 115 via the selection unit 113. 115.

The selection unit 113 indicates the supply destination of the image output from the frame memory 112. For example, in the case of intra prediction, the selection unit 113 reads an image (reconstructed image) that has not been subjected to filter processing from the frame memory 112 and supplies it to the intra prediction unit 114 as peripheral pixels.

Also, for example, in the case of inter prediction, the selection unit 113 reads out an image (decoded image) that has been filtered from the frame memory 112, and supplies it as a reference image to the motion prediction / compensation unit 115.

When the intra prediction unit 114 acquires an image (peripheral image) of a peripheral region located around the target region to be processed from the frame memory 112, the intra prediction unit 114 uses the pixel value of the peripheral image to generate a predicted image of the target region. Perform intra prediction (intra-screen prediction) to be generated. The intra prediction unit 114 performs this intra prediction in a plurality of modes (intra prediction modes) prepared in advance.

The intra prediction unit 114 generates predicted images in all candidate intra prediction modes, evaluates the cost function value of each predicted image using the input image supplied from the screen rearrangement buffer 102, and selects the optimum mode. select. When the intra prediction unit 114 selects the optimal intra prediction mode, the intra prediction unit 114 supplies the predicted image generated in the optimal mode to the predicted image selection unit 116.

In addition, the intra prediction unit 114 appropriately supplies intra prediction information including information related to intra prediction, such as an optimal intra prediction mode, to the lossless encoding unit 106 to be encoded.

The motion prediction / compensation unit 115 basically uses the input image supplied from the screen rearrangement buffer 102 and the reference image supplied from the frame memory 112 as a processing unit, with the prediction unit (PU) as a processing unit. Prediction (inter prediction) is performed, motion compensation processing is performed according to the detected motion vector, and a predicted image (inter predicted image information) is generated. The motion prediction / compensation unit 115 performs such inter prediction in a plurality of modes (inter prediction modes) prepared in advance.

The motion prediction / compensation unit 115 generates prediction images in all candidate inter prediction modes, evaluates the cost function value of each prediction image, and selects an optimal mode. When the optimal inter prediction mode is selected, the motion prediction / compensation unit 115 supplies the predicted image generated in the optimal mode to the predicted image selection unit 116.

Also, the motion prediction / compensation unit 115 supplies inter prediction information including information related to inter prediction, such as an optimal inter prediction mode, to the lossless encoding unit 106 to be encoded.

The predicted image selection unit 116 selects a supply source of a predicted image to be supplied to the calculation unit 103 or the calculation unit 110. For example, in the case of intra coding, the prediction image selection unit 116 selects the intra prediction unit 114 as a supply source of the prediction image, and supplies the prediction image supplied from the intra prediction unit 114 to the calculation unit 103 and the calculation unit 110. To do. Also, for example, in the case of inter coding, the predicted image selection unit 116 selects the motion prediction / compensation unit 115 as a supply source of the predicted image, and calculates the predicted image supplied from the motion prediction / compensation unit 115 as the calculation unit 103. To the arithmetic unit 110.

The rate control unit 117 controls the quantization operation rate of the quantization unit 105 based on the code amount of the encoded data stored in the storage buffer 107 so that overflow or underflow does not occur.

The quantization parameter encoding unit 121 generates a differential quantization parameter. For this purpose, first, the quantization parameter encoding unit 121 generates a prediction value (predicted quantization parameter) of the quantization parameter in the region of interest. The quantization parameter encoding unit 121 generates the predicted quantization parameter using the quantization parameter (peripheral region quantization parameter) of the peripheral region that has been well positioned around the region of interest and has been processed in the past.

Also, the quantization parameter encoding unit 121 acquires the attention area quantization parameter from the quantization unit 105 in order to generate a differential quantization parameter. Furthermore, the quantization parameter encoding unit 121 acquires information on the attention area, such as prediction mode information and slice type, from the lossless encoding unit 106 in order to generate a differential quantization parameter.

The quantization parameter encoding unit 121 calculates a difference quantization parameter using the attention area quantization parameter and the predicted quantization parameter. However, at that time, the quantization parameter encoding unit 121 performs a predetermined condition determination using information on the region of interest, and adds an offset according to the result.

When the differential quantization parameter is generated in this way, the quantization parameter encoding unit 121 supplies the differential quantization parameter to the quantization unit 105. Also, the quantization parameter encoding unit 121 supplies the offset value to the lossless encoding unit 106 and transmits it to the decoding side.

[Coding unit]
Here, the HEVC encoding method will be described. First, a coding unit defined in the HEVC encoding method will be described.

Coding Unit (CU) is also called Coding Block (CTB), and is a partial area of a picture unit image that plays the same role as a macroblock in AVC. The latter is fixed to a size of 16 × 16 pixels, whereas the size of the former is not fixed, and is specified in the image compression information in each sequence.

In particular, the CU having the largest size is called LCU (Largest Coding Unit), and the CU having the smallest size is called SCU (Smallest Coding Unit). For example, in the sequence parameter set included in the image compression information, the sizes of these regions are specified, but each is limited to a square and a size represented by a power of 2.

Figure 2 shows an example of coding unit (Coding Unit) defined in HEVC. In the example of FIG. 2, the LCU size is 128 and the maximum hierarchical depth is 5. When the value of split_flag is “1”, the 2N × 2N size CU is divided into N × N size CUs that are one level below.

Further, the CU is divided into prediction units (Prediction Units (PU)) that are regions (partial regions of images in units of pictures) that are processing units of intra or inter prediction, and are regions that are processing units of orthogonal transformation It is divided into transform units (Transform Unit (TU)), which is (a partial area of an image in units of pictures).

In the following, “area” includes all areas (for example, AVC macroblocks and sub-macroblocks, LCU, CU, SCU, PU, TU, etc.), which may be any of them. . Of course, units other than those described above may be included, and units that are impossible according to the content of the description are appropriately excluded.

[PSNR]
By the way, in HEVC, the prediction unit (PU) by which intra prediction is carried out and the prediction unit (PU) by which inter prediction is carried out can be mixed in B slice and P slice. However, generally, since the prediction accuracy of inter prediction is higher than that of intra prediction, the image quality of a PU predicted intra is often worse than that of an inter predicted PU.

Therefore, for example, as shown in FIG. 3A, when a part of the region in the inter-predicted frame is intra-predicted, as shown in FIG. There was a risk of lowering. As described above, when the image quality is partially deteriorated, it is easy to compare with the surrounding images, so that the partial image quality deterioration may be conspicuous.

Therefore, the quantization unit 105 sets (adjusts) the quantization parameter used for the quantization process so as to suppress the local change of the PSNR in the decoded image as much as possible. That is, the quantization unit 105 sets the quantization parameter for a region where the PSNR in the decoded image is significantly different from other regions to a value different from the others.

However, in this case, the value of the quantization parameter changes in a fine unit (for each region of the processing unit) where inter prediction region and intra prediction region are mixed, such as B slice and P slice. Will do. For this reason, the value of the differential quantization parameter also changes in fine units. In addition, since the prediction accuracy is reduced, the value of the differential quantization parameter may be increased. Therefore, there is a possibility that the amount of code of information to be transmitted related to the quantization parameter may increase, which may greatly reduce the encoding efficiency.

Therefore, the quantization parameter encoding unit 121 generates a differential quantization parameter by adding a predetermined offset to the quantization parameter whose value has been adjusted in the quantization unit 105 as described above. By doing so, the value of the differential quantization parameter can be stabilized to a small value, and an increase in the code amount of information to be transmitted regarding the quantization parameter can be suppressed. That is, the image encoding device 100 can improve the image quality of the decoded image while suppressing a decrease in encoding efficiency.

[Quantization unit and quantization parameter encoding unit]
FIG. 4 is a block diagram illustrating a main configuration example of the quantization unit 105 and the quantization parameter encoding unit 121 of FIG.

As shown in FIG. 4, the quantization unit 105 includes a region of interest quantization parameter generation unit 131, a quantization processing unit 132, a peripheral region quantization parameter buffer 133, and a differential quantization parameter buffer 134.

Also, the quantization parameter encoding unit 121 includes a predictive quantization parameter generation unit 141, a condition determination unit 142, an offset storage unit 143, and a differential quantization parameter generation unit 144.

The condition determination unit 142 of the quantization parameter encoding unit 121 acquires information on the attention area, such as prediction mode information and slice type, from the lossless encoding unit 106. The condition determination unit 142 determines whether or not the attention area meets a predetermined condition based on the information. That is, based on the information acquired from the lossless encoding unit 106, the condition determination unit determines whether the region of interest is a region where the PSNR is significantly different from other regions in the decoded image. More specifically, for example, the condition determination unit 142 is configured such that the slice where the region of interest exists (target slice) is a P slice or a B slice (hereinafter also referred to as an inter slice), and the region of interest is intra-predicted. It is determined whether it is a region (hereinafter also referred to as an intra region).

The condition determination unit 142 supplies the determination result to the attention area quantization parameter generation unit 131 and the difference quantization parameter generation unit 144.

The attention area quantization parameter generation unit 131 generates a quantization parameter (attention area quantization parameter) for the attention area. The attention area quantization parameter generation unit 131 generates the attention area quantization parameter based on the rate control information supplied from the rate control unit 117, for example. In addition, the attention area quantization parameter generation unit 131 determines (adjusts) the value of the attention area quantization parameter according to the determination result supplied from the condition determination unit 142. For example, when it is determined that the region of interest meets a predetermined condition, that is, the region of interest is an intra region in the inter slice, the region of interest quantization parameter generation unit 131 in the decoded image The quantization parameter is set to a value smaller than that of the other region so that the PSNR is comparable to that of the other region.

The attention area quantization parameter generation unit 131 supplies the attention area quantization parameter generated in this way to the quantization processing unit 132. The quantization processing unit 132 quantizes the orthogonal transform coefficient supplied from the orthogonal transform unit 104 using the attention area quantization parameter, and supplies the quantized orthogonal transform coefficient to the lossless encoding unit 106. To be transmitted to the decoding side.

Note that the quantization processing unit 132 also supplies the quantized orthogonal transform coefficient to the inverse quantization unit 108. The attention area quantization parameter generation unit 131 also supplies the calculated attention area quantization parameter to the inverse quantization unit 108. The inverse quantization unit 108 performs inverse orthogonal transformation on the quantized orthogonal transform coefficient supplied from the quantization processing unit 132 using the attention region quantization parameter supplied from the attention region quantization parameter generation unit 131. To do.

The attention area quantization parameter generation unit 131 also supplies the calculated attention area quantization parameter to the peripheral area quantization parameter buffer 133. The peripheral area quantization parameter buffer 133 stores the supplied attention area quantization parameter. The peripheral region quantization parameter buffer 133 locates the stored region-of-interest quantization parameter in the periphery of the region of interest in the processing in which another region processed later in time than the region of interest is the region of interest. This is supplied to the predicted quantization parameter generation unit 141 as a quantization parameter (peripheral region quantization parameter) of a peripheral region having a predetermined positional relationship with the region of interest.

The predicted quantization parameter generation unit 141 acquires the peripheral region quantization parameter from the peripheral region quantization parameter buffer 133, and generates a prediction value (predictive quantization parameter) of the quantization parameter of the attention region using the acquired parameter.

Note that, as described above, the quantization parameter in the intra region of the inter slice has a particularly small value compared to the quantization parameter in other regions. Therefore, if this quantization parameter is used, the prediction accuracy of the predicted quantization parameter may be reduced. Therefore, it is desirable not to use the quantization parameter of the region that meets the predetermined condition of the condition determination unit 142 as the peripheral region quantization parameter.

The predicted quantization parameter generation unit 141 supplies the generated predicted quantization parameter to the difference quantization parameter generation unit 144.

Also, the attention area quantization parameter generation unit 131 supplies the generated attention area quantization parameter to the differential quantization parameter generation unit 144.

The offset storage unit 143 stores a predetermined offset (iqp_offset) in advance. For example, when the attention area quantization parameter generation unit 131 sets the quantization parameter to a smaller value than the other areas for the intra area in the inter slice, the offset becomes a negative value (minus).

Note that the value of this offset is arbitrary, but is desirably a value that restores the variation in the value of the attention area quantization parameter due to the adjustment of the attention area quantization parameter generation unit 131. That is, it is desirable that the offset value is set in association with the adjustment amount of the attention area quantization parameter when the condition is satisfied by the condition determination section 142 by the attention area quantization parameter generation section 131. The offset may be a predetermined fixed value, or may be set by a user, for example.

The offset storage unit 143 supplies the stored offset to the differential quantization parameter generation unit 144 at a predetermined timing or based on an external request.

Further, the offset storage unit 143 supplies the stored offset to the lossless encoding unit 106 at a predetermined timing or based on a request from the outside, encodes it, and transmits it to the decoding side.

The difference quantization parameter generation unit 144 is a difference (difference quantization parameter) between the attention region quantization parameter acquired from the attention region quantization parameter generation unit 131 and the prediction quantization parameter acquired from the prediction quantization parameter generation unit 141. Is generated. At that time, the differential quantization parameter generation unit 144 determines a differential quantization parameter generation method based on the determination result supplied from the condition determination unit 142.

FIG. 5 is a diagram for explaining an example of how the differential quantization parameter generation method is selected. In the example shown in the table of FIG. 5, the slice type of the target slice is inter slice (P slice or B slice), and the prediction mode of the target region is inter prediction (that is, the target region is the inter region). If the slice type of the target slice is an intra slice (I slice), the differential quantization parameter generation unit 144 generates a differential quantization parameter using the following equation (1).

DQP = CurrQP−RefQP (1)

In Equation (1), dQP indicates a differential quantization parameter, CurrQP indicates a region of interest quantization parameter, and RefQP indicates a prediction quantization parameter.

Further, when the slice type of the target slice is an inter slice (P slice or B slice) and the prediction mode of the target region is intra prediction (that is, the target region is an intra region), a differential quantization parameter generation unit 144 generates a differential quantization parameter using the following equation (2).

DQP = CurrQP−RefQP−iqp_offset (2)

In Equation (2), dQP indicates the differential quantization parameter, CurrQP indicates the attention area quantization parameter, and RefQP indicates the prediction quantization parameter. Further, iqp_offset is an offset supplied from the offset storage unit 143.

As described above, the differential quantization parameter generation unit 144 selects a differential quantization parameter generation method based on the condition determination result of the region of interest, and generates the differential quantization parameter by the method. The differential quantization parameter generation unit 144 supplies the generated differential quantization parameter to the differential quantization parameter buffer 134 of the quantization unit 105.

The differential quantization parameter buffer 134 stores the supplied differential quantization parameter, and supplies the differential quantization parameter to the lossless encoding unit 106 at a predetermined timing or in response to occurrence of a predetermined event. To be transmitted to the decoding side.

[Differential quantization parameter generator]
FIG. 6 is a block diagram illustrating a main configuration example of the differential quantization parameter generation unit 144. As illustrated in FIG. 4, the differential quantization parameter generation unit 144 includes a calculation unit 151, a calculation unit 152, and a selection unit 153.

The calculation unit 151 subtracts the prediction quantization parameter (RefQP) supplied from the prediction quantization parameter generation unit 141 from the attention region quantization parameter (CurrQP) supplied from the attention region quantization parameter generation unit 131, and The difference value (CurrQP−RefQP) is supplied to the calculation unit 152 and the selection unit 153.

The calculation unit 152 subtracts the offset (iqp_offset) supplied from the offset storage unit 143 from the difference value (CurrQP−RefQP) supplied from the calculation unit 151 and selects the difference value (CurrQP−RefQP−iqp_offset). 153.

The selection unit 153 acquires the condition determination result supplied from the condition determination unit 142, that is, control information, and in accordance with the control information, the difference value (CurrQP−RefQP) supplied from the calculation unit 151 or the calculation unit 152 One of the difference values (CurrQP−RefQP−iqp_offset) supplied from is selected and supplied to the difference quantization parameter buffer 134 as a difference quantization parameter (dQP).

For example, when the condition determination unit 142 determines that the region of interest is an intra region of an inter slice, the selection unit 153 selects a difference value (CurrQP−RefQP−iqp_offset) using an offset and calculates the difference The quantization parameter (dQP) is supplied to the differential quantization parameter buffer 134.

Also, for example, when the condition determining unit 142 determines that the region of interest is not an intra region of an inter slice, the selecting unit 153 selects a difference value (CurrQP−RefQP) that does not use an offset, and uses that as a difference quantum. Is supplied to the differential quantization parameter buffer 134 as a quantization parameter (dQP).

As described above, by configuring and operating each unit, the image encoding device 100 can improve the image quality of a decoded image while suppressing a decrease in encoding efficiency.

[Flow of encoding process]
Next, the flow of each process executed by the image encoding device 100 as described above will be described. First, an example of the flow of the encoding process will be described with reference to the flowchart of FIG.

In step S101, the A / D converter 101 performs A / D conversion on the input image. In step S102, the screen rearrangement buffer 102 stores the A / D converted image, and rearranges the picture from the display order to the encoding order.

In step S103, the intra prediction unit 114 performs an intra prediction process. In step S104, the motion prediction / compensation unit 115 performs an inter motion prediction process. In step S105, the predicted image selection unit 116 selects one of a predicted image generated by intra prediction and a predicted image generated by inter prediction.

In step S106, the calculation unit 103 calculates a difference between the image rearranged by the process of step S103 and the predicted image selected by the process of step S105 (generates a difference image). The generated difference image has a reduced data amount compared to the original image. Therefore, the data amount can be compressed as compared with the case where the image is encoded as it is.

In step S107, the orthogonal transform unit 104 orthogonally transforms the difference image generated by the process in step S106. Specifically, orthogonal transformation such as discrete cosine transformation and Karhunen-Loeve transformation is performed, and orthogonal transformation coefficients are output. In step S108, the quantization unit 105 quantizes the orthogonal transform coefficient obtained by the process in step S107.

The difference image quantized by the process in step S108 is locally decoded as follows. That is, in step S109, the inverse quantization unit 108 inversely quantizes the quantized orthogonal transform coefficient (also referred to as a quantization coefficient) generated by the quantization process in step S108. In step S <b> 110, the inverse orthogonal transform unit 109 performs inverse orthogonal transform on the orthogonal transform coefficient obtained by the inverse quantization process in step S <b> 109 with characteristics corresponding to the characteristics of the orthogonal transform unit 104. Thereby, the difference image is restored.

In step S111, the calculation unit 110 adds the predicted image selected in step S105 to the difference image generated in step S110, and generates a locally decoded image (reconstructed image). In step S112, the loop filter 111 appropriately performs a loop filter process including a deblocking filter process and an adaptive loop filter process on the reconstructed image obtained by the process of step S111 to generate a decoded image.

In step S113, the frame memory 112 stores the decoded image generated by the process of step S112 or the reconstructed image generated by the process of step S111.

In step S114, the lossless encoding unit 106 encodes the orthogonal transform coefficient quantized by the process in step S107. That is, lossless encoding such as variable length encoding or arithmetic encoding is performed on the difference image. Note that the lossless encoding unit 106 encodes information about prediction, information about quantization, information about filter processing, and the like, and adds the information to the bitstream.

In step S115, the accumulation buffer 107 accumulates the bit stream obtained by the process in step S114. The encoded data stored in the storage buffer 107 is appropriately read and transmitted to the decoding side via a transmission path or a recording medium.

In step S116, the rate control unit 117 causes the quantization unit 105 to prevent overflow or underflow based on the code amount (generated code amount) of the encoded data accumulated in the accumulation buffer 107 by the process of step S115. Controls the rate of quantization operation.

When the process of step S116 is finished, the encoding process is finished.

[Flow of quantization processing]
Next, an example of the flow of the quantization process executed in step S108 of FIG. 7 will be described with reference to the flowchart of FIG.

When the quantization process is started, the condition determination unit 142 confirms the slice type of the target slice and the prediction mode of the target region in step S131, and determines whether or not the target region is an intra region of the inter slice. .

In step S132, the attention area quantization parameter generation unit 131 generates the attention area quantization parameter by a method according to the determination result in step S131. As described above, for example, when it is determined in step S131 that the attention area is an intra area of the inter slice, the attention area quantization parameter generation unit 131 sets the attention area quantization parameter to a small value.

In step S133, the peripheral region quantization parameter buffer 133 stores the attention region quantization parameter generated in step S132.

In step S134, the quantization processing unit 132 quantizes the orthogonal transformation coefficient of the attention area using the attention area quantization parameter generated in step S132.

In step S135, the predicted quantization parameter generation unit 141 generates a predicted quantization parameter using the peripheral region quantization parameter read from the peripheral region quantization parameter buffer 133.

In step S136, the condition determination unit 142 determines whether the target slice is an inter slice and the target region is an intra region. If it is determined that the target slice is an inter slice and the target region is an intra region, the condition determination unit 142 proceeds with the process to step S137.

In step S137, the differential quantization parameter generation unit 144 generates a differential quantization parameter using an offset read from the offset storage unit 143, for example, as in Expression (2). That is, the difference quantization parameter generation unit 144 subtracts the prediction quantization parameter and the offset from the attention area quantization parameter to obtain the difference quantization parameter. The difference quantization parameter generation unit 144 causes the lossless encoding unit 106 to encode the generated difference quantization parameter. When the process of step S137 ends, the differential quantization parameter generation unit 144 ends the quantization process and returns the process to FIG.

If it is determined in step S136 of FIG. 8 that the target slice is not an inter slice, or the target region is not an intra region, the condition determination unit 142 advances the process to step S138.

In step S138, the differential quantization parameter generation unit 144 generates a differential quantization parameter, for example, as shown in Expression (1). That is, the difference quantization parameter generation unit 144 subtracts the prediction quantization parameter from the attention area quantization parameter to obtain the difference quantization parameter. The difference quantization parameter generation unit 144 causes the lossless encoding unit 106 to encode the generated difference quantization parameter. When the process of step S138 ends, the differential quantization parameter generation unit 144 ends the quantization process and returns the process to FIG.

As described above, by performing each process, the image encoding device 100 can improve the image quality of the decoded image while suppressing a decrease in encoding efficiency.

<2. Second Embodiment>
[Image decoding device]
Next, decoding of the encoded data encoded as described above will be described. FIG. 9 is a block diagram illustrating a main configuration example of an image decoding apparatus that is an image processing apparatus corresponding to the image encoding apparatus 100 of FIG.

The image decoding apparatus 200 shown in FIG. 9 decodes the encoded data generated by the image encoding apparatus 100 using a decoding method corresponding to the encoding method.

As shown in FIG. 9, the image decoding apparatus 200 includes a storage buffer 201, a lossless decoding unit 202, an inverse quantization unit 203, an inverse orthogonal transform unit 204, a calculation unit 205, a loop filter 206, a screen rearrangement buffer 207, and a D A / A converter 208 is included. The image decoding apparatus 200 includes a frame memory 209, a selection unit 210, an intra prediction unit 211, a motion prediction / compensation unit 212, and a selection unit 213.

Furthermore, the image decoding device 200 includes a quantization parameter decoding unit 221.

The accumulation buffer 201 accumulates the transmitted encoded data, and supplies the encoded data to the lossless decoding unit 202 at a predetermined timing. The lossless decoding unit 202 decodes the information supplied from the accumulation buffer 201 and encoded by the lossless encoding unit 106 in FIG. 1 by a method corresponding to the encoding method of the lossless encoding unit 106. The lossless decoding unit 202 supplies the quantized orthogonal transform coefficient of the difference image obtained by decoding to the inverse quantization unit 203.

Also, the lossless decoding unit 202 supplies the differential quantization parameter obtained by decoding to the inverse quantization unit 203.

Further, the lossless decoding unit 202 supplies the quantization parameter decoding unit 221 with information related to the attention area such as the slice type and prediction mode information obtained by decoding. Also, the lossless decoding unit 202 supplies the quantization parameter offset (iqp_offset) obtained by decoding to the quantization parameter decoding unit 221.

Furthermore, the lossless decoding unit 202 refers to information about the optimal prediction mode obtained by decoding the encoded data, and determines whether the intra prediction mode or the inter prediction mode is selected as the optimal prediction mode. . That is, the lossless decoding unit 202 determines whether the prediction mode employed in the transmitted encoded data is intra prediction or inter prediction.

The lossless decoding unit 202 supplies information on the prediction mode to the intra prediction unit 211 or the motion prediction / compensation unit 212 based on the determination result. For example, when the intra prediction mode is selected as the optimal prediction mode in the image encoding device 100, the lossless decoding unit 202 is intra prediction information, which is information about the selected intra prediction mode supplied from the encoding side. Is supplied to the intra prediction unit 211. Further, for example, when the inter prediction mode is selected as the optimum prediction mode in the image encoding device 100, the lossless decoding unit 202 is an inter that is information about the selected inter prediction mode supplied from the encoding side. The prediction information is supplied to the motion prediction / compensation unit 212.

The inverse quantization unit 203 inversely quantizes the quantized orthogonal transform coefficient obtained by decoding by the lossless decoding unit 202. At that time, the inverse quantization unit 203 causes the quantization parameter decoding unit 221 to reconstruct the attention area quantization parameter used on the encoding side.

That is, the inverse quantization unit 203 performs inverse quantization by a method corresponding to the quantization method of the quantization unit 105 in FIG. The inverse quantization unit 203 supplies the coefficient data obtained by the inverse quantization to the inverse orthogonal transform unit 204.

The inverse orthogonal transform unit 204 performs inverse orthogonal transform on the coefficient data supplied from the inverse quantization unit 203 in a method corresponding to the orthogonal transform method of the orthogonal transform unit 104 in FIG. The inverse orthogonal transform unit 204 obtains a difference image corresponding to the difference image before being orthogonally transformed in the image encoding device 100 by the inverse orthogonal transform process.

The difference image obtained by the inverse orthogonal transform is supplied to the calculation unit 205. In addition, a prediction image is supplied to the calculation unit 205 from the intra prediction unit 211 or the motion prediction / compensation unit 212 via the selection unit 213.

The calculation unit 205 adds the difference image and the prediction image, and obtains a reconstructed image corresponding to the image before the prediction image is subtracted by the calculation unit 103 of the image encoding device 100. The arithmetic unit 205 supplies the reconstructed image to the loop filter 206.

The loop filter 206 appropriately performs a loop filter process including a deblock filter process and an adaptive loop filter process on the supplied reconstructed image to generate a decoded image. For example, the loop filter 206 removes block distortion by performing a deblocking filter process on the reconstructed image. Further, for example, the loop filter 206 performs image quality improvement by performing loop filter processing using a Wiener filter on the deblock filter processing result (reconstructed image from which block distortion has been removed). I do.

Note that the type of filter processing performed by the loop filter 206 is arbitrary, and filter processing other than that described above may be performed. Further, the loop filter 206 may perform filter processing using the filter coefficient supplied from the image encoding device 100 of FIG.

The loop filter 206 supplies the decoded image as the filter processing result to the screen rearrangement buffer 207 and the frame memory 209. Note that the filter processing by the loop filter 206 can be omitted. That is, the output of the calculation unit 205 can be stored in the frame memory 209 without being subjected to filter processing. For example, the intra prediction unit 211 uses pixel values of pixels included in this image as pixel values of peripheral pixels.

The screen rearrangement buffer 207 rearranges the supplied decoded images. That is, the order of frames rearranged for the encoding order by the screen rearrangement buffer 102 in FIG. 1 is rearranged in the original display order. The D / A conversion unit 208 D / A converts the decoded image supplied from the screen rearrangement buffer 207, and outputs and displays the decoded image on a display (not shown).

The frame memory 209 stores supplied reconstructed images and decoded images. Also, the frame memory 209 selects the stored reconstructed image or decoded image from the selection unit 210 at a predetermined timing or based on an external request such as the intra prediction unit 211 or the motion prediction / compensation unit 212. To the intra prediction unit 211 and the motion prediction / compensation unit 212.

The selection unit 210 selects the supply destination of the image read from the frame memory 209. For example, the selection unit 210 supplies the reconstructed image read from the frame memory 209 to the intra prediction unit 211. For example, the selection unit 210 supplies the decoded image read from the frame memory 209 to the motion prediction / compensation unit 212.

The intra prediction unit 211 performs basically the same processing as the intra prediction unit 114 in FIG. However, the intra prediction unit 211 performs intra prediction only on a region where a prediction image is generated by intra prediction at the time of encoding.

The motion prediction / compensation unit 212 performs an inter motion prediction process based on the inter prediction information supplied from the lossless decoding unit 202, and generates a predicted image. Note that the motion prediction / compensation unit 212 performs the inter motion prediction process only on the region where the inter prediction is performed at the time of encoding, based on the inter prediction information supplied from the lossless decoding unit 202.

The intra prediction unit 211 or the motion prediction / compensation unit 212 supplies the generated predicted image to the calculation unit 205 via the selection unit 213 for each region of the prediction processing unit.

The selection unit 213 supplies the prediction image supplied from the intra prediction unit 211 or the prediction image supplied from the motion prediction / compensation unit 212 to the calculation unit 205.

Based on the information supplied from the lossless decoding unit 202 or the inverse quantization unit 203, the quantization parameter decoding unit 221 reconstructs the attention area quantization parameter used in the inverse quantization process in the inverse quantization unit 203, It is supplied to the inverse quantization unit 203.

[Inverse quantization unit and quantization parameter decoding unit]
FIG. 10 is a block diagram illustrating a main configuration example of the inverse quantization unit 203 and the quantization parameter decoding unit 221 in FIG.

As shown in FIG. 10, the inverse quantization unit 203 includes a differential quantization parameter buffer 231, a peripheral region quantization parameter buffer 232, a quantized orthogonal transform coefficient buffer 233, and an inverse quantization processing unit 234.

Also, the quantization parameter decoding unit 221 includes an offset storage unit 241, a predicted quantization parameter generation unit 242, a condition determination unit 243, and a region of interest quantization parameter reconstruction unit 244.

The differential quantization parameter buffer 231 stores the differential quantization parameter transmitted from the image encoding device 100 supplied from the lossless decoding unit 202. The difference quantization parameter buffer 231 supplies the stored difference quantization parameter to the attention area quantization parameter reconstruction unit 244 at a predetermined timing or based on an external request or the like.

The peripheral region quantization parameter buffer 232 stores the attention region quantization parameter supplied from the attention region quantization parameter reconstruction unit 244. The peripheral region quantization parameter buffer 232 predicts the stored attention region quantization parameter as a peripheral region quantization parameter in the processing in which another region processed after the attention region is the attention region. This is supplied to the quantization parameter generation unit 242.

The quantized orthogonal transform coefficient buffer 233 stores the quantized orthogonal transform coefficient transmitted from the image encoding device 100 and supplied from the lossless decoding unit 202. The quantized orthogonal transform coefficient buffer 233 supplies the stored quantized orthogonal transform coefficient to the inverse quantization processing unit 234 at a predetermined timing or based on an external request or the like.

The inverse quantization processing unit 234 uses the attention area quantization parameter acquired from the attention area quantization parameter reconstruction unit 244 to perform the orthogonal transform coefficient obtained from the quantized orthogonal transform coefficient buffer 233. Perform inverse quantization. The inverse quantization processing unit 234 supplies the orthogonal transform coefficient obtained by inverse quantization to the inverse orthogonal transform unit 204.

The offset storage unit 241 acquires and stores the quantization parameter offset (iqp_offset) supplied from the lossless decoding unit 202. The offset storage unit 241 supplies the offset (iqp_offset) to the attention area quantization parameter reconstruction unit 244 at a predetermined timing or based on an external request or the like. The offset (iqp_offset) may be the same as the offset (iqp_offset) used on the encoding side, and may be stored in advance in the offset storage unit 241 or set by a user or the like. You may do it.

The predictive quantization parameter generation unit 242 acquires the peripheral region quantization parameter supplied from the peripheral region quantization parameter buffer 232 and generates a predictive quantization parameter using it. This generation method is arbitrary. However, the same method as that on the encoding side is desirable. Further, as described in the first embodiment, it is desirable not to use a quantization parameter in a region using an offset, such as an intra region of an inter slice.

The predicted quantization parameter generation unit 242 supplies the generated predicted quantization parameter to the attention area quantization parameter reconstruction unit 244.

The condition determination unit 243 acquires information related to the attention area such as the slice type and the prediction mode information supplied from the lossless decoding unit 202. The condition determination unit 243 determines whether or not the attention area satisfies a predetermined condition using the information as in the case of the condition determination unit 142. The condition determination unit 243 supplies the determination result to the attention area quantization parameter reconstruction unit 244.

The attention area quantization parameter reconstructing unit 244 adds the difference quantization parameter acquired from the difference quantization parameter buffer 231 and the predicted quantization parameter acquired from the predicted quantization parameter generation part 242 to thereby add the attention area quantum. Reconstruction parameters. At that time, the attention area quantization parameter reconstructing unit 244 determines a reconstructing method of the attention area quantization parameter based on the determination result supplied from the condition determination unit 243.

FIG. 11 is a diagram for explaining an example of how to select the reconstruction method for the attention area quantization parameter. In the example shown in the table of FIG. 11, the slice type of the target slice is inter slice (P slice or B slice), and the prediction mode of the target region is inter prediction (that is, the target region is the inter region). If the slice type of the target slice is an intra slice (I slice), the target region quantization parameter reconstruction unit 244 reconstructs the target region quantization parameter using the following equation (3).

CurrQP = RefQP + dQP (3)

In Equation (3), dQP represents a differential quantization parameter, CurrQP represents a region of interest quantization parameter, and RefQP represents a predicted quantization parameter.

Further, when the slice type of the target slice is an inter slice (P slice or B slice) and the prediction mode of the target region is intra prediction (that is, the target region is an intra region), the target region quantization parameter re-sampling is performed. The construction unit 244 reconstructs the attention area quantization parameter using the following equation (4).

CurrQP = RefQP + dQP + iqp_offset (4)

In Equation (4), dQP represents a differential quantization parameter, CurrQP represents a region of interest quantization parameter, and RefQP represents a predicted quantization parameter. Further, iqp_offset is an offset supplied from the offset storage unit 241.

As described above, the attention area quantization parameter reconstructing unit 244 selects the attention area quantization parameter reconstruction method based on the condition determination result of the attention area, and reconstructs the attention area quantization parameter by the method. To do. The attention region quantization parameter reconstruction unit 244 supplies the reconstructed attention region quantization parameter to the inverse quantization processing unit 234 and the peripheral region quantization parameter buffer 232.

[Differential quantization parameter reconstruction unit]
FIG. 12 is a block diagram illustrating a main configuration example of the attention area quantization parameter reconstruction unit 244. As illustrated in FIG. 12, the attention area quantization parameter reconstruction unit 244 includes a calculation unit 251, a calculation unit 252, and a selection unit 253.

The calculation unit 151 adds the difference quantization parameter (dQP) supplied from the difference quantization parameter buffer 231 and the prediction quantization parameter (RefQP) supplied from the prediction quantization parameter generation unit 242 and adds the added value. (DQP + RefQP) is supplied to the calculation unit 252 and the selection unit 253.

The calculation unit 252 further adds the offset (iqp_offset) supplied from the offset storage unit 241 to the addition value (dQP + RefQP) supplied from the calculation unit 251, and supplies the addition value (dQP + RefQP + iqp_offset) to the selection unit 253.

The selection unit 253 acquires the condition determination result supplied from the condition determination unit 243, that is, control information, and supplies the addition value (dQP + RefQP) supplied from the calculation unit 251 or the calculation unit 252 according to the control information. One of the added values (dQP + RefQP + iqp_offset) is selected and supplied to the inverse quantization processing unit 234 and the peripheral region quantization parameter buffer 232 as the attention region quantization parameter (CurrQP).

For example, when the condition determination unit 243 determines that the region of interest is an intra region of an inter slice, the selection unit 253 selects an addition value (dQP + RefQP + iqp_offset) using an offset, and uses it as a region of interest quantization parameter (CurrQP) is supplied to the inverse quantization processing unit 234 and the peripheral region quantization parameter buffer 232.

For example, when the condition determination unit 243 determines that the attention area is not an intra area of the inter slice, the selection unit 253 selects an addition value (dQP + RefQP) that does not use an offset, and quantizes the attention area quantization. The parameter (CurrQP) is supplied to the inverse quantization processing unit 234 and the peripheral region quantization parameter buffer 232.

As each unit performs processing in this way, the quantization parameter decoding unit 221 can correctly reconstruct the attention area quantization parameter used in the quantization processing in the image encoding device 100, and the inverse quantization unit. 203 can perform inverse quantization by a method corresponding to the quantization processing by the quantization unit 105 of the image encoding device 100. That is, the image decoding apparatus 200 can realize improvement of the image quality of the decoded image while suppressing reduction in encoding efficiency.

[Decoding process flow]
Next, the flow of each process executed by the image decoding apparatus 200 as described above will be described. First, an example of the flow of decoding processing will be described with reference to the flowchart of FIG.

When the decoding process is started, in step S201, the accumulation buffer 201 accumulates the transmitted bit stream. In step S202, the lossless decoding unit 202 decodes the bit stream (encoded difference image information) supplied from the accumulation buffer 201. At this time, various types of information other than the difference image information included in the bitstream, such as information on the prediction mode information, is also decoded.

In step S203, the inverse quantization unit 203 inversely quantizes the quantized orthogonal transform coefficient obtained by the process in step S202. In step S204, the inverse orthogonal transform unit 204 performs inverse orthogonal transform on the orthogonal transform coefficient inversely quantized in step S203.

In step S205, the intra prediction unit 211 or the motion prediction / compensation unit 212 performs a prediction process using the supplied information. In step S206, the selection unit 213 selects a predicted image. In step S207, the calculation unit 205 adds the predicted image generated in step S205 to the difference image information obtained by the inverse orthogonal transform in step S204. Thereby, a reconstructed image is generated.

In step S208, the loop filter 206 appropriately performs a loop filter process including a deblock filter process and an adaptive loop filter process on the reconstructed image obtained in step S207.

In step S209, the screen rearrangement buffer 207 rearranges the decoded images generated by the filtering process in step S208. That is, the order of frames rearranged for encoding by the screen rearrangement buffer 102 of the image encoding device 100 is rearranged to the original display order.

In step S210, the D / A converter 208 D / A converts the decoded image in which the frame order is rearranged. The decoded image is output and displayed on a display (not shown).

In step S211, the frame memory 209 stores the decoded image obtained by the filtering process in step S208. This decoded image is used as a reference image in the inter prediction process.

When the process of step S211 is completed, the decryption process is terminated.

[Flow of inverse quantization processing]
Next, an example of the flow of the inverse quantization process executed in step S203 of FIG. 13 will be described with reference to the flowchart of FIG.

When the inverse quantization process is started, the offset storage unit 241 stores the offset (ipd_offset) transmitted from the image encoding device 100 in step S231.

In step S232, the differential quantization parameter buffer 231 acquires the differential quantization parameter generated in the image encoding device 100.

In step S233, the predicted quantization parameter generation unit 242 generates a predicted quantization parameter using the peripheral region quantization parameter read from the peripheral region quantization parameter buffer 232.

In step S234, the condition determination unit 243 confirms the slice type of the target slice and the prediction mode of the target region.

In step S235, the condition determination unit 243 determines whether or not the target slice is an inter slice and the target region is an intra region. If it is determined that the target slice is an inter slice and the target region is an intra region, the condition determination unit 243 advances the process to step S236.

In step S236, the attention area quantization parameter reconstruction unit 244 reconstructs the attention area quantization parameter using, for example, Expression (4), using the offset read from the offset storage unit 241. That is, the attention area quantization parameter reconstruction unit 244 adds the predicted quantization parameter and the offset to the difference quantization parameter to obtain the attention area quantization parameter. When the process of step S236 ends, the attention area quantization parameter reconstruction unit 244 advances the process to step S238.

If it is determined in step S235 that the target slice is not an inter slice or the target region is not an intra region, the condition determination unit 243 advances the process to step S237.

In step S237, the attention area quantization parameter reconstruction unit 244 reconstructs the attention area quantization parameter, for example, as shown in Expression (3). That is, the attention area quantization parameter reconstruction unit 244 adds the predicted quantization parameter to the difference quantization parameter, and sets it as the attention area quantization parameter. When the process of step S237 ends, the attention area quantization parameter reconstruction unit 244 advances the process to step S238.

In step S238, the peripheral region quantization parameter buffer 232 stores the attention region quantization parameter reconstructed by the processing in step S236 or step S237.

In step S239, the quantized orthogonal transform coefficient buffer 233 obtains the quantized orthogonal transform coefficient transmitted from the image coding apparatus 100. In step S240, the inverse quantization processing unit 234 inversely quantizes the quantized orthogonal transform coefficient acquired in step S239.

When the process of step S240 is completed, the inverse quantization processing unit 234 ends the inverse quantization process and returns the process to FIG.

As described above, by performing various processes, the image decoding apparatus 200 can realize an improvement in the image quality of a decoded image while suppressing a decrease in encoding efficiency.

In the above description, as illustrated in FIG. 3, the quantization parameter of the intra region existing in the inter slice is described to be set to a value smaller than that of the surrounding inter region. The quantization parameter in the inter area may be set to a value larger than that in the intra area.

In this case, the offset (iqp_offset) is a positive value because it is used when generating the differential quantization parameter in the inter region where the quantization parameter is set to a large value.

Note that the quantization parameter of the intra area existing in the inter slice as shown in FIG. 3 may be set to a value larger than that of the surrounding inter area. In this case, the offset (iqp_offset) is a positive value because it is used to generate the differential quantization parameter in the intra region. Furthermore, the quantization parameter of the inter area may be set to a value smaller than that of the intra area. In this case, the offset (iqp_offset) is a negative value because it is used to generate the inter region differential quantization parameter.

The adjustment of the quantization parameter as described above is based on the difference in prediction accuracy between intra prediction and inter prediction. However, this is not the only cause of local changes in the image quality of the decoded image. The present technology can be applied to any case as long as it suppresses a reduction in encoding efficiency when suppressing a local change in the image quality of a decoded image.

That is, the present technology can be applied not only to the difference in prediction accuracy between intra prediction and inter prediction, but also to all factors. For example, whether the size of the region is large, whether the partition type is the same, whether the motion vector is long or short, whether the prediction direction of intra prediction is the same, or the quantization parameter of the reference destination May be high or low. In either case, the condition determination unit 142 or the condition determination unit 243 may perform threshold determination to determine whether or not a large difference occurs between the image quality of the attention area and the surrounding image quality in the decoded image. .

Note that the image quality evaluation method is arbitrary and may be other than the PSNR described above.

Note that this technology is, for example, MPEG, H.264. When receiving image information (bitstream) compressed by orthogonal transform such as discrete cosine transform and motion compensation, such as 26x, via network media such as satellite broadcasting, cable television, the Internet, or mobile phones. The present invention can be applied to an image encoding device and an image decoding device used in the above. In addition, the present technology can be applied to an image encoding device and an image decoding device that are used when processing is performed on a storage medium such as an optical disk, a magnetic disk, and a flash memory. Furthermore, the present technology can also be applied to motion prediction / compensation devices included in such image encoding devices and image decoding devices.

<3. Third Embodiment>
[Computer]
The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software is installed in the computer. Here, the computer includes a computer incorporated in dedicated hardware, a general-purpose personal computer capable of executing various functions by installing various programs, and the like.

In FIG. 15, a CPU (Central Processing Unit) 501 of the personal computer 500 performs various processes according to a program stored in a ROM (Read Only Memory) 502 or a program loaded from a storage unit 513 to a RAM (Random Access Memory) 503. Execute the process. The RAM 503 also appropriately stores data necessary for the CPU 501 to execute various processes.

The CPU 501, the ROM 502, and the RAM 503 are connected to each other via a bus 504. An input / output interface 510 is also connected to the bus 504.

The input / output interface 510 includes an input unit 511 including a keyboard and a mouse, a display including a CRT (Cathode Ray Tube) and an LCD (Liquid Crystal Display), an output unit 512 including a speaker, and a hard disk. A communication unit 514 including a storage unit 513 and a modem is connected. The communication unit 514 performs communication processing via a network including the Internet.

A drive 515 is connected to the input / output interface 510 as necessary, and a removable medium 521 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is appropriately mounted, and a computer program read from them is It is installed in the storage unit 513 as necessary.

When the above-described series of processing is executed by software, a program constituting the software is installed from a network or a recording medium.

For example, as shown in FIG. 15, the recording medium is distributed to distribute the program to the user separately from the apparatus main body, and includes a magnetic disk (including a flexible disk) on which the program is recorded, an optical disk ( It is only composed of removable media 521 consisting of CD-ROM (compact disc-read only memory), DVD (including digital versatile disc), magneto-optical disc (including MD (mini disc)), or semiconductor memory. Rather, it is composed of a ROM 502 on which a program is recorded and a hard disk included in the storage unit 513, which is distributed to the user in a state of being incorporated in the apparatus main body in advance.

The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

Further, in the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in chronological order according to the described order, but may be performed in parallel or It also includes processes that are executed individually.

In addition, in this specification, the system represents the entire apparatus composed of a plurality of devices (apparatuses).

Also, in the above, the configuration described as one device (or processing unit) may be divided and configured as a plurality of devices (or processing units). Conversely, the configurations described above as a plurality of devices (or processing units) may be combined into a single device (or processing unit). Of course, a configuration other than that described above may be added to the configuration of each device (or each processing unit). Furthermore, if the configuration and operation of the entire system are substantially the same, a part of the configuration of a certain device (or processing unit) may be included in the configuration of another device (or other processing unit). . That is, the present technology is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present technology.

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

<4. Fourth Embodiment>
[First application example: television receiver]
FIG. 16 shows an example of a schematic configuration of a television apparatus to which the above-described embodiment is applied. The television apparatus 900 includes an antenna 901, a tuner 902, a demultiplexer 903, a decoder 904, a video signal processing unit 905, a display unit 906, an audio signal processing unit 907, a speaker 908, an external interface 909, a control unit 910, a user interface 911, And a bus 912.

Tuner 902 extracts a signal of a desired channel from a broadcast signal received via antenna 901, and demodulates the extracted signal. Then, the tuner 902 outputs the encoded bit stream obtained by the demodulation to the demultiplexer 903. That is, the tuner 902 has a role as a transmission unit in the television device 900 that receives an encoded stream in which an image is encoded.

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

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

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

The display unit 906 is driven by a drive signal supplied from the video signal processing unit 905, and displays an image on a video screen of a display device (for example, a liquid crystal display, a plasma display, or an OELD (Organic ElectroLuminescence Display) (organic EL display)). Or an image is displayed.

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

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

The control unit 910 includes a processor such as a CPU and memories such as a RAM and a ROM. The memory stores a program executed by the CPU, program data, EPG data, data acquired via a network, and the like. For example, the program stored in the memory is read and executed by the CPU when the television apparatus 900 is activated. The CPU executes the program to control the operation of the television device 900 according to an operation signal input from the user interface 911, for example.

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

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

In the thus configured television apparatus 900, the decoder 904 has the function of the image decoding apparatus according to the above-described embodiment. Thereby, when the image is decoded by the television device 900, it is possible to improve the image quality of the decoded image while suppressing the reduction of the encoding efficiency.

<5. Fifth embodiment>
[Second application example: mobile phone]
FIG. 17 shows an example of a schematic configuration of a mobile phone to which the above-described embodiment is applied. A mobile phone 920 includes an antenna 921, a communication unit 922, an audio codec 923, a speaker 924, a microphone 925, a camera unit 926, an image processing unit 927, a demultiplexing unit 928, a recording / reproducing unit 929, a display unit 930, a control unit 931, an operation A portion 932 and a bus 933.

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

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

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

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

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

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

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

In the mobile phone 920 configured as described above, the image processing unit 927 has the functions of the image encoding device and the image decoding device according to the above-described embodiment. Accordingly, when encoding and decoding an image with the mobile phone 920, the image quality of the decoded image can be improved while suppressing a decrease in encoding efficiency.

<6. Sixth Embodiment>
[Third application example: recording / reproducing apparatus]
FIG. 18 shows an example of a schematic configuration of a recording / reproducing apparatus to which the above-described embodiment is applied. For example, the recording / reproducing device 940 encodes audio data and video data of a received broadcast program and records the encoded data on a recording medium. In addition, the recording / reproducing device 940 may encode audio data and video data acquired from another device and record them on a recording medium, for example. In addition, the recording / reproducing device 940 reproduces data recorded on the recording medium on a monitor and a speaker, for example, in accordance with a user instruction. At this time, the recording / reproducing device 940 decodes the audio data and the video data.

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

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

The external interface 942 is an interface for connecting the recording / reproducing apparatus 940 to an external device or a network. The external interface 942 may be, for example, an IEEE1394 interface, a network interface, a USB interface, or a flash memory interface. For example, video data and audio data received via the external interface 942 are input to the encoder 943. That is, the external interface 942 serves as a transmission unit in the recording / reproducing device 940.

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

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

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

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

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

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

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

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

In the thus configured recording / reproducing apparatus 940, the encoder 943 has the function of the image encoding apparatus according to the above-described embodiment. The decoder 947 has the function of the image decoding apparatus according to the above-described embodiment. Thereby, when encoding and decoding an image by the recording / reproducing apparatus 940, it is possible to improve the image quality of the decoded image while suppressing a decrease in encoding efficiency.

<7. Seventh Embodiment>
[Fourth Application Example: Imaging Device]
FIG. 19 illustrates an example of a schematic configuration of an imaging apparatus to which the above-described embodiment is applied. The imaging device 960 images a subject to generate an image, encodes the image data, and records it on a recording medium.

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

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

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

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

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

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

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

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

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

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

In the imaging device 960 configured as described above, the image processing unit 964 has the functions of the image encoding device and the image decoding device according to the above-described embodiment. Thereby, when encoding and decoding an image by the imaging device 960, it is possible to improve the image quality of the decoded image while suppressing a decrease in encoding efficiency.

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

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

In addition, this technique can also take the following structures.
(1) a determination unit that determines whether or not there is a large difference between the image quality of a target area to be processed and the image quality of a surrounding area in the decoded image;
When the determination unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization that generates the difference quantization parameter of the region of interest by calculation using a predetermined offset A parameter generator;
An image processing apparatus comprising: a transmission unit that transmits the differential quantization parameter generated by the differential quantization parameter generation unit.
(2) It further includes a region-of-interest quantization parameter generating unit that generates a quantization parameter of the region of interest.
When the determination unit determines that the difference between the image quality of the attention region and the image quality of the surrounding region is large by the determination unit, the quantization parameter of the surrounding region is greatly different from the value. The image processing apparatus according to (1), wherein a quantization parameter for the region of interest is generated.
(3) When the determination unit determines that the image quality of the attention region is particularly low compared with the image quality of the surrounding region, the attention region quantization parameter generation unit compares the quantization parameter of the surrounding region with the quantization parameter of the surrounding region. The image processing device according to (2), wherein a quantization parameter for the region of interest having a particularly small value is generated.
(4) When the determination unit determines that the image quality of the attention region is particularly higher than the image quality of the surrounding region, the attention region quantization parameter generation unit compares it with the quantization parameter of the surrounding region. The image processing device according to (2), wherein a quantization parameter for the region of interest having a particularly large value is generated.
(5) The offset value is a value that reduces a difference between a quantization parameter of the attention area and a quantization parameter of the surrounding area. Any one of (2) to (4) An image processing apparatus according to 1.
(6) When the difference quantization parameter generation unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large by the determination unit, the difference quantization parameter generation unit uses the quantization parameter of the region of interest to calculate the attention The image processing device according to any one of (1) to (5), wherein the difference quantization parameter is generated by subtracting a prediction value of a quantization parameter of a region and further subtracting the offset.
(7) If the difference quantization parameter generation unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is not large by the determination unit, The image processing apparatus according to any one of (1) to (6), wherein the difference quantization parameter is generated by subtracting a predicted value of a quantization parameter of a region of interest.
(8) The difference between the image quality of the attention area and the image quality of the surrounding area is due to a difference in prediction accuracy between inter prediction and intra prediction,
The condition determination unit determines whether or not there is a large difference between the image quality of the attention area and the image quality of the surrounding area by checking respective prediction methods of the attention area and the surrounding area. The image processing device according to any one of (7) to (7).
(9) Whether the difference between the image quality of the region of interest and the image quality of the surrounding region is large by confirming the prediction method of the region of interest and the type of slice in which the region of interest exists. The image processing apparatus according to (8).
(10) An image processing method for an image processing apparatus,
The determination unit determines whether or not the difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large in the decoded image;
When the difference quantization parameter generation unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization parameter generation unit generates the difference quantization parameter of the region of interest by calculation using a predetermined offset. ,
An image processing method in which a transmission unit transmits the generated differential quantization parameter.
(11) a receiving unit that receives a differential quantization parameter of a region of interest that is a processing target;
A determination unit that determines whether or not a difference between an image quality of a target region to be processed and an image quality of a surrounding region is large in the decoded image;
When the determination unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization parameter received by the reception unit is calculated from the difference quantization parameter by a calculation using a predetermined offset. An image processing apparatus comprising: an attention area quantization parameter reconstruction unit that reconstructs a quantization parameter of an attention area.
(12) An image processing method for an image processing apparatus,
The receiving unit receives the difference quantization parameter of the attention area to be processed,
The determination unit determines whether or not the difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large in the decoded image;
When the region-of-interest quantization parameter reconstructing unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, from the received difference quantization parameter by an operation using a predetermined offset An image processing method for reconstructing a quantization parameter of the region of interest.

100 image encoding device, 105 quantization unit, 121 quantization parameter encoding unit, 131 attention region quantization parameter generation unit, 132 quantization processing unit, 133 peripheral region quantization parameter buffer, 134 differential quantization parameter buffer, 141 Predictive quantization parameter generation unit, 142 condition determination unit, 143 offset storage unit, 144 differential quantization parameter generation unit, 200 image decoding device, 203 inverse quantization unit, 221 quantization parameter decoding unit, 231 differential quantization parameter buffer, 232 peripheral region quantization parameter buffer, 233 quantization orthogonal transform coefficient buffer, 234 inverse quantization processing unit, 241 offset storage unit, 242 prediction quantization parameter generation unit, 243 conditions Tough, 244 attention area quantization parameter reconstruction unit

Claims (12)

1. A determination unit that determines whether or not a difference between an image quality of a target region to be processed and an image quality of a surrounding region is large in the decoded image;
   When the determination unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization that generates the difference quantization parameter of the region of interest by calculation using a predetermined offset A parameter generator;
   An image processing apparatus comprising: a transmission unit that transmits the differential quantization parameter generated by the differential quantization parameter generation unit.
2. A region-of-interest quantization parameter generating unit that generates a quantization parameter of the region of interest;
   When the determination unit determines that the difference between the image quality of the attention region and the image quality of the surrounding region is large by the determination unit, the quantization parameter of the surrounding region is greatly different from the value. The image processing device according to claim 1, wherein a quantization parameter for the region of interest is generated.
3. The region-of-interest quantization parameter generation unit, when the determination unit determines that the image quality of the region of interest is particularly low compared to the image quality of the surrounding region, the value is particularly greater than the quantization parameter of the surrounding region The image processing apparatus according to claim 2, wherein a small quantization parameter for the attention area is generated.
4. The region-of-interest quantization parameter generation unit, when the determination unit determines that the image quality of the region of interest is particularly high compared to the image quality of the surrounding region, the value is particularly greater than the quantization parameter of the surrounding region. The image processing apparatus according to claim 2, wherein a large quantization parameter for the attention area is generated.
5. The image processing apparatus according to claim 2, wherein the offset value is a value that reduces a difference between a quantization parameter of the region of interest and a quantization parameter of the surrounding region.
6. The differential quantization parameter generation unit, when the determination unit determines that the difference between the image quality of the attention area and the image quality of the surrounding area is large, the quantization parameter of the attention area is determined from the quantization parameter of the attention area. The image processing apparatus according to claim 1, wherein the difference quantization parameter is generated by subtracting a predicted value of the quantization parameter and further subtracting the offset.
7. When the determination unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is not large, the difference quantization parameter generation unit determines the region of interest from the quantization parameter of the region of interest. The image processing apparatus according to claim 1, wherein the differential quantization parameter is generated by subtracting a predicted value of the quantization parameter.
8. The difference between the image quality of the attention area and the image quality of the surrounding area is due to the difference in prediction accuracy between inter prediction and intra prediction,
   The condition determination unit determines whether or not a difference between the image quality of the attention area and the image quality of the surrounding area is large by checking respective prediction methods of the attention area and the surrounding area. The image processing apparatus described.
9. The condition determination unit determines whether or not a difference between the image quality of the attention area and the image quality of the surrounding area is large by confirming a prediction method of the attention area and a type of a slice in which the attention area exists. The image processing apparatus according to claim 8.
10. An image processing method of an image processing apparatus,
    The determination unit determines whether or not the difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large in the decoded image;
    When the difference quantization parameter generation unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization parameter generation unit generates the difference quantization parameter of the region of interest by calculation using a predetermined offset. ,
    An image processing method in which a transmission unit transmits the generated differential quantization parameter.
11. A receiving unit for receiving the differential quantization parameter of the attention area to be processed;
    A determination unit that determines whether or not a difference between an image quality of a target region to be processed and an image quality of a surrounding region is large in the decoded image;
    When the determination unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, the difference quantization parameter received by the reception unit is calculated from the difference quantization parameter by a calculation using a predetermined offset. An image processing apparatus comprising: an attention area quantization parameter reconstruction unit that reconstructs a quantization parameter of an attention area.
12. An image processing method of an image processing apparatus,
    The receiving unit receives the difference quantization parameter of the attention area to be processed,
    The determination unit determines whether or not the difference between the image quality of the attention area to be processed and the image quality of the surrounding area is large in the decoded image;
    When the region-of-interest quantization parameter reconstructing unit determines that the difference between the image quality of the region of interest and the image quality of the surrounding region is large, from the received difference quantization parameter by an operation using a predetermined offset An image processing method for reconstructing a quantization parameter of the region of interest.

Images