JP2004064702A - Video data compressing apparatus, method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video data compressing apparatus, method and program in which picture quality deterioration in a concerned region projecting an object or the like to pay attention in video data is reduced rather than a background region of the other region when the video data are compressed, and compressibility of the video data is improved. <P>SOLUTION: A video data compressing apparatus 1 is provided with a region division control means 10 for performing division into regions by judging whether inputted video data belong to the moving concerned region or the other background region for the unit of a video frame for each block of a specific size, and a gradation reduction control means 20 for individually reducing gradation indicating the number of colors expressible with pixels in the concerned region and the background region. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for compressing video data, and more particularly, to a video data compression apparatus, a method, and a program for compressing video data by reducing image quality deterioration of a region of interest in the video data.
[0002]
[Prior art]
At present, services for distributing video data to information terminals such as mobile terminals and PDAs (Personal Digital Assistants) have begun to spread. In this case, even if an attempt is made to distribute high-definition video data, the bandwidth of the transmission path for distributing the video data is limited, so that the video data is compressed using MPEG-4 (Moving Picture Experts Group 4) or the like. Has been delivered.
[0003]
Conventionally, with regard to the video data compression technique, for example, as in MPEG-2 (Moving Picture Experts Group 2), motion compensation inter-frame prediction (MC: Motion Compensation) and discrete cosine transform (DCT: Discrete Cosine Transform) Is generally used.
[0004]
That is, in the compression of video data according to MPEG-2 or the like, first, a prediction error between video frames of video data is generated in units of 16 × 16 pixels (macroblock) by motion compensation inter-frame prediction, and the prediction error is discrete. By performing the cosine transform, a DCT coefficient indicating the amplitude of the frequency component is generated. Utilizing the fact that human visual sensitivity to high-frequency components is weak, video data is compressed by reducing the number of digits of DCT coefficients of high-frequency components.
[0005]
[Problems to be solved by the invention]
However, in the above-described conventional technique, compression of video data such as MPEG-2 reduces the amount of information depending on the size of a motion vector in motion compensation inter-frame prediction or the frequency component of a macroblock. It did not consider the content of the data.
[0006]
For this reason, when attempting to distribute high-definition video data to a small portable terminal such as a portable terminal or a PDA, a large amount of information is reduced by band compression, and a display for displaying the video data on the distributed portable terminal is performed. The image is an image in which the image quality is deteriorated on the entire screen. In other words, the display image displayed on the mobile terminal has a problem that the image quality of a region of interest in which a notable subject or the like in the image is deteriorated to the same extent as the background region, which is the other region. Was.
[0007]
The present invention has been made in view of the above-described problems, and when image data is compressed, image quality degradation of a region of interest in which a notable subject or the like in the image data is projected is reduced. It is an object of the present invention to provide a video data compression device, a method thereof, and a program thereof, which are capable of reducing the compression ratio of video data while reducing the size of the video data from the background region.
[0008]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made to achieve the above object. First, a video data compression apparatus according to claim 1 provides, for input video data, a gradation indicating the number of colors that each pixel can represent. A video data compression apparatus for compressing the video data by reducing the video data, wherein the video data compression device divides the video data into a region of interest where a subject is present for each video frame and a background region other than the region. And a gradation reduction control means for individually reducing the gradation for each of the attention area and the background area divided by the area division control means.
[0009]
According to this configuration, the video data compression device divides the video data into the attention area and the background area other than the attention area for each video frame by the area division control unit. At this time, if the attention area is a moving area, a motion vector of the attention area is obtained, the attention area and the background area are identified, and the area is divided. Further, when the attention area can be identified by characteristics such as colors as compared with the background area, the area may be divided by performing threshold processing based on the characteristics such as colors.
[0010]
Then, in the video data compression device, for each of the regions divided by the region division control unit, the gradation of the region is individually reduced by the gradation reduction control unit. For example, when compressing video data by reducing video data, reducing the gradation of the background region more than the gradation of the region of interest reduces the degradation of the image quality of the region of interest to the degradation of the image quality of the background region. Acts to suppress.
[0011]
The video data compression apparatus according to claim 2 is the video data compression apparatus according to claim 1, wherein the area division control unit is configured to control each block of a specific size between successive video frames of the video data. A motion vector calculation unit for calculating a motion vector, and based on the motion vector calculated by the motion vector calculation unit, the block in the video frame is a block included in the attention area or the background other than the block. And an area identifying means for identifying whether the block is included in the area.
[0012]
According to this configuration, the video data compression device calculates a motion vector for each block of a specific size between continuous video frames of video data by the motion vector calculation unit. For example, this block is a macroblock used for motion compensation prediction such as MPEG-2. Then, based on the magnitude of the motion vector calculated by the motion vector calculating means, the block (macroblock) in the video frame is determined by the area identifying means to be a block included in the moving attention area or to a background area other than the block. Is included in the block. This makes it possible to divide a video frame into a target area and a background area in units of blocks (macroblocks), and to independently process (reduce) the video data of the target area and the background area.
[0013]
Further, in the video data compression device according to claim 3, in the video data compression device according to claim 2, the region division control unit determines that the region of interest and the background region identified by the region identification unit are different from each other. In an adjacent area, the image processing apparatus is provided with an area expanding unit that expands the block of the background area as the block of the area of interest based on the correlation between the block of the area of interest and the block of the background area.
[0014]
According to this configuration, the video data compression device uses the area expansion unit to perform similarity in the correlation between adjacent blocks (macroblocks), for example, in a feature amount such as luminance or color in an area where the attention area and the background area are adjacent. A block in a background region having a characteristic is defined as a block in a region of interest. As a result, it is possible to extend a region with little motion that is not recognized as a region of interest in the detection of a motion vector as a region of interest.
[0015]
According to a fourth aspect of the present invention, in the video data compression apparatus according to any one of the first to third aspects, the gradation reduction control unit is assigned to the background area. It is characterized in that the gradation is reduced more than the gradation assigned to the attention area.
[0016]
According to this configuration, the video data compression device causes the gradation reduction control unit to set the gradation assigned to the background area lower than the gradation assigned to the attention area. This makes it possible to increase the compression ratio of the region of interest when compressing video data.
[0017]
Further, in the video data compression apparatus according to claim 5, in the video data apparatus according to any one of claims 1 to 4, the gradation reduction control unit is configured to control the gradation reduction control unit for each of the attention area and the background area. The present invention is characterized in that the tone assigned to the color difference component is reduced more than the tone assigned to the luminance component.
[0018]
According to this configuration, in the video data compression device, the tone reduction control unit sets the tone assigned to the color difference component for each attention area and the background area lower than the tone assigned to the luminance component. Thus, when compressing the video data, the sensitivity of the chrominance component is lower for the human visual sense than the luminance component, so that it is possible to increase the compression efficiency while suppressing the deterioration of the image quality of the video data.
[0019]
Further, the video data compression method according to claim 6 is a video data compression method for compressing the video data by reducing the gradation indicating the number of colors that can be represented by each pixel in the input video data. An area dividing step of dividing the video data into an attention area where a subject is present for each video frame and a background area other than the attention area; and an area division step for each of the attention area and the background area divided in the area division step. A tone reduction step of individually reducing the tone, wherein the tone reduction step reduces the tone assigned to the background area more than the tone assigned to the attention area. It is characterized by doing.
[0020]
According to this method, the video data compression method divides the video data into a region of interest and a background region other than the region of interest for each video frame in the region dividing step. At this time, if the attention area is a moving area, a motion vector of the attention area is obtained, the attention area and the background area are identified, and the area is divided. Further, when the attention area can be identified by characteristics such as colors as compared with the background area, the area may be divided by performing threshold processing based on the characteristics such as colors.
[0021]
Then, in the video data compression method, in the gradation reduction step, for each region divided in the region division step, the gradation of the region is individually reduced. At this time, by reducing the gradation of the background area more than the gradation of the attention area, the image quality of the attention area is reduced more than the image quality of the background area.
[0022]
Furthermore, the video data compression program according to claim 7 reduces a gradation indicating the number of colors that can be represented by each pixel with respect to the input video data, and compresses the video data. A region division control unit that divides the video data into a region of interest in which a subject is present for each video frame and a background region other than the region, for each of the region of interest and the background region divided by the region division control unit, Functioning as tone reduction control means for individually reducing the tone, the tone reduction control means reducing the tone assigned to the background area more than the tone assigned to the attention area It is characterized by doing.
[0023]
According to this configuration, the video data compression program divides the video data into the attention area and the background area other than the attention area for each video frame by the area division control means, and controls the area division control by the gradation reduction control means. For each area divided by the means, the gradation of the area is individually reduced. At this time, by reducing the gradation of the background area more than the gradation of the attention area, the degradation of the image quality of the attention area is suppressed as compared with the degradation of the image quality of the background area.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Configuration of Video Data Compression Device: First Embodiment)
FIG. 1 is a block diagram showing a configuration of a video data compression device 1 according to a first embodiment of the present invention. The video data compression device 1 shown in FIG. 1 divides input video data into a moving region of interest and a background region, which is another region, and expresses a pixel value for each of the divided regions. The image data is compressed and output by reducing the number of gradations required for the image processing, and is configured to include a region division control unit 10 and a gradation reduction control unit 20.
[0025]
Here, the region of interest refers to a region (attention region FG) where a person or the like appears on the video frame F as shown in FIG. 7 and the background region is a region other than the region of interest FG (background region). BG). Note that a plurality of attention areas FG may exist on the video frame F as shown in FIG.
[0026]
The area division control unit 10 divides the input video data into blocks each having a specific size by determining whether the input video data is an attention area having motion or a background area other than the motion area. Is what you do. Here, the area division control means 10 includes a motion vector calculation unit 11, a global vector calculation unit 12, and an area identification unit 13.
[0027]
Further, the gradation reduction control means 20 individually reduces the gradation for expressing the pixel values of the attention area and the background area of the input video data. The gradation reduction control means 20 includes a gradation setting unit 21 and a gradation reduction unit 22.
Here, a block of a specific size is a macroblock (16 × 16 pixels) used for motion compensation prediction such as MPEG-2.
[0028]
The motion vector calculation unit (motion vector calculation unit) 11 calculates a motion vector from video frames of video data that is continuously input. Here, the motion vector calculation unit 11 is composed of a video delay unit 11a and a motion vector detection unit 11b.
[0029]
The video delay unit 11a delays input video data (input video data) in video frame units. The video data (delayed video data) delayed by one video frame in the video delay unit 11a is output to the motion vector detection unit 11b.
[0030]
The motion vector detecting unit 11b detects a motion vector in macroblock units of a video frame based on the input video data (input video data) and the delayed video data delayed by the video delay unit 11a. . The motion vector detected by the motion vector detection section 11b is output to the global vector calculation section 12 and the area identification section 13. The motion vector is obtained by a block matching method for each macroblock between the video frame of the input video data and the video frame of the delayed video data, that is, between adjacent video frames.
[0031]
The global vector calculation unit 12 calculates the most frequently detected motion vector among the plurality of motion vectors as a global vector based on the motion vector for each macroblock input from the motion vector detection unit 11b. is there. The global vector calculated by the global vector calculation unit 12 is output to the area identification unit 13. The global vector calculated here can be regarded as a motion vector of a background area having the largest area in the input video data.
[0032]
The region identification unit (region identification means) 13 has a macroblock having a motion based on the motion vector for each macroblock detected by the motion vector detection unit 11b and the global vector calculated by the global vector calculation unit 12. It is to identify whether it is included in the attention area or in the background area which is the other area. The region (attention region or background region) for each macroblock identified by the region identification unit 13 is output to the gradation setting unit 21 of the gradation reduction control unit 20 as region information together with the coordinates of the macroblock.
[0033]
Here, a video (macroblock) that moves differently from the global vector is regarded as a region of interest. For example, comparing the motion vector of each macroblock with the global vector, if the difference between the two vectors is equal to or greater than a preset value (for example, 4 pixels per video frame), the macroblock is included in the attention area. Judge.
[0034]
The gradation setting unit 21 sets a gradation reduction amount for each macroblock of the attention area and the background area identified by the area identification unit 13 of the area division control unit 10, and sets the reduction amount as reduction information together with the macroblock coordinates. This is output to the tone reduction unit 22. Here, based on C / N (Carrier to Noise Ratio) information of a transmission path for transmitting video (video data), buffer occupation information of a network server that stores video, and the like, a reduction amount of video data (video The amount of reduction is determined in advance, and the image reduction amount is input to the gradation setting unit 21 from input means (not shown) such as a keyboard. Then, the gradation setting unit 21 sets the gradation reduction amount of each region based on the image reduction amount such that the gradation of the background region is lower than the gradation of the attention region.
[0035]
Here, with reference to FIG. 3 and FIG. 4, a method of setting the gradation reduction amount of the attention area and the background area in the gradation setting unit 21 will be described. Here, it is assumed that the video data is a YC (luminance / color difference) video signal, and its gradation is expressed by 8 bits. FIG. 3 shows a configuration of a macroblock in MPEG-2 as an example of a YC (luminance / color difference) video signal. FIG. 4 shows the priorities of the deletion contents for reducing the gradation.
[0036]
As shown in FIG. 3, in MPEG-2, a macroblock is composed of a 16 × 16 pixel Y (luminance) video signal and an 8 × 8 pixel C (color difference) video signal (C _r Video signal and C _b Video signal). Here, to reduce the gradation means to reduce the number of bits representing each pixel, thereby reducing the level that the pixel can represent. For example, by reducing 3 bits from the original pixel B1 capable of expressing an image of 256 gradations with 8 bits, the reduced pixel B2 can only express up to 32 gradations with 5 bits.
[0037]
Then, as shown in FIG. 4, the gradation setting unit 21 (FIG. 1) sets the gradation reduction amount to each macroblock in the order of priority (1) to (8).
In the priority order (1), the gradation of the C (color difference) video signal in the background area is set to be reduced, and in the priority order (2), the gradation of the Y (luminance) video signal in the background area is reduced. Set to. In the priority order (3), the gradation of the C (color difference) video signal in the attention area is set to be reduced, and in the priority order (4), the gradation of the Y (luminance) video signal in the attention area is reduced. Set to It should be noted that the above-described reduction can be performed until the gradation becomes a minimum of 5 bits.
[0038]
Here, the reason why the reduction of the C (color difference) video signal is prioritized over the reduction of the Y (luminance) video signal is that human vision has a characteristic that the sensitivity of the color difference component is lower than the luminance component. It is. Further, the reason why the minimum gradation is set to 5 bits here is that it is reported that if the gradation is reduced to 4 bits or less for an original image having 8 bits of gradation, the image quality is remarkably deteriorated (see References). : Otsuka et al., "Temporal / spatial / gradation resolution and TV image quality," IEICE Technical Committee on Image Engineering, IE 87-114, pp. 17-24, 1987).
[0039]
If further reduction of the gradation is required, the priority (5) is to reduce the gradation of the C (color difference) video signal in the background area to less than 5 bits (up to a minimum of 0 bits), and then to the priority (6). The gradation of the C (color difference) video signal in the region of interest is reduced to less than 5 bits (to a minimum of 0 bits). In the priority order (7), the gradation of the Y (luminance) video signal in the background area is reduced to less than 5 bits (to a minimum of 0 bits). In the priority order (8), the Y (luminance) video signal in the attention area is reduced. The signal gradation is reduced to less than 5 bits (to a minimum of 0 bits).
The priority (6) and the priority (7) may be reversed. If there is no region of interest in the video frame, the priorities (3), (4), (6) and (8) are not considered.
[0040]
In the priorities (1) to (4), the minimum gradation is 5 bits, but may be changed depending on the resolution of the video to be processed. For example, in the case of a high-definition or NTSC broadcast video, the minimum gradation is 6 bits, and in the case of SIF (352 horizontal × 240 vertical pixels) or QSIF (176 horizontal × 120 vertical pixels), the minimum gray scale is 5 bits. I do.
Returning to FIG. 1, the description will be continued.
[0041]
The gradation reduction unit 22 reduces the gradation of each macroblock based on the amount of gradation deletion (reduction information) for each macroblock set by the gradation setting unit 21. The video data whose gradation has been reduced by the gradation reduction unit 22 is output as compressed video data (output video data). For example, if the pixel of the video data is composed of 8 bits and the reduction information notified from the gradation setting unit 21 indicates that the reduction amount of the gradation of a certain macroblock is 2 bits, the gradation reduction unit 22 Sets the gradation of the macro block to 6 (8 minus 2) bits. Thus, the information amount of the video data can be compressed.
[0042]
As described above, the configuration of the video data compression device 1 has been described based on one embodiment, but the present invention is not limited to this. For example, the attention area extraction performed by the area division control means 10 may be performed by using a specific gradation value as a threshold when the attention area and the background area have different color feature amounts besides using the motion vector. It is also possible. In the extraction of the attention area using the threshold value, the subject in the attention area does not need to be moving.
[0043]
Further, in the video data compression device 1, each means in the computer can be realized as each functional program, and each functional program can be combined and operated as a video data compression program.
[0044]
(Operation of Video Data Compression Device 1)
Next, the operation of the video data compression device 1 will be described with reference to FIGS. FIG. 5 is a flowchart showing the operation of the video data compression device 1.
[Region division step]
First, the video data compression device 1 causes the video delay unit 11a to delay the input video data (input video data) by one video frame (Step S1). Then, the motion vector detecting unit 11b performs block matching for each macroblock between the video frame of the input video data and the video frame one video frame delayed by the video delay unit 11a (between adjacent video frames). Thus, a motion vector is detected (step S2).
[0045]
Based on the motion vectors detected by the motion vector detection unit 11b, the global vector calculation unit 12 calculates the most frequently detected motion vector among the plurality of motion vectors as a global vector (step S3). This global vector can be regarded as a motion vector of the background area.
[0046]
Then, the video data compression device 1 compares the motion vector of the macroblock detected in step S2 with the global vector calculated in step S3 by the area identifying unit 13 and determines the difference between the two vectors as a preset value ( For example, a macroblock having 4 pixels or more per video frame) is identified as being included in the attention area. Thus, the video frame is divided into the attention area and the background area (Step S4).
[0047]
[Gradation reduction step]
Then, in the video data compression device 1, the gradation setting unit 21 changes the gradation of the background area based on the reduction amount (video reduction amount) of the video data input from input means (not shown) such as a keyboard. The amount of gradation reduction of the macro block in each region is set so as to be lower than the gradation of the region of interest (step S5). At this time, the gradation reduction amount is set based on a specific priority (see FIG. 3).
[0048]
Then, in the video data compression device 1, for the macroblock for which the gradation reduction amount is set in step S5, the gradation reduction unit 22 reduces the gradation by the set gradation reduction amount (step S6). Then, a video frame whose gradation is reduced for each macro block is output in time series as compressed video data (output video data) (step S7). Then, it is determined whether or not the input of the video data (input video data) has been completed (step S8). If the input has been completed (Yes), the operation is terminated. On the other hand, if video data is still input (No in step S8), the process returns to step S1 to continue the operation.
[0049]
Through the above steps, the video data compression device 1 can identify the attention area and the background area in the input video data, and can independently reduce the gradation of each area. Then, the video data reduced and compressed by the video data compression device 1 becomes video data in which the deterioration of the image quality of the attention area is reduced more than that of the background area.
[0050]
(Configuration of Video Data Compression Device: Second Embodiment)
Next, a video data compression device 1B according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration of the video data compression device 1B. The video data compression device 1B shown in FIG. 2 divides the input video data into a moving area of interest and a background area, which is another area, and expresses a pixel value for each of the divided areas. In this case, the video data is compressed and output by reducing the number of gray scales required.
[0051]
The video data compression device 1B is configured by adding a camera data vector calculation unit 14 instead of the global vector calculation unit 12 of the video data compression device 1 (FIG. 1), and further adding an area extension unit 15. Except for the added configuration of the camera data vector calculation unit 14 and the area expansion unit 15 and the function of the area identification unit 13B, the image data compression apparatus 1 is the same as the video data compression apparatus 1 shown in FIG. The description is omitted.
[0052]
The camera data vector calculation unit 14 converts a motion of a video frame of the input video data into a video frame of the input video data based on camera data such as pan, tilt, and zoom of a video camera (not shown) at the time of capturing the video data (input video data). This is to calculate a motion vector (background motion vector) of a macroblock when it is assumed that a certain attention area does not exist. The camera data is data that is input in chronological order in conjunction with the input video data. The background motion vector calculated by the camera data vector calculation unit 14 is output to the area identification unit 13B.
[0053]
The calculation of the motion vector using the camera data in the camera data vector calculation unit 14 is performed, for example, in “A High-Prication Camera Operational Parameter Measurement System and It's Application to Electronic Transactions, Information and Information Technology 47, No. 1, pp. 46-55, March 2001 ".
[0054]
That is, the camera data vector calculation unit 14 calculates where a certain macroblock in a video frame moves in the video frame by the movement of the camera (pan, tilt, zoom, etc.), and determines the moving direction and the moving direction of the macroblock. The moving amount is set as a background motion vector. For example, when the camera is panned to the right of the screen, the area reflected as the background appears to move to the left. The moved area has a motion in the video frame, but is actually a background area. As described above, the camera data vector calculation unit 14 calculates the background motion vector due to the camera motion.
[0055]
Based on the motion vector for each macroblock detected by the motion vector detection unit 11b and the background motion vector calculated by the camera data vector calculation unit 14, the region identification unit 13B determines that the macroblock This is to identify whether the image is included in the background area or the other area. The region (attention region or background region) for each macroblock identified by the region identification unit 13B is output to the region extension unit 15 as region information together with the macroblock coordinates.
[0056]
The area identification unit 13B compares the motion vector for each macroblock detected by the motion vector detection unit 11b with the background motion vector calculated by the camera data vector calculation unit 14 to determine the motion other than the background motion vector. Is determined to be a macroblock included in the attention area.
[0057]
The region extension unit (region extension unit) 15 checks the correlation between the macroblocks of the region adjacent to the attention region and the background region based on the region information output from the region identification unit 13B, and sets the correlation between the two regions. If the correlation value is higher than the calculated correlation value, the macroblock in the background area is regarded as a macroblock in the attention area, and the attention area is extended. For example, the correlation is examined by comparing the feature amounts of each macroblock such as luminance and color. The region information obtained by expanding the region of interest by the region expanding unit 15 is output to the gradation setting unit 21 of the gradation reduction control unit 20.
[0058]
The configuration of the video data compression device 1B has been described above. However, in the video data compression device 1B, it is also possible to realize each unit in the computer as each function program, and combine each function program to form a video data compression program. It is also possible to operate.
[0059]
(Operation of Video Data Compression Device 1B)
Next, the operation of the video data compression device 1B will be described with reference to FIGS. FIG. 6 is a flowchart showing the operation of the video data compression device 1B.
First, the video data compression device 1B delays the input video data (input video data) by one video frame by the video delay unit 11a (Step S10). Then, the motion vector detecting unit 11b performs block matching for each macroblock between the video frame of the input video data and the video frame one video frame delayed by the video delay unit 11a (between adjacent video frames). Thus, a motion vector is detected (step S11).
[0060]
Then, the video data compression device 1B uses the camera data vector calculation unit 14 based on camera data such as pan, tilt, and zoom of a photographic camera (not shown) at the time of capturing the video data (input video data). A motion vector (background motion vector) in which the background area moves within the video frame is calculated (step S12).
[0061]
Next, the video data compression apparatus 1B compares the motion vector of the macroblock detected in step S11 with the background motion vector calculated in step S12 by the area identifying unit 13B, and determines a motion vector different from the background motion vector. Is identified as a macroblock included in the attention area. Thus, the video frame is divided into the attention area and the background area (Step S13).
[0062]
Furthermore, the video data compression device 1B checks the correlation between the macroblocks of the two regions in the region where the attention region and the background region are adjacent to each other by the region expansion unit 15, and when the correlation is higher than a predetermined correlation value, The macro block in the background area is regarded as the macro block in the area of interest, and the area of interest is extended (step S14).
Note that the subsequent operation is the same as the gradation deletion step (step S5 and subsequent steps) in FIG. 5, and a description thereof will be omitted.
[0063]
Through the above steps, the video data compression device 1B identifies the attention area and the background area in the input video data for the video data obtained by photographing the subject by operating a camera such as a moving camera. , It is possible to independently reduce the gradation of each region. The video data compressed and reduced in gradation by the video data compression device 1B is video data in which the deterioration of the image quality of the attention area is reduced more than that of the background area.
[0064]
【The invention's effect】
As described above, the video data compression apparatus, method, and program according to the present invention have the following excellent effects.
[0065]
According to the first, sixth, or seventh aspect of the present invention, a region of interest is extracted from input video data, a region of interest is distinguished from a background region that is another region, and each region is identified. Can be individually reduced. Thus, by lowering the gradation of the background area than the gradation of the attention area, it is possible to reduce the deterioration of the image quality of the attention area and increase the compression ratio of the video data.
[0066]
For example, on a small screen such as a mobile terminal, it is more important to obtain information included in the video data than to watch the entire video, and thus, it is necessary to reduce the deterioration of the image quality of the attention area including the information. This is effective in a service that distributes video data.
[0067]
According to the invention described in claim 2, it is possible to recognize a moving area as a target area in block units. This makes it possible to easily reduce the gradation of the attention area and the background area, which is the other area, individually in block units.
[0068]
According to the third aspect of the present invention, even a region recognized as a background region by a motion vector can be determined as a region of interest by a feature amount such as a color. As a result, for example, it is possible to recognize, as a region of interest, a region where movement is small, such as at the edge of clothes, even though a person is moving.
[0069]
According to the fourth aspect of the invention, the gradation of the background region is made lower than the gradation of the region of interest, so that the ratio of the region of interest to the compressed data is increased as compared with the conventional compression. It is possible to reduce the deterioration of the image quality of the area and increase the compression ratio of the video data.
[0070]
According to the invention described in claim 5, since the sensitivity of the chrominance component to human vision is lower than that of the luminance component, the gradation assigned to the chrominance component is smaller than the gradation assigned to the luminance component for each attention area and background area. , The compression ratio can be increased while suppressing the deterioration of the image quality.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a video data compression device according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an overall configuration of a video data compression device according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram for describing a configuration example of a macroblock.
FIG. 4 is an explanatory diagram for explaining gradation reduction contents for reducing gradation in a gradation setting unit and their priorities;
FIG. 5 is a flowchart showing an operation of the video data compression device according to the first embodiment of the present invention.
FIG. 6 is a flowchart showing an operation of the video data compression device according to the second embodiment of the present invention.
FIG. 7 is an explanatory diagram for describing an example of an attention area and a background area.
[Explanation of symbols]
1, 1B ... video data compression device
10, 10B ... area division control means
11 ... Motion vector calculation unit (motion vector calculation means)
11a Video delay unit
11b ... Motion vector detection unit
12 ... Global vector calculator
13, 13B... Area identification unit (area identification means)
14 Camera data vector calculation unit
15 Area expansion unit (area expansion means)
20: gradation reduction control means
21: gradation setting section
22: gradation reduction unit

Claims (7)

A video data compression device that compresses the video data by reducing the gradation indicating the number of colors that can be represented by each pixel for the input video data,
An area division control unit that divides the video data into an attention area where a subject is present for each video frame and another background area.
Tone reduction control means for individually reducing the tone for each of the attention area and the background area divided by the area division control means;
A video data compression device, comprising: The area division control means,
Motion vector calculation means for calculating a motion vector for each block of a specific size between consecutive video frames of the video data,
Area identification means for identifying whether the block in the video frame is a block included in the attention area or a block included in the other background area based on the motion vector calculated by the motion vector calculation means When,
The video data compression device according to claim 1, further comprising: The area division control means,
In a region where the region of interest and the background region identified by the region identification means are adjacent to each other, the block of the background region is determined based on the correlation between the block of the region of interest and the block of the background region. Area expansion means for expanding as a block,
The video data compression apparatus according to claim 2, comprising: 4. The gray scale reduction control unit according to claim 1, wherein the gray scale assigned to the background area is reduced more than the gray scale assigned to the attention area. 2. The video data device according to claim 1. 2. The image processing apparatus according to claim 1, wherein the tone reduction control unit reduces the tone assigned to the color difference component for each of the attention area and the background area more than the tone assigned to the luminance component. The video data device according to claim 4. A video data compression method for compressing the video data by reducing the gradation indicating the number of colors that can be represented by each pixel for the input video data,
An area dividing step of dividing the video data into an attention area where a subject is present for each video frame and a background area other than the attention area;
A gradation reduction step of individually reducing the gradation for each of the attention area and the background area divided in the area division step,
The video data compression method, wherein the gradation reduction step reduces a gradation assigned to the background area more than a gradation assigned to the attention area. For the input video data, reduce the gradation indicating the number of colors that can be represented by each pixel, in order to compress the video data, a computer,
A region division control unit that divides the video data into a region of interest where a subject is present for each video frame and a background region other than that;
For each of the attention area and the background area divided by the area division control means, function as a gradation reduction control means for individually reducing the gradation,
A video data compression program, wherein the tone reduction control means reduces the tone assigned to the background area more than the tone assigned to the attention area.

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