JP2011049645A - Device and method for estimating video quality, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily estimate video quality with high accuracy by considering content dependency and codec implementation dependency of video quality. <P>SOLUTION: Based on a bit rate extracted from encoded video data of received video, average video quality corresponding to the bit rate is calculated by an average video quality calculation section 14; based on the bit rate and a video signal S of the received video, differential video quality representing a difference between the average video quality and the video quality of the received video is calculated by a differential video quality calculation section 15; video quality is calculated by a video quality calculation section 16 by correcting the average video quality with the differential video quality; and differential video quality is calculated based on a content influence rate, a differential global motion amount and a differential local motion amount in a differential video quality calculation section 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a video quality estimation technique, and more particularly to a technique for estimating video quality related to video communication performed via an IP network.

With the development of IP networks and terminal devices, video communication services using video media, such as IPTV services, video distribution services, and TV phone services, have become widespread.
In the case of communication using video media, information amount compression (encoding) is performed in order to improve network utilization efficiency. The encoded video media causes phenomena such as blurring, blurring, mosaic distortion, and jerky feeling due to missing high frequency components and increased block noise compared to the original video, that is, a video signal without deterioration. . For this reason, the quality perceived by the user, that is, the quality of experience (QoE) is lowered.
In order to provide such a video communication service with high quality, quality design prior to service provision and quality management during service provision are important. For this purpose, the quality enjoyed by the user can be expressed appropriately. A simple and efficient video quality evaluation technique is required.

  Conventionally, for example, Non-Patent Document 1 proposes a video quality evaluation method for estimating video quality from quality parameters such as bit rate and packet loss rate that affect video quality. For example, in Non-Patent Documents 2 and 3, video quality is estimated by comparing an original video signal, that is, a video signal without deterioration, and a degraded video signal, that is, a video signal including encoding degradation and packet loss degradation. A video quality evaluation method has been proposed. These objective evaluation techniques can estimate the subjective quality with an estimation error similar to the statistical ambiguity of the subjective quality under a certain condition.

ITU-T Recommendation G. 1070 ITU-T Recommendation J.I. 144 ITU-T Recommendation J.I. 247

  However, in such a conventional technique, there is a problem that the video quality cannot be easily estimated with high accuracy in consideration of the content dependency of the video quality and the codec mounting dependency. For this reason, it cannot be determined more accurately whether or not a certain level of quality is maintained for a user who uses the service.

  That is, according to the technique of Non-Patent Document 1 described above, since the video quality is estimated from the quality parameter, the average of the video quality related to video communication in which the quality parameters such as the bit rate are the same, that is, the average video quality Is estimated. Therefore, the influence on the quality due to the difference in the video contents such as the difference in the amount of motion and the difference in the complexity of the image, that is, the content dependency is not considered.

  Further, according to the techniques of Non-Patent Document 1 and Non-Patent Document described above, the video quality that takes into account the content dependency based on the original video signal, that is, the video quality for each video content is estimated, but the received video Since the original video signal is required in addition to the signal, it is difficult to easily estimate the video quality at the end terminal such as a set top box or home gateway used by the user.

  The present invention is for solving such problems, and provides a video quality estimation technique that can easily estimate video quality with high accuracy in consideration of content dependency and codec implementation dependency of video quality. It is an object.

  In order to achieve such an object, a video quality estimation apparatus according to the present invention uses a packet storing encoded video data between a video distribution apparatus and a video reception terminal connected via an IP network. A video quality estimation device that calculates a video quality indicating a user experience quality perceived by a user who has viewed the received video for the received video received by the video receiving terminal from the video distribution device by performing communication, A bit rate extraction unit that extracts the bit rate of the video communication based on the amount of encoded video data counted from the encoded video data, and a video of the bit rate based on the bit rate extracted by the bit rate extraction unit Average video quality calculation that calculates the average video quality obtained from multiple test video received via communication as the average video quality And a differential video quality indicating a difference between the average video quality obtained by the average video quality calculation unit and the video quality of the received video based on the bit rate extracted by the bit rate extraction unit and the video signal of the received video. Video for calculating the video quality of the received video by correcting the average video quality obtained by the average video quality calculation unit with the difference video quality obtained by the difference video quality calculation unit and the difference video quality calculation unit A quality calculation unit, and the difference video quality calculation unit calculated based on the bit rate, the content influence degree indicating the magnitude of the influence of the content of the received video on the video quality of the received video, the bit rate and the video Difference global motion amount indicating the amount of overall motion of the video screen, and difference indicating the amount of local motion within the video screen, calculated as a value specific to the received video based on the signal Karu based on the motion amount, calculates the differential image quality.

  At this time, the content for calculating the content influence level indicating the magnitude of the influence of the received video content on the video quality of the received video based on the bit rate extracted by the bit rate extracting unit in the differential video quality calculating unit Based on the influence rate calculation unit, the bit rate extracted by the bit rate extraction unit and the video signal of the received video, the global motion amount indicating the overall motion amount of the video screen in the received video, and the test reception The difference global motion amount calculation unit that calculates a difference value from the average global motion amount indicating the average global motion amount obtained from the video as the difference global motion amount, the bit rate extracted by the bit rate extraction unit, and the received video Of the received video, the local motion amount indicating the amount of local motion within the video screen, and the average received from the test received video. A difference local motion amount calculation unit that calculates a difference value from an average local motion amount indicating a local local motion amount as a difference local motion amount, and a content influence degree and a difference global motion amount calculation obtained by the content influence degree calculation unit A difference video quality calculation unit that calculates difference video quality may be provided based on the difference global motion amount obtained by the unit and the difference local motion amount obtained by the difference local motion amount calculation unit.

  In addition, the content influence degree calculation unit shows the maximum video quality characteristic indicating the relationship between the bit rate of the test reception video and the bit rate indicating the maximum value of the video quality obtained from the test reception video of the bit rate minus the maximum video quality. A maximum video quality calculation unit that calculates the maximum video quality obtained from the test reception video of the bit rate extracted by the bit rate extraction unit, the test video reception bit rate and the test reception of the bit rate The minimum video obtained from the received video for test of the bit rate extracted by the bit rate extraction unit based on the bit rate-minimum video quality characteristic indicating the relationship with the minimum video quality indicating the minimum value of the video quality obtained from the video The minimum video quality calculation unit that calculates quality, and the minimum video quality obtained by the minimum video quality calculation unit from the maximum video quality obtained by the maximum video quality calculation unit. By subtracting the quality may be provided a content influence degree calculation unit that calculates a content influence.

  In addition, the difference global motion amount calculation unit indicates a bit rate-average indicating a relationship between the bit rate of the test reception video and the average global motion amount indicating the average global motion amount obtained from the test reception video of the bit rate. Based on the global motion amount characteristics, based on the video signal of the received video, the average global motion amount calculating unit that calculates the average global motion amount obtained from the test reception video of the bit rate extracted by the bit rate extraction unit, A global motion amount calculation unit that calculates the global motion amount of the received video from the number of pixels moved by the overall motion of the video screen between adjacent frames in the video signal and the movement distance, and an average global motion amount calculation The global motion amount obtained by the global motion amount calculation unit is subtracted from the average global motion amount obtained by the part. And a may be provided with differential global motion amount calculation unit for calculating a difference global motion amount.

  In addition, the difference local motion amount calculation unit indicates a bit rate-average indicating a relationship between the bit rate of the test received video and the average local motion amount indicating the average local motion amount obtained from the test received video of the bit rate. Based on the local motion amount characteristics, based on the average local motion amount calculation unit that calculates the average local motion amount obtained from the test reception video of the bit rate extracted by the bit rate extraction unit, based on the video signal of the reception video, A local motion amount calculation unit that calculates the local motion amount of the received video from the number of pixels moved by the local motion in the video screen between adjacent frames in the video signal and the movement distance; and an average local motion amount By subtracting the local motion amount obtained by the local motion amount calculation unit from the average local motion amount obtained by the calculation unit, the difference local motion amount is obtained. It may be provided with differential local motion amount calculation unit for calculating a motion amount.

  In addition, when the global motion amount calculation unit fixes one frame for each adjacent frame and translates the other frame vertically and horizontally one pixel at a time, the absolute value of the difference value of the pixel values of the overlapping region where these frames overlap It is also possible to calculate the global movement amount by calculating the parallel movement distance when the value obtained by averaging the values with the number of pixels of the overlapping region is the smallest, and averaging the parallel movement distance with the number of the adjacent frames. Good.

  In addition, when the local motion amount calculation unit fixes one frame for each adjacent frame and translates the other frame vertically and horizontally one pixel at a time, the absolute value of the difference value of the pixel values of the overlapping region where these frames overlap each other Calculate the standard deviation of the difference value when the value averaged with the number of pixels in the overlap region is the smallest, and calculate the local motion amount by averaging these standard deviations with the number of adjacent frames. May be.

  Alternatively, the local motion amount calculation unit fixes one of the adjacent frames and translates the other frame vertically and horizontally one pixel at a time, and the absolute value of the difference value of the pixel values of the overlapping region where these frames overlap. After shifting both frames in a positional relationship where the average value of the number of pixels in the overlapping area becomes the smallest, both frames of these adjacent frames are divided into rectangular shapes, and one block is provided for each block. When the block of the frame is fixed and the block of the other frame is translated horizontally and vertically by one pixel, the value obtained by averaging the absolute value of the difference value of the pixel values of the overlapping region where these blocks overlap with the number of pixels of the block is Calculate the parallel movement distance for each block when it was the smallest, and average these parallel movement distances with the number of blocks. It may be calculated local motion amount by Rukoto.

  The bit extracted by the bit rate extraction unit based on the bit rate-average video quality characteristic that the average video quality calculation unit converges to an arbitrary value after the average video quality monotonously increases as the bit rate increases. The average video quality corresponding to the rate may be calculated.

  Also, the bit extracted by the bit rate extraction unit based on the bit rate-maximum video quality characteristic that the maximum video quality calculation unit converges to an arbitrary value after the maximum video quality monotonously increases as the bit rate increases. The maximum video quality corresponding to the rate may be calculated.

  The bit extracted by the bit rate extraction unit based on the bit rate-minimum video quality characteristic in which the minimum video quality is monotonously increased as the bit rate increases and then converges to an arbitrary value. The minimum video quality corresponding to the rate may be calculated.

  Also, the average global motion amount calculation unit extracts the bit rate based on the bit rate-average global motion amount characteristic that converges to an arbitrary value after the average global motion amount decreases monotonously as the bit rate increases. An average global motion amount corresponding to the determined bit rate may be calculated.

  Also, the average local motion amount calculation unit extracts the bit rate based on the bit rate-average local motion amount characteristic that converges to an arbitrary value after the average local motion amount monotonously decreases as the bit rate increases. The average local motion amount corresponding to the determined bit rate may be calculated.

  Also, the difference video quality calculation unit causes the difference video quality to decrease as the product of the content impact level and the difference global motion amount and the sum of the product of the content impact level and the difference local motion amount increase. Corresponds to the content influence obtained by the content influence calculation unit, the difference global motion obtained by the difference global motion calculation unit, and the difference local motion obtained by the difference local motion calculation unit based on the characteristics The difference video quality may be calculated.

  Also, the video quality estimation method according to the present invention performs video communication between a video distribution device and a video receiving terminal connected via an IP network by using a packet storing encoded video data. A video quality estimation method used in a video quality estimation device for calculating video quality indicating a user experience quality perceived by a user who views a received video from a distribution device received by the video receiving terminal, Based on the amount of encoded video data counted from the encoded video data by the rate extraction unit, a bit rate extraction step for extracting the bit rate of the video communication and an average video quality calculation unit are extracted by the bit rate extraction unit. Based on the average bit rate obtained from a plurality of received video images for testing received by video communication at the bit rate. An average video quality calculating step for calculating the image quality as an average video quality, and a difference video quality calculating unit, based on the bit rate extracted by the bit rate extracting unit and the video signal of the received video, A difference video quality calculation step for calculating a difference video quality indicating a difference between the obtained average video quality and the video quality of the received video, and the video quality calculation unit is a difference video quality obtained by the difference video quality calculation unit, A video quality calculation step for calculating the video quality of the received video by correcting the average video quality obtained by the average video quality calculation unit, and the received video calculated based on the bit rate in the differential video quality calculation step Specific to the received video based on the content influence level indicating the magnitude of the influence of the content on the video quality of the received video, the bit rate, and the video signal. Calculating the difference video quality based on the difference global motion amount indicating the overall motion amount of the video screen and the difference local motion amount indicating the local motion amount in the video screen, calculated as Contains.

  Further, the program according to the present invention is a program for causing a computer to function as each unit constituting any one of the above-described video quality estimation apparatuses.

According to the present invention, if the video signal of the received video and the packet of the encoded video data can be acquired, the differential video quality specific to the received video in consideration of the content dependency and codec implementation dependency of the video quality. Can be calculated accurately, and the video quality of the received video can be easily estimated with high accuracy.
Therefore, the service provider can more accurately determine whether or not the video communication service maintains a certain level of quality for the user, and can accurately grasp the actual quality of the video communication service being provided. It becomes possible to manage.

It is a block diagram which shows the structure of the video quality estimation apparatus concerning this Embodiment. It is explanatory drawing which shows global movement. It is explanatory drawing which shows a local motion. It is a graph which shows the relationship between difference local motion amount and difference image quality. It is a graph which shows the relationship between difference local motion amount and difference image quality. It is a graph which shows the relationship between a bit rate and a content influence degree. It is a block diagram which shows the structure of the difference video quality calculation part used with the video quality estimation apparatus concerning this Embodiment. It is a structural example of a characteristic coefficient table. It is a flowchart which shows the video quality estimation process of the video quality estimation apparatus concerning this Embodiment. It is a graph which shows a bit rate-average video quality characteristic. It is a graph which shows a bit rate-average global motion amount characteristic. It is explanatory drawing which shows a global motion amount calculation process. It is another explanatory view showing the global motion amount calculation processing. It is a graph which shows a bit rate-average local motion amount characteristic.

Next, an embodiment of the present invention will be described with reference to the drawings.
[Video quality estimation device]
First, a video quality estimation apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the video quality estimation apparatus according to this embodiment.

  The video quality estimation device 10 is composed of an information processing device such as a server device or a personal computer as a whole, and encodes video data between a video distribution device 1 and a video reception terminal 2 connected via an IP network 3. A function of calculating video quality indicating user perceived quality perceived by a user who has viewed the received video with respect to the received video received by the video receiving terminal 2 from the video distribution device 1 by performing video communication using a packet storing Have.

The video distribution device 1 is composed of a communication processing device such as a server device as a whole, and has a function of performing video communication with the video receiving terminal 2 via the IP network 3 and the encoded video to the video receiving terminal 2 through this video communication. It has a function to distribute.
The video receiving terminal 2 consists of end terminal devices such as a set-top box and a home gateway as a whole. The video receiving terminal 2 has a function of performing video communication with the video distribution device 1 via the IP network 3 and a packet received by this video communication. It has a function of displaying the received video obtained by decoding the stored encoded video data on the screen.

[Principle of the present invention]
The present invention extracts the bit rate of the video communication from the encoded video data transmitted from the video distribution apparatus 1 to the video receiving terminal 2, and is obtained from a plurality of test received videos received by video communication at this bit rate. An average video quality, that is, an average video quality V _ave is calculated, and the average video quality V _ave is corrected with the difference video quality dV calculated from the bit rate and the video signal S received and reproduced by the video receiving terminal 2. Thus, the video quality V related to the received video received by the video receiving terminal 2 is estimated.
Among these, since the average video quality value V _ave can be calculated using a known technique such as Non-Patent Document 1, for example, the concept for calculating the differential video quality dV will be described here.

[Differential video quality]
Among various video contents distributed by video communication, the amount of change in pixel value per time, that is, video content with a large amount of motion, is encoded with a large amount of encoded video when the video content is encoded into encoded video data and distributed. Requires a large amount of data. For this reason, the video quality related to such video content tends to be lower than the average video quality obtained from a plurality of test received videos received by video communication at the same bit rate, that is, the average video quality. is there. In the present invention, based on such a tendency, the difference video quality is estimated from the feature quantity obtained by quantifying the motion quantity of the received video.

[Movement amount]
Video motion can be broadly divided into global motion and local motion.
Global movement is movement that the entire screen moves in parallel, such as camera panning. FIG. 2 is an explanatory diagram showing global movement. Therefore, the amount of information can be easily reduced by motion compensation at the time of encoding, and encoding can be performed with a small amount of information.
The local movement is a movement in which a part of the screen such as a person or an object in the screen moves or changes. FIG. 3 is an explanatory diagram showing local motion. Therefore, it is difficult to reduce the amount of information by motion compensation at the time of encoding, and a large amount of information is required.

  The amount of information required differs depending on the type of motion such as global motion and local motion video, and the video quality differs. Therefore, when using the amount of motion for video quality, it is effective to separately quantify global motion and local motion. In the present invention, this fact is used to quantify the two types of motion.

[Global motion amount]
First, a method for calculating the global motion amount will be described. For the two adjacent frames extracted from the video signal of the received video, the previous frame is fixed, and the entire rear frame is translated by one pixel vertically and horizontally within a certain range, that is, globally moved. Then, the sum of absolute values of the difference values of the pixel values between the two frames in the overlapping region where both frames overlap is calculated, and a value obtained by averaging the total value with the number of pixels in the overlapping region of both frames is used as an average inter-frame difference value. calculate. The pixel value referred to in the present invention is composed of the luminance value and color difference value of the pixel.

  Next, a vector indicating global movement when the average inter-frame difference value is minimized, that is, the absolute value of the global vector is calculated by the root mean square of the horizontal component and the vertical component of the global vector. A value obtained by averaging the calculated distances by the number of adjacent frames is set as a global motion magnitude, that is, a global motion amount.

[Local movement amount]
Next, two methods for calculating the local motion amount will be described.
First, in the first calculation method, the previous frame is fixed and the subsequent frame is globally moved with respect to two adjacent frames extracted from the video signal of the received video. Then, the standard deviation of the difference value of the pixel value between both frames in the overlapping region where both frames overlap is calculated. A value obtained by averaging the calculated standard deviations with the number of adjacent frames is set as a local motion magnitude, that is, a local motion amount.

  Next, the second calculation method divides the screen of the video signal of the received video into rectangular blocks of, for example, 8 pixels × 8 pixels, fixes the previous frame to two adjacent frames, and The blocks in the frame are moved in parallel by one pixel vertically and horizontally within a certain range, that is, locally moved. Then, the sum of absolute values of the difference values of the pixel values between the two blocks in the overlapping region where the blocks overlap is calculated, and a value obtained by averaging this total value with the number of pixels in the overlapping region of both blocks is calculated as the average inter-block difference value. To do.

  Next, for the vector indicating local movement when the average inter-block difference value is minimum, that is, the local vector, the absolute value of the vector obtained by subtracting the global vector between the adjacent frames from the local vector is calculated between the adjacent frames. Calculate for each block. The calculated absolute value is averaged by the number of blocks in the screen, and the value averaged by the number of adjacent frames is defined as the local motion magnitude, that is, the local motion amount.

  In video communication performed under the same bit rate condition, when focusing on the global motion amount of video content and the average global motion amount obtained from a video set consisting of multiple test received images, that is, the average global motion amount There is a linear approximation relationship between the difference global motion amount indicating the difference between the global motion amount and the average global motion amount, and the difference video quality. FIG. 4 is a graph showing the relationship between the difference local motion amount and the difference video quality.

  Similarly, in video communication performed under the same bit rate condition, the local motion amount of the video content and the average local motion amount obtained from a video set composed of a plurality of received video images for testing, that is, the average local motion amount. When attention is paid, there is also a linear approximation relationship between the difference local motion amount indicating the difference between the local motion amount and the average local motion amount and the difference video quality. FIG. 5 is a graph showing the relationship between the difference local motion amount and the difference video quality.

  In addition, even with the same video content (motion amount), the degree of influence of the video content on the video quality varies depending on the bit rate. FIG. 6 is a graph showing the relationship between the bit rate and the content influence level. Here, the difference between the maximum video quality indicating the maximum video quality and the minimum video quality indicating the minimum video quality for the video quality obtained from a plurality of test reception videos received by video communication under the same bit rate condition The relationship between the content influence level and the bit rate is shown.

Further, the difference video quality has a first-order approximation relationship with respect to the sum of the product of the content influence degree and the difference global motion amount and the product of the content influence degree and the difference local motion amount.
Based on such a relationship, the present invention calculates the difference video quality dV from the bit rate of the received video and the video signal, and calculates the average video quality calculated from the header information of the received packet with the calculated difference video quality dV. The video quality V perceived by the user is calculated by correcting V _ave .

[Configuration of the embodiment]
Next, the configuration of the video quality estimation apparatus 10 according to the present embodiment will be described in detail with reference to FIGS. 1 and 7. FIG. 7 is a block diagram showing a configuration of a difference video quality calculation unit used in the video quality estimation apparatus according to the present embodiment.

  The video quality estimation device 10 is composed of an information processing device such as a server device or a personal computer as a whole, and the main functional units include a packet acquisition unit 11, a bit rate extraction unit 12, a video signal acquisition unit 13, an average video quality calculation. A unit 14, a difference video quality calculation unit 15, and a video quality calculation unit 16 are provided.

  The packet acquisition unit 11 includes a communication interface circuit, and distributes encoded video data from the video distribution device 1 to the video reception terminal 2 through a communication path between the video reception terminal 2 or the IP network 3 and the video reception terminal 2. For obtaining the packet in the quality estimation section used for the estimation of the received video.

The bit rate extracting unit 12, the various information contained in the packet acquired by the packet acquisition unit 11 has a function of calculating a bit rate B _r of the coded video data. In the packet, in addition to header information, there are a transport stream (TS: Transport stream) and an elementary stream (ES: Elementary stream) related to encoded video data. The bit rate extraction unit 12 counts the data amount of the encoded video data in the quality estimation section from the packet acquired by the packet acquisition unit 11, and converts the data amount into a data amount per unit time, thereby obtaining a bit rate. _Br is calculated.

  The video signal acquisition unit 13 includes a dedicated video interface circuit. The video reception terminal 2 receives and decodes the video signal from the video distribution device 1 and outputs the video signal S output from the video reception terminal 2 to a display device such as an LCD or a PDP. It has a function to acquire.

The average video quality calculation unit 14, based on the bit rate B _r obtained by the bit rate extracting unit 12, average mean images obtained from a plurality of test received video received by the video communication bit rate B _r It has a function to calculate the quality V _ave .

Specifically, in the average video quality calculation unit 14, the bit rate extraction unit 12 is based on a bit rate-average video quality characteristic that converges to an arbitrary value after the average video quality monotonously increases with an increase in the bit rate. The average video quality V _ave corresponding to the bit rate _Br extracted in step S is calculated.
As a method for calculating the average video quality value V _ave , for example, a known technique such as Non-Patent Document 1 may be used.

The difference video quality calculation unit 15 calculates the average video obtained by the average video quality calculation unit 14 based on the bit rate _Br obtained by the bit rate extraction unit 12 and the video signal S obtained by the video signal acquisition unit 13. It has a function of calculating the difference video quality dV indicating the difference between the quality _Vave and the video quality V of the received video.

The video quality calculation unit 16 corrects the average video quality value V _ave calculated by the average video quality calculation unit 14 with the differential video quality dV calculated by the differential video quality calculation unit 15, thereby receiving the video quality at the video receiving terminal 2. It has a function of calculating the video quality V indicating the user experience quality perceived by the user who viewed the received video.

[Configuration of difference video quality calculation unit]
The difference video quality calculation unit 15 includes a content influence calculation unit 21, a difference global motion amount calculation unit 22, a difference local motion amount calculation unit 23, and a difference video quality calculation unit 24 as main functional units. .

Based on the bit rate _Br obtained by the bit rate extraction unit 12, the content influence degree calculation unit 21 calculates a content influence degree C indicating the magnitude of the influence of the received video content on the video quality of the received video. It has a function to do.
The content influence level calculation unit 21 includes a maximum video quality calculation unit 21A, a minimum video quality calculation unit 21B, and a content influence level calculation unit 21C as main processing units.

The maximum video quality calculation unit 21A sets a bit rate-maximum video quality characteristic indicating the relationship between the bit rate of the test reception video and the maximum video quality indicating the maximum value of the video quality obtained from the test reception video of the bit rate. based on, and has a function of calculating the maximum image quality V _max obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12.

Specifically, in the maximum video quality calculation unit 21A, the bit rate extraction unit 12 is based on the bit rate-maximum video quality characteristic that converges to an arbitrary value after the maximum video quality monotonously increases as the bit rate increases. The maximum video quality V _max corresponding to the bit rate _Br extracted in step S is calculated.

The minimum video quality calculation unit 21B sets the bit rate-minimum video quality characteristic indicating the relationship between the bit rate of the test reception video and the minimum video quality indicating the minimum value of the video quality obtained from the test reception video of the bit rate. based on, and has a function of calculating the minimum video quality V _min obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12.

Specifically, in the minimum video quality calculation unit 21B, the bit rate extraction unit 12 is based on the bit rate-minimum video quality characteristic that converges to an arbitrary value after the minimum video quality monotonously increases as the bit rate increases. The minimum video quality V _min corresponding to the bit rate _Br extracted in step S is calculated.

The content influence level calculation unit 21C subtracts the minimum video quality V _min obtained by the minimum video quality calculation unit 21B from the maximum video quality V _max obtained by the maximum video quality calculation unit 21A, thereby obtaining the content influence level C Has the function to calculate

Based on the bit rate extracted by the bit rate extraction unit 12 and the video signal S of the received video acquired by the video signal acquisition unit 13, the difference global motion amount calculation unit 22 determines the overall video screen of the received video. A function of calculating a difference value between the global motion amount GMV indicating the amount of motion and the average global motion amount GMV _ave indicating the average global motion amount obtained from the test received video as a differential global motion amount dGMV ing.
The difference global motion amount calculation unit 22 includes an average global motion amount calculation unit 22A, a global motion amount calculation unit 22B, and a difference global motion amount calculation unit 22C as main processing units.

The average global motion amount calculation unit 22A is configured to determine the relationship between the bit rate of the test received video and the average global motion amount indicating the average global motion amount obtained from the test received video having the bit rate. based on the amount of motion characteristics, and has a function of calculating the average global motion amount GMV _ave obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12.

Specifically, the average global motion amount calculation unit 22A determines the bit rate based on the bit rate-average global motion amount characteristic that converges to an arbitrary value after the average global motion amount monotonously decreases in accordance with the increase in the bit rate. calculating the average global motion amount GMV _ave corresponding to the bit rate B _r extracted by the extraction unit 12.

  Based on the video signal S acquired by the video signal acquisition unit 13, the global motion amount calculation unit 22B determines the number of pixels moved by the overall motion of the video screen between adjacent frames in the video signal S and the movement distance thereof. From this, it has a function of calculating the global motion amount GMV of the received video.

  Specifically, in the global motion amount calculation unit 22B, when one frame is fixed for each adjacent frame and the other frame is translated horizontally and vertically one pixel at a time, the pixel values of the overlapping region where these two frames overlap are determined. The parallel movement distance when the absolute value of the difference value is averaged by the number of pixels in the overlap region is the smallest, and the global movement amount GMV is calculated by averaging the parallel movement distance by the number of the adjacent frames. To do.

The difference global motion amount calculation unit 22C subtracts the global motion amount GMV obtained by the global motion amount calculation unit 22B from the average global motion amount GMV _ave obtained by the average global motion amount calculation unit 22A. It has a function of calculating the motion amount dGMV.

Differential local motion amount calculation unit 23, based on the video signal S of the bit rate extracting unit 12 a bit rate B _r and the received image extracted in indicates the amount of local motion of the video screen in the received video It has a function of calculating a difference value between the local motion amount LMV and the average local motion amount LMV _ave indicating the average local motion amount obtained from the test received video as the difference local motion amount dLMV.
The difference local motion amount calculation unit 23 includes an average local motion amount calculation unit 23A, a local motion amount calculation unit 23B, and a difference local motion amount calculation unit 23C as main processing units.

The average local motion amount calculation unit 23A is a bit rate-average local that indicates the relationship between the bit rate of the test reception video and the average local motion amount indicating the average local motion amount obtained from the test reception video of the bit rate. Based on the motion amount characteristic, it has a function of calculating the average local motion amount LMV _ave obtained from the test received video of the bit rate _Br extracted by the bit rate extraction unit 12.

Specifically, the average local motion amount calculation unit 23A determines the bit rate based on the bit rate-average local motion amount characteristic that converges to an arbitrary value after the average local motion amount monotonously decreases in accordance with the increase in the bit rate. It means corresponding to the bit rate B _r extracted by the extraction unit 12 calculates the local motion amount LMV _ave.

  Based on the video signal S acquired by the video signal acquisition unit 13, the local motion amount calculation unit 23B determines the number of pixels moved by the local motion in the video screen between adjacent frames in the video signal S and the moving distance thereof. And the function of calculating the local motion amount LMV of the received video.

  The first specific local motion amount calculation method is that when the local motion amount calculation unit 23B fixes one frame for each adjacent frame and translates the other frame vertically and horizontally one pixel at a time. Calculate the translation distance when the standard deviation of the difference value of the pixel value of the overlapping area where the frames overlap is averaged by the number of pixels of the overlapping area, and calculate the average of these translation distances based on the number of adjacent frames. Thus, the local motion amount is calculated.

  The second specific local motion amount calculation method is that the local motion amount calculation unit 23B fixes a block of one frame for each block provided by dividing both frames of adjacent frames into rectangular shapes. When the block of the other frame is translated horizontally and vertically by 1 pixel, the translation when the absolute value of the difference value of the pixel values of the overlapping region where these blocks overlap is the smallest value averaged by the number of pixels of the block. The distance is calculated for each block, and the local motion amount is calculated by averaging the values obtained by averaging these parallel movement distances by the number of blocks with the number of adjacent frames.

The difference local motion amount calculation unit 23C subtracts the local motion amount LMV obtained by the local motion amount calculation unit 23B from the average local motion amount LMV _ave obtained by the average local motion amount calculation unit 23A, thereby obtaining the difference local motion amount LMV _ave. It has a function of calculating the movement amount dLMV.

  The difference video quality calculation unit 24 is obtained by the content influence degree C obtained by the content influence degree calculation unit 21, the difference global movement amount dGMV obtained by the difference global movement amount calculation unit 22, and the difference local movement amount calculation unit 23. Based on the obtained difference local motion amount dLMV, it has a function of calculating the difference video quality dV.

  Specifically, in the difference video quality calculation unit 24, the difference is determined in accordance with an increase in the sum of the product of the content influence degree C and the difference global motion amount dGMV and the product of the content influence degree C and the difference local motion amount dLMV. Based on the difference video quality characteristic in which the video quality is degraded, the content influence degree C obtained by the content influence degree calculation unit 21, the difference global movement amount dGMV obtained by the difference global movement amount calculation unit 22, and the difference local movement amount The difference video quality dV corresponding to the difference local motion amount dLMV obtained by the calculation unit 23 is calculated.

  Of the functional units in the video quality estimation apparatus 10, the bit rate extraction unit 12, the average video quality calculation unit 14, the difference video quality calculation unit 15, and the video quality calculation unit 16 may be realized by an arithmetic processing unit. The arithmetic processing unit includes a microcomputer such as a CPU and its peripheral circuits, and implements various functional units by reading and executing a program from the storage unit.

  The video quality estimation apparatus 10 includes an arithmetic processing unit and a storage unit, a display device such as an LCD, and an operation input device such as a keyboard and a mouse, as in an information processing device such as a general server device or personal computer. It is assumed that various functional units such as a communication interface and a data input / output interface are provided.

  Further, the bit rate used in the average video quality calculation unit 14—average video quality characteristic, the bit rate used in the maximum video quality calculation unit 21A—maximum video quality characteristic, the bit rate used in the minimum video quality calculation unit 21B—minimum video quality characteristic, Regarding the bit rate-average global motion amount characteristic used in the average global motion amount calculation unit 22A, the bit rate-average local motion amount characteristic used in the average local motion amount calculation unit 23A, and the difference video quality characteristic used in the difference video quality calculation unit 24 The video communication is conducted experimentally at different bit rates in advance, and from the calculation results obtained from the received received video for testing, function expressions indicating the respective characteristics are derived and stored in the storage unit (not shown). Store it.

  These characteristics may change depending on quality parameters such as codec type, service type, and video resolution in each video communication. Therefore, a characteristic coefficient for determining a function expression indicating these characteristics is calculated in advance for each combination of these quality parameters, stored together with the function expression in a storage unit (not shown) as a characteristic coefficient table, The characteristic coefficient corresponding to the quality parameter of the video communication is read from the storage unit, and each characteristic may be determined. FIG. 8 is a configuration example of the characteristic coefficient table.

[Operation of this embodiment]
Next, the operation of the video quality estimation apparatus 10 according to the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing video quality estimation processing of the video quality estimation apparatus according to the present embodiment.
The video quality estimation apparatus 10 starts the video quality estimation process of FIG. 9 in response to an instruction operation from an operator or an instruction from an external device (not shown).

First, the video quality estimation apparatus 10 acquires a video communication packet to be estimated from the video receiving terminal 2 or the communication path by the packet acquisition unit 11, and from the video receiving terminal 2 by the video signal acquisition unit 13. S is acquired (step 100).
The video quality estimation apparatus 10, the bit rate extracting unit 12, the various information contained in the packet extracted by the packet acquisition unit 11 calculates a bit rate B _r of the coded video data (step 101).

Subsequently, the video quality estimation apparatus 10 uses the average video quality calculation unit 14 based on the bit rate _Br obtained by the bit rate extraction unit 12 to perform a plurality of tests received by video communication at the bit rate _Br . An average average video quality V _ave obtained from the received video is calculated (step 102).

Further, the video quality estimation apparatus 10 acquires the bit rate _Br obtained by the bit rate extraction unit 12 and the video signal acquisition unit 13 by executing the steps 110 to 116 by the differential video quality calculation unit 15. Based on the video signal S, a differential video quality dV indicating a difference between the average video quality _Vave obtained by the average video quality calculation unit 14 and the video quality V of the received video is calculated (step 103).

In this case, the difference image quality calculator 15 maximum, first, that the maximum video quality calculation unit 21A of the content influence calculation unit 21 is obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12 calculates a video quality V _max, the minimum image quality calculator 21B, calculates the minimum video quality V _min obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12 (step 110) .

Subsequently, the difference video quality calculation unit 15 uses the minimum video quality calculation unit 21B from the maximum video quality V _max obtained by the maximum video quality calculation unit 21A by the content influence calculation unit 21C of the content influence calculation unit 21. The content influence degree C is calculated by subtracting the obtained minimum video quality V _min (step 111).

Also, the difference video quality calculator 15, the average global motion amount calculation unit 22A of the differential global motion amount calculation unit 22, the average global obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12 The motion amount GMV _ave is calculated, and based on the video signal S acquired by the video signal acquisition unit 13 by the global motion amount calculation unit 22B, the overall motion of the video screen between adjacent frames in the video signal S is calculated. The global motion amount GMV of the received video is calculated from the number of moved pixels and the moving distance (step 112).

Subsequently, the difference video quality calculation unit 15 calculates the global motion amount from the average global motion amount GMV _ave obtained by the average global motion amount calculation unit 22A by the difference global motion amount calculation unit 22C of the difference global motion amount calculation unit 22. The difference global motion amount dGMV is calculated by subtracting the global motion amount GMV obtained by the calculation unit 22B (step 113).

Also, the difference video quality calculator 15, the difference with the average local motion amount calculation unit 23A of the local motion amount calculation unit 23, the average local obtained from the test received video bit rate B _r extracted by the bit rate extracting unit 12 The motion amount LMV _ave is calculated, and the local motion in the video screen between adjacent frames in the video signal S based on the video signal S acquired by the video signal acquisition unit 13 by the local motion amount calculation unit 23B. The local motion amount LMV of the received video is calculated from the number of pixels moved by the above and the moving distance (step 114).

Then, the difference image quality calculation section 15, the differential local motion amount calculation unit 23C of the differential local motion amount calculation unit 23, the average from the local motion amount LMV _ave obtained in average local motion amount calculation unit 23A, a local motion amount The difference local motion amount dLMV is calculated by subtracting the local motion amount LMV obtained by the calculation unit 23B (step 115).

  In this way, after calculating the content influence level C, the difference global motion amount dGMV, and the difference local motion amount dLMV, the difference video quality calculation unit 15 obtains the content effect level C, The difference video quality dV is calculated based on the difference global motion amount dGMV obtained by the difference global motion amount calculation unit 22 and the difference local motion amount dLMV obtained by the difference local motion amount calculation unit 23 (step 116). .

Thereafter, in the video quality estimation apparatus 10, the video quality calculation unit 16 corrects the average video quality value V _ave calculated by the average video quality calculation unit 14 with the differential video quality dV calculated by the differential video quality calculation unit 15. Thus, the video quality V indicating the user experience quality perceived by the user who has viewed the received video received by the video receiving terminal 2 is calculated (step 104), and the series of video quality estimation processing ends.

[Average video quality calculation processing]
Next, the average video quality calculation process in the average video quality calculation unit 14 will be described in detail.
The average video quality calculation unit 14 calculates the average video quality V corresponding to the bit rate _Br obtained by the bit rate extraction unit 12 based on the bit rate-average video quality characteristic indicating the relationship between the bit rate and the average video quality. Calculate _ave .

  FIG. 10 is a graph showing the bit rate-average video quality characteristic, where the horizontal axis shows the bit rate and the vertical axis shows the average video quality. The average video quality is an average value of user experience qualities obtained by performing an opinion evaluation in advance for each received video for a video set including a plurality of received video images for testing with each bit rate as a quality parameter.

As shown in FIG. 10, the bit rate-average video quality characteristic 51 has a characteristic of converging to an arbitrary maximum value after the average video quality monotonously increases in accordance with the increase of the bit rate. When the average video quality is expressed as a MOS value, the lower limit value is 1. When the average video quality that is not limited to the range that the MOS value can take is V _ave _tmp and the characteristic coefficients related to the bit rate-average video quality characteristic are v ₁ , v ₂ , v ₃ , the average video quality V expressed by the MOS value _ave is expressed by the following equation (1).

[Maximum video quality calculation processing]
Next, the maximum video quality calculation process in the maximum video quality calculation unit 21A will be described in detail.
The maximum video quality calculation unit 21A sets a bit rate-maximum video quality characteristic indicating the relationship between the bit rate of the test reception video and the maximum video quality indicating the maximum value of the video quality obtained from the test reception video of the bit rate. Based on this, the maximum video quality V _max corresponding to the bit rate _Br extracted by the bit rate extraction unit 12 is calculated.

  FIG. 10 shows a bit rate-maximum video quality characteristic 52 indicating the relationship between the bit rate and the maximum video quality. The maximum video quality is the maximum value of the user experience quality obtained by conducting an opinion evaluation in advance for each received video for a video set made up of a plurality of test received videos having the respective bit rates as quality parameters.

As shown in FIG. 10, the bit rate-maximum video quality characteristic has a characteristic of converging to an arbitrary maximum value after the maximum video quality monotonously increases as the bit rate increases. When the maximum video quality is expressed as a MOS value, the lower limit value is 1. When the maximum video quality that is not limited to the range that the MOS value can take is V _{max_tmp,} and the characteristic coefficients regarding the bit rate-maximum video quality characteristic are v ₄ , v ₅ , v ₆ , the maximum video quality V _max expressed in MOS value Is represented by the following equation (2).

[Minimum video quality calculation processing]
Next, the minimum video quality calculation process in the minimum video quality calculation unit 21B will be described in detail.
The minimum video quality calculation unit 21B sets the bit rate-minimum video quality characteristic indicating the relationship between the bit rate of the test reception video and the minimum video quality indicating the minimum value of the video quality obtained from the test reception video of the bit rate. Based on this, the minimum video quality V _min corresponding to the bit rate _Br extracted by the bit rate extraction unit 12 is calculated.

  FIG. 10 shows a bit rate-minimum video quality characteristic 53 indicating the relationship between the bit rate and the minimum video quality. The minimum video quality is a minimum value of the user experience quality obtained by conducting an opinion evaluation in advance for each received video for a video set including a plurality of test received videos each having a bit rate as a quality parameter.

As shown in FIG. 10, the bit rate-minimum video quality characteristic has a characteristic that the minimum video quality monotonously increases with an increase in the bit rate and then converges to an arbitrary maximum value. When the minimum video quality is expressed by a MOS value, the lower limit value is 1. When the minimum video quality that is not limited to the range that the MOS value can take is V _min — _tmp and the characteristic coefficients related to the bit rate-minimum video quality characteristics are v ₇ , v ₈ , v ₉ , the minimum video quality V _min expressed by the MOS value Is represented by the following equation (3).

[Content impact calculation processing]
Next, the content influence degree calculation processing in the content influence degree calculation unit 21C will be described in detail.
As shown in the following equation (4), the content influence calculation unit 21C calculates the minimum video quality V obtained by the minimum video quality calculation unit 21B from the maximum video quality V _max obtained by the maximum video quality calculation unit 21A. _The content influence degree C is calculated by subtracting _min .

  As shown in FIG. 6 described above, the bit rate-content influence level characteristic indicating the relationship between the bit rate and the content influence level is monotonically increased as the bit rate increases and reaches the maximum value. It has a convex characteristic that the content influence degree monotonously decreases as the bit rate further increases. In the case of FIG. 6, the content influence degree C has a vertex in the vicinity of a bit rate of 4 Mbps. This means that the greater the content influence level C, the greater the influence on the video quality due to the difference in video content at the corresponding bit rate.

[Average global motion calculation processing]
Next, the average global motion amount calculation process in the average global motion amount calculation unit 22A will be described in detail.
The average global motion amount calculation unit 22A is configured to calculate the average corresponding to the bit rate _Br extracted by the bit rate extraction unit 12 based on the bit rate-average global motion amount characteristic indicating the relationship between the bit rate and the average global motion amount. The global motion amount GMV _ave is calculated.

  FIG. 11 is a graph showing the bit rate-average global motion amount characteristic, in which the horizontal axis indicates the bit rate and the vertical axis indicates the average global motion amount. The average global motion amount is determined in advance for each received video, based on the same calculation method as that of the global motion amount calculation unit 22B described above, for a video set including a plurality of test received videos having respective bit rates as quality parameters. The global motion amount is calculated, and the obtained global motion amount is an average value of these received videos.

As shown in FIG. 11, the bit rate-average global motion amount characteristic has a characteristic of converging to an arbitrary minimum value after the average global motion amount monotonously decreases in accordance with an increase in the bit rate. When the characteristic coefficients regarding the bit rate-average global motion amount characteristics are v ₁₀ , v ₁₁ , and v ₁₂ , the average global motion amount GMV _ave is expressed by the following equation (5).

[Global motion calculation processing]
Next, the global motion amount calculation processing in the global motion amount calculation unit 22B will be described in detail. FIG. 12 is an explanatory diagram illustrating the global motion amount calculation processing. FIG. 13 is another explanatory diagram showing the global motion amount calculation processing.

  Based on the video signal S acquired by the video signal acquisition unit 13, the global motion amount calculation unit 22B fixes one f-th frame f and fixes the other f + 1-th frame for each adjacent frame in the video signal S. The frame f + 1 is translated by one pixel vertically and horizontally within an arbitrary movement range. Next, for each pixel included in the overlapping region where these two frames overlap, a difference value between the pixel value in the frame f and the pixel value in the frame f + 1, that is, the inter-frame difference value D is obtained, and the absolute value thereof is calculated in the overlapping region. An average value averaged by the number of pixels is calculated.

The horizontal pixel position at the left end of the overlapping portion of the fixed frame f is W _start , the horizontal pixel position at the right end of the overlapping portion of the fixed frame f is W _end, and the vertical direction of the upper end of the overlapping portion of the fixed frame f The pixel position is H _start , the vertical pixel position at the lower end of the overlapping part of the fixed frame f is H _end , the function that outputs the absolute value of the argument is abs (), and the pixel position (w, h) of the frame f Where y (f, w, h) is the total number of pixels in the horizontal direction and W is the total number of pixels in the vertical direction, the frame f + 1 is j pixels in the horizontal direction and j in the vertical direction. The inter-frame difference value D (f, i, j) relating to the overlapping region between the frame f and the frame f + 1 when the pixel is moved in parallel is expressed by the following equation (6).

In this formula (6), i and j are changed within an arbitrary movement range, and i and j that minimize D (f, i, j) are calculated. These i and j correspond to the horizontal component GMV _w (f) and the vertical component GMV _h (f) of the global vector indicating the global movement when the inter-frame difference value D (f, i, j) is minimized.

Subsequently, as shown in the following equation (7), the root mean square of GMVv (f) and GMV _h (f) is calculated, and the global motion amount GMVf (f) indicating the magnitude (absolute value) of the global vector related to the frame f )

Using this equation (7), the global motion amount GMVf (f) obtained for each adjacent frame in the quality estimation section is expressed as the number of adjacent frames (adjacent frame pairs) as shown in the following equation (8). The global motion amount GMV related to the received video is calculated by averaging with N-1. N is the total number of frames in the quality estimation section.

[Difference global motion calculation processing]
Next, the difference global motion amount calculation processing in the difference global motion amount calculation unit 22C will be described in detail.
As shown in the following equation (9), the difference global motion amount calculation unit 22C calculates the global motion amount obtained by the global motion amount calculation unit 22B from the average global motion amount GMV _ave obtained by the average global motion amount calculation unit 22A. The difference global motion amount dGMV is calculated by subtracting the motion amount GMV.

[Average local motion calculation]
Next, the average local motion amount calculation process in the average local motion amount calculation unit 23A will be described in detail.
The average local motion amount calculation unit 23A is based on the bit rate-average local motion amount characteristic indicating the relationship between the bit rate and the average local motion amount, and the average corresponding to the bit rate _Br extracted by the bit rate extraction unit 12. The local motion amount LMV _ave is calculated.

  FIG. 14 is a graph showing bit rate-average local motion amount characteristics, where the horizontal axis indicates the bit rate and the vertical axis indicates the average local motion amount. The average local motion amount is determined in advance for each received video, based on a calculation method similar to that of the local motion amount calculation unit 23B described above, for a video set including a plurality of test received videos having respective bit rates as quality parameters. The local motion amount is calculated, and the obtained local motion amount is an average value of these received images.

As shown in FIG. 14, the bit rate-average local motion amount characteristic has a characteristic that converges to an arbitrary minimum value after the average local motion amount monotonously decreases in accordance with an increase in the bit rate. When the characteristic coefficients related to the bit rate-average local motion amount characteristics are v ₁₃ , v ₁₄ , and v ₁₅ , the average local motion amount LMV _ave is expressed by the following equation (10).

[Local motion calculation processing]
Next, the local motion amount calculation processing in the local motion amount calculation unit 23B will be described in detail. There are two calculation methods for the local motion amount calculation processing.

In the first local motion amount calculation method, GMV _w (f) and GMV _h (f) calculated in the process of deriving the global motion amount GMV are used.
First, based on the video signal S acquired by the video signal acquisition unit 13, for each adjacent frame in the video signal S, the f + 1-th frame f + 1 is GMV _w (f) pixels in the horizontal direction and GMV _{h in} the vertical direction. (F) The inter-frame difference value M (f, w, h) regarding the overlapping region of the pixel values of the f-th frame f and the frame f + 1 when translated by the number of pixels is based on the following equation (11). To calculate. In the formula (11), f, w, h, and y () have the same meanings as the above formula (6) and FIGS.

Subsequently, the standard deviation M _std (f) of the inter-frame difference value M (f, w, h) regarding the overlapping region obtained by the equation (11) is calculated by the following equation (12). In Equation (12), W _start , W _end , H _start , and H _end have the same meanings as in Equation (6) and FIGS. M _ave (f) is an average value obtained by averaging the inter-frame difference values M (f, w, h) by the number of pixels in the overlapping region, and M _var (f) is an inter-frame difference value M (f, w, h). w, h).

The local motion amount LMV is calculated by averaging the standard deviation M _std (f) obtained by this equation (11) with the number of adjacent frames (adjacent frame pairs) as shown in the following equation (13). To do. N is the total number of frames in the quality estimation section.

  Next, in the second local motion amount calculation method, the screen of the adjacent frame is divided into rectangular blocks, and the pixels are locally moved in units of these blocks. In this embodiment, a case where the block size is 8 pixels × 8 pixels will be described as an example.

  First, as in the global motion amount calculation method described above, one f-th frame f is fixed for each adjacent frame in the video signal S based on the video signal S acquired by the video signal acquisition unit 13. The other f + 1-th frame f + 1 is moved in parallel in an arbitrary movement range by one pixel vertically and horizontally. Next, for each pixel included in the overlapping region where these two frames overlap, a difference value between the pixel value in the frame f and the pixel value in the frame f + 1, that is, the inter-frame difference value D is obtained, and the absolute value thereof is calculated in the overlapping region. An average value averaged by the number of pixels is calculated. Then, the frame f + 1 is translated in an arbitrary movement range, and both frames are translated in such a positional relationship that the average value becomes the smallest at that time.

  Thereafter, with respect to these adjacent frames, the block of the previous frame f is fixed, and the same block in the subsequent frame f + 1 is translated in an arbitrary range by one pixel vertically and horizontally. Next, for each pixel included in the overlapping region where the blocks of both frames overlap, the difference value between the pixel value in frame f and the pixel value in frame f + 1, that is, the inter-frame difference value D is obtained, and the absolute value is overlapped. An average value obtained by averaging the number of pixels in the area is calculated.

The horizontal pixel position at the left end of the block is W _start , the vertical pixel position at the upper end of the block is H _start , the vertical pixel number of the block is H _b, and the horizontal pixel number of the block is W _b , When the function that outputs the absolute value of the argument is abs () and the pixel value at the pixel position (w, h) of the frame f is y (f, w, h), the nth block n in the frame f + 1 is The inter-frame difference value D _b (f, n, i, j) relating to the overlapping region between the frame f and the frame f + 1 when the horizontal movement is performed by i pixels and the j pixels in the vertical direction is expressed by the following formula ( 14).

In this equation (14), i and j are changed within an arbitrary movement range, and i and j that minimize D _b (f, n, i, j) are calculated. These i and j represent the local movement when the inter-frame difference value D _b (f, i, j) is minimum, the horizontal component MV _w (f, n) and the vertical component of the local vector not including the global movement. It corresponds to MV _h (f, n).

Subsequently, GMV _w (f) calculated in the process of deriving MV _w (f, n), MV _h (f, n) and global motion amount GMV for each block as in the following equation (15). , GMV _h (f), the horizontal component LMV _w (f, n) and the vertical component LMV _h (f, n) of the local vector including the global movement are calculated.

Using this equation (15), the average value of the absolute values of the local vectors is averaged by the number N-1 of adjacent frames (adjacent frame pairs) as in the following equation (16). Thus, the local motion amount LMV is calculated. Here, N is the total number of frames in the quality estimation section, and N _b is the number of blocks in the screen.

[Differential local motion calculation processing]
Next, the difference local motion amount calculation processing in the difference local motion amount calculation unit 23C will be described in detail.
The difference local motion amount calculation unit 23C, as shown in the following equation (17), uses the local motion amount calculation unit 23B obtained from the average local motion amount LMV _ave obtained by the average local motion amount calculation unit 23A. The difference local motion amount dLMV is calculated by subtracting the motion amount LMV.

[Difference video quality calculation processing]
Next, the difference video quality calculation process in the difference video quality calculation unit 24 will be described in detail.
The difference video quality calculation unit 24 decreases the difference image quality in accordance with the increase of the product of the content influence degree C and the difference global motion amount dGMV and the sum of the products of the content influence degree C and the difference local motion amount dLMV. Based on the difference video quality characteristic, the content influence degree C obtained by the content influence degree calculation unit 21, the difference global movement amount dGMV obtained by the difference global movement amount calculation unit 22, and the difference local movement amount calculation unit 23 are obtained. The difference video quality dV corresponding to the obtained difference local motion amount dLMV is calculated.

As described above, the difference video quality dV indicates a first-order approximation relationship with respect to the sum of the product of the content influence degree C and the difference global motion amount dGMV and the product of the content influence degree C and the difference local motion amount dLMV. Has differential video quality characteristics.
When the characteristic coefficients related to the differential video quality characteristic are v ₁₅ and v ₁₆ , the differential video quality dV is expressed by the following equation (18).

[Video quality calculation processing]
Next, the video quality calculation process in the video quality calculation unit 16 will be described in detail.
The video quality calculation unit 16 adds the differential video quality dV calculated by the differential video quality calculation unit 15 to the average video quality value V _ave calculated by the average video quality calculation unit 14 as shown in the following equation (19). Thus, the video quality V indicating the user experience quality perceived by the user who has viewed the received video received by the video receiving terminal 2 is calculated.

[Effects of the present embodiment]
In this manner, in the present embodiment, the average video quality calculation unit 14, based on the bit rate B _r extracted from the received image coded video data, a plurality of test received by the video communication of the bit rate B _r the average image quality obtained from use received image is calculated as the average image quality V _ave, the differential image quality calculation section 15, based on the video signal S bit rate B _r and the received image, the average image quality V _ave Difference video quality dV indicating the difference between the received video quality V and the received video quality V, and the video quality calculation unit 16 calculates the video quality V by correcting the average video quality V _ave with the difference video quality dV. , in the difference video quality calculation unit 15, it is calculated based on the bit rate B _r, and content influence C of the contents of the received image indicates the magnitude of the effect on the video quality of the received video, It was calculated on the received image as a unique value based on the said bit rate B _r and the video signal S, the difference global motion amount indicating the amount of global motion of the image screen DGMV, and local motion picture screen The difference video quality dV is calculated based on the difference local motion amount dLMV indicating the amount.

As a result, in an environment where the video signal of the received video and the packet of the encoded video data can be acquired, the differential video quality specific to the received video is accurately considered in consideration of the content dependency and codec implementation dependency of the video quality. Thus, the video quality of the received video can be easily estimated with high accuracy.
Therefore, the service provider can more accurately determine whether or not the video communication service maintains a certain level of quality for the user, and can accurately grasp the actual quality of the video communication service being provided. It becomes possible to manage.

[Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Video delivery apparatus, 2 ... Video receiving terminal, 3 ... IP network, 10 ... Video quality estimation apparatus, 11 ... Packet acquisition part, 12 ... Bit rate extraction part, 13 ... Video signal acquisition part, 14 ... Average video quality calculation 15, difference video quality calculation unit 16, video quality calculation unit 21, content influence degree calculation unit, 21 A, maximum video quality calculation part, 21 B, minimum video quality calculation part, 21 C, content influence degree calculation part, 22 ... difference global motion amount calculation unit, 22A ... average global motion amount calculation unit, 22B ... global motion amount calculation unit, 22C ... difference global motion amount calculation unit, 23 ... difference local motion amount calculation unit, 23A ... average local motion amount calculation parts, 23B ... local motion amount calculation unit, 23C ... differential local motion amount calculation unit, 24 ... differential image quality calculating unit, B _r ... bit rate, S ... video No., V _max ... maximum image quality, V _min ... minimum video quality, C ... content influence, GMV _ave ... average global motion amount, GMV ... global motion amount, dGMV ... differential global motion amount, LMV _ave ... average local motion amount , LMV ... Local motion amount, dLMV ... Differential local motion amount, dV ... Differential video quality, V ... Video quality.

Claims (16)

Received video received by the video receiving terminal from the video distributing device by performing video communication between the video distributing device and the video receiving terminal connected via the IP network using a packet storing encoded video data. A video quality estimation device for calculating video quality indicating user experience quality perceived by a user who viewed the received video,
A bit rate extraction unit that extracts the bit rate of the video communication based on the encoded video data amount counted from the encoded video data;
Based on the bit rate extracted by the bit rate extraction unit, an average video quality calculation that calculates an average video quality obtained from a plurality of test received videos received by video communication at the bit rate as an average video quality And
Based on the bit rate extracted by the bit rate extraction unit and the video signal of the received video, a difference between the average video quality obtained by the average video quality calculation unit and the video quality of the received video is indicated. A difference video quality calculation unit for calculating the difference video quality;
A video quality calculating unit for calculating the video quality of the received video by correcting the average video quality obtained by the average video quality calculating unit with the differential video quality obtained by the differential video quality calculating unit; With
The difference video quality calculation unit calculates a content influence level indicating the degree of influence of the content of the received video on the video quality of the received video calculated based on the bit rate, the bit rate, and the video signal. Based on the difference global motion amount indicating the amount of overall motion of the video screen and the difference local motion amount indicating the amount of local motion in the video screen, calculated as a value specific to the received video based on The video quality estimation apparatus characterized by calculating the difference video quality. The video quality estimation apparatus according to claim 1,
The difference video quality calculation unit
Based on the bit rate extracted by the bit rate extraction unit, a content influence calculation unit that calculates the content influence degree indicating the magnitude of the influence of the content of the received video on the video quality of the received video;
Based on the bit rate extracted by the bit rate extraction unit and the video signal of the received video, a global motion amount indicating an overall motion amount of the video screen of the received video, and the test received video A difference global motion amount calculating unit that calculates a difference value with an average global motion amount indicating an average global motion amount obtained from the difference global motion amount;
Based on the bit rate extracted by the bit rate extraction unit and the video signal of the received video, a local motion amount indicating a local motion amount in the video screen of the received video, and the test reception A difference local motion amount calculating unit that calculates a difference value with an average local motion amount indicating an average local motion amount obtained from video as the difference local motion amount;
The content influence level obtained by the content influence level calculation unit, the difference global motion amount obtained by the difference global motion amount calculation unit, and the difference local motion amount obtained by the difference local motion amount calculation unit A video quality estimation apparatus comprising: a differential video quality calculation unit that calculates the differential video quality based on The video quality estimation apparatus according to claim 2, wherein
The content influence calculation unit
The bit rate extraction based on the maximum video quality characteristic indicating the relationship between the bit rate of the test received video and the bit rate indicating the maximum value of the video quality obtained from the test received video of the bit rate-maximum video quality A maximum video quality calculation unit that calculates the maximum video quality obtained from the test reception video of the bit rate extracted by the unit,
The bit rate extraction based on the bit rate-minimum video quality characteristic indicating the relationship between the bit rate of the test received video and the minimum video quality indicating the minimum value of the video quality obtained from the test received video of the bit rate A minimum video quality calculation unit for calculating a minimum video quality obtained from the test reception video of the bit rate extracted by the unit,
A content impact calculation unit that calculates the content impact by subtracting the minimum video quality obtained by the minimum video quality calculation unit from the maximum video quality obtained by the maximum video quality calculation unit. A video quality estimation apparatus characterized by the above. The video quality estimation apparatus according to claim 2, wherein
The difference global motion amount calculation unit
Based on the bit rate-average global motion amount characteristic indicating the relationship between the bit rate of the test reception video and the average global motion amount indicating the average global motion amount obtained from the test reception video of the bit rate, An average global motion amount calculation unit that calculates an average global motion amount obtained from the test received video of the bit rate extracted by the bit rate extraction unit;
Based on the video signal of the received video, the global motion that calculates the global motion amount of the received video from the number of pixels moved by the overall motion of the video screen between adjacent frames in the video signal and the moving distance thereof A quantity calculator;
The difference global motion amount for calculating the difference global motion amount by subtracting the global motion amount obtained by the global motion amount calculation unit from the average global motion amount obtained by the average global motion amount calculation unit. A video quality estimation apparatus comprising: a calculation unit. The video quality estimation apparatus according to claim 2, wherein
The difference local motion amount calculation unit includes:
Based on the bit rate-average local motion amount characteristic indicating the relationship between the bit rate of the test reception video and the average local motion amount indicating the average local motion amount obtained from the test reception video of the bit rate, An average local motion amount calculation unit for calculating an average local motion amount obtained from the test received video of the bit rate extracted by the bit rate extraction unit;
Based on the video signal of the received video, the local motion amount of the received video is calculated from the number of pixels moved by the local motion in the video screen between adjacent frames in the video signal and the moving distance thereof. A motion amount calculation unit;
The difference local motion amount for calculating the difference local motion amount by subtracting the local motion amount obtained by the local motion amount calculation unit from the average local motion amount obtained by the average local motion amount calculation unit. A video quality estimation apparatus comprising: a calculation unit. The video quality estimation apparatus according to claim 4,
When the global motion amount calculation unit fixes one frame for each adjacent frame and translates the other frame vertically and horizontally by one pixel at a time, the absolute value of the difference value of the pixel values of the overlapping region where these frames overlap each other is calculated. A parallel movement distance when a value obtained by averaging the values with the number of pixels of the overlapping region is the smallest is calculated, and the global movement amount is calculated by averaging the parallel movement distances with the number of the adjacent frames. A video quality estimation device. The video quality estimation apparatus according to claim 5, wherein
When the local motion amount calculation unit fixes one frame for each adjacent frame and translates the other frame vertically and horizontally one pixel at a time, the local motion amount calculation unit calculates the absolute value of the difference value of the pixel values of the overlapping region where these frames overlap. Calculating the standard deviation of the difference value when the value obtained by averaging the values with the number of pixels in the overlap region is the smallest, and calculating the local motion amount by averaging these standard deviations with the number of adjacent frames. A video quality estimation device characterized by the above. The video quality estimation apparatus according to claim 5, wherein
The local motion amount calculation unit fixes one of the adjacent frames, translates the other frame vertically and horizontally one pixel at a time, and calculates an absolute value of a difference value of pixel values in an overlapping region where these frames overlap. After shifting both frames in a positional relationship where the average value of the number of pixels in the overlapping area becomes the smallest, both frames of these adjacent frames are divided into rectangular shapes, and one block is provided for each block. When the block of the frame is fixed and the block of the other frame is translated horizontally and vertically by one pixel, the value obtained by averaging the absolute value of the difference value of the pixel values of the overlapping region where these blocks overlap with the number of pixels of the block is Calculate the parallel movement distance for each block when it was the smallest, and average the parallel movement distance by the number of blocks in the number of adjacent frames. The video quality estimation apparatus and calculates the local motion amount by. The video quality estimation apparatus according to claim 1,
The average video quality calculation unit is extracted by the bit rate extraction unit based on a bit rate-average video quality characteristic that converges to an arbitrary value after the average video quality monotonously increases with an increase in the bit rate. A video quality estimation apparatus that calculates the average video quality corresponding to a bit rate. The video quality estimation apparatus according to claim 4,
The maximum video quality calculation unit is extracted by the bit rate extraction unit based on the bit rate-maximum video quality characteristic that converges to an arbitrary value after the maximum video quality monotonously increases as the bit rate increases. A video quality estimation apparatus that calculates the maximum video quality corresponding to the bit rate. The video quality estimation apparatus according to claim 4,
The minimum video quality calculation unit is extracted by the bit rate extraction unit based on the bit rate-minimum video quality characteristic that converges to an arbitrary value after the minimum video quality monotonously increases as the bit rate increases. A video quality estimation apparatus that calculates the minimum video quality corresponding to the bit rate. The video quality estimation apparatus according to claim 5, wherein
The average global motion amount calculation unit is a bit rate extraction unit based on the bit rate-average global motion amount characteristic that converges to an arbitrary value after the average global motion amount monotonously decreases as the bit rate increases. A video quality estimation apparatus, wherein the average global motion amount corresponding to the extracted bit rate is calculated. The video quality estimation apparatus according to claim 6,
The average local motion amount calculation unit is a bit rate extraction unit based on the bit rate-average local motion amount characteristic that converges to an arbitrary value after the average local motion amount monotonously decreases as the bit rate increases. A video quality estimation apparatus, wherein the average local motion amount corresponding to the extracted bit rate is calculated. The video quality estimation apparatus according to claim 2, wherein
The difference video quality calculation unit is a difference video quality characteristic in which the difference video quality decreases in accordance with an increase in a product of the content influence level and the difference global motion amount and a sum of products of the content impact degree and the difference local motion amount. Based on the content influence degree obtained by the content influence degree calculation unit, the difference global movement amount obtained by the difference global movement amount calculation unit, and the difference obtained by the difference local movement amount calculation unit A video quality estimation apparatus that calculates the difference video quality corresponding to a local motion amount. Received video received by the video receiving terminal from the video distributing device by performing video communication between the video distributing device and the video receiving terminal connected via the IP network using a packet storing encoded video data. A video quality estimation method used in a video quality estimation device for calculating video quality indicating a user experience quality perceived by a user who viewed the received video,
A bit rate extraction unit that extracts a bit rate of the video communication based on the encoded video data amount counted from the encoded video data;
Based on the bit rate extracted by the bit rate extraction unit, an average video quality calculation unit calculates an average video quality obtained from a plurality of test received videos received by video communication at the bit rate. An average video quality calculation step to calculate as
The difference video quality calculation unit, based on the bit rate extracted by the bit rate extraction unit and the video signal of the received video, the average video quality obtained by the average video quality calculation unit and the received video A difference video quality calculating step for calculating a difference video quality indicating a difference from the video quality;
The video quality calculating unit calculates the video quality of the received video by correcting the average video quality obtained by the average video quality calculating unit with the differential video quality obtained by the differential video quality calculating unit. And a video quality calculation step for
In the difference video quality calculation step, the content influence degree indicating the magnitude of the influence of the received video content on the video quality of the received video calculated based on the bit rate, the bit rate, and the video signal Based on the difference global motion amount indicating the amount of overall motion of the video screen and the difference local motion amount indicating the amount of local motion in the video screen, calculated as a value specific to the received video based on A method for estimating video quality, comprising: calculating the difference video quality.   The program for functioning a computer as each part which comprises the video quality estimation apparatus in any one of Claims 1-14.

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