Selectable bit rate determination device and selectable bit rate determination method

Abstract

A selectable bit rate determination device disclosed herein comprises: a perceived quality estimation unit that calculates an estimated value of perceived quality for a bit rate in a range designated for a Web conference service; a power consumption estimation unit that calculates an estimated value of power consumption for the bit rate in the range on the basis of the characteristic that the increase in power consumption per unit bit rate decreases as the bit rate increases; a normalization unit that normalizes each of the estimated value of perceived quality and the estimated value of power consumption; an index calculation unit that, on the basis of the normalized estimated values, calculates an index that increases as perceived quality increases and power consumption decreases; and a selection unit that selects, as a bit rate that can be selected in the Web conference service, a bit rate related to the estimated value of perceived quality corresponding to the maximum point of the index in the relationship between the index and the estimated value of perceived quality calculated for the bit rate in the range. The selectable bit rate determination device thus supports bit rate control capable of suppressing power consumption while increasing perceived quality.

Description

Selectable bit rate determining device and selectable bit rate determining method

[0001] The present invention relates to a selectable bit rate determining device and a selectable bit rate determining method.

[0002] With the increase in remote work, web conferencing services are now widely used on a variety of devices. Providers of web conferencing services are required to maintain quality for users so that they can use the service comfortably. To improve user quality, it is necessary to increase the video bitrate of web conferencing. However, excessively increasing the bitrate increases the amount of data transferred, leading to increased operational costs. Therefore, it is necessary to reduce the amount of data transferred while maintaining the quality required by users.

[0003] To address this issue, a video bit rate control method has been proposed that reduces the amount of data transfer while maintaining the quality desired for users at a target value (Non-Patent Document 1).

[0004] In Non-Patent Document 1, the quality of experience of each user is estimated from the audio and video information received by each user. Based on this information, a future video bit rate is predicted to achieve a preset target quality of experience, and a bit rate that minimizes the amount of data transferred while still achieving the target quality of experience is selected, and the bit rate for transmitting video is indicated to each user.

[0005] Meanwhile, environmental conservation efforts have become increasingly important in recent years, leading to growing demands for reduced ICT power consumption. Therefore, it is necessary to consider not only the user's quality of experience and operational costs, but also power consumption. Furthermore, from the user's perspective, the promotion of remote work means that participants in web conferences are expected to participate in a variety of environments. When using web conferences while away from home, high power consumption means that participants' participation time in web conferences will be shortened, so it is important to be aware of power consumption from the perspective of convenience.

[0006] M. Yokota and K. Yamagishi, "Quality-based video bitrate control for WebRTC-based tele-conference services", Electronic imaging 2022, IQSP-333, Jan. 2022P. Lebreton and K. Yamagishi, "Transferring adaptive bit rate streaming quality models from H.264 / HD to H.265 / 4K-UHD", IEICE Transactions on Communications, vol. E102-B, no. 12, pp. 2226-2242, Dec. 2019, 10.1587 / transcom.2019EBP3045

[0007] In Non-Patent Document 1, control that takes into account the quality of experience and the amount of data transfer is realized, but power consumption cannot be taken into account, and therefore control that increases user convenience cannot necessarily be achieved.

[0008] The present invention has been made in view of the above points, and has an object to support bit rate control that can reduce power consumption while improving quality of experience.

[0009] In order to solve the above problem, a selectable bit rate determination device is characterized by having: a quality of experience estimation unit configured to calculate an estimated value of quality of experience for a bit rate within a range specified for a Web conference service; a power consumption estimation unit configured to calculate an estimated value of power consumption for the bit rate within the range based on the characteristic that the increase in power consumption per unit bit rate decreases as the bit rate increases; a normalization unit configured to normalize each of the estimated value of quality of experience and the estimated value of power consumption; an index calculation unit configured to calculate, based on the normalized estimate, an index that increases as the quality of experience increases and increases as power consumption decreases; and a selection unit configured to select, as a selectable bit rate for the Web conference service, a bit rate associated with the estimated value of quality of experience that corresponds to a maximum point of the index in the relationship between the estimated value of quality of experience calculated for the bit rate within the range and the index.

[0010] It is possible to support bit rate control that can reduce power consumption while improving the quality of experience.

[0011] FIG. 1 is a diagram showing an example of a hardware configuration of a selectable bit rate determination device 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a functional configuration of a selectable bit rate determination device 10 according to an embodiment of the present invention. FIG. 3 is a flowchart for explaining an example of a processing procedure executed by the selectable bit rate determination device 10. ｓｃａｌｉｎｇ 1 is a diagram showing the relationship between QoE and index. ｓｃａｌｉｎｇ FIG. 1 is a diagram for explaining the QoE that maximizes the closest distance. ｓｃａｌｉｎｇ FIG. 10 is a diagram for explaining the selection of .

[0012] The reason why the conventional technology is unable to control the video bit rate while taking power consumption into consideration (hereinafter referred to as "Problem 1") is that, for web conferencing services, the relationship between the transmission bit rate and the power consumption of the sending client, taking into consideration encoding processing in the web browser, etc., is unclear, making it impossible to control the video bit rate while taking into consideration the characteristics of power consumption (hereinafter referred to as "Problem 2").

[0013] Therefore, in this embodiment, in order to solve the second problem, a technique for estimating power consumption from a transmission bit rate is realized.

[0014] Furthermore, in the bit rate control technology as in Non-Patent Document 1, the bit rate to be controlled is selected from a selectable bit rate group. Therefore, in this embodiment, in order to solve Problem 1, the selectable bit rate group is determined using a technology for estimating power consumption from the transmission bit rate, which is used to solve Problem 2, and a technology for estimating the quality of experience (the quality of experience of video viewers (participants in a web conference)) from the bit rate (Non-Patent Document 2, etc.).

[0015] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a diagram showing an example of the hardware configuration of a selectable bit rate determination device 10 according to an embodiment of the present invention. The selectable bit rate determination device 10 in Fig. 1 includes a drive device 100, an auxiliary storage device 102, a memory device 103, a processor 104, and an interface device 105, all of which are interconnected via a bus B.

[0016] A program that realizes the processing in the selectable bit rate determination device 10 is provided by a recording medium 101 such as a CD-ROM. When the recording medium 101 storing the program is set in the drive device 100, the program is installed from the recording medium 101 to the auxiliary storage device 102 via the drive device 100. However, the program does not necessarily have to be installed from the recording medium 101, but may be downloaded from another computer via a network. The auxiliary storage device 102 stores the installed program as well as necessary files, data, etc.

[0017] When an instruction to start the program is received, the memory device 103 reads and stores the program from the auxiliary storage device 102. The processor 104 is a CPU or a GPU (Graphics Processing Unit), or a CPU and a GPU, and executes functions related to the selectable bitrate determination device 10 in accordance with the program stored in the memory device 103. The interface device 105 is used as an interface for connecting to a network.

[0018] 2 is a diagram showing an example of the functional configuration of a selectable bitrate determination device 10 according to an embodiment of the present invention. In Fig. 2, the selectable bitrate determination device 10 includes an input unit 11, a quality of experience estimator 12, a power consumption estimator 13, a normalizer 14, an index calculator 15, a selector 16, and an output unit 17. Each of these units is realized by a process executed by a processor 104 of one or more programs installed in the selectable bitrate determination device 10.

[0019] The processing procedure executed by the selectable bit rate determination device 10 will be described below. Fig. 3 is a flowchart illustrating an example of the processing procedure executed by the selectable bit rate determination device 10. The processing procedure shown in Fig. 3 only needs to be performed once, asynchronously with a certain Web conference service, before the Web conference service is provided. The selectable bit rates obtained as a result of the processing can be set as Config (setting information) of a control technology such as that described in Non-Patent Document 1, before the Web conference service is provided.

[0020] In step S101, the input unit 11 receives from the user a specification of the range (minimum value, maximum value) of the bit rate (br) for the Web conference service for which the selectable bit rate is to be calculated. The input unit 11 sets the minimum value as a variable br ｍｉｎ and assign the maximum value to the variable br ｍａｘ In the current Web conferencing service, 2Mbps video is enough to achieve high quality, so for example, ｍｉｎ is set to 0Mbps, and ｍａｘ It is conceivable that 2 Mbps is set to .

[0021] Next, the quality of experience estimator 12 calculates the minimum bit rate (br ｍｉｎ ) for the minimum estimated quality of experience (QoE ｍｉｎ ) and calculate the maximum bit rate (br ｍａｘ ) for the maximum estimated value of the quality of experience (QoE ｍａｘ ) is calculated (S102).

[0022] In this case, the quality of experience estimator 12 calculates an estimated value of the quality of experience using a model that can estimate the quality of experience of a user receiving video at a bit rate from the bit rate, as formulated in Non-Patent Document 2. In Non-Patent Document 2, information on the resolution and frame rate in addition to the bit rate is required to estimate the quality of experience, so the quality of experience estimator 12 is assumed to be given in advance the values ​​of the resolution and frame rate that are set in each bit rate section.

[0023] Next, the power consumption estimation unit 13 calculates the minimum value of the bit rate (br ｍｉｎ ) for the minimum estimated value of power consumption (pc ｍｉｎ ) and calculate the maximum bit rate (br ｍａｘ ) for the maximum estimated value of power consumption (pc ｍａｘ ) is calculated (S103).

[0024] In this case, the power consumption estimation unit 13 calculates an estimated value of power consumption using a model that can estimate power consumption from the transmission bit rate (br). As described in Problem 2, such an estimation model does not exist, so in this embodiment, a specific estimation model and its characteristics are constructed based on the following idea.

[0025] For a client hosting a web conference, the main processing during the web conference is considered to be encoding video and audio and transmitting the encoded video. The higher the bit rate of the transmitted video, the more processing is required for encoding, and the larger the amount of data transferred, resulting in increased power consumption. Furthermore, by taking into account the fact that the increase in power consumption per unit bit rate decreases as the transmission bit rate increases, the power consumption (pc) can be estimated from the transmission bit rate using the model described in Equation (1).

[0026] That is, the power consumption estimation unit 13 calculates br ｍｉｎ Substituting pc ｍｉｎ Calculate br in Equation (1) ｍａｘ Substituting pc ｍａｘ Calculate.

[0027] Here, β ０ , β １ , β ２ , β ３ are the parameters of the model.

[0028] In this embodiment, it is assumed that such a model is used, but other models can also be used as long as they are capable of estimating power consumption from the transmission bit rate.

[0029] Next, the input unit 11 sets the variable br to br ｍｉｎ Then, the initialization is performed (S104).

[0030] Next, the quality of experience estimator 12 calculates an estimated value of the quality of experience for br and assigns the calculation result to the variable QoE (S105). The method of calculating the estimated value of the quality of experience may be the same as in step S102.

[0031] Next, the power consumption estimating unit 13 calculates an estimated value of power consumption for br and assigns the calculation result to the variable pc (S106). The method of calculating the estimated value of power consumption may be the same as in step S103.

[0032] In the subsequent steps S107 and S108, the normalization unit 14 performs processing to align (unify) the scales of the power consumption and the quality of experience so that the power consumption estimated by the power consumption estimation unit 13 and the quality of experience estimated by the quality of experience estimation unit 12 can be compared.

[0033] In step S107, the normalization unit 14 calculates the QoE, QoE ｍｉｎ and QoE ｍａｘ By substituting into the following equation (2), the scaled (normalized) QoE ｓｃａｌｉｎｇ Calculate.

[0034] That is, the normalization unit 14 normalizes the QoE so that the minimum value of the QoE is 0 and the maximum value is 1.

[0035] Next, the normalization unit 14 calculates the above-calculated pc and pc ｍｉｎ and PC ｍａｘ By substituting into the following equation (3), the scale is unified (normalized) pc ｓｃａｌｉｎｇ Calculate.

[0036] That is, the normalization unit 14 normalizes pc so that the minimum value of pc is 0 and the maximum value is 1.

[0037] Next, the index calculation unit 15 calculates the quality of experience (QoE) values ​​that are standardized (normalized) and can be compared. ｓｃａｌｉｎｇ ) and power consumption (pc ｓｃａｌｉｎｇ ), an index for evaluating the Web conference service is calculated taking into consideration both the quality of experience and power consumption (S109).

[0038] In a Web conference service, it is desirable to have a high quality of experience and low power consumption (requirement 1). Taking these into account, an index that takes into account both quality of experience and power consumption is shown in equation (4).

[0039] Here, α is a parameter (coefficient) that changes the weighting given to quality of experience and power consumption. The smaller the value of α, the more importance is placed on power consumption, and the larger the value, the more importance is placed on quality of experience.

[0040] That is, the index is an example of an index that increases as the quality of experience increases and as the power consumption decreases. ｓｃａｌｉｎｇ and PC ｓｃａｌｉｎｇ is substituted to calculate the index.

[0041] Next, the index calculation unit 15 calculates the QoE ｓｃａｌｉｎｇ , index) is recorded in the memory device 103 (S110).

[0042] Next, the index calculation unit 15 calculates the value of br+Δbr as br ｍａｘ Here, it is determined whether Δbr exceeds br ｍｉｎ From br ｍａｘ (QoE ｓｃａｌｉｎｇ , index). Therefore, the smaller Δbr is, the higher the QoE is. ｓｃａｌｉｎｇ For example, Δbr=1 may be used.

[0043] The value of br+Δbr is br ｍａｘ If it is equal to or less than this (No in S111), the index calculation unit 15 updates br by substituting br+Δbr for br (S112). Subsequently, step S105 and subsequent steps are repeated based on the updated br.

[0044] The value of br+Δbr is br ｍａｘ (Yes in S111), the selector 16 executes a process in steps S113 and after to select a pre-specified number of selectable bit rates based on the index so that a bit rate that can improve the quality of experience while reducing power consumption and achieve a wide range of quality of experience can be selected in the Web conference service. In this process, the selector 16 selects the bit rate (QoE ｓｃａｌｉｎｇ , index) is used. The set is expressed as the power consumption (pc ｓｃａｌｉｎｇ ) QoE that also takes into account ｓｃａｌｉｎｇThe relationship between the QoE and the index (the relationship based on the formula (4)) is shown in FIG. ｓｃａｌｉｎｇ and the y-axis is assigned index. ｓｃａｌｉｎｇ A curve showing the relationship between the index and the QoE is shown, but in reality it is a set of points at intervals of Δbr. However, the selection unit 16 may derive an approximate curve based on the set of points. ｓｃａｌｉｎｇ The "relationship between the index and the point" may be a set of points or an approximate curve.

[0045] When selecting a selectable bit rate in a Web conference service, it is required to select a bit rate that will result in a high index.

[0046] Furthermore, the selectable bitrates must be set to accommodate fluctuating network bandwidth conditions. For example, in situations where the network bandwidth is narrow (e.g., while traveling on a train or in an enclosed environment), selecting a high bitrate will cause the video to freeze and the quality of experience to deteriorate, so a low bitrate must be prepared to match the bandwidth conditions. In this way, it is necessary to prepare bitrates that do not deteriorate the quality of experience in accordance with various network fluctuations, so it is also necessary to select a bitrate that allows for a wide range of quality of experience (Requirement 2).

[0047] In order to select selectable bit rates from the number (N) of selectable bit rates set in advance while satisfying the above two requirements, requirement 1 and requirement 2, the selection unit 16 selects bit rates as follows.

[0048] In step S113, the selection unit 16 selects the QoE ｓｃａｌｉｎｇ In the relationship between the index and the QoE (Fig. 4), ｓｃａｌｉｎｇ Identify.

[0049] FIG. 5 shows the QoE corresponding to the maximum point of the index. ｓｃａｌｉｎｇ 5 is a diagram for explaining the QoE shown in FIG. ｓｃａｌｉｎｇThe maximum point of the index is indicated by a dashed line in the relationship between the QoE and the index. The value of the x-axis on the dashed line corresponds to the maximum point of the index. ｓｃａｌｉｎｇ is.

[0050] Here, the number of maximum points is k (k≦N). Therefore, in step S113, k QoE ｓｃａｌｉｎｇ is selected.

[0051] Next, the selector 16 selects k QoE ｓｃａｌｉｎｇ The bit rates for each of the above are acquired as selectable bit rates (S114). Therefore, k bit rates are acquired. ｓｃａｌｉｎｇ The bit rate related to the QoE in steps S105 and S107 is ｓｃａｌｉｎｇ Therefore, in steps S105 and S107, br and QoE ｓｃａｌｉｎｇ It is sufficient to store the above in association with each other.

[0052] Steps S113 and S114 correspond to requirement 1 above.

[0053] Next, the selection unit 16 determines whether k is less than N (S115). If k is less than N (Yes in S115), the selection unit 16 determines the quality of experience (QoE) in order to meet the above requirement 2. ｓｃａｌｉｎｇ ) so that the nearest neighbor distance is maximized. ｓｃａｌｉｎｇ (S116). Here, the nearest distance is the N QoEs corresponding to the selected br. ｓｃａｌｉｎｇ The neighboring QoEs in ｓｃａｌｉｎｇ Therefore, the QoE of Nk points is determined so that the nearest neighbor distance is maximized. ｓｃａｌｉｎｇ is selected so that the minimum value is maximized. ｓｃａｌｉｎｇ This means selecting such a QoE. ｓｃａｌｉｎｇ The selection can be made, for example, by the logic shown in FIG. ｓｃａｌｉｎｇ is the QoE corresponding to the selected br ｓｃａｌｉｎｇ When the set of QoEs is sorted in ascending or descending order, the adjacent QoEs are ｓｃａｌｉｎｇ This refers to

[0054] FIG. 6 shows the QoE that maximizes the nearest neighbor distance. ｓｃａｌｉｎｇ FIG. 11 is a diagram illustrating the selection of QoE in step S116. ｓｃａｌｉｎｇ The selection of N−k QoE ｓｃａｌｉｎｇ This is repeated until one QoE is selected. ｓｃａｌｉｎｇ is selected, the process is repeated Nk times. FIG. 6 shows specific examples of the first to fourth iterations.

[0055] In the first round, the selection unit 16 selects the QoE ｓｃａｌｉｎｇ The minimum value of QoE ｓｃａｌｉｎｇ The maximum value of the index, the QoE corresponding to the maximum point of the index ｓｃａｌｉｎｇ In the set of ｓｃａｌｉｎｇ In the first iteration of FIG. 6, the intervals are indicated by double-headed arrows. The selector 16 selects the median value (the value indicated by the vertical line L1 in the figure) of the longest interval (the second double-headed arrow from the left in the first iteration of FIG. 6) from among these intervals as one of the N-k QoE ｓｃａｌｉｎｇ Here, if k+1=N, step S116 is completed, and if k+1<N, the process proceeds to the second iteration.

[0056] In the second round, the selection unit 16 selects the QoE ｓｃａｌｉｎｇ The minimum value of QoE ｓｃａｌｉｎｇ The maximum value of the index, the QoE corresponding to the maximum point of the index ｓｃａｌｉｎｇ , the QoE selected in the first round ｓｃａｌｉｎｇ In the set of (perpendicular lines L1), the adjacent QoE ｓｃａｌｉｎｇ In the second time of FIG. 6, the interval is indicated by a double-headed arrow. The selection unit 16 selects the median value (the value indicated by the vertical line L2 in the figure) of the longest interval (the double-headed arrow at the right end in the second time of FIG. 6) from among these intervals as one of the N-k QoE ｓｃａｌｉｎｇ Here, if k+2=N, step S116 is completed, and if k+2<N, the process proceeds to the third iteration.

[0057] The third time, the same process as the second time is performed, and the selector 16 selects the value indicated by the perpendicular line L3 as one of the N−k QoEｓｃａｌｉｎｇ Here, if k+3=N, step S116 is completed, and if k+2<N, the process proceeds to the fourth iteration.

[0058] In the fourth round, the selection unit 16 selects the QoE ｓｃａｌｉｎｇ The minimum value of QoE ｓｃａｌｉｎｇ The maximum value of the index, the QoE corresponding to the maximum point of the index ｓｃａｌｉｎｇ , QoE selected in the first to third times ｓｃａｌｉｎｇ In the set of (perpendicular lines L1, L2, L3), the adjacent QoE ｓｃａｌｉｎｇ In the fourth iteration of FIG. 6, the intervals are indicated by double-headed arrows. The selector 16 selects the longest interval (the third double-headed arrow from the left in the fourth iteration of FIG. 6) from among these intervals. Here, one of the third arrows from the left (the left end) represents the QoE ｓｃａｌｉｎｇ (perpendicular line L1) (i.e., L1 is a QoE that is not included in the k ｓｃａｌｉｎｇ In this case, the selector 16 selects a new QoE ｓｃａｌｉｎｇ Instead of selecting the QoE corresponding to the maximum point of the index that includes the double arrow, ｓｃａｌｉｎｇ Two QoEs that divide the interval (indicated by the dashed double arrows in the figure) into thirds ｓｃａｌｉｎｇ The perpendicular line L1 is shifted to one of the Nk positions to create a perpendicular line L1', and the other (perpendicular line L4) is set to one of the Nk positions. ｓｃａｌｉｎｇ Select as.

[0059] Therefore, at the end of the fourth iteration, the perpendicular lines L1', L2, L3, and L4 are the four QoEs out of Nk. ｓｃａｌｉｎｇ This becomes:

[0060] That is, the selection unit 16 basically repeats the same process as the first time, and in the same situation as the fourth time, executes the same process as the fourth time. This is repeated Nk times.

[0061] In the above, QoE ｓｃａｌｉｎｇ The minimum and maximum values ​​of QoE ｓｃａｌｉｎｇ is the boundary of the values ​​that can be taken, and Nk QoEs are ｓｃａｌｉｎｇHowever, depending on the quality of experience model used, there may be a quality of experience value that cannot be achieved no matter what bit rate is selected. ｓｃａｌｉｎｇ It may also be the boundary of the values ​​that can be taken.

[0062] Next, the selection unit 16 selects the QoE ｓｃａｌｉｎｇ The bit rate (br) for the above is acquired (S117).

[0063] If the answer is No in step S115, or following step S117, the output unit 17 outputs the acquired N bit rates as candidates for bit rates selectable in bit rate control in the Web conference service (S118).

[0064] As described above, according to the present embodiment, it is possible to support bit rate control that can reduce power consumption while improving the quality of experience. That is, when controlling the bit rate in a Web conference service, a user can select a selectable bit rate according to the present embodiment, thereby enabling bit rate control that can reduce power consumption while improving the quality of experience.

[0065] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0066] REFERENCE SIGNS LIST 10 Selectable bitrate determination device 11 Input unit 12 Quality of experience estimation unit 13 Power consumption estimation unit 14 Normalization unit 15 Index calculation unit 16 Selection unit 17 Output unit 100 Drive device 101 Recording medium 102 Auxiliary storage device 103 Memory device 104 Processor 105 Interface device B Bus

Claims

1. A perceived quality estimation unit configured to calculate an estimated value of the perceived quality for a specified range of bitrates for a Web conferencing service; a power consumption estimation unit configured to calculate an estimated value of the power consumption for the range of bitrates based on the characteristic that the increase width of the power consumption per unit bitrate decreases as the bitrate increases; a normalization unit configured to normalize each of the estimated value of the perceived quality and the estimated value of the power consumption; an index calculation unit configured to calculate an index that increases as the perceived quality is higher and increases as the power consumption is lower based on the normalized estimated values; and a selection unit configured to select, as a selectable bitrate in the Web conferencing service, the bitrate corresponding to the estimated value of the perceived quality corresponding to the maximum point of the index in the relationship between the estimated value of the perceived quality calculated for the range of bitrates and the index. A selectable bitrate determination device characterized by comprising the above components.

2. The selectable bitrate determination device according to claim 1, wherein the selection unit is further configured to select, as the selectable bitrate, the bitrate corresponding to the estimated value of the perceived quality corresponding to the center of the maximum interval among the intervals between a plurality of the maximum points.

3. The selectable bitrate determination device according to claim 2, wherein the selection unit is further configured to select, as the selectable bitrate, the bitrate corresponding to the estimated value of the perceived quality corresponding to between the center and the maximum point.

4. A perceived quality estimation procedure for calculating an estimated value of the perceived quality for a specified range of bitrates for a Web conferencing service, a power consumption estimation procedure for calculating an estimated value of the power consumption for the range of bitrates based on the characteristic that the increase width of the power consumption per unit bitrate decreases as the bitrate increases, a normalization procedure for normalizing each of the estimated value of the perceived quality and the estimated value of the power consumption, an index calculation procedure for calculating an index that increases as the perceived quality is higher and increases as the power consumption is lower based on the normalized estimated values, and in the relationship between the estimated value of the perceived quality calculated for the range of bitrates and the index, a selection procedure for selecting, as a selectable bitrate in the Web conferencing service, the bitrate corresponding to the estimated value of the perceived quality corresponding to the maximum point of the index, wherein a computer executes the procedures.

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