JP2005311599A - Communication system, communication method and streaming server - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system controlling the quality of a content being provided to a user appropriately while dealing with request of every content and user flexibly, and increasing the communication capacity, and also to provide a communication method and a streaming server. <P>SOLUTION: The communication system comprises: a communication terminal 10; and a streaming server 20 for delivering a multimedia content to the communication terminal 10 by streaming system. The streaming server 20 comprises: a means for setting parameters being employed in encoding of the content based on a perception quality value; and a means for delivering the content while encoding with the parameters set by the parameter setting means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication system, a communication method, and a streaming server suitable for use in distributing multimedia contents such as music and video.

  In recent years, the transmission speed of mobile communication devices represented by mobile phones has been increasing. In the forth-generation fourth generation mobile communication, it is expected that communication with a wide band and a high data rate will be realized, and various services will be provided accordingly. One example is a music or video streaming service using a mobile phone. Conventionally, QoS (Quality of Service) control for this type of service has been performed based on a delay amount and a bit error rate (BER). Specifically, it improves quality by improving the bit error rate by adding an error correction code to reduce the error rate, or by using an automatic repeat request and buffering to compensate for errors. I tried to plan.

However, in the above conventional control method, as described above, since the quality is improved by improving the bit error rate, it is extremely difficult to respond flexibly to requests for each content and each user. . Also, the quality that humans feel with their five senses (perceptual quality) cannot be evaluated simply by the bit error rate alone, so there may be a gap between the quality assumed by the service provider and the quality actually felt by the user. was there.
In addition, since the quality could only be improved by improving the bit error rate, it was necessary to use more power and bandwidth than necessary, resulting in a reduction in communication capacity. .

  The present invention has been made in view of such circumstances, and can appropriately control the quality of content provided to users while flexibly responding to requests for each content and each user. An object of the present invention is to provide a communication system, a communication method, and a streaming server that can reduce power consumption, effectively use a band, and thereby increase communication capacity.

  As a result of intensive research to solve the above problems, the present inventors have found that the characteristics of the perceptual quality value are different for each content even if the bit error rate is the same, and QoS control is performed based on this perceptual quality value. As a result, it has been found that the quality of content can be appropriately controlled while flexibly responding to requests for each content and each user, and the present invention has been completed.

  That is, the invention described in claim 1 is a communication system having a communication terminal and a server that distributes multimedia content to the communication terminal by a streaming method. The degree is evaluated by the perceptual quality value, and based on this perceptual quality value, the parameter setting means for setting the parameter used for encoding the content, and the content is encoded and distributed by the parameter set by the parameter setting means. And a content distribution means.

Here, examples of the multimedia content include music and video.
Perceptual quality refers to the quality that humans feel with their five senses for content such as music and video, and as evaluation methods there are already established evaluation methods according to the characteristics of each content type. . For example, if the content is music, the BS of the ITU-R (International Telecommunication Union-Radiocommunication sector). It is possible to adopt the objective evaluation method for sound (for wideband signal) specified in 1387 (PEAQ: Perceived Evaluation of Audio Quality), and the output value ODG (Objective Difference Grade) is the perceived quality value. Can be used. In addition, when content is video, many objective evaluation methods have been proposed for estimating values equivalent to MOS (Mean Opinion Score), which is widely known as a subjective evaluation method, by measuring physical features. Therefore, it is possible to use the output value of these objective evaluation methods as the perceptual quality value.

  According to a second aspect of the present invention, in the communication system according to the first aspect, the parameters include at least an information source coding rate (content compression rate) and a channel coding rate (error correction coding rate). Is included.

  According to a third aspect of the present invention, in the communication system according to the second aspect, the parameter setting means includes a plurality of information source coding rates and communication channel coding rates at which the transmission rate is the same when setting the parameters. Among the combination patterns, a combination pattern having the highest perceptual quality value is selected.

  According to a fourth aspect of the present invention, in the communication system according to the second aspect, the parameter setting means compares the perceptual quality value with a predetermined value at predetermined time intervals. If not reached, the parameter setting is changed by searching for a combination pattern of parameters such that the perceptual quality value exceeds a specified value.

  According to a fifth aspect of the present invention, in the communication system according to any one of the first to fourth aspects, the communication terminal estimates a perceptual quality value from a processing signal of content received and decoded from the server. A quality value estimation unit; and a perceptual quality value transmission unit that transmits the estimated perceptual quality value to the server. The parameter setting unit sets the parameter based on the perceptual quality value received from the communication terminal. It is characterized by doing.

A sixth aspect of the present invention is the communication system according to any one of the first to fourth aspects, wherein the communication terminal receives information from the processing signal of the content received from the server and decrypted, and relates to the state of the transmission path. Information calculating means for calculating the transmission path and information transmitting means for transmitting information relating to the state of the transmission path to the server, wherein the server receives information and content relating to the state of the transmission path received from the communication terminal. And a perceptual quality value estimating means for estimating a perceptual quality value from the original signal, and the parameter setting means sets the parameter based on the estimated perceptual quality value. It is.
Here, information on the state of the transmission path includes, for example, bit error rate (BER), error detection signal (CRC), FER (Frame Error Rate), BLER (Block Error Rate), NACK (Nagative ACKnowledgement), pilot symbol In addition to information on errors such as, SNR is also included.

  According to a seventh aspect of the present invention, in the communication system according to any one of the first to fourth aspects, a TDD (Time Division Duplex) method is adopted as a reciprocal method for communication between the communication terminal and the server. The server creates a characteristic table representing the relationship between the information about the state of the transmission path and the perceived quality value for each of a plurality of combination patterns of the information source coding rate and the channel coding rate for the content to be distributed. Characteristic table creating means, and the parameter setting means estimates information on the state of the transmission path from the received signal when setting the parameter, and the perceptual quality value is obtained from the information on the state of the transmission path and the characteristic table. The combination pattern of the information source coding rate and the channel coding rate that is the highest is selected.

  When creating the above characteristic table, first, it is assumed that when the original signal is distributed, degradation according to the information source coding rate and degradation according to the transmission path state and the channel coding rate occur. Then, the processing signal is estimated by adding the deterioration to the original signal. Next, the perceived quality value is obtained by inputting the estimated processed signal and the original signal to the perceptual quality value evaluation model. Then, by repeatedly executing the above processing while changing the transmission line state setting little by little, the perceptual quality value in each state of the transmission line is obtained, and the above characteristic table is created by associating them with each other. To do.

  The invention according to claim 8 is the communication system according to any one of claims 1 to 7, wherein the content distribution unit encodes the content to be distributed and compresses the information amount; A communication path encoding means for converting the signal encoded by the information source encoding means into a signal capable of error correction; and a transmission means for transmitting the signal encoded by the communication path encoding means. On the other hand, the communication terminal includes receiving means for receiving an encoded signal from the server, decoding means for decoding the received signal, and reproducing means for reproducing the decoded content. To do.

  The invention according to claim 9 is the communication system according to any one of claims 1 to 8, wherein the communication terminal is a mobile phone.

  According to a tenth aspect of the present invention, in the communication method when the server distributes the multimedia content by the streaming method, the server evaluates the degree of quality degradation of the content to be distributed by the perceptual quality value, and this perception. A parameter setting step for setting parameters used for content encoding based on a quality value, and a content distribution step for encoding and distributing content by the parameters set in the parameter setting step are provided. is there.

  In the invention according to claim 11, in a streaming server that distributes multimedia content to a communication terminal by a streaming method, the degree of quality degradation of the content to be distributed is evaluated by a perceptual quality value, and the perceived quality value is obtained. On the basis of this, there is provided a parameter setting means for setting a parameter used for encoding the content, and a content distribution means for encoding and distributing the content according to the parameter set by the parameter setting means. .

According to the present invention, since the parameters used for encoding the content are set based on the perceptual quality value, the quality of the content provided to the user while flexibly responding to the request for each content and each user. Can be controlled appropriately. That is, it is possible to apply an encoding method suitable for the type of content and the state of the transmission path, and it is possible to efficiently and reliably provide the user with the desired perceptual quality.
Therefore, wasteful power consumption can be suppressed and effective use of bandwidth can be achieved, thereby increasing communication capacity.

[First Embodiment]
FIG. 1 shows an embodiment of a communication system according to the present invention. In FIG. 1, reference numeral 10 denotes a communication terminal, and 20 denotes a streaming server (server).
The communication terminal 10 includes a mobile phone, a PDA, a personal computer, and the like that can communicate with the streaming server 20 via a wireless communication network such as a mobile communication network or an ad hoc network. The communication terminal 10 includes an arithmetic processing unit, a storage unit, a display unit, an input unit, a communication unit, and the like. The arithmetic processing unit reads and executes various application programs stored in the storage unit as follows. Various functions are added.

That is, the communication terminal 10 has a function of receiving an encoded signal from the streaming server 20 (reception unit), a function of decoding the received signal (decoding unit), and a function of reproducing the decoded content ( Reproducing means).
The storage unit of the communication terminal 10 includes a storage area for storing various processing programs executed by the arithmetic processing unit (streaming application software or the like that reproduces data simultaneously while downloading data), control data, and the like. A storage area for storing multimedia contents is provided.
The communication unit of the communication terminal 10 includes a transmitter, a receiver, an antenna, and the like. In this embodiment, a TDD-CDMA (Code Division Multiple Access) system is used for communication with the streaming server 20. ing.

  On the other hand, the streaming server 20 includes a known computer having a CPU (Central Processing Unit), a RAM (Random Access Memory), a display device, an input device, a storage device, a communication device, etc., or a plurality of such computers via a network. It is comprised by the computer system formed by connecting to. The storage device stores various processing programs (including streaming server software) executed by the CPU, control data, and the like, as well as a storage region for storing multimedia content source files to be distributed. Etc. are provided.

This streaming server 20 uses a function (parameter setting means) for setting various parameters (information source coding rate, channel coding rate, power, etc.) used for distribution for each content, and the set parameters. A function of distributing contents (content distribution means).
In this embodiment, the streaming server 20 obtains the characteristics of the perceived quality value of the content to be distributed, estimates information about the state of the transmission path from the received signal, and information about the state of the transmission path and the characteristics of the perceptual quality value Based on the above, parameters such as an information source coding rate, a channel coding rate, and power are set. In addition, when content is distributed, the content source file (original signal) is read from the storage device, encoded at the information source encoding rate set as described above, and the amount of information is compressed. The encoded signal is converted into a signal that can be error-corrected at the channel coding rate and transmitted with the power.

Next, a method for setting parameters used for content encoding will be described in detail.
In the present embodiment, first, a characteristic table representing the relationship between the information about the state of the transmission path and the perceived quality value is created for each combination pattern of the above parameters for the content to be distributed. The relationship between the information on the state of the transmission path and the perceived quality value can be obtained by setting various parameters as shown in Table 1 and performing a simulation, for example. That is, as shown in FIG. 2, a pseudo error is estimated from each state of the transmission path, the processed signal generated by adding the error to the original signal, and the original signal are used as a perceptual quality evaluation model (PEAQ described later). Etc.), the perceptual quality value in each state of the transmission path can be obtained.

  Among the above parameters, for the information source coding rate and the channel coding rate set at the time of content distribution, as shown in Table 2, there are a plurality of combination patterns such that the transmission rate is constant (here, 192 Kbps). For each of them, the relationship between the information about the state of the transmission path and the perceptual quality value is obtained.

  For example, using the CD sound source sample shown in Table 3 below, the relationship between the information about the state of the transmission path and the perceived quality value is obtained and graphed, for example, as shown in FIGS. A characteristic diagram is obtained.

  3 to 7, while using a power-to-noise ratio (SNR) as information regarding the state of the transmission path, the BS. ODG which is an output value of the objective evaluation method for acoustics defined by 1387 (PEAQ) is used. This ODG is an evaluation of how much a person feels a difference in quality between an original signal and a processed signal (signal after distribution processing), with 0 being the best and -4 being the worst. In the PEAQ evaluation method, the original signal and the processed signal are input to an auditory model simulating the function of the human ear, and the respective outputs are obtained. Then, from these output values, the acoustic signal degradation when the human hears A model output value representing the degree is obtained, and then an objective quality of the processed signal is obtained from the model output value using a recognition model having a neural network structure.

  Comparing FIGS. 3 to 7, it can be seen that the characteristics of the perceptual quality value are greatly different for each sample. Further, when the characteristics of each sample are viewed individually, the method A and the method B have a strong error correction capability, and thus reach a constant perceptual quality value with a relatively low SNR. On the other hand, since the compression rate is high and the original information is largely lost, no matter how much errors are reduced, high perceptual quality cannot be achieved. On the other hand, since method D and method E have low error correction capability, the perceptual quality value does not increase because there are many errors unless a high SNR is reached. Higher perceptual quality can be achieved as it decreases.

  Therefore, in the present embodiment, a parameter combination pattern that provides the highest perceptual quality value in each SNR is selected and set as a parameter used at the time of distribution. Incidentally, if a curve having the highest perceived quality value in each SNR is selected and traced, a characteristic diagram as shown in FIG. 8 is obtained. According to this characteristic diagram, it is understood that when a constant perceptual quality value, for example, ODG = -1, is to be achieved, a gain close to 5 dB at maximum can be obtained.

  In this embodiment, since the TDD-CDMA system is adopted for communication between the streaming server 20 and the communication terminal 10, it can be considered that the transmission paths of the upper and lower lines are very similar. Therefore, in the present embodiment, an SNR is estimated from the received signal of the streaming server 20, and a coding method (combination of information source coding rate and channel coding rate) that gives the highest perceptual quality value at this SNR is selected. The characteristic table is selected and set as a parameter used for distribution.

  Thereafter, the streaming server 20 performs processing for encoding the content with the parameters set as described above and distributing the content to the communication terminal 10, and the communication terminal 10 receives the encoded signal from the streaming server 20. The received signal is decoded and reproduced. In addition, while delivering the content, the streaming server 20 obtains a combination of parameters such that the perceived quality value is the highest by estimating the SNR at regular intervals, which is different from the currently used parameter. In this case, a process for changing the parameter setting is performed.

As described above, according to the present embodiment, parameters such as the information source coding rate and the channel coding rate are set based on the perceptual quality value. It is possible to appropriately control the quality of the content provided to the user while complying with. That is, it is possible to apply an encoding method suitable for the type of content and the state of the transmission path, and it is possible to efficiently and reliably provide the user with the desired perceptual quality.
Therefore, wasteful power consumption can be suppressed and effective use of bandwidth can be achieved, thereby increasing communication capacity.

  In the present embodiment, a combination of parameters that obtains the highest perceptual quality value is obtained at regular time intervals, and the parameter settings are changed as appropriate. However, the present invention is limited to this. For example, only when the perceived quality value is lower than a predetermined value (perceived quality value that is required for the content) set in advance for the content to be distributed, the perceived quality value exceeds the specified value. The parameter combination may be changed by searching for a combination of parameters.

Further, in the present embodiment, the case of distributing music content has been illustrated, but the present invention can also be applied to the case of distributing other content.
For example, when the content to be distributed is video, by setting various parameters as shown in Table 4, the relationship between the information on the state of the transmission path and the perceived quality value is obtained by simulation, as in the case of music. be able to. Here, as a combination pattern not using a convolutional code, a combination pattern with an information source coding rate of 2 Mb / s and a channel coding rate of 1 bpp, and a channel with an information source coding rate of 1.5 Mb / s There are three types of combination patterns: a combination pattern with a coding rate of 0.75 bpp and a combination pattern with an information source coding rate of 1 Mb / s and a channel coding rate of 1 bpp. 2 is a combination pattern with an information source coding rate of 2 Mb / s and a channel coding rate of 0.75 bpp, and a combination pattern with an information source coding rate of 2 Mb / s and a channel coding rate of 0.5 bpp. The type is set.

  For example, using the video samples shown in Table 5 below, the relationship between the information about the state of the transmission path and the perceived quality value is obtained and graphed. For example, characteristic diagrams as shown in FIGS. Is obtained. The video samples shown in Table 5 are selected from several test sequences provided by VQEG (Video Quality Expert Group). Among these video samples, “news” with little movement and Representative images with different characteristics such as “football” with a lot of movement are included. These image samples are all color images, and have a resolution of 352 × 240 pixels, a frame rate of 25 frames / sec, and a YUV format.

In FIGS. 9 to 11, the bit error rate (BER) is used as information regarding the state of the transmission line, while the perceptual quality value is an objective evaluation that can obtain an evaluation close to a MOS widely known as a subjective evaluation method. The output value of the modulo is used.
As shown in FIGS. 9 to 11, it can be seen that the characteristics of the perceptual quality value are different for each sample in the video as well as the music. That is, when the BER is low and the channel condition is good, the perceptual quality value of the combination pattern having a low compression rate and a high channel coding rate is high. When the BER is high and the channel condition is bad, the compression rate is high. The perceptual quality value of a combination pattern having a low path coding rate or a combination pattern using a convolutional code is high.

  Therefore, if a combination pattern of parameters that gives the highest perceptual quality value at each BER is selected and used at the time of distribution, the minimum amount of video content is the same as that of the music content described above. The perceptual quality value can be maximized with power.

[Second Embodiment]
In the first embodiment described above, the streaming server 20 estimates the perceptual quality value, whereas in the second embodiment, the communication terminal 10 estimates the perceptual quality value. .

That is, as shown in FIG. 12, the communication terminal 10 has a function (perceptual quality value estimation means) for estimating a perceptual quality value from the processing signal of the content received and decoded from the streaming server 20, and the estimated perceptual quality value. As feedback information to the streaming server 20 (perceptual quality value transmission means). When estimating the perceptual quality value from the processing signal of the content, it is possible to use a non-reference type objective evaluation method such as “Video PQoS ^™ ” manufactured by Genista.

  The streaming server 20 compares the specified value set for the currently distributed content with the perceptual quality value fed back from the communication terminal 10 at regular intervals, and as a result, the fed back perceptual quality value is When the specified value is not reached, a combination of parameters whose perceived quality value exceeds the specified value is searched, and the parameter setting is changed. Specifically, the state of the transmission path is estimated from the combination pattern of the parameters currently used and the perceptual quality value fed back from the communication terminal 10, and the combination pattern of parameters suitable for the state of the transmission path is estimated. Ask for. For example, when it is estimated that the state of the transmission path is bad, a combination pattern of parameters that has a higher compression rate and higher error correction capability than the present is adopted, while when it is estimated that the state of the transmission path is good, A parameter combination pattern is adopted that has a smaller compression ratio and lower error correction capability than the present one. Further, if the specified value is not reached even if the combination pattern of the information source coding rate and the channel coding rate is changed, control is performed to increase the transmission power within an allowable range.

  Therefore, also in the second embodiment, the perceptual quality value can be maximized with the minimum power as in the first embodiment. In the second embodiment, since the perceived quality value is obtained by the communication terminal 10, the load on the communication terminal 10 increases as compared with the first embodiment. The effect that the load can be reduced is obtained.

[Third Embodiment]
In the second embodiment described above, the perceptual quality value is transmitted as feedback information from the communication terminal 10 to the streaming server 20, whereas in the third embodiment, the feedback information relates to an error. I am trying to send information.
That is, as shown in FIG. 13, the communication terminal 10 calculates information about errors (for example, BER, FER, BLER, NACK, pilot symbols, etc.) from the processing signal of the content received from the streaming server 20 and decoded. And a function (information transmitting means) for transmitting information related to the error to the streaming server 20.

On the other hand, the streaming server 20 is provided with a function (perceptual quality value estimating means) for estimating a perceptual quality value from information related to the error received from the communication terminal 10, and encodes content based on the estimated perceptual quality value. In other words, the streaming server 20 estimates the perceptual quality value from the information about the error received from the communication terminal 10 and the original signal of the content at regular intervals, and this perceptual quality value is set. If the estimated value of the value is compared with the specified value set in the content and the estimated value of the perceptual quality value does not reach the specified value, the perceived quality is the same as in the second embodiment. The parameter setting is changed by searching for a combination of parameters such that the estimated value exceeds the specified value.

  Therefore, also in the third embodiment, the perceptual quality value can be maximized with the minimum power as in the first and second embodiments. Moreover, in this 3rd Embodiment, since the perceptual quality value is calculated | required by the streaming server 20, compared with 2nd Embodiment, the burden of the communication terminal 10 can also be reduced.

1 is a schematic configuration diagram showing an embodiment of a communication system according to the present invention. It is a schematic diagram for demonstrating the setting method of a parameter. It is a characteristic view which shows the relationship between SNR of sample 1 of Table 3, and a perceptual quality value. It is a characteristic view which shows the relationship between SNR of sample 2 of Table 3, and a perceptual quality value. It is a characteristic view which shows the relationship between SNR of sample 3 of Table 3, and a perceptual quality value. It is a characteristic view which shows the relationship between SNR of sample 4 of Table 3, and a perceptual quality value. It is a characteristic view which shows the relationship between SNR of sample 5 of Table 3, and a perceptual quality value. It is a characteristic view when a parameter is selected so that the perceptual quality value is maximized for each sample of Table 3. 6 is a characteristic diagram illustrating a relationship between a BER of “news” in a video sample of Table 5 and a perceived quality value. FIG. FIG. 6 is a characteristic diagram illustrating a relationship between a BER of “football” in a video sample of Table 5 and a perceived quality value. 6 is a characteristic diagram illustrating a relationship between a BER of “mobile” in a video sample of Table 5 and a perceived quality value. FIG. It is a schematic diagram which shows schematic structure of the communication system of 2nd Embodiment. It is a schematic diagram which shows schematic structure of the communication system of 3rd Embodiment.

Explanation of symbols

10 communication terminal 20 streaming server (server)

Claims (11)

In a communication system having a communication terminal and a server that distributes multimedia content to the communication terminal in a streaming manner,
The server evaluates the degree of quality degradation of the content to be distributed with a perceptual quality value, and sets a parameter used for encoding the content based on the perceptual quality value;
A communication system comprising: content distribution means for encoding and distributing content according to the parameters set by the parameter setting means.   The communication system according to claim 1, wherein the parameters include at least an information source coding rate and a channel coding rate.   The parameter setting means selects a combination pattern having the highest perceptual quality value from among a plurality of combination patterns of an information source coding rate and a channel coding rate having the same transmission rate when setting the parameter. The communication system according to claim 2.   The parameter setting means compares the perceptual quality value with a specified value every predetermined time. As a result, when the perceived quality value does not reach the specified value, a combination of parameters such that the perceived quality value exceeds the specified value. The communication system according to claim 2, wherein the parameter setting is changed by searching for a pattern. The communication terminal includes a perceptual quality value estimating unit that estimates a perceptual quality value from a content processing signal received and decoded from the server, and a perceptual quality value transmitting unit that transmits the estimated perceptual quality value to the server. And
The communication system according to claim 1, wherein the parameter setting unit sets the parameter based on a perceptual quality value received from the communication terminal. The communication terminal includes information calculation means for calculating information on a transmission path state from a content processing signal received and decrypted from the server, and information for transmitting information on the transmission path state to the server. A transmission means,
The server includes a perceptual quality value estimating unit that estimates a perceptual quality value from information on the state of the transmission path received from the communication terminal and an original signal of content, and based on the estimated perceptual quality value, the parameter The communication system according to claim 1, wherein the setting means sets the parameter. For the communication between the communication terminal and the server, the TDD method is adopted as a reciprocal method,
The server creates a characteristic table that represents the relationship between the information about the state of the transmission path and the perceived quality value for each of a plurality of combination patterns of the information source coding rate and the channel coding rate for the content to be distributed. With table creation means,
The parameter setting means estimates information relating to the state of the transmission path from the received signal when setting the parameter, and uses the information relating to the state of the transmission path and the characteristic table to obtain an information source that provides the highest perceived quality value. 5. The communication system according to claim 1, wherein a combination pattern of a coding rate and a channel coding rate is selected. The content distribution unit includes an information source encoding unit that encodes the content to be distributed and compresses an information amount, and a communication path that converts the signal encoded by the information source encoding unit into a signal that can be error-corrected While comprising an encoding means and a transmission means for transmitting the signal encoded by the channel encoding means,
The communication terminal includes receiving means for receiving an encoded signal from the server, decoding means for decoding the received signal, and reproducing means for reproducing the decoded content. Item 8. The communication system according to any one of Items 1-7.   The communication system according to claim 1, wherein the communication terminal is a mobile phone. In the communication method when the server distributes multimedia content by streaming method,
A parameter setting step in which the server evaluates the degree of quality degradation of the content to be distributed by a perceptual quality value and sets a parameter used for encoding the content based on the perceptual quality value;
A content distribution step of encoding and distributing content according to the parameters set in the parameter setting step. In a streaming server that delivers multimedia content to a communication terminal in a streaming manner,
A parameter setting unit that evaluates the degree of quality degradation of the content to be distributed by a perceptual quality value and sets a parameter used for encoding the content based on the perceptual quality value;
A streaming server, comprising: content distribution means for encoding and distributing content according to the parameters set by the parameter setting means.

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