KR100896676B1 - Method for measuring video telephony - Google Patents

Abstract

According to the present invention, a network state for video telephony can be diagnosed by comparing image quality between a transmitter image input to a transmitter terminal and a receiver image input to the receiver terminal as the transmitter image passes through a communication network. It relates to a method of measuring image quality of a videophone.

In addition, the method for measuring the image quality of a videophone according to an embodiment of the present invention is a state in which a monitoring device equipped with a driver module for driving a terminal equipped with a videophone function is connected to a transmitting terminal and a receiving terminal, respectively. (A) a video call connection performed by the monitoring apparatus in operation of the transmitter terminal and the receiver terminal; (B) receiving a reference image transmitted from the transmitting terminal to the receiving terminal from the transmitting terminal and receiving a test image received from the receiving terminal through the mobile communication network from the receiving terminal; ; (C) decoding the reference image received from the transmitting terminal, decoding the test image received from the receiving terminal, and measuring the quality of the decoded test image based on the decoded reference image. and (d) step.

 Mobile terminal, gateway, DM, image quality, MOS, synchronization, video call

Description

How to measure the quality of a video phone {method for measuring video telephony}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the image quality of a videophone, and in particular, to compare the image quality between a transmission side image that is substantially input to a transmission terminal and a reception side image that is input to a reception terminal as the transmission side image passes through a communication network. The present invention relates to a video quality measurement method for diagnosing a network condition for a video call.

In recent years, thanks to the rapid development of information and communication fields, mobile communication terminals have become so popular that they are essential portable devices for the whole nation. Furthermore, voice calls and text messages have been the main functions. With the advent of the new models with various functions are released one after another to replace the old models quickly. In particular, the third generation (Generation) communication network, which supports the video telephony and video conferencing system, that is, the W-CDMA network is established, the video telephony service that can send and receive voice and video with the other party through the mobile communication terminal even during stop or moving Is introduced.

On the other hand, in case of a terminal manufacturer, it is necessary to check the image quality of the actual image received by the terminal manufactured by the terminal in order to provide a better image quality to the customer. For the purpose of optimizing the performance and status of the mobile communication network, it is necessary to confirm the image quality of the actual image that has passed through the network. A system capable of automatically monitoring the image quality according to such a need has been proposed. In the conventional automatic image quality monitoring system, reference image data (hereinafter, simply referred to as 'reference image') as a reference for video telephone test should be stored on a notebook computer used as a monitoring device. In addition, test image data (hereinafter, simply referred to as a 'test image') passed through a communication network is transmitted to the monitoring apparatus, and the monitoring apparatus calculates an image quality of the test image compared to the stored reference image. . That is, based on this, it is possible to diagnose the network state for the video call.

However, according to the conventional automatic image quality monitoring system as described above, that the reference image is pre-stored in the monitoring device indicates that the test image is made in advance for the purpose of the video telephone test, which is a terminal connected to the video telephone. There was a problem that the analysis of the image that is actually transmitted and received between them is not made. In other words, it is ultimately difficult to accurately diagnose a terminal or a network that implements a video phone because a reference for reference image quality analysis of a test image is not produced by a transmitter terminal itself.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. When performing an image quality analysis on a test image input to a receiving terminal through a communication network, the reference image is obtained from the transmitting terminal, thereby obtaining a reference image. The purpose of the present invention is to provide a method for measuring the quality of a videophone so as to analyze the actual state of the videophone.

In addition, the present invention by analyzing the image quality of the test image output from the gateway on the basis of the reference image input to the gateway connecting the network between the network, the video telephony of the video telephone Another object is to provide a method for measuring image quality.

In order to achieve the above object, in the image quality measurement method of a videophone according to an embodiment of the present invention, a monitoring device equipped with a driver module capable of driving a terminal having a videophone function is provided with a transmitting terminal and a receiving side. (A) being performed by the monitoring apparatus in a state of being connected to each terminal, driving a transmitting terminal and a receiving terminal to establish a video telephone connection; (B) receiving a reference image transmitted from the transmitting terminal to the receiving terminal from the transmitting terminal and receiving a test image received from the receiving terminal through the mobile communication network from the receiving terminal; ; (C) decoding the reference image received from the transmitting terminal, decoding the test image received from the receiving terminal, and measuring the quality of the decoded test image based on the decoded reference image. and (d) step.

In the above configuration, it is preferable that the transmitting terminal or the receiving terminal is a mobile communication terminal, and the monitoring apparatus performs the step (a) using a DM port provided in the mobile communication terminal.

In addition, the step (d) comprises the step of synchronizing the test image to the reference image as a reference (d1) and the step of measuring the MOS value of the test image compared to the reference image (d2) It is preferable. Here, the synchronization in the step (d1) may be made with reference to a communication protocol serving as a transmission / reception of data or a decoding protocol serving as a decoding of video data. In this case, when the communication protocol is a real-time transmission protocol (RTP), the synchronization in the step (d1) is preferably made with reference to the RTP sequence of the real-time transmission protocol (RTP). In addition, when the decoding protocol is MPEG-4, H.263 or H.264, the synchronization in the step (d1) is recorded in the header or payload of the MPEG-4, the H.263 or the H.264. It is preferably made with reference to a temporary reference.

On the other hand, according to another embodiment of the present invention, a method of measuring image quality of a videophone is performed by the monitoring apparatus in a state in which a monitoring apparatus capable of capturing image data at a gateway is connected to the gateway and is input to the gateway. Capturing an image and capturing a test image output from the gateway to a communication network; (B) decoding the captured reference image, decoding the captured test image, and (c) measuring image quality of the decoded test image based on the decoded reference image. .

In the above configuration, the step (c), the step (c1) of synchronizing the test image to the reference image as a reference and the step of measuring the MOS value of the test image compared to the reference image (c2) It is preferred that made, including. Here, the synchronization in the step (c1) may be made with reference to a communication protocol serving as a transmission / reception of data or a decoding protocol serving as a decoding of video data. In this case, when the communication protocol is a real-time transmission protocol (RTP), the synchronization in the step (c1) is preferably made with reference to the RTP sequence of the real-time transmission protocol (RTP). If the decoding protocol is MPEG-4, H.263, or H.264, the synchronization in step (c1) is recorded in the header or payload of the MPEG-4, H.263, or H.264. It is preferably made with reference to a temporary reference.

According to the method for measuring the image quality of a videophone according to the present invention, the image quality comparison between the reference image input to the transmitting terminal and the test image input to the receiving terminal is performed as the reference image passes through the communication network. Therefore, there is an effect that can be monitored of the video call is actually made a call.

In addition, by analyzing the image quality of the test image output from the gateway on the basis of the reference image input to the gateway, there is an effect that can diagnose the video phone connection state of the gateway.

Hereinafter, a method for measuring image quality of a videophone according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. A brief description will be made of a general protocol used for videophone. Of course, it should be noted that the invention is not limited to the protocols illustrated below.

As is well known, the H.324M protocol is a terminal system protocol for video telephony and conferencing over general telephone networks, and is a proposed protocol for mobile communication environments that overcomes the limited mobility of multimedia set-top boxes based on the H.323 protocol. . The H.324M protocol is designed to exchange information required for communication by relying on a lower level protocol divided into a plurality of protocol stacks rather than defining all protocols and methods for multimedia communication as a single unit entity. To describe this sub-protocol of H.324M, H.245 is a protocol that handles control messages exchanged by both ends of H.324M-based terminals to initiate or end communication. It acts as a control protocol of the H.324M protocol. do. H.261, H.263, H.264 and MPEG-4 are protocols for encoding an image, and G.711, G.723.1 and G.728 are protocols for speech encoding. H.223 is a protocol for multiplexing / demultiplexing actual data and exchanging data.

In addition, session initiation protocol (SIP) is a simpler protocol that corresponds to H.324M, which was proposed in 1999 as RFC 2543 by the IETF Multiparty Multimedia Session Control (MMUSIC) Working Group. It is a signaling protocol of an application layer that specifies a procedure for identifying terminals to find each other, find their location, and create or delete a multimedia communication session between them. SIP is a request / response structure that controls the creation, modification, and termination of multimedia service sessions such as Internet-based video conferencing, video telephony, voice mail, event notification, instant messaging, and can be used for both TCP and UDP. By using a SIP URL similar to an email address to distinguish it, you can provide services without being tied to an IP address.

On the other hand, real time transport protocol (RTP) is a protocol corresponding to the above-mentioned H.223 adopted in H.323, the predecessor of H.324M, and is a transport layer communication protocol for transmitting and receiving voice or video in real time. Unlike Resource Reservation Protocol (RSVP), it is executed between terminals without relying on a network device such as a router.

1 is a diagram illustrating a network configuration of a method for measuring image quality of a videophone according to an embodiment of the present invention. As shown in FIG. 1, a network configuration of a system in which a method for measuring image quality of a videophone according to the present invention is implemented may be a computer used as a videophone monitoring apparatus (hereinafter, simply referred to as a "monitoring apparatus") 100. For example, the notebook computer is connected to a transmitting terminal 200 (hereinafter referred to as a 'Tx terminal') 200 and a receiving terminal (hereinafter referred to as an 'Rx terminal') 400 on the other side thereof.

Here, the Rx terminal 400 is connected to the Tx terminal 200 through the W-CDMA network, which is a 3G mobile communication network. The Rx terminal 400 is a wired video telephone 420, a mobile communication terminal having a video telephone function ( 410, a computer 440 equipped with a webcam, or a VOD server 430. In addition, although the Tx terminal 200 is limited to the mobile communication terminal in the example of FIG. 1, this may also be a wired video telephone or a VOD server. In addition, if the monitoring device 100 is equipped with a webcam may itself be a Tx terminal 200.

In addition, the W-CDMA network transmits and receives radio signals, wireless channel encoding and decoding, signal strength and quality measurement, baseband signal processing, diversity, radio resource management, and self-maintenance with a mobile station, that is, the Tx terminal 200. A base station 300 performing a function, a radio network controller 310 that controls a plurality of base stations 300 to perform functions such as matching with the base station 300, inter-cell handover processing, and call control, And a circuit-switching network 340 for video telephony, which is connected to a wired video telephone 420 that is an Rx terminal, a mobile communication terminal 410 having a video call function, or a computer 440 equipped with a webcam, and a circuit-switching network 340 for video telephony. A mobile switching center (MSC) 320 that provides video calls and various additional functions between the wireless network controller 310, sets up a call path, and provides a connection with various other devices and external networks. VOD server that is an Rx terminal (400) GGSN serving as a gateway between the external network as a serving node of GPRS (General Packet Radio Service) providing packet service to the VOD packet switching network 350 and Tx terminal 200 for transmission of the connected video data. (Gateway GPRS Support Node) 330 and Support GPRS Serving Node (SGSN) 360 that performs packet data processing between the wireless network controller 310 and the GGSN 330.

2 is a diagram illustrating a network configuration of a method for measuring image quality of a videophone according to another embodiment of the present invention. As shown in FIG. 2, the network configuration of the system in which the image quality measuring method of the videophone of the present invention is implemented may include a gateway 330 connecting two communication networks having different structures, such as a GGSN. It is connected to each data input / output stage.

3 is a configuration diagram of a function module of a monitoring apparatus for implementing a method for measuring image quality of a videophone according to an embodiment of the present invention. As shown in FIG. 3, the notebook computer, which is the monitoring device 100, includes a user interface (UI) module 110, a command transmission module 120, a Tx data collection module 130, and an Rx data collection module ( 140), an audio / video codec (hereinafter, also referred to as an 'A / V codec') module 150, a MOS analysis module 160, and a driver module 170.

In the above-described configuration, the UI module 110 is connected to the connection terminal of the Tx terminal 200 and the Rx terminal 400, which has an identification number of the Rx / Tx terminal, for example, a telephone number or a VOD of the terminal. URL input of the server 400, setting of various log commands to be transmitted to the Tx terminal 200 or the Rx terminal 400, and displaying various monitoring results for the video call. In addition, the UI module 110 is connected to the connection terminal of the data input / output terminal of the gateway 330, respectively, to display various monitoring results for the video call.

The command transmitting module 120 transmits various log commands set by the user to the Tx terminal 200 or the Rx terminal 400.

Tx data collection module 130 is a variety of data through the Tx terminal 200, for example, data (message) of the setup process of H.324M or SIP, the image transmitted from the Tx terminal 200 to the Rx terminal 400 / Capture the audio / video or audio data transmitted from the Tx terminal 200 to the data input terminal of the gateway 330.

The Rx data collection module 140 receives a variety of data through the Rx terminal 400, for example, data (message) of the H.324M or SIP setup process, and a video / audio received through the mobile communication network to the Rx terminal 400. Data or video / audio data transmitted to the Rx terminal 400 through the data output terminal of the gateway 330 is captured.

The A / V codec module 150 decodes (restores) video / audio data that is compressed and input to the Tx / Rx data collection modules 130 and 140.

The MOS analysis module 160 measures the image quality by comparing the image received from the Rx terminal 400 through the mobile communication network, that is, the test image, with the image transmitted from the Tx terminal 200, that is, the reference image. It is. In addition, the MOS analysis module 160 measures the image quality of the test image output from the gateway 330 based on the reference image input to the gateway 330.

The driver module 170 drives the Tx terminal 200 and the Rx terminal 400 by the command transmission module 120 described above.

As described above, according to the monitoring apparatus 100, the UI module 110 and the command transmitting module 120 may perform their functions through a modem or a DM (Diagnostic Monitoring) port, in particular, a Tx terminal or an Rx. When the terminal is implemented as a mobile communication terminal, the UI module 110 and the command transmitting module 120 preferably perform their functions through the DM port. As is well known, such a DM port is a logical device used to analyze or monitor the operation of a terminal among data transmitted / received through a serial transmission / reception terminal of a mobile communication terminal, for example, a standard connection terminal. Refers to the port.

In addition, the MOS (Mean Opinion Score) algorithm is a proposed algorithm for objectively measuring the image quality of an image through a communication network, and compares a test image received through a communication network with a reference image as a reference to be compared with a reference image. The grade of the image quality of the test image is automatically calculated. For example, the quality level of the test image may be evaluated in five steps as shown in Table 1 below. Such a MOS algorithm is specifically defined in J.144 (rev. 1) recommended by ITU-T. It would be desirable to have a MOS algorithm. In this case, the MOS algorithm may also be used when calculating sound quality of voice.

MOS value Image quality rating 5 Excel 4 Good 3 Fair 2 Poor One Bad

4 is a flowchart illustrating a method of measuring image quality of a videophone according to an embodiment of the present invention.

As shown in Figure 4, according to the method for measuring the image quality of the video telephone of the present invention, first, the driver in a state in which the Tx terminal 200 and the Rx terminal 400 are connected to the notebook computer which is the monitoring device 100, respectively, by a cable. For example, the module 170 may be opened to open DM ports of the Tx terminal 200 and the Rx terminal 400.

Next, in step S13, a DM key press command including the identification number of the mobile communication terminal 410 is transmitted to the Tx terminal 200 for connection with the Rx terminal. Accordingly, the Tx terminal 200 performs step S15 to establish a video telephone connection to the Rx terminal 400. When the video phone connection is established between the Tx terminal 200 and the Rx terminal 400 as described above, the Tx terminal 200 transmits the video phone connection completion message to the monitoring apparatus 100 in step S17.

Thereafter, the monitoring apparatus 100 performs the step S19 by the command transmitting module 120 to uplink the message (data) during the setup of the H.324M or the SIP and the reference image to the Rx terminal 400. The corresponding log commands are sequentially transmitted to the Tx terminal 200. At the same time, the monitoring apparatus 100 performs the step S21 by the command transmitting module 120 to downlink the message (data) during the setup process of the H.324M or the SIP and the test image from the Tx terminal 400. The corresponding log commands below are sequentially transmitted to the Rx terminal 400. Accordingly, an operation based on a log command is performed between the Tx terminal 200 and the Rx terminal 400.

Here, the log command transmitted to the Tx terminal 200 or the Rx terminal 400 may have a different value depending on a protocol used for video telephony. For example, in accordance with H.324M, it is as follows.

H324 Downlink 223 MUX PDU (receive PDU data before demultiplexing)

H324 Downlink Audio SDU (received audio data before being demultiplexed and input to the codec)

H324 Downlink Video SDU (received video data before being demultiplexed and input to the codec)

H324 Downlink 245 SIG SDU (received H.245 signaling message data)

H324 Uplink 223 MUX PDU

H324 Uplink Audio SDU

H324 Uplink Video SDU

H324 Uplink 245 SIG SDU

H324 Uplink Adaptation Layer 245

H324 Downlink Adaptation Layer 245

H324 Video Statistics

H324 Video Encoder

H324 Audio Decoder

H324 Uplink Audio Sequence Number Time Stamp

H324 Downlink Audio Sequence Number Time Stamp

H324 Uplink Video Time Stamp

H324 Downlink Video Time Stamp

In other words, H.324M is related to the above log command, H.245, H.223, H.263 (or H.264 or MPEG-4) and G.711 (or G.723.1 or G.728). Will be made.

3 again, in step S23, the Tx terminal 200 transmits the Tx terminal side message to the monitoring apparatus 100 as a result of the log command. In addition, in step S25, the Rx terminal 400 also transmits the Rx terminal side message to the monitoring apparatus 100 as a result of the log command.

Then, the monitoring apparatus 100 performs step S27 to parse the message received from the Tx terminal 200 by the Tx data collection module 130 and displays it through the monitor. It may also include a message according to the SIP setup process. At the same time, the monitoring apparatus 100 performs step S29 to parse the message received from the Rx terminal 400 by the Rx data collection module 140 and displays it through the monitor, even in such a message, H.324M or SIP. The message may be included according to the setup process of the.

In addition, the monitoring apparatus 100 performs step S31 by the Tx data collection module 130 to extract an Audio SDU (Service Data Unit) and a Video SDU from the data (message) received from the Tx terminal 200 and at the same time In step S33, the Rx data collection module 140 extracts an Audio SDU (Service Data Unit) and a Video SDU from the data received from the Rx terminal 400.

Next, the monitoring apparatus 100 performs step S35 and inputs a payload except for a header portion of the extracted Tx terminal-side extracted data to the A / V codec module 150. To decode it. In addition, the monitoring apparatus 100 performs step S37 and inputs and decodes the payload excluding the header part from the Rx terminal-side extracted data extracted through the S33 to the A / V codec module 150. That is, the decoded Rx terminal-side extracted data becomes a 'test image', and the decoded Tx terminal-side extracted data becomes a 'reference image' which is a reference of the test image. In addition, the decoded and output image data may be YUV or RGB.

Next, the monitoring device 110 performs step S39 to synchronize the test image to the reference image as a reference thereof, and then performs step S41 to convert the test image compared to the reference image to the MOS analysis module 160. MOS is measured to calculate the quality of the audio and video. Finally, in step S43, the measured MOS value is displayed on the monitor. In addition, the test image and the reference image may be stored in predetermined storage as a video file such as AVI so that the MOS algorithm can be performed later.

In the above description, the monitoring apparatus 100 may include a communication protocol (eg, H.223, RTP) that plays a role of data transmission / reception, or a decoding protocol (eg, MPEG-4, H.263 or H. Referring to step 264, each image frame constituting the image data is identified and based on this, step S39, that is, synchronization of the test image and the reference image is preferably performed. In detail, when the RTP is used for transmitting / receiving image data, the monitoring apparatus 100 checks an RTP sequence of each of the test image and the reference image, thereby performing synchronization between the test image and the reference image. Or, as shown in Table 2 below, by using the 'temporal reference' contained in the header or payload of MPEG-4, H-263 or H.264 to identify the image frame of each test image and reference image and Based on this, the synchronization between the test image and the reference image will be performed.

5 is a flowchart illustrating a method of measuring image quality of a videophone according to another embodiment of the present invention.

As shown in FIG. 5, according to the method for measuring image quality of a videophone of the present invention, first, a videophone connection is established between the Tx terminal 200 and the Rx terminal 400, and the notebook computer serving as the monitoring device 100 is gateway. 330 to the data input / output terminal. Next, in step S51 the monitoring device 51 captures a message being input to the data input terminal using the Tx data collection module 130 and at the same time, in step S53 the data output terminal using the Rx data collection module 140. Will capture the message being output.

After capturing the data from the gateway 330 in this manner, the monitoring apparatus 100 performs step S55 to parse the data input end message by the Tx data collection module 130 and display it through the monitor, and at the same time, step S57. In the data output terminal message is parsed by the Rx data collection module 140 and displayed on the monitor.

In addition, the monitoring apparatus 100 performs step S59 by the Tx data collection module 130 to extract an Audio SDU (Service Data Unit) and a Video SDU from the data input side data (message), and at the same time, the Rx data collection module. Step S33 is performed by 140 to extract an audio data service unit (SDU) and a video SDU from the data output data.

Next, the monitoring apparatus 100 performs step S63 to input the payload excluding the header portion of the data input-side extracted data according to the result of the step S59 to the A / V codec module 150. To decode it. In addition, the monitoring apparatus 100 performs step S65 to input and decode the payload excluding the header portion of the data output-side extracted data to the A / V codec module 150. That is, the decoded data output-side extracted data is a test image, and the decoded data input-side extracted data is a 'reference image' which is a reference of the test image.

Next, the monitoring device 110 performs step S67 to synchronize the test image to the reference image as a reference thereof, and then performs step S69 to convert the test image compared to the reference image to the MOS analysis module 160. MOS is measured to calculate the quality of the audio and video. Finally, in step S71, the measured MOS value is displayed on the monitor. In addition, the test image and the reference image may be stored in predetermined storage as a video file such as AVI so that the MOS algorithm can be performed later. In addition, step S67 described above will be performed in the same manner as step S39 described above.

The method for measuring the image quality of a videophone according to the present invention is not limited to the above-described embodiments, and may be modified in various ways within the scope of the technical idea of the present invention.

1 and 2 are each a network configuration diagram implementing a method for measuring image quality of a videophone according to the present invention;

3 is a configuration diagram of a functional module of a monitoring apparatus for implementing a method for measuring image quality of a videophone according to an embodiment of the present invention;

4 and 5 are flowcharts for explaining the image quality measuring method of the video telephone according to the present invention, respectively.

*** Explanation of symbols for the main parts of the drawing ***

100: monitoring device 110: UI module

120: command transmission module 130: Tx data acquisition module

140: Rx data acquisition module 150: A / V codec module

160: MOS analysis module 170: driver module,

200: Tx terminal, 300: base station

310: RNC 320: MSC

330: gateway 340: a circuit-switched network for video telephony,

350: VOD packet switching network 360: SGSN

400: Rx terminal 410: mobile communication terminal

420: videophone 430: VOD server

440: computer

Claims (11)

In the method for measuring the image quality of a video telephone performed by the monitoring apparatus in a state in which a monitoring device equipped with a driver module capable of driving a terminal equipped with a video telephone function is connected to a transmitting terminal and a receiving terminal, respectively, (A) driving a transmitting terminal and a receiving terminal to establish a video telephone connection; (B) receiving a reference image transmitted from the transmitting terminal to the receiving terminal from the transmitting terminal and receiving a test image received from the receiving terminal through the mobile communication network from the receiving terminal; ; (C) decoding the reference image received from the transmitting terminal and decoding the test image received from the receiving terminal; And (d) comparing the decoded reference image with the decoded test image to measure the image quality of the decoded test image. The method of claim 1, The transmitting terminal or the receiving terminal is a mobile communication terminal, The monitoring apparatus performs the step (a) using a DM (Diagnostic Monitoring) port provided in the mobile communication terminal, characterized in that the video phone. The method of claim 2, In step (d), (D1) synchronizing the test image to the reference image as a reference thereof; and And (d2) measuring a MOS (Mean Opinion Score) value of the test image compared to the reference image. The method of claim 3, wherein The synchronization in the step (d1) is the image quality measurement method of a video telephone, characterized in that the reference to the communication protocol that serves to transmit and receive data or the decoding protocol that serves to decode the video data. The method of claim 4, wherein The communication protocol is a real-time transmission protocol (RTP), And the synchronization in the step (d1) is made with reference to the RTP sequence of the real-time transmission protocol (RTP). The method of claim 4, wherein The decoding protocol is MPEG-4, H.263 or H.264, The synchronization in the step (d1) is made by referring to a temporary reference number contained in the header or payload of the MPEG-4, the H.263, or the H.264. How to measure. In the image quality measurement method of a video telephone that is performed by the monitoring device in a state in which a monitoring device capable of capturing video data at the gateway is connected to the gateway, Capturing a reference image input to the gateway and capturing a test image output from the gateway to a communication network; (B) decoding the captured reference image and decoding the captured test image; And comparing the decoded reference image with the decoded test image to measure the image quality of the decoded test image. The method of claim 7, wherein In step (c), (C1) synchronizing the test image with the reference image as a reference; and And (c2) measuring a MOS (Mean Opinion Score) value of the test image compared to the reference image. The method of claim 8, And the synchronization in the step (c1) is made with reference to a communication protocol serving as a transmission / reception of data or a decoding protocol serving as a decoding of video data. The method of claim 9, The communication protocol is a real-time transmission protocol (RTP), And the synchronization in the step (c1) is made with reference to the RTP sequence of the real-time transmission protocol (RTP). The method of claim 9, The decoding protocol is MPEG-4, H.263 or H.264, The synchronization in the step (c1) is made by referring to a temporary reference number contained in the header or payload of the MPEG-4, the H.263, or the H.264. How to measure.

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