JP2007274066A - Content distribution system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content distribution system of simple configuration in which distribution of content data can be sustained at an optimal bit rate, even if switching is made to the line of a different communication band during distribution of content from a content distribution server to a client terminal. <P>SOLUTION: A client terminal 40 connected through a network 30 with a content distribution server 20 which distributes inputted content data while compressing based on compression value information acquired from the client terminal 40 generates and transmits compression value information suitable for a communication medium selected among a plurality of communication media of different communication band, and acquires and outputs the content data distributed based on the compression value information thus transmitted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a content distribution system that provides content in a streaming format from a server storing content to a communication terminal via a communication network.

  2. Description of the Related Art Conventionally, terminals that are equipped with a plurality of interfaces for performing communication between information terminals and are compatible with both wired and wireless terminals have been widely used.

  As an example of a terminal capable of supporting both wired and wireless, there is a mobile client terminal such as a notebook personal computer equipped with an interface corresponding to wireless according to IEEE802.11g and an interface compatible with wired according to IEEE802.3u.

  By using this mobile client terminal, a user can acquire content data from a server in which the content data is stored while switching between wired and wireless.

  For example, in an environment where wired can be used, high-quality content data is acquired from the server at a high bit rate using wired, and when wired cannot be used, switch to wireless and use a low bit rate. There is a usage method in which content data is continuously acquired in different usage environments by acquiring content data.

  On the other hand, as a general streaming distribution technique for distributing content data to a client terminal, there are a method of distributing using a Web server and a method of distributing using a streaming server specialized for a streaming task.

  The distribution method using a Web server can be used by existing equipment, but when browsing content data on a client terminal, all data must be received and played back. There is a disadvantage that browsing is not possible on a line with a low transfer rate.

  On the other hand, since the method of distributing using a streaming server reproduces data while receiving it at the client terminal, the content data can be reproduced in real time even on a low-speed line.

  When a streaming server is used, the bit rate corresponding to the network bandwidth is notified to the server on the content playback application executed on the client, and content data suitable for the user's usage environment is distributed from the server to the client terminal. can do.

  However, when content data distributed from a streaming server is received by a terminal that can handle both wired and wireless communication, for example, processing at a low bit rate from wired communication that is processed at a high bit rate. When switching to wireless communication, there is a problem that the band that can be occupied is insufficient, and frame dropping of video data occurs or the screen freezes.

  On the other hand, when switching from wireless communication processed at a low bit rate to wired communication processed at a high bit rate, there is a problem that an image utilizing high speed cannot be obtained.

  In order to solve these problems, there is a method of measuring available bandwidth using a pathload method, which is a network bandwidth measurement method, and distributing content data based on the measured result.

  However, in this pathload method, test packets for response time measurement called probe packets are continuously transmitted from the server to the client terminal, and the arrival interval of responses transmitted from the client terminal to the transmitted probe packets is measured. In order to determine the congestion state of the band, this probe packet itself has a drawback that it imposes a load on the network.

  As another method for solving the above-described problem, there is a technique described in Patent Document 1.

  In this technique, content data input to a server is encoded at various bit rates to generate a plurality of stream groups, and an appropriate stream is selected according to the effective bandwidth of the network.

With this technology, even when the effective bandwidth changes in the network, it is possible to switch to a stream encoded at a bit rate suitable for the effective bandwidth after the change, and the server always provides an appropriate stream for the effective bandwidth. can do.
JP 2005-516547 A

  However, the technique disclosed in Patent Document 1 has a problem in that a plurality of streams having different bit rates are generated, which makes the processing complicated and requires a large-capacity memory in the server.

  The present invention has been made in view of the above circumstances, and even when content is switched from a content distribution server to a client terminal while switching to a line with a different communication band, content data is distributed at an optimum bit rate. It is to provide a content distribution system that can be continued and has a simple configuration.

  In order to achieve the above object, the content distribution system (1) of the present invention is connected via a network (30) and communicates with a content distribution server (20) that distributes content data and receives the distributed content data. A content distribution system (1) comprising a terminal (40), wherein the content distribution server (20) is transmitted from a content data input unit (21) for inputting content data from the outside and the communication terminal (40). A compressed value information receiving unit (23) for receiving compressed value information for compressing the input content data, and a content data compressing unit for compressing the input content data based on the received compressed value information (24) and content data for transmitting the compressed content data to the communication terminal (40). The communication terminal (40) includes a plurality of communication interface units (41, 42) connected to the network (30) with different communication bandwidths, and the plurality of communication interface units. (41, 42) A communication interface unit that is in a communication state connectable to the network (30) and has the highest priority set in advance is selected, and the connection to the network (30) is switched or the connection is switched. An interface switching unit (43) to perform, a compressed value information storage unit (44) for storing compressed value information determined for each communication bandwidth, and compressed value information corresponding to the communication bandwidth of the selected communication interface unit Acquired from the compressed value information storage unit (44), and acquires the acquired compressed value information from the selected communication interface unit to the content distribution server (2 ) And a content data receiving unit (46) that receives the compressed content data transmitted from the content distribution server (20) based on the transmitted compressed value information. And a content data decompression unit (47) for decompressing the received compressed content data.

  Moreover, Claim 2 is the content distribution system (1) according to Claim 1, and the communication terminal (40) transmits the compressed value information from the compressed value information acquisition / transmission unit (45) to the content distribution server (20). A timer unit (48f) that starts time measurement when the time is set, and the packet data transmitted from the content distribution server (20) when the measurement time of the timer unit (48f) exceeds a preset time. Packet data transmitted from the content distribution server (20) when the measurement time of the packet loss frequency calculation unit (48a) and the timer unit (48f) for calculating the frequency of loss in a predetermined period exceeds a preset time. A packet average arrival interval calculation unit (48b) for calculating an average arrival interval in a predetermined period of time, and a case where the calculated number of losses exceeds a preset value. Or, when the number of losses is less than or equal to a preset value and the calculated average arrival interval exceeds a preset value, modified compression value information with a compression rate lower than the compression value information currently being processed is generated On the other hand, when the number of losses is equal to or less than a preset value and the average arrival interval is equal to or less than a preset value, a change is generated that generates compressed value information with a higher compression ratio than the currently processed compression value information. A communication state monitoring unit having a compression value information generation unit (48c) and a modified compression value information transmission unit (48e) that transmits the generated modified compression value information to the content distribution server (20) from the selected communication interface unit. (48) is further provided.

  According to the content distribution system of the present invention, even when switching to a line with a different communication band during distribution of content from the content distribution server to the client terminal with a simple configuration, frame dropping of video data occurs or the screen The content data can be distributed at an optimum bit rate without being frozen.

<Configuration of Content Distribution System According to One Embodiment>
A configuration of a content distribution system 1 according to an embodiment of the present invention will be described with reference to FIG.

  The content distribution system 1 according to this embodiment includes a digital video camera 10 that performs shooting, a content distribution server 20 that inputs and distributes video captured by the digital video camera 10 as content data, a network 30, and the network 30. The client terminal 40 as a communication terminal that receives content data from the content distribution server 20, the display device 50 that displays the content data received by the client terminal 40, and the client terminal 40 used when communicating with the network 30 wirelessly. Access point 60.

  The content distribution server 20 includes a content data input unit 21, a content data conversion unit 22, a compressed value information reception unit 23, a content data compression unit 24, and a content data transmission unit 25.

  The content data input unit 21 inputs content data from the digital video camera 10.

  The content data converter 22 converts the input content data from DV format to YUV format.

  The compressed value information receiving unit 23 receives the compressed value information from the client terminal 40 via the network 30 and holds the IP address of the client terminal 40 that is the transmission source of this information.

  The content data compression unit 24 compresses the content data converted into the YUV format based on the received compression value information using the JPEG format or the MPEG format.

  The content data transmission unit 25 acquires the IP address of the client terminal 40 from the compressed value information reception unit 23 and transmits the compressed content data to the client terminal 40 via the network 30.

  The client terminal 40 includes a wired interface unit 41, a wireless interface unit 42, an interface switching unit 43, a compressed value information storage unit 44, a compressed value information acquisition / transmission unit 45, a content data receiving unit 46, a content A data decompression unit 47 and a communication state monitoring unit 48 are provided.

  The wired interface unit 41 is a LAN interface card that enables communication by wired connection to the network 30 at a data transfer speed of 1 Gbps or less.

  The wireless interface unit 42 is an interface defined by IEEE802.11g that enables communication by wirelessly connecting to the network 30 at a data transfer speed of 54 Mbps or less.

  The interface switching unit 43 selects any one of the wired interface unit 41 and the wireless interface unit 42 to enable communication with the network 30.

  The compression value information storage unit 44 stores the compression value information of content determined for each communication band.

  The compressed value information acquisition / transmission unit 45 acquires compressed value information corresponding to the communication bandwidth of the interface unit selected by the interface switching unit 43 from the compressed value information storage unit 44, and transmits the network 30 from the selected interface unit. To the content distribution server 20.

  The content data receiving unit 46 receives the compressed content data transmitted from the content distribution server 20 based on the transmitted compressed value information.

  The content data decompression unit 47 decompresses the received compressed content data and outputs it to the display device 50.

  The communication state monitoring unit 48 includes a timer unit 48f that starts time measurement when the compressed value information is transmitted from the compressed value information acquisition and transmission unit 45 to the content distribution server, and a measurement time of the timer unit 48f is set in advance. When the time of the packet data transmitted from the content distribution server 20 exceeds the predetermined time, the packet loss frequency calculation unit 48a that calculates the number of loss of the packet data transmitted from the content distribution server 20 and the timer unit 48f exceeds a preset time. In addition, a packet average arrival interval calculation unit 48b that calculates an average arrival interval in a predetermined period of packet data transmitted from the content distribution server 20, and a case where the calculated loss count exceeds a preset value, or the loss count is If it is less than or equal to a preset value and the calculated average arrival interval exceeds a preset value, While changing compression value information having a compression rate lower than the compression value information being processed is generated, the current processing is performed when the number of losses is less than or equal to a preset value and the average arrival interval is less than or equal to a preset value Modified compression value information generating unit 48c that generates modified compressed value information having a higher compression ratio than the compressed value information of the received data, and modified compression that transmits the generated modified compressed value information to the content distribution server 20 from the selected communication interface unit A value information transmission unit 48e.

<Operation of Content Distribution System According to One Embodiment>
The operation of the content distribution system according to the present embodiment will be described with reference to FIG.

  In the present embodiment, a case will be described in which video content captured by the digital video camera 10 is distributed to the client terminal 40 by the content distribution server 20 in a streaming format.

  First, video captured by the digital video camera 10 is transmitted to the content distribution server 20 as content data.

  In the content distribution server 20, when content data is received, it is input from the content data input unit 21 (S1).

  The content data input from the content data input unit 21 is converted from the DV format to the YUV format by the content data conversion unit 22 (S2).

  On the other hand, the client terminal 40 becomes communicable with the content distribution server 20 via the network 30 by selecting one of the wired interface unit 41 and the wireless interface unit 42 and connecting to the network 30. Yes.

  At this time, when it is an environment that can be connected to the network 30 by wire, the wired interface unit 41 is selected by the interface switching unit 43 to perform communication at a high bit rate, and cannot be connected to the network 30 by wire. In the environment, the interface switching unit 43 selects the wireless interface unit 42 and performs communication at a low bit rate.

  Here, it is assumed that the environment can be connected to the network 30 by wire, and the wire interface unit 41 is selected by the interface switching unit 43 (S3).

  When the wired interface unit 41 is selected by the interface switching unit 43 and communication with the network 30 is performed by wire, the compressed value information corresponding to the communication band of the wired interface unit 41 is compressed value information in the compressed value information acquisition and transmission unit 45. Obtained from the storage unit 44 (S4).

  The compressed value information stored in the compressed value information storage unit 44 will be described.

  In this embodiment, the compression value information storage unit 44 stores compression value information when an image is compressed using the JPEG format.

An example of the compressed value information is shown in Table 1.

  In the present embodiment, the compressed value information is an integer from 1 to 100. This compression value information is a parameter for weighting the quantization coefficient of the quantization table. The larger the value of the compression value information, the lower the compression data.

  Data compression by the JPEG method or MPEG method causes variations in the data size after compression due to the characteristics of the original image data. Therefore, the compression value information shown in Table 1 is the type of image captured by the digital video camera 10 and the application of the system. It is desirable to determine appropriately according to.

  By changing the compression value in this way, the size of the compressed image data transmitted on the network 30 is changed, and the traffic load on the network 30 can be adjusted.

  Here, the compressed value information “75”, which is compressed value information corresponding to the communication band of the wired interface unit 41, is acquired by the compressed value information acquiring / transmitting unit 45.

  The acquired compressed value information “75” is transmitted from the wired interface unit 41 to the content distribution server 20 via the interface switching unit 43 (S5).

  In the content distribution server 20, the compressed value information “75” is received by the compressed value information receiving unit 23 (S 6) and sent to the content data compressing unit 24, and at the client terminal 40 that is the transmission source of the compressed value information. The IP address is held.

  In the content data compression unit 24, the content data converted into the YUV format in step S2 is data-compressed based on the acquired information (S7).

  Next, the IP address of the client terminal 40 is acquired from the compressed value information receiving unit 23 by the content data transmitting unit 25, and the compressed content data is streamed as a unicast UDP packet from the content data transmitting unit 25 via the network 30. Is transmitted to the client terminal 40 (S8).

  Since wired is used here, transmission is performed with a performance of a communication speed of 1 Gbps or less.

  The client terminal 40 receives the content data compressed by the content data receiving unit 46 via the wired interface unit 41 and the interface switching unit 43 (S9).

  The content data received by the content data receiving unit 46 is decompressed by the content data decompressing unit 47 and output for display on the display device 50 (S10). The processes in steps S1, S2, S7, and S8 are repeated while the interface unit is not switched and content data is being distributed.

  Here, the operation of the content distribution system when the user moves with the client terminal 40 such as a notebook personal computer to change to an environment in which the client terminal 40 cannot be connected by wire will be described.

  In the content distribution server 20, content data is continuously input from the digital video camera 10 in the streaming format regardless of the status of the client terminal 40, and converted into the YUV format (S11, S12).

  In the client terminal 40, when the connection to the network 30 by the wired interface unit 41 is disconnected, this disconnection is detected by the interface switching unit 43 by the link signal (S13).

  When disconnection of the connection to the network 30 by the wired interface unit 41 is detected by the interface switching unit 43, the connection is switched to the connection to the network 30 by the wireless interface unit 42 (S14).

  When the wireless interface unit 42 is switched to the connection to the network 30, the compressed value information “25”, which is compressed value information corresponding to the communication band of the wireless interface unit 42, is stored in the compressed value information storage unit 45. 44 (S15).

  The acquired compressed value information “25” is transmitted via the interface switching unit 43 and the wireless interface unit 42, and is transmitted to the content distribution server 20 via the access point 60 (S16).

  In the content data compressing unit 24, the compressed value information “25” is received by the compressed value information receiving unit 23 (S17) and sent to the content data compressing unit 24, and at the same time, the client terminal 40 that is the transmission source of the compressed value information Is held.

  In the content data compression unit 24, the content data converted into the YUV format in step S12 is data-compressed based on the acquired information (S18).

  Next, the content data transmission unit 25 obtains the IP address of the client terminal 40 from the compressed value information reception unit 23, and the compressed content data is streamed as a unicast UDP packet from the content data transmission unit 25 to the network 30. It is transmitted to the client terminal 40 via the point 60 (S19).

  Here, since radio is used, transmission is performed with a performance of 54 Mbps or less.

  The client terminal 40 receives the content data compressed by the content data receiving unit 46 through the wireless interface unit 42 and the interface switching unit 43 (S20).

  The content data received by the content data receiving unit 46 is decompressed by the content data decompressing unit 47 and output for display on the display device 50 (S21). The processes in steps S11, S12, S18, and S19 are repeated while the interface is not switched and content data is being distributed.

  As described above, the compressed value information acquisition control in the client terminal 40 while the content data is being distributed from the content distribution server 20 to the client terminal 40 using the wired interface unit 41 or the wireless interface unit 42 will be described. To do.

  While the content data is being distributed from the content distribution server 20 to the client terminal 40, the communication state monitoring unit 48 measures the packet loss count and the average arrival interval time of the packets every predetermined period, thereby determining the communication state. Monitored and controlled compression value.

  The configuration of the communication state monitoring unit 48 will be described with reference to FIG.

  The communication state monitoring unit 48 includes a packet loss frequency calculating unit 48a, a packet average arrival interval calculating unit 48b, a modified compressed value information generating unit 48c, a compressed value recording unit 48d, a modified compressed value information transmitting unit 48e, a timer. 48f.

  When the value of the timer 48f exceeds a preset value, the packet loss frequency calculation unit 48a calculates the number of times that a packet transmitted from the content distribution server 20 is lost in a certain period.

  When the value of the timer 48f exceeds a preset value, the packet average arrival interval calculation unit 48b calculates the average arrival interval of packets transmitted from the content distribution server 20 over a certain period.

  The modified compressed value information generation unit 48c generates modified compressed value information that is a compressed value to be changed from the number of losses calculated by the packet loss frequency calculation unit 48a and the average arrival interval calculated by the packet average arrival interval calculation unit 48b. To do.

  The compressed value recording unit 48d uses the compressed value information when new compressed value information is acquired by the compressed value information acquisition / transmission unit 45, or the changed compressed value information is generated by the changed compressed value information generating unit 48c. Record changed compression value information.

  The changed compressed value information transmitting unit 48e provides the changed distribution value information generated by the changed compressed value information generating unit 48c to the content distribution server 20 from any interface unit via the network 30.

  The timer 48f measures an elapsed time when new compressed value information is transmitted from the compressed value information acquisition / transmission unit 45, or after the changed compressed value information is transmitted from the changed compressed value information transmission unit 48e.

  The communication state monitoring operation and the compression value control in the communication state monitoring unit 48 will be described with reference to FIG.

  First, the timer 48f has elapsed since the new compressed value information was transmitted from the compressed value information acquisition / transmission unit 45, or has elapsed since the changed compressed value information was transmitted from the changed compressed value information transmitting unit 48e. It is determined whether or not the remaining time exceeds a preset time (S31).

  This is performed in order to prevent malfunction of the communication state monitoring unit 48 immediately after acquisition of compressed value information. For example, immediately after requesting the content distribution server 20 to increase the compression value from the client terminal 40, packets are sent from the content distribution server 20 at a low bit rate, so the packet arrival interval becomes longer. In this case, a change is required to lower the compression value, and the change of the compression value is frequently requested and becomes unstable.

  Therefore, the operation of the communication state monitoring unit 48 can be stabilized by preventing the compressed value from being changed for a certain period after the acquisition of the compressed value information.

  As a result of the determination, if the preset time has been exceeded (“YES” in S31), for example, for 10 frames of content data that arrived in sequence, (1) the integrated value of the number of lost UDP packets is the number of lost packets. The calculation unit 48a calculates (2) the average packet arrival interval is calculated by the packet average arrival interval calculation unit 48b (S32, S33).

  The number of lost UDP packets is calculated by adding a serial number to each packet when the UDP packet is transmitted from the content distribution server 20, and detecting the missing number by the packet loss number calculating unit 48a.

  When data for 10 frames is calculated for the above (1) and (2) (“YES” in S33), (1) whether or not the cumulative value of the number of lost UDP packets exceeds a preset threshold value The changed compressed value information generation unit 48c determines (S34).

  As a result of the determination, when the changed compressed value information generation unit 48c determines that the integrated value of the number of times of loss of the UDP packet exceeds a preset threshold value ("YES" in S34), it is determined that the line is busy, In order to reduce the traffic load, changed compression value information lower than the compression value being processed is generated.

  The changed compressed value information is generated by acquiring the compressed value being processed recorded in the compressed value recording unit 48d and calculating a compressed value obtained by lowering the predetermined value from the compressed value being processed (S35). .

  Here, the compressed value information being processed recorded in the compressed value recording unit 48d is “25”, and “20”, which is lower by 5 steps set in advance from this value, is generated as the changed compressed value information.

  If it is determined in step S34 that the cumulative value of the number of lost UDP packets is equal to or less than the threshold ("NO" in S34), (2) the average packet arrival interval exceeds a preset threshold. It is determined whether or not (S36).

  As a result of the determination, when it is determined that the average arrival interval of packets exceeds a preset threshold (“YES” in S36), it is also determined that the line is busy, and processing is being performed to reduce the traffic load. Changed compressed value information lower than the compressed value is generated (S35).

  If it is determined in step S36 that the average packet arrival interval does not exceed the preset value (“NO” in S36), it is determined that there is a margin in the line usage status, and the compressed value being processed Higher compressed compression value information is generated (S37).

  Here, the compressed value information being processed recorded in the compressed value recording unit 48d is “20”, and “22” that is two steps higher than this value is generated as the changed compressed value information.

  By making the change value when the compression value is lowered in this way larger than the change value when the compression value is raised, the traffic load is greatly reduced when the line is busy, and then the traffic is gradually increased. be able to.

  The changed compressed value information generated in step S35 or step S37 is recorded in the compressed value recording unit 48d (S38), and from the changed compressed value information transmitting unit 48e to the interface switching unit 43 and any interface unit. It is transmitted to the content distribution server 20 (S39).

  When the changed compressed value information is transmitted from the changed compressed value information transmitting unit 48e, the timer 48f is activated (S40) and used for the determination in step S31.

  The processes in steps S31 to S40 described above are repeated until the content distribution is completed or a stop operation is performed by the user (S41).

  According to the above embodiment, the content distribution server can provide the client terminal with content data compressed with a compression value suitable for the communication band of the communication medium. Even when switched to, the distribution of content data can be continued with a compression value suitable for the communication medium to be used.

  Also, through the communication status monitoring operation and compression value control performed by the communication status monitoring unit, the content distribution server distributes the content data compressed with the optimal compression value to the client terminal according to the change in the traffic state of the communication line. can do.

  Further, since it is not necessary to store a plurality of content data having different compression values in the content distribution server, a large-capacity memory is not required and the configuration can be simplified.

  In this embodiment, in the compression value control in the communication state monitoring unit 48, the change value of the compression value is set to 5 steps when the compression value is lowered, and 2 steps when the compression value is raised. It is possible to set a change value according to the usage environment of each device and communication medium.

  In the present embodiment, the digital video camera is provided separately from the content distribution server as an apparatus for inputting content. However, the present invention is not limited to this. For example, a security camera equipped with the function of the content distribution server is used. The digital video camera and the content distribution server may be integrated.

It is a block diagram which shows the structure of the content delivery system in one Embodiment of this invention. It is a sequence diagram which shows operation | movement of the content delivery system in one Embodiment of this invention. It is a block diagram which shows the structure of the communication status monitoring part of the content delivery system in one Embodiment of this invention. It is a flowchart which shows operation | movement of the communication status monitoring part of the content delivery system in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Content delivery system 10 ... Digital video camera 20 ... Content delivery server 21 ... Content data input part 22 ... Content data conversion part 23 ... Compression value information receiving part 24 ... Content data compression part 25 ... Content data transmission part 30 ... Network 40 ... Client terminal 41 ... Wired interface unit 42 ... Wireless interface unit 43 ... Interface switching unit 44 ... Compressed value information storage unit 45 ... Compressed value information acquisition / transmitting unit 46 ... Content data receiving unit 47 ... Content data expanding unit 48 ... Communication state monitoring Unit 48a ... packet loss frequency calculation unit 48b ... packet average arrival interval calculation unit 48c ... changed compressed value information generating unit 48d ... compressed value recording unit 48e ... changed compressed value information transmitting unit 48f ... timer 50 ... display device 60 ... access point

Claims (2)

A content distribution system, each connected via a network, comprising a content distribution server for distributing content data and a communication terminal for receiving the distributed content data,
The content distribution server is
A content data input unit for inputting content data from the outside;
A compressed value information receiving unit that receives compressed value information for data compression of the input content data transmitted from the communication terminal;
A content data compression unit that compresses the input content data based on the received compression value information;
A content data transmission unit that transmits the compressed content data to the communication terminal;
The communication terminal is
A plurality of communication interface units each connected to the network with different communication bandwidths;
Interface switching for selecting a communication interface unit that is in a communication state connectable to the network and having the highest preset priority from among the plurality of communication interface units, and performs opening connection or switching of the connection to the network And
A compressed value information storage unit for storing compressed value information determined for each communication bandwidth;
The compressed value information corresponding to the communication bandwidth of the selected communication interface unit is acquired from the compressed value information storage unit, and the acquired compressed value information is transmitted from the selected communication interface unit to the content distribution server. A compressed value information acquisition and transmission unit for transmission;
A content data receiving unit for receiving compressed content data transmitted from the content distribution server based on the transmitted compressed value information;
A content data decompression unit for decompressing the received compressed content data;
A content distribution system comprising: The communication terminal is
A timer unit that starts time measurement when the compressed value information is transmitted from the compressed value information acquisition transmission unit to the content distribution server;
A packet loss frequency calculation unit that calculates the number of loss of packet data transmitted from the content distribution server in a predetermined period when the measurement time of the timer unit exceeds a preset time;
A packet average arrival interval calculation unit that calculates an average arrival interval in a predetermined period of packet data transmitted from the content distribution server when the measurement time of the timer unit exceeds a preset time;
When the calculated loss count exceeds a preset value, or when the loss count is equal to or less than a preset value and the calculated average arrival interval exceeds a preset value, the current processing The processing is performed when the changed compression value information having a compression rate lower than the compression value information in the medium is generated, while the loss count is equal to or less than a preset value and the average arrival interval is equal to or less than a preset value. A modified compressed value information generating unit for generating modified compressed value information having a higher compression ratio than the compressed value information in the medium,
A modified compressed value information transmitting unit that transmits the generated modified compressed value information from the selected communication interface unit to the content distribution server;
The content distribution system according to claim 1, further comprising: a communication state monitoring unit including:

Images