JP4992568B2 - Client device, data processing method and program thereof - Google Patents

Description

  The present invention relates to a client device that communicates with a server that provides content data of a plurality of resolutions, a data processing method performed by the client device, and a program thereof.

There is a technique called UPnP_AV, which is a standard for exchanging moving images and still images between a server and a client using a network, and is disclosed in Patent Document 1 below.
Also, there is a standard called DLNA (Digital Living Network Alliance) that applies UPnP_AV technology.

DLNA is a standard by an organization that makes arrangements for interconnecting devices between different manufacturers. As long as the devices comply with the standard, the user can automatically recognize each other's devices and construct a network without being aware of the network settings.
DLNA supports moving images, still images and music content, and DMP (Digital
This can be realized by connecting a client called “Media Player” and a server called “DMS (Digital Media Server)”. The DMP can view moving images, still images, and music contents stored in the DMS via a network. At this time, the DMS does not immediately transmit all the content information to the DMP, but first transmits resource information indicating a list of contents stored in the DMS to the DMP.

  In DLNA, when resource information of content in DMS is transmitted to DMP, there is a case where information in which a plurality of resources are added to one content, called multi-resource, is transmitted by DMS. For example, assume that still image content A with a resolution of 4000 × 4000 is accumulated in the DMS. In this case, when the DMS does not process anything and transmits the information of the still image content A, the resolution is 4000 × 4000. However, in the case of multi-resources, 4000 × 4000, 2000 × 2000, Information of four still picture contents A of 1000 × 1000 and 500 × 500 is transmitted. In DLNA, there is no provision for multi-resource information, and the number of multi-resources depends on DMS. For example, even if a certain DMS is multi-resource, there are cases where only two types of information are sent, and another DMS may send seven types of information. In DMP, multi-resource information transmitted from DMS may be handled in any way.

Special table 2007-510195

When multi-resource information of a predetermined content is input from the DMS to the DMP, it is assumed that the DMP holds all the resources, and if the amount of information of one resource is A and the number of resources is N, per content A × N information amount is required.
Therefore, when the number of DMS contents is B, a memory capacity of A × N × B is required as a whole. For example, if one resource data amount A is 1 Kbyte, the number of resources N is 5, and the number of contents is 100, 1 × 5 × 100 = 500 Kbytes are required. In this example, it is assumed that the resource information is 1 Kbyte. However, if the real information or the like is held, a larger data amount is required, so that a larger memory capacity is required.

In a system with a limited memory capacity such as a digital television, the increase in the number of resources and the number of contents described above may exceed the usable memory capacity.
In such a case, the client cannot hold all the content data. For example, if priority is given to holding the content data of a high-resolution image, the output of the thumbnail-displayed image is delayed. If priority is given to holding the content data of thumbnail images, problems such as poor quality of the displayed image arise.

  The present invention has been made in view of the above-described problems of the prior art. When a client device receives content data from a server device that provides a plurality of content data having different resolutions for the same content, the client device has a shortage of memory capacity. It is an object to provide a client device, a data processing method, and a program thereof that can be effectively solved.

  In order to solve the above-described problems of the prior art and achieve the above-described object, a client device according to a first aspect of the present invention provides the content data from a server device that provides a plurality of content data with different resolutions for the same content A communication unit that communicates with the server device, a memory that stores content data, a playback unit that plays back the content data, and the resolution of the content data that the playback unit plays back Based on the setting data set in advance, the server device requests and acquires a part of the plurality of content data provided by the server device, and the acquired content data is stored in the memory. Control means for performing a writing process, and the control means Each attribute data indicating the attribute of the server device and the attributes of the plurality of content data received by the communication means is written to the memory, and a part of the content data among the plurality of content data is stored on the basis of the attribute data. When requested to the server device and the free space equal to or larger than a predetermined threshold is in the memory, the content data received by the communication means is written into the memory, and the free space equal to or larger than the threshold is stored in the memory. If not, the resolution of the content data received by the communication means is stored in the memory on condition that the setting data indicates a resolution closer to the resolution of the content data already stored in the memory. Overwriting the stored content data with the content data received by the communication means .

  The data processing method according to the second aspect of the present invention is such that the content data is received from a server device that provides a plurality of content data having different resolutions for the same content, and the resolution of the content data to be played back by the playback means is preset. Based on the set data, the server device requests and acquires a part of the plurality of content data provided by the server device, and performs processing for writing the acquired content data to a memory. A data processing method executed by a client device including a reproduction unit and the memory, wherein a first step of writing each attribute data indicating the received attribute of the server device and the attributes of the plurality of content data into the memory And the plurality of content data based on the attribute data. A second step of requesting a part of the content data to the server device, and if the memory has a free space equal to or greater than a predetermined threshold, the content data received by the communication means is stored in the memory. And if the memory has no free space equal to or greater than the threshold value, the resolution of the content data received by the communication means is the resolution of the content data already stored in the memory. And a fourth step of overwriting the content data stored in the memory with the content data received by the communication means on the condition that the resolution is close to the resolution indicated by the setting data.

According to a third aspect of the invention, there is provided a program that receives the content data from a server device that provides a plurality of content data having different resolutions for the same content, and that is set in advance for the resolution of the content data that is played back by a playback unit. The reproduction means for performing a process of requesting and acquiring a part of the content data of the plurality of content data provided by the server device from the server device and writing the acquired content data in a memory based on the data And a program executed by a client device including the memory, wherein the attribute information indicating the received attribute of the server device and the plurality of content data is written to the memory, and the attribute One of the plurality of content data based on the data A second procedure for requesting the server to request the content data, and a third capacity for writing the content data received by the communication means to the memory when the memory has a free space equal to or greater than a predetermined threshold. And when there is no free space equal to or greater than the threshold in the memory, the resolution of the content data received by the communication means is compared with the resolution of the content data already stored in the memory, The client apparatus is caused to execute a fourth procedure for overwriting the content data stored in the memory with the content data received by the communication unit on condition that the resolution indicated by the setting data is close.

  According to the present invention, when a client device receives content data from a server device that provides a plurality of content data with different resolutions for the same content, the client device and data that can effectively solve the shortage of memory capacity in the client device A processing method and its program can be provided.

A server / client system according to an embodiment of the present invention will be described below.
FIG. 1 is a configuration diagram of a server / client system 1 according to an embodiment of the present invention.
As shown in FIG. 1, the server / client system 1 includes, for example, a server device 3 and a client device 4. The server / client system 1 is a home network system constructed in a home, for example.
The server device 3 is a DMS having functions such as storage and distribution of digital content, and the client device 4 serves as a DMP for reproducing the content.

Communication between the server device 3 and the client device 4 is performed using UPnP (universal
Although it is performed by the DLNA method using plug and play), other communication methods may be used.
In the present embodiment, the case where there is one server device 3 and one client device 4 is illustrated, but at least one of the server device 3 and the client device 4 may be plural. Moreover, you may use the apparatus provided with the function of both the server apparatus 3 and the client apparatus 4. FIG.

An example of the correspondence between the components of the present embodiment and the components of the present invention is as follows.
The server device 3 is an example of the server device of the present invention, and the client device 4 is an example of the client device or the computer of the present invention.
The cache 14 is an example of the memory of the present invention, the communication unit 20 is an example of the communication unit of the present invention, and the processing unit 12 is an example of the reproducing unit of the present invention. The instruction analysis unit 16, the cache control unit 18, and the client request creation unit 24 are examples of the control unit of the present invention.

The outline of the server / client system 1 will be described below.
In the server / client system 1, the client device 4 writes only content data that conforms to its own performance and user's request into the memory. That is, the client device 4 does not receive the content data of all resolutions provided by the server device 3 for each content and store it in the memory.
Thereby, the memory capacity used by the client device 4 can be reduced, and the network communication load can also be reduced. Also, during streaming playback, the received content data is directly output to the playback processing system, thereby achieving efficient use of memory and shortening of processing time.
The client apparatus 4 receives the list data of the content resolution from the server apparatus 3 in advance, and requests the server apparatus 3 to download the content data of the necessary resolution based on the list data, and the server apparatus 3 provides Any operation of receiving content data of all resolutions, selecting content data of a necessary resolution from among them, and writing it to the cache may be performed.

Hereinafter, each component shown in FIG. 1 will be described in detail.
[Server device 3]
Examples of the server device 3 include a personal computer, a set top box, a digital camera, a video camera, and a multifunctional mobile phone.
The server device 3 accumulates content data of a plurality of resolutions for each of a plurality of contents, and creates content data of a plurality of resolutions at appropriate times whenever a request is made from the client device 4. The server device 3 distributes the content data of the plurality of resolutions for each content.

At this time, the server device 3 transmits, for example, list data (resource information) such as a list of contents stored in the server device 3 and a resolution thereof to the client device 4. Then, a request including the designation of resolution is received from the client device 4, and the content data of the designated resolution is transmitted to the client device 4.
Note that the server device 3 may transmit content data of a plurality of resolutions for predetermined content to the client device 4 without the above request.
Further, the server device 3 may transmit content data of the previous and subsequent resolutions to the client device 4 in addition to the requested resolution content data.

As described above, in DLNA, when content data in the server device 3 is transmitted to the client device 4, the server device 3 may transmit information called a multi-resource, in which a plurality of resources are added to one content. is there.
For example, when the server apparatus 3 is a single resource, assuming that still image content A with a resolution of 4000 × 4000 is stored, when a request for the still image content A is received, content data with a resolution of 4000 × 4000 is obtained. Send.
On the other hand, the server device 3 is multi-resource, and the original still image data is 4000 × 4000, and in addition to 2000 × 2000, 1000 × 1000, 500 × 500, 200 × 200, and 120 × 120, a total of six still images. When data A is stored, list data indicating that the above-described six-resolution still image data exists is transmitted to the client apparatus 4. Then, only still image data with a resolution corresponding to the request from the client device 4 is transmitted to the client device 4.
In DLNA, there is no provision for multi-resource information, and the number of multi-resources depends on DMS.

  For example, a certain DMS is multi-resource, and two types of information are transmitted, and another DMS may transmit seven types of information. DLNA does not define how the DMP such as the client apparatus 4 handles multi-resource information transmitted from the DMS.

[Client device 4]
As shown in FIG. 1, the client device 4 includes, for example, a display 10, a processing unit 12, a cache 14, a command analysis unit 16, a cache control unit 18, a communication unit 20, an external command input unit 22, and a client request creation unit 24. Have.
Here, all or part of the functions of the processing unit 12, the instruction analysis unit 16, the cache control unit 18, the external command input unit 22, and the client request creation unit 24 are realized by a processing circuit (CPU) executing a program. The

The client device 4 receives the list data of the content data held by the server device 3 from the server device 3.
In the example described above, the client device 4 specifies that there are data of six types of resolution in total for the still image data based on the list data.
For example, the client apparatus 4 requests the client apparatus 4 for 4000 × 4000 still image data having the highest image quality.
By the way, when the client apparatus 4 is a device having a limited memory such as a television receiver or the like, it is wasteful to use the memory to hold all the above-described six types of still image data. For example, when the client device 4 displays only two types of images, that is, an image to be displayed by the player and an image to display a thumbnail, a large amount of unused data is stored in the memory.

  In consideration of such points, the client apparatus 4 presets attribute data indicating the resolution of an image displayed on the display 10 and predetermines a condition for data to be written to the cache 14 based on the attribute data. The client device 4 writes only the image data that satisfies the above conditions (actually used) into the cache 14 among a plurality of resolution images indicated in the list data from the server device 3.

  As the above-mentioned conditions, for example, “If the client can only decode a still image up to 1000 × 1000, data of 1000 × 1000 or more is not necessary”, “Since thumbnail images are displayed in a small size, Such as “hold data with small resolution” and “hold the smallest data among resolutions larger than 1280 × 720 because the resolution of the client display device is 1280 × 720”.

  The display 10 displays an image corresponding to the image data input from the processing unit 12. Note that the display 10 may have an audio output function, for example.

The processing unit 12 receives the stream reproduction content data input from the cache control unit 18, decodes it, and displays an image corresponding to the stream reproduction data on the display 10.
For example, the processing unit 12 decodes the moving image encoded data input from the cache control unit 18 and outputs the decoded moving image data to the display 10.
Further, when acquiring the still image data for the thumbnail image, the processing unit 12 outputs a thumbnail still image acquisition command to the command analysis unit 16.

  The cache 14 stores data that the cache control unit 18 determines to save. Further, when information is requested from the cache control unit 18, it is read out and output to the cache control unit 18. The cache 14 stores data in, for example, a semiconductor memory, an optical recording medium, a magneto-optical recording medium, or the like.

The instruction analysis unit 16 analyzes an instruction input from the processing unit 12 or the external instruction input unit 22 and outputs information to the cache control unit 18.
The cache control unit 18 analyzes the data received by the communication unit 20 and writes the data to the cache 14 if it is determined that the data needs to be written to the cache 14.
Specifically, the cache control unit 18 analyzes to which classification shown in FIG. 2 the data received by the communication unit 20 belongs, and determines whether to write to the cache 14 based on the analysis result. .
The classification shown in FIG. 2 is an example, and the present invention is not limited to this.
Class 1 shown in FIG. 2 is a category of data to be written to the cache 14. The classification 2 is a category of data to be output to the processing unit 12 (processing system) although it is not necessary to write in the cache 14. The classification 3 is a category of data that does not belong to the classification 1 and the classification 2 and is neither written to the cache 14 nor output to the processing unit 12.

  For example, the cache control unit 18 analyzes the data received by the communication unit 20 and writes it to the cache 14 when it is determined that it belongs to the category 1 shown in FIG. The data is output to the unit 12 and discarded otherwise.

  In addition, when data to be output to the processing unit 12 is input during stream reproduction or the like, the cache control unit 18 outputs the data to the processing unit 12.

  The client device 4 performs processing according to the command input from the external command input unit 22 and analyzed by the command analysis unit 16, and uses the information held in the cache 14 as necessary, to create a client request creation unit The command information is output to 24. These processes will be described in detail later.

The communication unit 20 outputs the data input from the server device 3 to the cache control unit 18. In addition, the communication unit 20 outputs the information input from the client request creation unit 24 to the server device 3. The communication unit 20 also performs communication protocol conversion with the server device 3.
The external command input unit 22 receives a command according to the operation of the operation unit such as a user, and outputs the command to the command analysis unit 16. In the present embodiment, a person who issues a command is a person, but the present invention is not limited to this.
The client request creation unit 24 creates information requested by the client using the information output from the cache control unit 18, and outputs the created information to the communication unit 20.

Hereinafter, an operation example of the client device 4 illustrated in FIG. 1 will be described.
[Operation example when command is input]
Hereinafter, an operation example when a command is input from the external command input unit 22 shown in FIG. 1 will be described.
FIG. 3 is a flowchart for explaining the operation example.

  For example, the client device 4 receives list data indicating content data held in advance by the server device 3 from the server device 3 and stores the list data in the cache 14.

For example, if the external command input unit 22 determines that a command corresponding to the operation of the operation unit by the user has been input, the external command input unit 22 outputs the command to the command analysis unit 16 (step ST11).
The instruction analysis unit 16 analyzes the instruction input from the external instruction input unit 22, and determines whether or not the attribute data and list data stored in the cache 14 are required for execution of the instruction (step ST12). .
Specifically, the instruction analysis unit 16 requires attribute data stored in the cache 14 when the instruction is related to content acquisition, server switching, special playback during content playback, and the like as a result of the analysis. In other cases, it is determined that it is unnecessary.
The command analysis unit 16 outputs the command to the client request creation unit 24.

When the instruction analysis unit 16 determines that the attribute data stored in the cache 14 is necessary, the instruction analysis unit 16 causes the cache control unit 18 to read the attribute data or the like from the cache 14 and causes the client request creation unit 24 to read the attribute data. Output (step ST14).
For example, when the user inputs a command indicating a still image reproduction request, the command analysis unit 16 transmits attribute data defining the link destination, resolution, and the like of the corresponding still image held in the cache 14 to the cache control unit 18. To read.

  The client request creation unit 24 generates a client request signal based on the command input from the command analysis unit 16 (step ST15). The client request signal includes at least information for specifying the content data requested by the instruction and information for specifying the server device 3 that provides the content data.

  The client request creation unit 24 transmits the generated client request signal to the server device 3 via the communication unit 20 (step ST16).

[Operation example when the communication unit 20 inputs data]
Hereinafter, an operation example when the communication unit 20 illustrated in FIG. 1 inputs data from the server device 3 will be described.
FIG. 4 is a flowchart for explaining the operation example.

  The cache control unit 18 determines whether or not the communication unit 20 has received data via the network. If the cache control unit 18 determines that the data has been received, the process proceeds to step ST22 (step ST21).

  The cache control unit 18 analyzes the data received by the communication unit 20 (step ST22). In the analysis, as described above, the cache control unit 18 determines whether the received data belongs to the classifications 1, 2, and 3 shown in FIG.

When the cache control unit 18 determines that the data received by the communication unit 20 belongs to the classification 1 (when it is determined to write to the cache 14), the cache control unit 18 proceeds to step ST26.
On the other hand, if the cache control unit 18 determines that the data received by the communication unit 20 belongs to the category 2, the process proceeds to step ST24 (step ST23).

When the cache control unit 18 determines that the data received by the communication unit 20 belongs to the category 2, the cache control unit 18 outputs the data input from the communication unit 20 to the processing unit 12. And the process part 12 carries out the stream reproduction | regeneration of the said input data (content data) (step ST24).
Then, the processing unit 12 outputs the reproduction data to the display 10 and displays it (step ST25).

  On the other hand, when the cache control unit 18 determines that the data received by the communication unit 20 belongs to the classification 1, the cache control unit 18 determines whether or not the free capacity of the storage capacity of the cache 14 is equal to or greater than a predetermined threshold value. (Step ST26).

  When the cache control unit 18 determines that the free capacity of the cache 14 is equal to or greater than a predetermined threshold value, the cache control unit 18 writes the data received by the communication unit 20 into the cache 14 as it is (step ST27).

On the other hand, when the cache control unit 18 determines that the free capacity of the cache 14 is not equal to or greater than a predetermined threshold, for example, the data received by the communication unit 20 is compared with the data already stored in the cache 14. Then, it is determined whether or not the setting data specified in advance is close to the setting (step ST28).
When the cache control unit 18 determines “close” in step ST28, the cache unit 18 updates (overwrites) the data stored in the cache 14 for the content with the data received by the communication unit 20 (step ST29).
On the other hand, if the cache control unit 18 does not determine “close” in step ST28, the cache control unit 18 discards the data received by the communication unit 20.

The operation shown in FIG. 4 will be described below with a specific example.
Assume that the number of caches storing multi-resource information of a certain still image content is two and the following conditions are satisfied.
(Condition 1): A cache for content that is displayed largely on a display device, and the setting is content with an image size of 1920 × 1080.
(Condition 2): It is a cache for thumbnail images, and the setting is that the image size is 200 × 100.
The cache 14 holds information A having an image size of 4000 × 4000 and information B having a size of 500 × 500.

When new information C having an image size of 2000 × 2000 is input under the above-described conditions, the display 10 compares the input information C with the information A in accordance with the condition 1 in step ST28. Since the content is requested to have a size close to 1920 × 1080, it is determined that the information C is more suitable than the information A.
Then, the cache control unit 18 overwrites the information C in the area where the information A of the cache 14 is stored.
If information D with an image size of 1000 × 1000 is input, it does not match condition 1 and condition 2, so it is determined in step ST28 that the cache 14 need not be updated, and the process ends.

  In the above-described example, the client device 4 acquires information close to the request for the image size 1920 × 1080. However, for example, when the client device 4 can resize the image size to high quality, High-quality information may be stored.

  As described above, in the server / client system 1, even when the client apparatus 4 is an electronic device having a relatively small memory capacity such as a digital television, the server apparatus 3 holds a large number of multi-resource information. Since information close to the information requested by the client device 4 can be efficiently written in the cache 14, the amount of memory used can be reduced as compared with the prior art.

  Further, in the client device 4, when the attribute data related to the image displayed on the display 10 by the processing of the processing unit 12 is held, for example, when displaying a plurality of small images on the display 10 such as thumbnail images, the original information If the file size is large, it takes time for processing. However, based on the attribute data, the small image size data for the thumbnail is received and written in the cache 14. And the client apparatus 4 can shorten the time which thumbnail acquisition requires by using the data of the said small image size.

  The same applies when acquiring information via a network, and information optimized for each processing system can be acquired, thereby reducing the load on the network.

The present invention is not limited to the embodiment described above.
That is, those skilled in the art may make various modifications, combinations, subcombinations, and alternatives regarding the components of the above-described embodiments within the technical scope of the present invention or an equivalent scope thereof.
In the above-described embodiment, information for display devices and thumbnails is held. However, for example, when an image is to be printed by a printer connected to a network via the client apparatus 4, information of the highest image quality is used. For example, the number of caches and setting items may be set according to the processing system.

In the above-described embodiment, the description has been given taking still image information as an example. However, moving image information, music information, information on the server device 3 and the like may be used.
In the above-described embodiment, the setting of information required by the client device 4 is set in advance, but the user may set it using the external command input unit 22.
Further, as shown in FIG. 5, the network monitoring unit 30 monitors the communication of the communication unit 20, and determines that the network bandwidth is narrowed, for example, when the amount of data input decreases, The cache 14 is set to a small resolution so that data can be exchanged smoothly.

  The present invention can be applied to a system in which a server transmits content data having a plurality of resolutions to a client.

It is a block diagram of the server client system which concerns on embodiment of this invention. It is a figure for demonstrating the classification | category used for the write operation etc. of the received data in the cache control part shown in FIG. It is a flowchart for demonstrating the operation example when a command is input from the external command input part shown in FIG. It is a flowchart for demonstrating the operation example when the communication part shown in FIG. 1 inputs data from a server apparatus. It is a figure for demonstrating the modification of the server client system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 '... Server client system 3 ... Server apparatus 4 ... Client apparatus 10 ... Display 12 ... Processing part 14 ... Cache 16 ... Instruction analysis part 18 ... Cache control part 20 ... Communication part 22 ... External instruction input part 24 ... Client Request creation unit 30 ... Network monitoring unit

Claims (4)

A client device that receives the content data from a server device that provides a plurality of content data with different resolutions for the same content,
Communication means for communicating with the server device;
A memory for storing content data;
Playback means for playing back the content data;
Based on the setting data set in advance for the resolution of the content data to be played back by the playback means, a part of the content data provided by the server device is requested to the server device. Control means for performing a process of acquiring and writing the acquired content data to the memory,
The control means includes
Writing each attribute data indicating the attribute of the server device and the attributes of the plurality of content data received by the communication means into the memory;
Requesting the server device for a part of the plurality of content data based on the attribute data,
If the memory has a free space equal to or greater than a predetermined threshold, the content data received by the communication means is written to the memory,
If the memory has no free space equal to or greater than the threshold, the resolution of the content data received by the communication means is greater than the resolution of the content data already stored in the memory. A client device that overwrites the content data stored in the memory with the content data received by the communication means on condition that the resolution is close to the indicated resolution. The client according to claim 1, wherein the control unit selects and writes the content data having the highest resolution and the content data having the lowest resolution among the plurality of content data provided by the server device to the memory. apparatus. The server apparatus provides the content data from a server apparatus that provides a plurality of pieces of content data having different resolutions for the same content, and is provided by the server apparatus based on setting data set in advance for the resolution of the content data to be reproduced by a reproduction unit A part of the plurality of content data to be requested is acquired by requesting the server device, and the playback unit that performs processing for writing the acquired content data to the memory and the client device including the memory are executed. A data processing method for
A first step of writing each attribute data indicating the received attribute of the server device and the plurality of content data into the memory;
A second step of requesting the server device for a part of the plurality of content data based on the attribute data;
A third step of writing the content data received by the communication means to the memory when there is free space equal to or greater than a predetermined threshold in the memory;
If the memory has no free space equal to or greater than the threshold, the resolution of the content data received by the communication means is greater than the resolution of the content data already stored in the memory. And a fourth step of overwriting the content data stored in the memory with the content data received by the communication means on condition that the resolution is close to the resolution shown. The server apparatus provides the content data from a server apparatus that provides a plurality of pieces of content data having different resolutions for the same content, and is provided by the server apparatus based on setting data set in advance for the resolution of the content data to be reproduced by a reproduction unit A part of the plurality of content data to be requested is acquired by requesting the server device, and the playback unit that performs processing for writing the acquired content data to the memory and the client device including the memory are executed. A program to
A first procedure for writing each attribute data indicating the received attribute of the server device and the attributes of the plurality of content data to the memory;
A second procedure for requesting a part of the plurality of content data to the server device based on the attribute data;
A third procedure for writing the content data received by the communication means to the memory when there is a free space equal to or greater than a predetermined threshold in the memory;
If the memory has no free space equal to or greater than the threshold, the resolution of the content data received by the communication means is greater than the resolution of the content data already stored in the memory. A program that causes the client device to execute a fourth procedure of overwriting the content data stored in the memory with the content data received by the communication unit on condition that the resolution is close to the resolution shown.