JP4707478B2 - Terminal device, content distribution system, content distribution method and program - Google Patents

Description

  The present invention relates to a content distribution system and method for distributing stream data, a terminal device that receives distribution in the system, and a program for executing processing for distributing the content.

  A terminal such as a mobile phone having a communication function can freely communicate with other terminals and servers while in an environment where communication is possible. For example, in the case of a mobile phone terminal, this is the case when it is within a range where radio waves from the base station can reach.

  In recent years, mobile phone terminals are not limited to simple communication functions, and have come to support a wide range of content reproduction such as music and moving images. On the other hand, contents such as music and moving images tend to have a relatively large amount of data. However, from the viewpoint of emphasizing portability or cost of a terminal, it is not a good idea to provide a terminal with a very large storage capacity. Therefore, in the past, we have been reluctant to limit the specifications of products so that the storage capacity is kept within a reasonable range while considering the balance with cost, and no more content can be stored.

  One idea is to delete infrequently used content from the storage and download the content again from the server as needed to allow storage of large amounts of content while reducing storage capacity. It can be corrected. This can be said to be a technique that takes advantage of the above-mentioned characteristics of the terminal “having a communication function”. However, in this case, the user is connected to the server, and the user waits until at least the top part of the content is taken out from the server and can be played back. This waiting time is expected to be a length that cannot be ignored in practice, and as a result, the user's comfortable viewing experience is impaired.

  Furthermore, in the case of a portable device that uses wireless communication, there is a possibility that the device may go out of a communicable environment during downloading again. Even if it is wired, it cannot be said that sufficient communication bandwidth cannot be secured depending on the traffic congestion. In these cases, although depending on the length of time during which communication is disabled, playback is interrupted in the worst case. In particular, when an operation of deleting content that is not frequently used is automatically performed inside the terminal, it is difficult for the user to distinguish between content that may be interrupted and content that is not. Sudden interruption of playback in such a situation is a source of greatly increasing distrust and discomfort for the user's equipment and services, and is unacceptable.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses disclosure of stream data processing from the viewpoint of aiming to reduce storage capacity. That is, when deleting stream data, it is possible to guarantee at least a certain continuity in video content by deleting the stream data from the content to be deleted by the cache server in units of a certain block. There is a description that a required content can be appropriately distributed under reliable management even for a distribution request, and a minimum distribution service can be provided. Further, in Patent Document 1, when access to a content server in response to a distribution request from a user is impossible, stream data deleted for each predetermined block unit from content stored in a cache server is distributed by fast-forward playback. There is a description about making it possible to image in a natural state.

Patent Document 1 discloses a technique for issuing a warning when it is detected that a signal from a terminal cannot be correctly received by a base station.
JP 2001-313919 A

  However, in the process described in Patent Document 1, content in the deleted state is played back fast-forwarded, and it must be said that the comfortable viewing experience is still impaired. Also, considering the fact that content is often played from the beginning of normal content, the stream data is deleted for every fixed block, conversely, the data remains uniformly for every fixed block throughout the content. That is not very efficient.

  The present invention has been made in view of such a point, and an object thereof is to enable efficient accumulation of distributed content in a terminal device.

In the present invention, when stream data as content data is distributed from a server to a terminal device, stored in the terminal device, and the stored stream data is played back, the terminal device is at least a start portion of the stream data. When data is stored in a predetermined data format and the stored stream data is reproduced, the stream data of the section following the stream data in the predetermined data format is downloaded from the server and stored, and the data of the start portion It is made to reproduce following. In this case, at least the start part of the stream data stored by the terminal device is stored in the data format at the time of download, and the parts other than the start part are stored in the data format compressed at a higher compression rate than the start part. When the data other than the start portion cannot be downloaded, the data stored in the terminal device after being compressed at a higher compression rate than the start portion is reproduced as data other than the start portion.

  By doing so, the amount of stream data stored in the terminal device can be reduced, and at the time of reproducing the stream data, all sections can be reproduced.

  According to the present invention, it is possible to reduce the amount of stream data stored in the terminal device, and it is possible to reproduce all sections when reproducing the stream data. For example, when the stream data of all sections is accumulated after compression, reproduction with minimum quality can be ensured even when downloading from the server is not possible. In addition, when trial listening data and head portion data are accumulated, the head portion stream data can be reproduced after the purchase procedure, and the reproduction after the purchase procedure can be quickly performed.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a system configuration example of this example. In the configuration example of FIG. 1, as a terminal device 110 on the user side, a communication unit 111 for communicating with a content server device or the like via the communication network 100, a content encoding unit 112, and a content decoding unit 113 are decoded. A content playback unit 114 for presenting content to the user, a storage device 115 for storing content and the like, a control unit 116 for controlling the entire system, and the like are provided. As the terminal device 110, for example, a mobile phone terminal is applicable.

  Further, a content server device 101 capable of providing content to the user terminal device 110 is connected to the communication network 100. However, the system configuration is not fixed to this example. For example, the storage device 115 may exist on another server or user side terminal via the communication network 100. Alternatively, the content encoding unit 112 may not be provided, and if it is necessary to re-encode the content, another server or a user-side terminal may be requested to perform re-encoding via the communication network 100. Further, it does not deny the existence of a device not shown in FIG. 1, such as a cache server for caching content.

  The control unit 116 provided in the terminal device 110 is configured to execute processing based on a flowchart described later, but is necessary for operating the entire terminal device 110 and the entire system without delay in addition to the processing described in the flowchart. Control. As an actual implementation configuration of the control unit 116, it may be possible to use a system including a so-called CPU, RAM, ROM, etc., but the configuration is not limited to such a configuration.

  The content encoding unit 112 is used, for example, when the content once decoded by the content decoding unit 113 is re-encoded. For this reason, it is desirable that the encoding unit 112 and the decoding unit 113 are connected so that the content decoded by the decoding unit 113 can be smoothly encoded.

  The communication unit 111 is a processing unit that enables communication with the content server apparatus 101 and the like through the communication network 100, but does not specifically ask a specific communication method such as wireless or wired communication. For example, when applied to a mobile phone terminal, it corresponds to a communication processing unit for a wireless phone. As the communication network 100, for example, the Internet accessed via a wireless telephone line is applicable.

  For example, when the content is music data, the content playback unit 114 included in the terminal device 110 includes a configuration for music playback (such as an audio output unit). When the content is video data, the content playback unit 114 is for video playback. (Including a display unit).

  As the storage device 115 provided in the terminal device 110, various storage means such as a hard disk drive device and a memory card can be applied, and stream data that is content data to be described later is accumulated. Here, music data and video data are mainly assumed as content data.

  Next, the data state at the time of distribution of the content data performed in the system shown in FIG. 1 and the storage of the distributed content data will be described with reference to FIG.

  FIG. 2 shows the concept of processing performed in one of the examples. The original content 201 shown in FIG. 2A is stream data prepared on the content server apparatus 101 side. This stream data is distributed to the terminal device 110 via the communication network. At the time of distribution, the data is basically distributed as it is and stored in the storage device 115 on the terminal device 110 side. The original content 201 shown in FIG. 2A is data in which the average data amount 204 is almost constant from the content start position 205 to the content end position 206.

  Here, the process of replacing the original content 201 with the data-reduced content 202 is performed in the terminal device 110 at an appropriate timing, such as when the available free space in the storage device 115 decreases below a predetermined amount. Done in the process. FIG. 2B shows the content 202 with the data amount reduced. As shown in FIG. 2B, the beginning portion 207 of the predetermined period from the content beginning position 205 is the data amount as the original content, and the data amount is compressed for other sections to reduce the data amount. A reduced data amount reduction portion 209 is provided. However, the important part 210 of the content data other than the head part may not be compressed.

  The configuration of the data amount reduction portion 209 will be described. The quasi-head portion 208 of the predetermined period following the head portion 207 is a section in which the data amount is reduced by slightly compressing data. Further, in the section following the quasi-head portion 208, there is a data amount gradually decreasing portion 209 in which the compression ratio is increased in order for each predetermined period, and the remaining sections are data compressed at the highest compression ratio. In this example, the portion following the important portion 210 is a data section compressed at the highest compression rate. However, the compression rate may be gradually increased as in the section following the head portion.

  When the content compressed and stored in this way is reproduced, only the data in the compressed section is distributed again from the content server device 101 and stored in the content complementing buffer. FIG. 2C shows the data 203 stored in the content complement buffer. This data 203 is composed only of the section of the data amount reduction portion 209 of the data amount reduced content 202 shown in FIG. 2B, and the data amount of each section is the original content data 201 that is not compressed. Is the same.

  As the content supplement data 203 received from the server apparatus 101 as described above, the data of the data amount reduced portion 209 of the data amount reduced content 202 shown in FIG. 2B and the data shown in FIG. The original content data 201 shown in FIG. 2A may be restored by arithmetic processing in the terminal device 110 as difference data from the content complement data 203.

  By processing in this way, the amount of content data stored in the storage device 115 of the terminal device 110 can be reduced, and the available capacity of the storage device 106 can be increased. The timing of performing the process of obtaining the data amount reduced content 202 shown in FIG. 2B from the original content data 201 shown in FIG. 2A is based on the remaining storage capacity of the storage device 115 and the like. In addition to the automatic determination by the control unit 116 of the apparatus 110, an instruction may be given by a user operation.

  When the content 202 with the reduced data amount is reproduced, it is reproduced while downloading a necessary part from the server to the content complement buffer 203. At this time, the data amount reduction content 202 and the content complementing buffer 203 are used properly so that the reproduction is not interrupted as much as possible and the reproduction quality is kept as high as possible. Furthermore, after the download is completed, the original content 201 can be restored from the content of the data amount reduced content 202 and the content complement buffer 203 as necessary. If the download cannot be sufficiently performed for some reason, it is possible to ensure the minimum reproduction quality by mainly using the content 202 with the data amount reduced for reproduction.

  Note that FIG. 2 is for explaining the concept of processing, and does not limit the technical details of the present invention. For example, in FIG. 2, it can be seen that the average data amount of the original content 201 is aligned with a constant value of the original average data amount 204 over the entire range of the content. However, in reality, the original content 201 is not intended to exclude the possibility of adopting a method in which the amount of data changes as needed, such as some kind of variable bit rate coding (VBR). Here, it is only trying to explain that the data amount of content can be reduced by comparing the original content 201 and the content 202 with reduced data amount.

  Next, an example of processing for generating the data amount reduced content 202 from the original content 201 will be described using the flowchart of FIG. When the data amount-reduced content generation process is started (step 301), content that is the target of data amount reduction is detected in step 302. As for how to select the target content, in addition to selecting the content that is not used frequently, the content that has the oldest last use date, the data that is relatively large, the content that is relatively cheap, For a genre with a small number of playlists containing the content, content or a low importance parameter preset for the content, direct or indirect designation by the user, or a low frequency of use Various selection methods are included, such as contents that belong to the contents, contents created date and time, and contents whose value is impaired when they become old, such as news. There are many variations, such as any combination of the above examples.

  This process is performed until the original content 201 that is the target of the data amount reduction is specified (step 303). If it can be specified, the process of creating the content 202 with the data amount actually reduced is entered from step 304. In this flowchart, a data amount reduced content 202 generation area is secured separately from the original content 201 and the data amount reduced content is sequentially generated. In the final step 310, the original content 201 on the storage is deleted. Then, although the procedure of replacing with the data amount reduced content 202 is taken, it is not necessarily limited to this procedure.

  First, in step 304, the target value of the total data amount in the entire data amount reduced content 202 after the data reduction processing is calculated. The target value of the total data amount is calculated based on the total data capacity of the original content 201, the remaining capacity of the storage device 106, and the like. It is also possible to adjust the target value using the parameters used when detecting. For example, if the content usage frequency is very low, setting the target value to a small value will significantly reduce the total data amount, while if the content usage frequency is relatively high, increase the total data amount target value. It is possible to apply such as setting to. When the target value is calculated, a processing part is set in step 305.

  In step 306, referring to the target value of the total data amount calculated in 304, the data amount allocated to each processing portion of the content is calculated. This allocation is adjusted based on various factors such as the position in the content and the content.

  For example, a relatively high average data amount, specifically, the same value as the original average data amount 204 can be assigned to the content start portion 207. As will be described later in the section on the reproduction process, when reproducing the data amount-reduced content 202, the content complementing portion 212 corresponding to the data amount reducing portion 211 is downloaded from the content server apparatus 101 through the communication network 100. At this time, depending on the characteristics of the communication network 100 and the content server device 101, a certain amount of response time is required until a necessary amount of data is downloaded. By playing back the start portion 207 during this response time, it is possible to configure the system so that the user does not wait until playback starts and playback is not interrupted during continuous playback of a plurality of contents. Here, by setting the average data amount of the start portion 207 to be large, the reproduction quality at the time of starting the content reproduction is ensured, and the content data is transferred to the user by shifting to the reproduction of the content complementing portion 212 without interruption. It is possible to reproduce the content with almost no awareness of the reduced amount. Considering that the start portion 207 has such an application, it is desirable that the length of the start portion 207 is set longer than the average worst download response time of the communication network 100 and the content server device 101.

  As described with reference to FIG. 2, a quasi-starting portion 208 may be provided following the content starting portion 207. Although the response time may be longer than usual depending on the degree of congestion of the communication network 100 or the content server device, it is intended to maintain a certain or higher reproduction quality in that case.

  In general, if the average amount of data is greatly reduced at one time during playback, the playback quality can be drastically deteriorated, causing the user to feel a great sense of discomfort. It can be considered that the reproduction quality is gradually deteriorated by reducing the average data amount stepwise as in the data amount gradually decreasing portion 209, thereby reducing the user's uncomfortable feeling.

  Note that the content start portion 207 is not limited to one location for one content. Accordingly, the semi-starting portion 208, the data amount gradually decreasing portion 209, and the like are not limited to one place.

  Furthermore, it is conceivable to assign a relatively high average amount of data to one or more important parts 210 in the content. The important part 210 of the content is, for example, a chorus part for music, a scene that is important in the structure of the content for a movie, or a part that has a large effect on quality if the amount of data is reduced due to human audiovisual characteristics. Compared to other parts, the average data volume should be avoided to some extent. Whether or not it is an important part 210 may be designated in advance by content sub-information, etc., may be designated directly or indirectly by the user, information on the content itself, for example, sound pressure of the content, It can also be derived from information such as frequency distribution, screen complexity, and motion magnitude by some kind of algorithm.

  A relatively low average data amount is assigned to other parts in the content other than those described above. If the communication network 100 and the content server apparatus 101 are sufficiently stable, the average data amount can be set to 0, that is, data for other portions can be completely deleted.

  Returning to the description of the flowchart in FIG. 3, in step 307, each part of the content 202 whose data amount has been reduced is generated so that the target average data amount for each part calculated in step 306 is obtained. As one of the data amount reduction processing methods, there is a method in which the content decoding unit 103 once decodes and then the content encoding unit 102 performs encoding again. In this case, in order to bring the average data amount closer to the target average data amount, in addition to adjusting parameters such as the compression rate at the time of encoding, a method that modifies the content itself, for example, reducing the resolution and frame rate of the video, audio Various methods are conceivable, such as reducing the sampling frequency and the number of channels.

  It is also conceivable to employ another encoding method with high compression efficiency during re-encoding. This is effective, for example, when the required power consumption is large but an encoding method with higher compression efficiency is available. Note that the data amount reduction processing described here is not limited to re-encoding. For example, although there is a possibility that the average data amount can be reduced without decoding and re-encoding once depending on the content encoding method, the description here does not exclude such possibility. When processing of one section is completed in step 307, the next processing portion is set in step 308.

  Then, in step 309, it is determined whether or not the data amount reduction process has been completed. If it has not been completed, the process returns to step 306 to process the next section. If it is determined in step 309 that the processing has been completed, processing for replacing the original content 201 with the data amount-reduced content 202 is performed in step 310, and the processing for one content is completed. Note that, as shown in the flowchart, the above processing can be repeatedly performed until a sufficient free space in the storage device 106 is secured.

  Next, an example of the reproduction processing of the data amount reduced content 202 in the terminal device 110 will be described using the flowchart of FIG. When the reproduction process is started (step 401), the content complementing process is started in step 402. The content complementing process is, for example, a process expressed in a flowchart of FIG. 5 described later, and the content complementing part 212 corresponding to the data amount reducing part 211 is downloaded from the content server apparatus 101 through the communication unit 111 and the communication network 100. Is. Details will be explained in the next section. Here, it is assumed that the content complementing process operates in the background in parallel with the playback process.

  After starting the complementary processing, in step 403, the content reproduction is started from an appropriate start portion of the data amount reduced content 202. Thereafter, the reproduction is continued until it is determined in step 404 or step 408 that the content has been reproduced to the end position. Although not shown in the flowchart of FIG. 4, it is naturally possible to interrupt the reproduction even during the content reproduction by the user's operation.

  In step 405, it is determined whether or not the data amount reduced portion 211 has been reached as a result of proceeding with the reproduction of the data amount reduced content 202. If the data amount reduction portion 211 has not been reached, the reproduction of the content 202 with the data amount reduced is continued.

  If the data amount reduction portion 211 has been reached, it is determined in step 406 whether or not a complement portion corresponding to the data amount reduction portion has been downloaded to the supplement content portion 212 in the content complement buffer 203. If the content complementing process started in step 402 is delayed for some reason, for example, when outside the environment where communication to the communication network 100 is possible, the supplementary part may not be downloaded yet. In that case, the reproduction of the content 202 with the reduced data amount is continued.

  On the other hand, if the content complementing process is executed without delay and the supplementary part has already been downloaded in the content complementing buffer 203, the process proceeds to step 407, and the reproduction is continued by switching to the supplemental part. Thereafter, the supplemental content portion 212 is preferentially reproduced as long as the supplemental content continues, but there is a possibility that a location where the supplemental content does not exist will be reached. For example, when the data amount reduction part 211 such as the important part 210 is reached, the content complementing process is delayed due to a change in the communication environment. For this reason, in step 409, it is confirmed whether or not the supplementary content continues to exist from the current reproduction position. If it does not exist, switching to content reproduction with reduced data amount is performed in step 410. When step 410 is switched, the process returns to step 404.

  Next, an example of content complement processing will be described using the flowchart of FIG. When the supplement processing is started in step 501, connection to the content server apparatus 101 is performed in step 502, and when the connection is completed, download of the content supplement portion 212 is started in step 503. At this time, referring to the current reproduction position in the reproduction process, the download is performed from the place where the reproduction is most likely to be performed next. For example, when the reproduction process is started from the middle of the data-reduced content 202 in accordance with a user instruction or the like, it is conceivable that the download is performed from the position where the response delay time is added to the current reproduction position. The response delay time referred to here is caused by the characteristics and the degree of congestion of the communication network 100 and the content server device 101, and the data is actually transmitted after a download request is issued from the communication unit 111 to the content server device 101. It can be calculated based on the time until the receipt of.

  In step 504, it is determined whether or not the downloading of the content complement portion 212 has been completed. Although not described in the flowchart of FIG. 5, when all of the supplemental content has been downloaded, the content corresponding to the original content 201 is restored by combining the content of the data amount reduced content 202 and the content complement buffer 203. Processing can be performed. Even if all of the supplementary content is not downloaded, it is possible to replace a part of the data amount reduction part 211 with the corresponding content supplement part 212 as necessary.

  Downloading continues while content download is not complete, but downloads are delayed due to changes in the communication environment, and the playback has overtaken the part that is about to be downloaded, or the user has changed the playback position in the middle Due to various factors, the location where the download is currently being made may not necessarily be optimal. If it is determined in step 505 that the part to be downloaded is not optimal, the process proceeds to step 506, and the download position can be adjusted by reissuing the request to the content server apparatus 101.

By performing the processing according to this embodiment as described above, the following effects are obtained.
1. By reducing the amount of data in the latter half of content that is less frequently used, the storage device can be used more efficiently.
2. By leaving the data at the beginning of the content with an appropriate quality, even if the amount of data is reduced, it is possible to perform playback without interruption so as not to make the user aware of it.
3. Even when the communication environment is not good, reproduction with the minimum quality can be continued.
4). Even in a situation where the communication environment is fluctuating, it is possible to perform reproduction with the best possible quality.
5. Even content whose data amount has been reduced can be efficiently restored at the same time as the reproduction process.

  In the above-described embodiment, the processing regarding the restriction on the reproduction of the content downloaded from the server has not been particularly described. For example, first, data for trial listening from the server or the like (data of only a part of the content) May be downloaded to the terminal device and all data may be downloaded by performing a purchase procedure after listening to the data.

  FIG. 6 is a diagram showing an example of sample content. First, the trial listening content 600 is stored in the storage device 106 by some processing. In this case, various processes other than downloading through the communication network 100 may be considered, such as transferring from an external storage device such as a memory card to the storage device 106, but details are not mentioned here. . In addition, although it is called “trial listening” content here, it is not limited to content to be listened to such as music, but naturally includes content having visual effects such as moving images.

  The audition content 600 includes a start part 601, a header part 602, an audition part 603, and a trailer part 604. Note that it is not necessary for the sample content to include all of these parts. For example, a configuration in which the trailer part 604 is not provided or a structure in which the sample part 603 does not exist is conceivable. As for the other parts, the contents with the data amount reduced may be stored as shown in the data amount reduced content 202. However, in FIG. It describes 0, that is, a case where it is completely deleted. Further, the header portion 602 and the trailer portion 604 do not necessarily have the same average data amount as the original average data amount 606.

  When the trial listening content 600 is auditioned, playback starts from the header portion 602, and ends when playback of the trailer portion 604 is completed. When the purchase procedure is not performed, the start portion is restricted so that it cannot be reproduced. If the user decides to purchase the audition content 600, it can be reproduced from the start portion 601 after appropriate settlement processing or the like is performed.

  Playback from the start portion 601 is executed in the same procedure as the playback processing and content complementing processing described in FIGS. As a result, the user can start the playback of the purchased content without waiting time, and if the content complementing process proceeds smoothly, the user can continue to play the content without interruption even after the start portion 601 has been played back. Can do. However, the header portion 602 and the trailer portion 604 of the sample content 600 may be different from the original content. Such a portion different from the original content is identified as a download-necessary portion 605 and is replaced by the content complement portion 212 downloaded from the content server device.

  By preparing trial listening content in this way, it is possible to start playback of the content immediately without waiting time if the purchase processing is performed after the trial listening content having a relatively small data capacity. Further, even after the purchase procedure is performed, the amount of data communication after the content purchase can be reduced by reusing part of the sample content.

  In the embodiment described so far, a case has been described in which a device such as a mobile phone terminal is mainly assumed as a terminal device, but the present invention can be applied to other terminal devices capable of data transfer with other servers. For example, a program for performing the processing of the present invention may be installed in a personal computer device to function as a similar terminal device. About a program, you may make it deliver using transmission means, such as the internet, besides memorize | storing and distributing on various media.

It is a block diagram which shows the system configuration example by one embodiment of this invention. It is explanatory drawing which shows the example of a data structure by one embodiment of this invention. It is the flowchart which showed the example of the data amount reduction process by one embodiment of this invention. It is the flowchart which showed the example of the reproduction | regeneration processing by one embodiment of this invention. It is a flowchart which shows the example of a content complementation process by one embodiment of this invention. It is explanatory drawing which shows the example of the trial listening content by one embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Communication network, 101 ... Content server, 110 ... Terminal device, 111 ... Communication part, 112 ... Content encoding part, 113 ... Content decoding part, 114 ... Content reproduction part, 115 ... Storage apparatus, 116 ... Control part

Claims (12)

In a terminal device that downloads and stores stream data as content data,
An accumulation unit for accumulating at least a start portion of the stream data in a predetermined data format;
A reproduction unit for reproducing the stream data accumulated in the accumulation unit;
A controller that downloads stream data of a section other than stream data in a predetermined data format from a server, stores the data in the storage unit, and continuously plays back the already stored data when the playback unit performs playback; Bei to give a,
The stream data accumulated by the accumulation unit is accumulated at least in the data format at the time of download, and other parts than the start part are accumulated in a data format compressed at a higher compression rate than the start part, A terminal device configured to reproduce data stored in the storage unit after being compressed at a higher compression rate than the start part as data other than the start part when downloading other than the start part is not possible . The terminal device according to claim 1 ,
The data accumulated by compressing at a higher compression rate than the starting portion is obtained by compressing a part of the stream data accumulated in the accumulation unit when the remaining storage capacity of the accumulation unit reaches a predetermined state. the generated to Ru terminal equipment. The terminal device according to claim 1 ,
A terminal apparatus in which a data format obtained by compressing a portion other than the start portion with a higher compression rate than the start portion is configured to increase the compression rate in a plurality of stages as the distance from the start portion increases. The terminal device according to claim 1,
The terminal device in which accumulation in the accumulation unit in the predetermined data format is also made to accumulate important parts other than the start part. The terminal device according to claim 1,
A terminal device that downloads only data that is different from the compressed and accumulated data when downloading other than the start portion. The terminal device according to claim 1,
The stream data stored by the storage unit is stored in a downloaded data format with at least a start part and a trial-listenable part, and only the playback of the data in the trial part is allowed until the purchase processing of the stream data is completed. ,
The purchase when the process is completed, the terminal device you data stored the start of the renewable. The terminal device according to claim 6 ,
A terminal device that downloads the remaining stream data not accumulated in the accumulation unit when the purchase process is completed. In a content distribution system that distributes stream data as content data from a server to a terminal device, stores the stream data in the terminal device, and reproduces the stored stream data.
The terminal device includes an accumulation unit that accumulates data of at least a start portion of the stream data in a predetermined data format;
A reproduction unit for reproducing the stream data accumulated in the accumulation unit;
A control unit that, when reproduced by the reproducing unit, downloads stream data of a section following stream data of a predetermined data format from the server, accumulates it in the accumulating unit, and reproduces the data following the start portion And
The stream data accumulated by the accumulation unit is accumulated at least in the data format at the time of download, and other parts than the start part are accumulated in a data format compressed at a higher compression rate than the start part, When the data other than the start part cannot be downloaded, the data stored in the storage unit after being compressed at a higher compression rate than the start part is played back by the playback unit as data other than the start part. Content distribution system. The content distribution system according to claim 8 , wherein
The stream data distributed from the server and accumulated in the accumulation unit of the terminal device is at least the data of the start part and the auditionable part, and the reproduction of the data of the audition part is completed until the purchase processing of the stream data is completed. Only to allow the terminal device,
When said purchase processing is completed, the content distribution system that the data stored the start of the renewable. The content distribution system according to claim 9 , wherein
A content delivery system in which, when the purchase process is completed, the remaining stream data not accumulated in the accumulation unit of the terminal device is distributed from the server. In a content distribution method for distributing stream data as content data from a server to a terminal device, storing the stream data in the terminal device, and reproducing the stored stream data,
The terminal device accumulates data of at least a start portion of the stream data in a predetermined data format;
When reproducing the accumulated stream data, the stream data in the section following the accumulated stream data in the predetermined data format is downloaded from the server and accumulated, and reproduced following the start portion data. It is what
The stream data accumulated by the terminal device is accumulated at least in the data format at the time of download, and other portions than the start portion are accumulated in a data format compressed at a higher compression rate than the start portion, A content delivery method in which when data other than the start part cannot be downloaded, data stored in the terminal device after being compressed at a higher compression rate than the start part is reproduced as data other than the start part . In a program for receiving and accumulating distribution of stream data as content data from a server and reproducing the accumulated stream data on a computer device,
A process of storing at least a start portion of the stream data in a predetermined data format;
When reproducing the accumulated stream data, the stream data in the section following the accumulated stream data in the predetermined data format is downloaded from the server and accumulated, and reproduced following the start portion data. Is also a program that performs processing
The stream data accumulated by the accumulation process is a process of accumulating at least the start part in the data format at the time of download and accumulating a part other than the start part in a data format compressed at a higher compression ratio than the start part. When,
A program for performing a process of reproducing data stored by compressing at a higher compression rate than the start portion as data other than the start portion when downloading other than the start portion is not possible .

Images