JP2007267144A - Method for distributing information, server device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a server device reducing a storage capacity required for corresponding to the requirement of a high-speed reproduction. <P>SOLUTION: The server device has a storage section storing an index file describing an information containing time stamps for key frames, the place of an appearance and the quantity of data at every image data and every key frame in the image data. The server device further has a control section specifying the key frame from the index file in response to the time elapsed and a scale factor after the time of the reception of a requirement signal and transmitting the specified key frame at an information terminal when the image data are reproduced and the requirement signal containing the indication of the high-speed reproduction or a reverse high-speed reproduction and the information of the scale factor is received from the information terminal during a transmission to the information terminal through a network. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information distribution method in streaming distribution, a server apparatus, and a program for causing a computer to execute the method.

  With the development of broadband transmission technology and information compression technology, it has become possible to distribute audio and video to many information terminals, such as radio and television, via networks such as the Internet. One of the information distribution methods is streaming distribution. In streaming distribution, a server providing a service transmits audio and video files via a network, and an information terminal on the client side using the service performs reproduction while storing the received file. Therefore, the client does not need to wait until all the files are downloaded, and can immediately play the music that the user wants to listen to or the video that the user wants to watch.

In the streaming distribution service, the server performs distribution in response to various viewing mode requests from clients. The viewing mode includes playback at the original speed (referred to as a normal mode), high-speed playback that performs playback while fast-forwarding (referred to as high-speed mode), and reverse high-speed playback that performs playback while rewinding (reverse high-speed mode). For example). In the conventional high-speed playback and reverse high-speed playback methods, the server creates a file for high-speed playback in advance, and when there is a request for high-speed playback or reverse high-speed playback, the file for high-speed playback created in advance is sent to the request source. (See Patent Document 1).
Japanese Patent Laid-Open No. 08-331509

  In high-speed playback and reverse high-speed playback, the magnification can be selected on the client side. In the conventional method, a plurality of types of files for high-speed playback are prepared in order to be able to handle a plurality of types of magnifications. When there is a request for high-speed playback during normal playback on the client side, the transmission file is switched from the normal playback file to the file for high-speed playback in accordance with the selected magnification, and video distribution at high speed is performed. For this reason, it was possible to distribute only videos of high-speed playback files with multiple magnifications prepared in advance. In addition, in order to store the file for high-speed playback created in advance, a disk capacity different from that for the normal playback file is required.

  The present invention has been made in order to solve the problems of the conventional techniques as described above, and an information distribution method, a server apparatus, and a method for reducing the storage capacity required to meet the demand for high-speed playback. An object is to provide a program for causing a computer to execute the method.

An information distribution method of the present invention for achieving the above object is an information distribution method by a server device for distributing video data to an information terminal connected via a network,
For each of the video data stored in the storage unit, an index file describing information including a time stamp, an appearance position, and a data amount of the key frame is generated and stored in the storage unit. And
While the video data is being reproduced and transmitted to the information terminal, if a request signal including a high-speed playback or reverse high-speed playback instruction and magnification information is received from the information terminal, the elapsed time from the reception of the request signal Identify keyframes from the index file corresponding to time and the magnification,
The identified key frame is transmitted to the information terminal.

  In the present invention, by registering the index file in advance, when receiving an instruction for high-speed playback or reverse high-speed playback and an instruction including magnification information, the index file is referred to and the elapsed time from the reception of the instruction A key frame to be reproduced at a time corresponding to the magnification can be specified by a time stamp, an appearance position, and a data amount. For this reason, video data can be transmitted to the information terminal for an arbitrary magnification.

On the other hand, a server device of the present invention for achieving the above object is a server device that distributes video data to information terminals connected via a network,
For each key frame in the video data and the video data, a storage unit in which an index file describing information including a time stamp of the key frame, an appearance position, and a data amount is stored;
When a request signal including a high-speed playback or reverse high-speed playback instruction and magnification information is received from the information terminal during playback of the video data and transmission to the information terminal, an elapsed time from the reception of the request signal And a control unit for identifying a key frame from the index file corresponding to the magnification and transmitting the identified key frame to the information terminal;
It is the structure which has.

A program of the present invention for achieving the above object is a program for causing a computer that distributes video data to an information terminal connected via a network,
For each of the video data stored in the storage unit, an index file describing information including the time stamp, appearance position, and data amount of the key frame is generated and stored in the storage unit. And steps to
While the video data is being reproduced and transmitted to the information terminal, if a request signal including a high-speed playback or reverse high-speed playback instruction and magnification information is received from the information terminal, the elapsed time from the reception of the request signal A key frame specifying step of specifying a key frame from the index file corresponding to the time and the magnification;
Transmitting the identified key frame to the information terminal;
The computer is caused to execute a process having

  According to the present invention, it is not necessary to create a high-speed playback file from video data in advance in order to perform high-speed playback and reverse high-speed playback. Therefore, it is possible to reduce the capacity of the file for high-speed playback stored in the storage area, and to use the storage area more effectively. In addition, even at an arbitrary magnification, the position and size of a key frame to be distributed can be easily obtained by referring to the index file, and high-speed reproduction and reverse high-speed reproduction can be distributed at an arbitrary magnification.

  In the information distribution method of the present invention, an index file describing information including a time stamp is registered in advance for each key frame in video data, and when there is a request for high-speed reproduction, a key frame to be transmitted with reference to the index file It is characterized by specifying.

  The configuration of the server of this embodiment will be described. FIG. 1 is a block diagram illustrating a configuration example of a server according to this embodiment.

  The server 11 includes a storage device 12, an index file creation unit 13, a distribution position calculation unit 14, and a video data distribution unit 15. The video data distribution unit 15 includes a data acquisition unit 18 and a data transmission unit 19. Further, the server 11 is provided with a CPU (Central Processing Unit) (not shown) that executes predetermined processing according to a program, and a memory (not shown) for storing the program. The index file creation unit 13 and the delivery position calculation unit 14 are virtually configured in the server 11 when the CPU executes a program. And the structure containing the index file preparation part 13 and the delivery position calculation part 14 functions as a control part. The data transmitter 19 is connected to an external information terminal (not shown) via a network. The external information terminal is provided on the client side that uses high-speed playback and reverse high-speed playback services for video data.

  The storage device 12 is a storage device such as a hard disk and a semiconductor memory. In the storage device 12, video data 16 is registered in advance as content data. In addition, various information relating to processing such as reproduction time and calculation results are stored. The video data includes video data related to images and audio data related to audio. Since the present invention relates to high-speed playback and reverse high-speed playback, video data will be mainly described below. In general, video data has a configuration including a key frame that is a frame inserted at a constant interval and a frame having difference information between the key frames. The key frame has image information and time stamp information indicating the time when the image is drawn from the start of reproduction. An image between key frames is restored using image information of key frames and difference information between key frames.

  The index file creation unit 13 extracts all the key frames in the video data 16, and for each key frame, an index that records information on the time stamp of the key frame, the appearance position of the key frame, and the size of the key frame. A file 17 is generated and stored in the storage unit 12.

  The distribution position calculation unit 14 obtains a distribution start position and distribution data amount (distribution size) in the video data 16 to be distributed. When the data acquisition unit 18 receives information on the distribution start position and the distribution size from the distribution position calculation unit 14, the data acquisition unit 18 extracts video data from the video data 16 in the storage unit 12 based on the information. The data transmission unit 19 transmits the video data extracted by the data acquisition unit 18 to the client information terminal through the network.

  Hereinafter, the video data 16 is video data in the MPEG2-TS (transport stream) format in which video data and audio data are multiplexed (hereinafter referred to as MPEG2 TS data).

  Here, the structure of the transport stream (TS) will be briefly described. FIG. 2 shows the structure of the transport stream. The transport stream is composed of a plurality of TS packets that are fixed-length packets of 188 bytes. One TS packet is composed of a TS header and a TS payload, and an identifier indicating a TS payload attribute called PID (Packet Identification) is recorded in the TS header. The same PID is recorded in the TS header of TS packets of the same image. In addition, the TS payload includes individual PES (Packetized Elementary Stream) packets for each of video data and audio data. The video data includes a sequence header (SH) necessary for the decoder to restore the video data. The SH includes a PES header having time stamp information. The PES header of the key frame includes information on the appearance position of the key frame and the key frame length in addition to the time stamp.

  Next, the configuration of the index file creation unit 13 will be described in detail. FIG. 3 is a block diagram illustrating a configuration example of the server according to the present embodiment. As shown in FIG. 3, the index file creation unit 13 has an A / V separation unit 20 and a video data processing unit 30. The A / V separator 20 separates video data and audio data from the MPEG2 TS data 26. The video data processing unit 30 searches for key frames from the video data.

  FIG. 4 is a block diagram showing a configuration example of the index file creation unit shown in FIG. As shown in FIG. 4, the A / V separator 20 includes a TS packet analyzer 21 and a TS packet separator 22. The video data processing unit 30 includes an SH search unit 31, a PES parameter extraction unit 32, and an index creation unit 33.

  The TS packet analysis unit 21 analyzes the PID included in the TS packet in the MPEG2 TS data 26. The TS packet separation unit 22 extracts video data from the PID analyzed by the TS packet analysis unit 21. The SH search unit 31 searches for the SH from the video data extracted by the TS packet separation unit 22. The PES parameter extraction unit 32 searches the PES header from the SH searched by the SH search unit 31, and acquires information on the key frame from the PES header. The index creation unit 33 appends to the index file 17 based on the parameters acquired by the PES parameter extraction unit 32.

  FIG. 5 shows a configuration image of video data and an index file. An index file creation method will be briefly described with reference to FIG. First, key frames 2a, 2b,... Are extracted from the video data 16. Subsequently, in the format of the index file 17 stored in the storage unit 12, in order from the key frame 2a to the last key frame (not shown), the key frame time stamp 4, the key frame appearance position (offset) 5, and The key frame size 6 is written for each key frame. Information including the time stamp 4, Offset 5 and size 6 for one key frame is referred to as an index.

  When the distribution position calculation unit 14 receives a signal requesting high-speed playback at n times speed from the information terminal while transmitting the video data to the client information terminal in the normal mode, the distribution position calculation unit 14 The playback time s [sec], which is the elapsed time when played back in the mode, is recorded in the storage unit 12. Subsequently, data for high speed reproduction is obtained from the MPEG2 TS data 26 as follows. Here, two functions Fo (x) and Fs (x) are defined. The function Fo (x) indicates a key frame whose offset value is the minimum value among the key frames whose offset value is x [sec] seconds or more in the index file 17. Further, Fs (x) indicates the size of the key frame having the smallest Offset among the key frames having the Offset value of x [sec] seconds or more in the index file 17. The distribution position calculation unit 14 obtains Fo (s + p × n) [byte] as the distribution start position of the video data corresponding to the elapsed time p [sec] from the start of the high-speed playback, and Fs (s + p) as the distribution size. Xn) Calculate [byte].

  Information on the distribution start position and distribution size of the video data obtained in this way is passed to the data acquisition unit 18. Processing for passing these pieces of information to the data acquisition unit 18 is performed at regular time intervals until the video data 16 is completed or a high-speed playback stop signal, which is a signal to stop high-speed playback, is received from the client information terminal. Repeat with.

  When the delivery position calculation unit 14 receives a reverse high-speed playback request signal that is a signal for requesting reverse high-speed playback at m times speed (m is a positive number), the distribution position calculation unit 14 receives a request signal as in the case of high-speed playback. The playback time s [sec] at the time is stored. Subsequently, Ro (s−p × m) [byte] is obtained as the distribution start position of the video data corresponding to the elapsed time p [sec] since the start of the reverse high-speed playback, and Rs (s− p × m) [byte] is obtained. However, the function Ro (x) indicates a key frame whose offset is the largest among the key frames whose offset is less than x [sec] seconds in the index file 17. The function Rs (x) indicates the size value of the key frame having the maximum offset among the key frames in which the offset is less than x [sec] seconds in the index file 17.

  The processing of passing the information on the distribution start position and distribution size of the video data obtained in this way to the data acquisition unit 18 is to stop reverse high-speed playback until the video data 16 ends or from the client information terminal. This is repeated at regular time intervals until a reverse fast playback stop signal, which is a signal, is received.

  Next, a key frame search method and an index file creation method by the server of this embodiment will be described. FIG. 6 is a flowchart showing a procedure for creating an index file using MPEG2 TS data.

  The TS packet analysis unit 21 acquires the PID of the video data from the MPEG2 TS data 26 (Step 101). The TS packet separation unit 22 searches video data from the MPEG2 TS data 26 based on the PID acquired by the TS packet analysis unit 21 (step 102). When the TS packet separation unit 22 finds a packet having a PID (step 103), the SH search unit 31 “00 00 01 B3 (SH start synchronization code) from the video data extracted by the TS packet separation unit 22 H) "is searched (step 104). If the SH is not found, the process is returned to the TS packet separator 22 in order to search for the next video data (step 105).

  On the other hand, when the SH search unit 31 finds SH in step 105, the PES parameter extraction unit 32 searches the PES header from the SH (step 106). When the PES header is found, key frame information including information on the time stamp of the key frame, the appearance position of the key frame, and the key frame length is acquired from the PES header (step 107). Due to the structure of the MPEG2 TS data 26, key frames are not stored continuously, so the amount of data from the appearance position of the key frame to the key frame length is recorded as the key frame size. The index creation unit 33 creates an index based on the parameters acquired by the PES parameter extraction unit 32 and adds the index to the index file 17 (step 108). In this way, the processing from step 103 to step 108 is performed up to the end of the video data in the MPEG2 TS data 26 (step 102).

  Next, the operation of high-speed playback by the server of this embodiment will be described. FIG. 7 is a flowchart showing an operation procedure of high-speed playback by the server of this embodiment. Here, it is assumed that at the time of the reproduction time s [sec] of the video data 16, a high-speed reproduction request signal, which is a signal requesting high-speed reproduction at n times speed, is received from the client information terminal, and the index file A high-speed mode distribution method using the above will be described. However, n is a positive number.

  When the distribution position calculation unit 14 receives the n-times high-speed reproduction request signal, the distribution position calculation unit 14 records the reproduction time s [sec] at the time of receiving the request signal in the storage unit 12 (step 201). Subsequently, Fo (s + p × n) [byte] is obtained as the video data distribution start position corresponding to the elapsed time p [sec] since the start of high-speed playback, and the distribution size is Fs (s + p × n) [ byte] is obtained (step 202).

  When the data acquisition unit 18 acquires the distribution start position and distribution size information obtained by the distribution position calculation unit 14, the data acquisition unit 18 extracts video data from the video data 16 based on the information (step 203). Subsequently, the data transmission unit 19 transmits the video data extracted by the data acquisition unit 18 to the client information terminal via the network (step 204). Thereafter, the processing from step 202 to step 204 is performed at regular time intervals until the end of the video data 16 or until a high-speed playback stop signal is received from the client information terminal (step 205). Note that the transmission bit rate of the client to the information terminal is set to the same speed as that in the normal mode so as not to increase the bandwidth used in the network.

  Next, the operation of reverse high-speed playback of the server of this embodiment will be briefly described. Here, it is assumed that an inverse high-speed playback request signal of m times speed (m is a positive number) is received from the client information terminal at the time of playback time s [sec] of the video data 16, and an index file is used. A delivery method in the reverse high-speed mode will be described. Further, a description will be made mainly on processing different from the case of the high-speed playback described in FIG.

  When the delivery position calculation unit 14 receives the m-times reverse high-speed playback request signal, it records the playback time s [sec] when the request signal is received, as in the case of high-speed playback. Subsequently, unlike high-speed playback, the video data distribution start position Ro (s−p × m) [byte] and distribution size Rs (s−p × m) [byte] corresponding to the elapsed time p [sec] Ask for. The data acquisition unit 18 extracts the video data of the distribution start position and the distribution size obtained in this way from the video data 16, and the data transmission unit 19 transmits the extracted video data to the information terminal of the client. The process is repeated at regular time intervals until the video data 16 is completed or a reverse fast playback stop signal is received from the client information terminal.

  As described above, when performing high-speed playback, the server according to the present embodiment obtains the position and size of data to be distributed from the index file, so that a plurality of types of high-speed playback files are not prepared in advance. Playback is possible. The same applies to reverse high-speed playback. Therefore, it is possible to reduce the required disk capacity as compared with the conventional case.

  In this embodiment, the case where the key frames are inserted into the video data at regular intervals has been described. However, the present invention may be applied to video data whose key frame insertion intervals are not constant. In this case, high-speed playback and reverse high-speed playback can be performed by the above-described method even for video data in which the key frame insertion interval is changed between a video with a lot of motion and a video with a small amount of motion. The present invention can also be applied to cases where key frames are not stored at a constant cycle, such as H.264 / AVC, which is a standard in which video data is compressed twice or more than before.

  In this embodiment, an index file is generated while live video data is dynamically accumulated with respect to video data for live distribution by streaming. High-speed playback and reverse high-speed playback are possible for video data for which distribution has been completed.

  FIG. 8 is a block diagram showing an example of the configuration of the server of this embodiment. In addition, the same code | symbol is attached | subjected about the structure similar to Example 1, and the detailed description is abbreviate | omitted.

  The server 51 of this embodiment includes a video data receiving unit 40 and a video data storage unit 41 connected to a network. The video data receiving unit 40 receives live video data from the outside via a network. The video data storage unit 41 adds the live video data received by the video data receiving unit 40 to the video data 16 of the storage unit 12.

  The index creation unit 43 extracts all the key frames in the live video data received by the video data reception unit 40, and for each key frame, the time stamp of the key frame, the appearance position of the key frame, and the size of the key frame. Information is recorded in the index file 17 of the storage unit 12. In this manner, extracting information on key frames from video data to generate an index file is referred to as “indexing”.

  The index creation unit 43 and the video data storage unit 41 are virtually configured in the server 51 when the CPU executes a program.

  Next, the operation of the server of this embodiment will be described with reference to FIG. Here, the description will focus on operations different from those of the first embodiment, and description of operations similar to those of the first embodiment will be omitted.

  The video data receiving unit 40 passes live video data received via the network to the video data storage unit 41 and the index creation unit 43. The index creating unit 43 indexes live video data received by the video data receiving unit 40. As a result, key frame information about the live video data is added to the index file 17. On the other hand, the video data storage unit 41 appends the live video data received from the video data receiving unit 40 to the video data 16 of the storage unit 12.

  As described above, the server of the present embodiment generates an index file for video data while storing the video data for dynamically stored video data. Therefore, even during live distribution of video data, it is possible to perform high-speed playback and reverse high-speed playback for the stored video data by the same processing as in the first embodiment.

  According to the present invention, by registering an index file in advance, when an instruction including a high-speed playback or reverse high-speed playback instruction and magnification information is received, the index file is referred to and the process from the time the instruction is received. It becomes possible to specify the key frame to be reproduced at the time corresponding to the time and the magnification by the time stamp, the appearance position, and the size. Therefore, it is not necessary to create a file for high speed reproduction from video data in advance in order to perform high speed reproduction and reverse high speed reproduction. As a result, it is possible to reduce the capacity of the file for high-speed playback stored in the storage area, and more effectively use the storage area and store more video data.

  In addition, since the position and size of the key frame to be distributed can be easily acquired by referring to the index file even at an arbitrary magnification, high-speed playback and reverse high-speed playback can be distributed at any magnification. As a result, high-speed playback is not fixed magnification, and high-speed playback video at an arbitrary magnification can be provided to the client.

  Furthermore, when performing high-speed playback and reverse high-speed playback, the transmission bit rate of the client to the information terminal is set to the same speed as that in the normal mode, so that high-speed playback can be realized without increasing the use band of the network.

  In addition, you may apply to the program for making a computer perform the information delivery method of this invention.

FIG. 3 is a block diagram illustrating a configuration example of a server according to the first embodiment. It is a figure which shows the structure of a transport stream. FIG. 3 is a block diagram illustrating a configuration example of a server according to the first embodiment. FIG. 4 is a block diagram illustrating a configuration example of an index file creation unit illustrated in FIG. 3. It is a figure which shows the structure image of video data and an index file. It is a flowchart which shows the procedure for producing an index file from MPEG2 TS data. 3 is a flowchart illustrating an operation procedure of high-speed playback by the server according to the first embodiment. 6 is a block diagram illustrating a configuration example of a server according to Embodiment 2. FIG.

Explanation of symbols

11 Server 12 Storage Device 13 Index File Creation Unit 14 Arrangement Position Calculation Unit 15 Video Data Distribution Unit

Claims (15)

An information delivery method by a server device for delivering video data to an information terminal connected via a network,
For each of the video data stored in the storage unit, an index file describing information including the time stamp, appearance position, and data amount of the key frame is generated and stored in the storage unit. And
While the video data is being reproduced and transmitted to the information terminal, if a request signal including a high-speed playback or reverse high-speed playback instruction and magnification information is received from the information terminal, the elapsed time from the reception of the request signal Identify keyframes from the index file corresponding to time and the magnification,
An information distribution method for transmitting the identified key frame to the information terminal. When the video data is reproduced from the beginning, the reproduction time from the beginning until the request signal is received is s, the magnification is n, and the elapsed time is p.
When the request signal indicates high-speed playback, a key frame having the maximum appearance position among key frames at a time later than the time stamp (s + n × p) is obtained in the index file.
The information distribution method according to claim 1, wherein an appearance position and a data amount of the obtained key frame are read, and a key frame having the data amount is specified from the appearance position in the video data. When the video data is reproduced from the beginning, the reproduction time from the beginning until the request signal is received is s, the magnification is m, and the elapsed time is p.
If the request signal indicates reverse high-speed playback, the key frame having the maximum appearance position among the key frames whose time stamp is earlier than (s−m × p) is stored in the index file. Seeking
The information distribution method according to claim 1, wherein an appearance position and a data amount of the obtained key frame are read, and a key frame having the data amount is specified from the appearance position in the video data.   For live video data received from the outside via the network, the live video data is stored in the storage unit every time the live video data is received, and the key frame information is added to the index file of the live video data The information distribution method according to any one of claims 1 to 3, wherein the information is stored in the storage unit.   5. The information distribution method according to claim 1, wherein when the identified key frame is transmitted to the information terminal, the transmission bit rate of the key frame is made equal to that during normal reproduction of the video data. A server device that distributes video data to an information terminal connected via a network,
For each key frame in the video data and the video data, a storage unit in which an index file describing information including a time stamp of the key frame, an appearance position, and a data amount is stored;
When a request signal including a high-speed playback or reverse high-speed playback instruction and magnification information is received from the information terminal during playback of the video data and transmission to the information terminal, an elapsed time from the reception of the request signal And a control unit for identifying a key frame from the index file corresponding to the magnification and transmitting the identified key frame to the information terminal;
A server device. When the video data is reproduced from the beginning, the reproduction time from the beginning until the request signal is received is s, the magnification is n, and the elapsed time is p.
The controller is
If the request signal indicates high-speed playback, a key frame having the maximum appearance position is determined in the index file from among key frames whose time stamp is later than (s + n × p). The server apparatus according to claim 6, wherein a key frame appearance position and a data amount are read, and a key frame having the data amount is specified from the appearance position in the video data. When the video data is reproduced from the beginning, the reproduction time from the beginning until the request signal is received is s, the magnification is m, and the elapsed time is p.
The controller is
If the request signal indicates reverse high-speed playback, the key frame having the maximum appearance position among the key frames whose time stamp is earlier than (s−m × p) is stored in the index file. The server device according to claim 6, wherein the server device obtains the obtained appearance position and data amount of the key frame, and specifies the key frame of the data amount from the appearance position in the video data. The controller is
For live video data received from the outside via the network, the live video data is stored in the storage unit every time the live video data is received, and the key frame information is added to the index file of the live video data The server device according to claim 6, which is stored in the storage unit. The controller is
10. The server device according to claim 6, wherein when the identified key frame is transmitted to the information terminal, the transmission bit rate of the key frame is made equal to that during normal reproduction of the video data. A program for causing a computer that distributes video data to an information terminal connected via a network,
For each of the video data stored in the storage unit, an index file describing information including the time stamp, appearance position, and data amount of the key frame is generated and stored in the storage unit. And steps to
While the video data is being reproduced and transmitted to the information terminal, if a request signal including a high-speed playback or reverse high-speed playback instruction and magnification information is received from the information terminal, the elapsed time from the reception of the request signal A key frame specifying step of specifying a key frame from the index file corresponding to the time and the magnification;
Transmitting the identified key frame to the information terminal;
A program for causing the computer to execute a process including: When the video data is reproduced from the beginning, the reproduction time from the beginning until the request signal is received is s, the magnification is n, and the elapsed time is p.
If the request signal indicates high-speed playback, the key frame specifying step includes:
Obtaining a key frame having the maximum appearance position in the index file among key frames at a time later than the time stamp (s + n × p);
Reading the appearance position and data amount of the obtained key frame, and identifying the key frame of the data amount from the appearance position in the video data;
The program according to claim 11. When the video data is reproduced from the beginning, the reproduction time from the beginning until the request signal is received is s, the magnification is m, and the elapsed time is p.
When the request signal indicates reverse high-speed playback, the key frame specifying step includes:
Obtaining in the index file a key frame having the maximum appearance position among key frames at a time earlier than the time stamp (s−m × p);
Reading the appearance position and data amount of the obtained key frame, and identifying the key frame of the data amount from the appearance position in the video data;
The program according to claim 11.   For live video data received from the outside via the network, the live video data is stored in the storage unit every time the live video data is received, and the key frame information is added to the index file of the live video data The program according to claim 11, which is stored in the storage unit. The program according to any one of claims 11 to 14, wherein in the step of transmitting the key frame to the information terminal, a transmission bit rate of the key frame is made equal to that during normal reproduction of the video data.

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