JP2008147973A - Content reproduction system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content reproduction system for enabling a client to more surely reproduce content at a designated time. <P>SOLUTION: A server transmits the client synchronous information including a sequence number and the designated time. When the client receives the synchronous information, the client calculates a reproduction start scheduled time of a packet specified by the sequence number by referring to the currently reproduced packet and the size of each packet. The client compares the reproduction start scheduled time with the designated time, and synchronizes the reproduction start time of the packet specified by the sequence number with the designated time when the reproduction start scheduled time does not coincide with the designated time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a content reproduction system that distributes content from a server to a client, and relates to a content reproduction system that adjusts the content reproduction time in the client.

  In recent years, with the development of the Internet, distribution of content (music or video data) from a server to a client has been performed in a streaming format with high real-time characteristics, not a download format. In order to solve the problem of exhaustion of reproduced content such as sound interruption, the client reproduces while accumulating the content in the buffer. As a result, there is a difference of at least about several seconds between the playback time of the content on the client assumed by the server operator and the playback time of the content on the actual client, not precisely in real time. In addition, even between clients, there is a slight difference in playback time depending on the network status of each client. This problem becomes a significant problem in providing a client with a service that requires real-time characteristics such as TV broadcasting and radio broadcasting.

RTP (Realtime
Transport Protocol (Protocol) proposes to distribute the content by describing the playback time of the content in the header of the content. However, when the playback time is designated by this method, the designated time is probably already passed when the packet arrives, which is not practical.

SMIL (Synchronized
Multimedia Integration Language) can synchronize the timing from the start of playback, but it is a relative timing, not an absolute synchronization with the actual time. Also, there is no description about how to deal with the timing deviation.

JP-A-2005-295100 JP 2006-229606 A

  An object of the present invention is to provide a content reproduction system in which a client can reproduce content at a specified time more reliably.

  A content reproduction system according to a preferred embodiment of the present invention includes a server and a client connectable to the server. The server includes storage means for storing a plurality of contents, content transmission means for transmitting the contents to the client in units of packets, a sequence number of a packet whose reproduction time is to be adjusted, and a packet specified by the sequence number Synchronization information transmitting means for transmitting synchronization information including the designated time. The client includes a receiving unit that receives the content and the synchronization information, a reproducing unit that reproduces the content, a unit that calculates a scheduled reproduction start time of a packet specified by the sequence number, and the scheduled reproduction start time. And a comparison means for comparing the designated time with the designated time, and if the scheduled reproduction start time is earlier than the designated time according to the comparison result of the comparison means, the reproduction start time of the packet specified by the sequence number is A time adjustment unit for delaying the reproduction start time of the packet specified by the sequence number to the designated time when the scheduled reproduction start time is later than the designated time.

  The server transmits synchronization information including the sequence number and the specified time to the client. When the client receives the synchronization information, the client calculates the scheduled reproduction start time of the packet specified by the sequence number by referring to the currently reproduced packet and the size of each packet. The client compares the scheduled reproduction start time with the designated time, and if they do not match, synchronizes the reproduction start time of the packet specified by the sequence number with the designated time. Therefore, by transmitting the synchronization information to the client before the packet specified by the sequence number, the client can adjust the reproduction start time of the packet specified by the sequence number to the time intended by the server operator. . Furthermore, since the data position to match the reproduction time is specified by the packet sequence number, the reproduction time can be synchronized not in the content unit but in the packet unit (that is, even from the middle of the content).

  A content reproduction system according to another preferred embodiment of the present invention includes a server and a client connectable to the server. The server includes a storage unit that stores a plurality of contents, a content transmission unit that transmits content including header information to the client, and synchronization information including a designated time of the content whose playback time is to be adjusted. Information is included in the header information of the content transmitted immediately before the content to be adjusted. The client includes receiving means for receiving the content and the synchronization information, means for calculating a reproduction start scheduled time of the content next to the content in which the synchronization information is included in the header information, the reproduction start scheduled time, Comparing means for comparing with the designated time, and when the scheduled reproduction start time is earlier than the designated time according to the comparison result of the comparing means, the synchronization information is next to the content included in the header information. When the reproduction start time of the content is delayed until the designated time and the scheduled reproduction start time is later than the designated time, the reproduction start time of the content next to the content in which the synchronization information is included in the header information is set to the designated time. Time adjustment means for accelerating the time.

  The server transmits the synchronization information including the designated time in the header information of the content immediately before the content whose playback time is to be adjusted. When the client receives the synchronization information, the client reproduces the scheduled playback start time of the content next to the content whose synchronization information is included in the header information (referred to as synchronization target content), and plays the content whose synchronization information is included in the header information. Calculation is performed based on the start time and the length of the content. The client compares the scheduled playback start time with the specified time, and if they do not match, synchronizes the playback start time of the synchronization target content with the specified time. Therefore, by sending the synchronization information included in the header information of the content immediately before the synchronization target content, the synchronization information does not arrive later than the specified time as in RTP, so that the client can be sure of the synchronization target content. The reproduction start time can be set to the time intended by the server operator. In addition, since the synchronization target content is the content next to the content whose synchronization information is included in the header information, it is not necessary to include information for specifying the synchronization target content in the synchronization information.

  A content reproduction system according to another preferred embodiment of the present invention includes a server and a client connectable to the server. The server stores a plurality of contents and time-adjusted contents, and the content and the content to be reproduced are transmitted immediately before the contents to be adjusted. The combination of the bit rate and the sampling frequency is different from that of other contents. Includes content transmission means for transmitting the time adjustment content that does not overlap to the client, and synchronization information transmission means for transmitting synchronization information including the bit rate and sampling frequency of the time adjustment content and time correction accuracy. The client includes a receiving unit that receives the content, the time adjustment content, and the synchronization information, a unit that calculates a scheduled reproduction end time of the time adjustment content, a scheduled reproduction end time of the time adjustment content, and the time Based on the correction accuracy, a means for calculating the designated time, a comparing means for comparing the reproduction end scheduled time with the designated time, and the reproduction end scheduled time according to the comparison result of the comparison means If it is earlier than the time, the playback start time of the next content after the time adjustment content is delayed to the specified time, and if the scheduled playback end time is later than the specified time, the playback start of the next content after the time adjustment content is started. Time adjustment means for advancing the time to the designated time.

  The server transmits time adjustment content and synchronization information including the bit rate, sampling frequency, and time correction accuracy of the time adjustment content to the client. Upon receipt of these, the client calculates the scheduled playback end time of the time adjustment content based on the playback start time of the time adjustment content and the length of the time adjustment content. The client calculates the designated time based on the scheduled reproduction end time of the time adjustment content and the time correction accuracy. The client compares the scheduled playback end time of the time adjustment content with the specified time, and if they do not match, the client synchronizes the playback start time of the content next to the time adjustment content (referred to as synchronization target content) to the specified time. Therefore, the client can adjust the reproduction start time of the synchronization target content to the time intended by the server operator. Since the specified time is calculated each time based on the playback end time of the time adjustment content, if the synchronization information is transmitted to the client only once, the client adjusts the playback start time of the synchronization target content every time the time adjustment content is received. it can. Therefore, the reproduction time can be synchronized in a multicast method in which header information can be sent only once from the server to the client.

  According to the present invention, the client can synchronize the playback time more reliably.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. However, the present invention is not limited to these embodiments. FIG. 1 is a block diagram showing a configuration of a content reproduction system 1 according to a preferred embodiment of the present invention. The content reproduction system 1 includes a server SV and one or more clients CL (in this example, three clients CL1 to CL3). The server SV and the client CL are connected via a network such as the Internet 50, for example. The client CL requests content from the server SV. In response to a request from the client CL, the server SV transmits the content to the client CL based on a content list such as a program guide that associates the time with the content to be reproduced at the time. The client CL receives content from the server SV and plays it.

  FIG. 2 is a schematic block diagram showing the configuration of the server SV. The server SV includes a storage unit 21 such as an HDD (hard disk drive), a control unit 22 such as a CPU processing unit, and a communication unit 23. The HDD 21 stores a plurality of contents and time adjustment contents (described later). Content is a general term for data such as music (music), video, and / or still images. In this example, the case of music data will be described as an example.

  The CPU processing unit 22 controls the operation of the entire server SV, and includes a database management unit 24, a network protocol processing unit 25, and a system operation unit 26. The database management unit 24 manages the HDD 21. Specifically, the database management unit 24 selects content in the HDD 21 based on a content list (program guide) generated by the operator of the server SV shown in FIG. The network protocol processing unit 25 executes protocol processing on input / output data. The system operation unit 26 reads the server program stored in the HDD 21 and executes various processes of the server SV described later. For example, the system operation unit 26 generates each synchronization information described later and transmits it to the client CL. The communication unit 23 transmits and receives signals between the server SV and the Internet.

  FIG. 4 is a schematic block diagram showing the configuration of the client CL. The client CL includes control means such as a microcomputer processing unit 31, a buffer 32, a memory 33 such as a ROM and a RAM, an audio processing unit 34 that decodes compressed digital content and generates uncompressed digital content, and digital content. A D / A converter (DAC) 35 that converts to analog content, a communication unit 36, an input device 37 that receives user operations, and a display device 38 such as an LCD that displays content information and the like are provided.

  The microcomputer processing unit 31 controls the operation of the entire client CL, and includes a network protocol processing unit 39 and a system operation unit 30. The network protocol processing unit 39 performs protocol processing on input / output data. The system operation unit 30 executes various processes of the client, which will be described later, based on a client program stored in the memory 33, for example. For example, the system operation unit 30 receives the synchronization information from the server, and executes a later-described reproduction time synchronization process based on the synchronization information. Further, the system operation unit 30 adjusts an internal system clock (not shown) to an accurate time by accessing the NTP server. The communication unit 36 transmits and receives signals between the client CL and the Internet 50.

The operation of the content reproduction system having the above configuration will be described.
[Example 1]
In this example, the content transmitted from the server SV to the client CL is transmitted in packet units, and header information (hereinafter referred to as a header) indicating the details of the packet is provided at the head of each data packet. FIG. 5 shows the data structure of the header. The header includes a sequence number (Sequence number) and a packet ID (Packet
ID) and UDP Sequence / TCP
flags and packet length (ie, playback time) (Packet
length). The sequence number is a serial number assigned in order for each packet.

  The server SV transmits a packet including synchronization information to the client CL separately from the content stream. The synchronization information is transmitted sufficiently before the content to be synchronized (at least enough time to analyze the synchronization information). The synchronization information is information for adjusting the time to start reproducing the packet having the sequence number specified in the synchronization information, that is, information for synchronizing the reproduction time of the client CL. The client CL that has received the synchronization information synchronizes the reproduction time of the entire content by reproducing the packet of the designated sequence number at the designated time. It is sufficient that the synchronization information is not transmitted for all packets, but is transmitted for some packets with an appropriate interval.

  FIG. 6 is a diagram showing the synchronization information. The synchronization information includes an expiration date, channel information, a specified time, a sequence number, a maximum correction time, and processing when the maximum correction time is exceeded. The expiry date is the expiry date (time) of processing for matching the playback time of the packet designated by the client CL using the synchronization information. For example, when the synchronization information is received later than the expiry date, Ignore the synchronization information and do not execute the synchronization process. The channel information indicates which channel is the synchronization information when the content transmitted from the server SV to the client CL includes a plurality of channels. The designated time designates the reproduction start time of the packet specified by the sequence number from the server side. The sequence number is information for specifying a packet for adjusting the reproduction time, and corresponds to the sequence number in the header shown in FIG.

  The maximum correction time is the maximum value of the difference between the scheduled reproduction start time of the packet specified by the sequence number and the specified time in the synchronization information. The process when the maximum correction time is exceeded indicates the process when the difference between the scheduled reproduction start time of the packet and the designated time in the synchronization information exceeds the maximum correction time. In this example, the process is stored in the buffer 32. For example, all the content packets are once cleared and the content is acquired again from the server SV. If the difference between the scheduled playback start time of the packet and the specified time is too large, it is easier to synchronize the playback time if the accumulation in the buffer 32 is reset once and content is newly acquired from that time. Because.

  FIG. 7 is a flowchart showing a synchronization process of the reproduction start time of the client CL. The CPU processing unit 22 waits for reception of the synchronization information packet (S11), and when receiving the synchronization information packet (S11: YES), the CPU processing unit 22 determines whether or not the synchronization information is valid (S12). That is, it is determined whether the current time has passed the expiration date included in the synchronization information. If not valid (S12: NO), the process is terminated. If valid (S12: YES), the CPU processing unit 22 corrects the system time of the client CL by accessing the NTP server (S13).

  Subsequently, the CPU processing unit 22 confirms the sequence number of the packet currently being reproduced (S14). The sequence number currently being reproduced is the sequence number of a packet that is taken out of the buffer 32 and processed by the audio processing unit 34 and the DAC 35 among the packets stored in the buffer 32.

  Next, the CPU processing unit 22 calculates the scheduled reproduction start time of the packet specified by the sequence number included in the synchronization information (S15). Specifically, for example, when all the sizes of one packet are the same (for example, 4 bytes), the CPU processing unit 22 determines the packet specified by the sequence number included in the synchronization information from the packet currently being reproduced. Count the number of packets that exist until. If the sequence number currently being reproduced is 10 and the sequence number in the synchronization information is 20, it will be 10 at 20-10. Then, the number of packets is multiplied by the reproduction time of one packet (for example, 0.3 seconds for 4 bytes). Finally, by adding the calculated time to the current time, the scheduled reproduction start time of the sequence number included in the synchronization information is calculated. In addition, when the length is different for each packet, the scheduled reproduction start time is calculated based on the length of the packet included in the header shown in FIG.

  Next, the CPU processing unit 22 extracts a designated time in the synchronization information (S16). Then, the CPU processing unit 22 compares the scheduled reproduction start time with the designated time (S17, S18, S20, S22).

  First, when the difference between the scheduled reproduction start time and the specified time exceeds the maximum correction time included in the synchronization information (S18: YES), the CPU processing unit 22 deletes all the packets stored in the buffer 32. Erase and re-acquire the packet of the song currently distributed from the server SV. As described above, if the scheduled playback start time and the specified time are too large, it is necessary to advance or delay the playback time of the packet with the specified sequence number by a considerable time in order to synchronize the playback time. This is because the user may feel uncomfortable.

  Hereinafter, a case will be described in which the difference between the scheduled reproduction start time and the specified time does not exceed the maximum correction time included in the synchronization information.

  When the scheduled reproduction start time is earlier than the designated time (S20: YES), if the reproduction is continued as it is, the packet with the sequence number is reproduced earlier than the designated time. Therefore, the CPU processing unit 22 waits for the reproduction of the packet having the sequence number in the synchronization information until the designated time and starts the reproduction (the reproduction time is delayed until the designated time) (S21). For example, if the reproduction start scheduled time is 18:59:55 and the specified time is 19:00:00, nothing is reproduced between 18:59:55 and 19:00:00. Alternatively, the previous packet is played back repeatedly for 5 seconds. Then, at 19:00:00, the CPU processing unit 22 starts reproducing the packet specified by the sequence number included in the synchronization information. As a result, when the reproduction time of the content is earlier by 5 seconds, the reproduction time of the entire content can be synchronized by delaying the reproduction time by 5 seconds and reproducing the packet specified by the sequence number.

  On the other hand, if the scheduled reproduction start time is later than the designated time (S22: YES), if the reproduction is continued as it is, the packet with the sequence number is reproduced later than the designated time. Therefore, the CPU processing unit 22 does not reproduce the packet with the previous sequence number, so that the reproduction of the packet with the sequence number in the synchronization information can be started at the designated time (the reproduction start time is advanced to the designated time) (S23). ). For example, if the scheduled playback start time is 19:00:05 and the specified time is 19:00:00, the playback is originally scheduled to start from 19:00:05 to 19:00:05. The received packet is cleared from the buffer 32. Then, at 19:00:00, the CPU processing unit 22 starts reproducing the packet specified by the sequence number included in the synchronization information. As a result, when the playback time of the content is delayed by 5 seconds, the playback time of the entire content can be synchronized by adjusting the playback time of the packet specified by the sequence number by increasing the playback time by 5 seconds.

  If the scheduled reproduction start time and the designated time are the same (S22: NO), the packet of the designated sequence number is synchronized, and the reproduction time of the entire content is synchronized, so the CPU The processing unit 22 continues the reproduction as it is.

  As described above, in this example, based on the synchronization information transmitted from the server separately from the content stream, the reproduction of the packet specified by the sequence number included in the synchronization information is started at the specified time included in the synchronization information. By controlling the playback time, the playback time can be synchronized.

[Example 2]
This example is suitably used for unicast in which the server SV and the client CL communicate one-on-one. In the unicast, as shown in FIG. 8, the content stream transmitted from the server SV to the client CL is provided with header information (hereinafter referred to as a header) indicating details of each content at the head of each content. . The header includes, for example, format information (Format Tag), channel information (Channels), sampling frequency (Samples / Seconds), average bit rate (Average Bitrate), title (Title), artist name (Author), , Timestamp (Time
Stump) and playback time (Play Time).

  The server SV includes the synchronization information packet in the header of the stream in FIG. 8 and transmits it to the client CL. Specifically, the synchronization information packet is transmitted by being included in the header of the content immediately before the content whose playback start time is to be adjusted. Accordingly, the synchronization information can be reliably analyzed when starting the reproduction of the content whose reproduction start time is to be adjusted. That is, the synchronization information is information for adjusting the time to start playback of the content next to the content whose synchronization information is included in the header, and is information for synchronizing the playback time of the client CL. The synchronization information is not included in the headers of all contents, but may be included in the headers of some contents with appropriate intervals. If necessary, the synchronization information may also be included in the header of the content whose playback start time is to be adjusted for confirmation when the playback time is synchronized.

  FIG. 9 is a diagram showing the synchronization information of this example, where (a) is the synchronization information included in the header of the content immediately before the content whose playback start time is to be adjusted, and (b) is the playback start time being adjusted. It is the synchronization information for confirmation contained in the header of the content to be. First, the synchronization information in (a) includes an expiration date, a specified time, a content length (playback time), and processing in asynchronous time. The expiry date is the expiry date (time) of processing for matching the playback time of the content designated by the client CL using the synchronization information. For example, when the synchronization information is received later than the expiry date, Ignore the synchronization information and do not execute the synchronization process. The designated time is the reproduction start time designated by the server side of the content next to the content including the synchronization information, that is, the reproduction end time of the content including the synchronization information. The length (time) of the content is a reproduction time of the content including the synchronization information, and is used to calculate a reproduction start scheduled time for the next content. Asynchronous processing indicates processing when the scheduled reproduction start time is different from the designated time. For example, in the asynchronous process, when the scheduled reproduction start time is earlier than the designated time, nothing is reproduced until the designated time, or the content is reproduced repeatedly until the designated time. Alternatively, when the scheduled reproduction start time is later than the designated time, a part of the content (which may be the last or middle) is not reproduced or faded out by the designated time.

  The synchronization information shown in FIG. 9B includes a designated time. The designated time is a reproduction start time designated by the server of the content including the synchronization information. When adjusting the reproduction start time of the content, it is confirmed whether or not it coincides with the designated time in FIG. It is information to do.

  FIG. 10 is a flowchart showing the synchronization processing of the playback start time of the client CL. In this example, the case where the reproduction start time of the content D in the content list shown in FIG. 3 is adjusted will be described as an example. The CPU processing unit 22 waits for reception of synchronization information (S31), and when receiving the header of the content C, receives the synchronization information shown in FIG. 9A included in the header (S31). : YES). Next, the CPU processing unit 22 determines whether or not the synchronization information is valid (S32). That is, it is determined whether the current time has passed the expiration date included in the synchronization information. If it is not valid (S32: NO), the process is terminated. If valid (S32: YES), the CPU processing unit 22 corrects the system time of the client CL by accessing the NTP server (S33).

  The CPU processing unit 22 waits for the reproduction start of the content C including the synchronization information included in the header (S34). When the content C starts to be reproduced (S34: YES), the CPU processing unit 22 stores the reproduction start time of the content C in the memory (S35). Next, the CPU processing unit 22 extracts the length (time) of the content from the synchronization information (S36).

  Next, the CPU processing unit 22 calculates the scheduled playback start time of the content D, that is, the scheduled playback end time of the content C (S37). Specifically, the reproduction start time of the content D is obtained by adding the length (reproduction time) of the content C acquired in S36 to the reproduction start time of the content C stored in S35.

  Next, the CPU processing unit 22 extracts a designated time in the synchronization information (S38). Then, the CPU processing unit 22 compares the scheduled reproduction start time of the content D with the designated time extracted from the synchronization information (S39, S41, S43).

  Note that when the header of the content D is received, the synchronization information shown in FIG. 9B included in the header is extracted, and the specified time included in the synchronization information is included in the header of the content C in S38. It is confirmed whether it is the same as the specified time extracted from the synchronization information (S40). When the designated times are different (S40: NO), the reproduction is continued without changing the reproduction time of the content D to the designated time (S45).

  Hereinafter, a case where the designated times are the same (S40: YES) will be described.

  When the scheduled playback start time of the content D is earlier than the specified time (S41: YES), if the playback is continued as it is, the content D is played earlier than the specified time. Therefore, the CPU processing unit 22 waits for the reproduction of the content D until the designated time and starts the reproduction (delays the reproduction start time until the designated time) (S42). For example, if the reproduction start scheduled time is 18:59:55 and the specified time is 19:00:00, nothing is reproduced between 18:59:55 and 19:00:00. Alternatively, the previous content C is reproduced repeatedly for 5 seconds. The selection of these processes is executed based on the “process when asynchronous” in the synchronization information. Then, at 19:00:00, the CPU processing unit 22 starts the reproduction of the content D. As a result, when the playback time of the content is earlier by 5 seconds, the playback time of all the content can be synchronized by delaying the playback time by 5 seconds.

  On the other hand, when the scheduled reproduction start time is later than the designated time (S43: YES), if the reproduction is continued as it is, the content D is reproduced with a delay from the designated time. Therefore, the CPU processing unit 22 does not reproduce a part of the previous content C so that the content D can be reproduced at the designated time (the reproduction start time is advanced to the designated time) (S44). For example, if the scheduled playback start time is 19:00:05 and the specified time is 19:00:00, the playback is originally scheduled to start from 19:00:05 to 19:00:05. A part of the content C is cleared from the buffer 32. The selection of these processes is executed based on the “process when asynchronous” in the synchronization information. Then, at 19:00:00, the CPU processing unit 22 starts the reproduction of the content D. As a result, when the playback time of the content is delayed by 5 seconds, the playback time of all the content can be synchronized by advancing the playback time by 5 seconds.

  If the scheduled playback start time and the designated time are the same (S43: NO), since the content playback is synchronized, the CPU processing unit 22 continues the playback as it is (S45).

  As described above, in this example, based on the synchronization information included in the header of the content immediately before the content to be matched with the playback start time, control is performed to start playback of the content at the specified time included in the synchronization information. Thus, the playback time can be synchronized.

[Example 3]
This example is employed for multicast in which the server SV communicates with a plurality of clients CL simultaneously. In multicast, the header cannot be transmitted for each content as in the second embodiment, and when the client CL connects to the server SV, the header is included in the NSC file (multicast information file) and transmitted to the client CL. In this example, as shown in FIG. 11, the time adjustment content is transmitted immediately before the content D whose reproduction time is to be adjusted. In order to adjust the reproduction time of the content D, the time adjustment content is content that is repeatedly reproduced when the reproduction time is delayed, and is partially not reproduced when the reproduction time is advanced. Since the time adjustment content is, for example, an advertisement of the broadcasting station itself, even if such processing is performed, viewers will not be uncomfortable. The combination of the bit rate and sampling frequency of the time adjustment content does not overlap with that of other content so that whether the content is time adjustment content can be determined by the bit rate and sampling frequency of the content. It has become.

  FIG. 12 is a diagram showing the synchronization information, and the synchronization information is included in the NSC file. Thus, the synchronization information can be reliably analyzed when the reproduction of the content D whose reproduction start time is to be adjusted is started. The synchronization information is information for adjusting the time to start playback of the next content after the time adjustment content, and is information for synchronizing the playback time of the client CL. Although there is only one synchronization information in the NSC file, when a plurality of time adjustment contents are distributed from the server SV, the reproduction start time of the next content of each time adjustment content is adjusted with reference to the same synchronization information. It has become so. That is, as will be described in detail later, the synchronization time in this example does not include the specified time, and the client side calculates the specified time each time.

  The synchronization information includes a bit rate, sampling frequency, time correction accuracy, maximum correction time, content length (reproduction time), and asynchronous processing. As described above, the bit rate and the sampling frequency are the bit rate and the sampling frequency of the time adjustment content used for specifying the time adjustment content.

  The time correction accuracy is information for calculating the designated time each time, and is either a time unit, a minute unit, or a second unit. Here, a method of calculating the designated time using the time correction accuracy will be described in detail with reference to FIG. The designated time is the closest time such that the scheduled playback end time of the time adjustment content is set to 00 in units of time correction accuracy or less. For example, when the reproduction end time of the time adjustment content is 19:00:50, and the time correction accuracy is in seconds, the designated time is from the scheduled end time of the time adjustment content among the times when the second becomes 00. It is the closest time, and in this case, it becomes 19:01:00 as in (1). (On the other hand, if the scheduled end time of the time adjustment content is 19:00:20, the specified time is 19:00:00). Next, if the time correction accuracy is in minutes, the designated time is the time closest to the scheduled end time of the time adjustment content among the times when the minutes and seconds become 00, and in this case, 19:00 as in (2) It becomes 00 minutes. Next, if the time correction accuracy is a time unit, the designated time is the time closest to the scheduled end time of the time-adjusted content among the times at which the hour, minute, and second become 00. In this case, 00 is set as 00. It becomes 00:00. Note that the time correction accuracy may include a day unit.

  The length (time) of the content is the reproduction time of the time adjustment content, and is used to calculate the scheduled reproduction start time of the content whose reproduction time should be adjusted. Asynchronous processing indicates processing when the scheduled reproduction start time is different from the designated time. For example, in the asynchronous process, when the scheduled reproduction start time is earlier than the designated time, nothing is reproduced until the designated time, or the time-adjusted content is reproduced repeatedly until the designated time. Alternatively, when the scheduled reproduction start time is later than the designated time, a part of the time adjustment content (which may be the last or middle) is not reproduced or faded out by the designated time.

  FIG. 14 is a flowchart showing synchronization processing of the reproduction start time of the client CL. In this example, as shown in FIG. 11, a case where the time adjustment content is included before the content D of the content list and the reproduction start time of the content D is adjusted will be described as an example.

  The CPU processing unit 22 stands by for the start of reproduction of the time adjustment content (S51). The start of reproduction of the time adjustment content is determined by checking the bit rate and sampling frequency of the content being reproduced. When the time adjustment content starts to be reproduced (S51: YES), the CPU processing unit 22 stores the reproduction start time of the time adjustment content in the memory (S52). Next, the CPU processing unit 22 extracts the length (reproduction time) of the time adjustment content from the synchronization information (S53).

  Next, the CPU processing unit 22 calculates the scheduled playback start time of the content D, that is, the scheduled playback end time of the time adjusted content (S54). Specifically, the reproduction start scheduled time of the content D is obtained by adding the length (reproduction time) of the time adjustment content acquired in S53 to the reproduction start time of the time adjustment content stored in S52.

  Next, the CPU processing unit 22 calculates a designated time based on the time correction accuracy and the scheduled reproduction end time of the time adjustment content (S55). Specifically, first, the time correction accuracy in the synchronization information is extracted. As described above, with reference to FIG. 13, if the scheduled end time of reproduction of the time adjustment content calculated in S54 is 19:00:50 and the time correction accuracy is, for example, minutes, the designated time is 19:00. It becomes 00 minutes. Then, the CPU processing unit 22 compares the scheduled reproduction start time of the content D with the designated time calculated in S55 (S56, S57, S58).

  If the scheduled playback start time of the content D is earlier than the specified time (S57: YES), if the playback is continued as it is, the content D is played earlier than the specified time. Therefore, the CPU processing unit 22 waits until the designated time and starts reproducing the content D (S58). For example, as shown in (1) of FIG. 13, if the scheduled reproduction start time is 19:00:50 and the calculated specified time is 19:01:00, 19:00:50 to 19:00 Nothing is played back until 01:00, or the time-adjusted content is played back repeatedly for 10 seconds. The selection of these processes is executed based on the “process when asynchronous” in the synchronization information. Then, at 19:01:00, the CPU processing unit 22 starts reproducing the content D. As a result, when the playback time of the content is 10 seconds earlier, the playback time of the content can be synchronized by delaying the playback time by 10 seconds.

  On the other hand, when the scheduled reproduction start time is later than the designated time (S59: YES), if the reproduction is continued as it is, the content D is reproduced with a delay from the designated time. Therefore, the CPU processing unit 22 does not reproduce part of the time adjustment content so that the reproduction of the content D can be started at the specified time (S60). For example, as shown in (2) of FIG. 3, if the scheduled reproduction start time is 19:00:50 and the specified time is 19:00:00, it is originally 19:00:00 to 19:00 A part of the time adjustment content scheduled to be played back by 50 seconds is cleared from the buffer 32. The selection of these processes is executed based on the “process when asynchronous” in the synchronization information. Then, at 19:00:00, the CPU processing unit 22 starts the reproduction of the content D. As a result, when the playback time of the content is delayed by 50 seconds, the playback time of the content can be synchronized by advancing the playback time by 50 seconds.

  If the scheduled reproduction start time is the same as the designated time (S59: NO), the content reproduction is synchronized, so the CPU processing unit 22 continues the reproduction as it is (S61).

  As described above, in this example, the time adjustment content is identified based on the synchronization information included in the NSC file, and the reproduction of the time adjustment content is controlled to control the designated time at which the next content of the time adjustment content is calculated. Start playing. As a result, even when a header cannot be assigned for each content as in multicast, it is possible to synchronize playback times. This is because the designated time is calculated each time from the scheduled end time of the time adjustment content and the time correction accuracy, so that the reproduction time can be adjusted multiple times with one synchronization information.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment. The present invention may be provided in the form of a computer program for operating the above server and client or a recording medium recording the computer program.

  The present invention can be suitably applied to broadcasting using Internet streaming.

It is a block diagram which shows the structure of the content reproduction apparatus 1 by preferable embodiment of this invention. It is a block diagram which shows the structure of server SV. It is a figure which shows a content list. It is a block diagram which shows the structure of the client CL. It is a figure which shows the header information of the packet of Example 1. FIG. It is a figure which shows the synchronous information of Example 1. 6 is a flowchart illustrating reproduction time adjustment processing according to the first exemplary embodiment. It is a figure which shows the stream of Example 2. FIG. It is a figure which shows the synchronous information of Example 2. 10 is a flowchart illustrating reproduction time adjustment processing according to the second embodiment. 10 is a flowchart illustrating a content list according to the third embodiment. It is a figure which shows the synchronous information of Example 3. It is a figure which shows the method of calculating the designated time of Example 3. FIG. 12 is a flowchart illustrating reproduction time adjustment processing according to the third embodiment.

Explanation of symbols

1 Content playback device 21 HDD
22 CPU processing unit 23 communication unit 31 microcomputer processing unit 32 buffer 33 memory 34 audio processing unit 35 DAC
36 Communication Unit 37 Input Device 38 Display Device SV Server CL Client

Claims (5)

A server and a client connectable to the server,
The server
Storage means for storing a plurality of contents;
Content transmitting means for transmitting the content to the client in units of packets;
Synchronization information transmitting means for transmitting synchronization information including a sequence number of a packet whose reproduction time is to be adjusted and a designated time of the packet specified by the sequence number;
The client
Receiving means for receiving the content and the synchronization information;
Playback means for playing back the content;
Means for calculating a scheduled reproduction start time of the packet specified by the sequence number;
A comparison means for comparing the scheduled reproduction start time with the designated time;
If the scheduled playback start time is earlier than the specified time according to the comparison result of the comparison means, the playback start time of the packet specified by the sequence number is delayed to the specified time, and the scheduled playback start time is A content reproduction system comprising: time adjustment means for advancing the reproduction start time of the packet specified by the sequence number to the designated time when it is later than the designated time. A server and a client connectable to the server,
The server
Storage means for storing a plurality of contents;
Content transmitting means each transmitting content including header information to the client;
Synchronization information transmitting means for transmitting the synchronization information including the specified time of the content whose playback time is to be adjusted included in the header information of the content transmitted immediately before the content whose playback time is to be adjusted,
The client
Receiving means for receiving the content and the synchronization information;
Playback means for playing back the content;
Means for calculating a scheduled reproduction start time of the content next to the content whose synchronization information is included in the header information;
A comparison means for comparing the scheduled reproduction start time with the designated time;
If the scheduled playback start time is earlier than the specified time according to the comparison result of the comparison means, the playback start time of the content next to the content whose synchronization information is included in the header information is delayed to the specified time. When the scheduled reproduction start time is later than the designated time, the content reproduction has time adjustment means for advancing the reproduction start time of the content next to the content whose synchronization information is included in the header information to the designated time. system. A server and a client connectable to the server,
The server
Storage means for storing a plurality of contents and time adjustment contents;
Content transmitting means for transmitting to the client the content and the time-adjusted content that is transmitted before the content whose playback time is to be adjusted, and whose combination of bit rate and sampling frequency does not overlap with other content;
Synchronization information transmitting means for transmitting synchronization information including the bit rate and sampling frequency of the time adjustment content and time correction accuracy;
The client
Receiving means for receiving the content, the time adjustment content and the synchronization information;
Playback means for playing back the content;
Means for calculating a scheduled reproduction end time of the time adjustment content;
Means for calculating a designated time based on the scheduled reproduction end time of the time adjustment content and the time correction accuracy;
A comparison means for comparing the reproduction end scheduled time with the designated time;
If the scheduled playback end time is earlier than the specified time according to the comparison result of the comparing means, the playback start time of the next content after the time adjustment content is delayed to the specified time, and the scheduled playback end time is A content reproduction system comprising time adjustment means for advancing the reproduction start time of the next content after the time adjustment content to the designated time when the time is later than the designated time.   The server used for the content reproduction system in any one of Claims 1-3.   The client used for the content reproduction system in any one of Claims 1-3.

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