JP3831323B2 - Stream receiving system and stream receiving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionA stream receiving system in which a stream receiving device receives an encoded stream distributed via an asynchronous network, and a stream receiving method executed in the stream receiving system;About.
[0002]
More specifically, the present invention provides a server that transmits request request data from a client using a stream transmission method in an asynchronous network such as an IP network in which the transmission time of a packet between two points is not constant. The present invention relates to a stream distribution technique that can improve the decoding accuracy when a client receives and decodes the data.
[0003]
[Prior art]
When high-quality digitized video and audio are transmitted in accordance with standardized standards, they are usually compressed using a compression technique such as MPEG (ITU-T recommendation H.222.0) or transmitted digitally. The signal is transmitted using a modulated radio wave.
[0004]
When digital data is compressed and transmitted, it is either a stream transmission type where data is transmitted as a stream that is continuous data subject to time constraints such as real-time video communication, or data is unilaterally without time constraints. Transmit using either the download transmission type transmission method.
[0005]
In a data stream type client / server system that performs stream type data transmission, when decoding is performed on the client side with respect to an information generation source generated on the server side such as output data and accumulated data of an encoding circuit. Needs to be decrypted while synchronizing with the information source.
[0006]
If it is possible for the client side to adjust the data rate to the server side using RTCP ("RTP: A Transport Protocol for Real-Time Applications", RFC1889) when decrypting on the client side Although it is possible to synchronize with the information generation source, if there is a time restriction such as real-time video communication, the time restriction cannot be maintained if the rate is controlled. If the data is data stored in advance, re-encoding is necessary.
[0007]
When the client cannot perform rate control on the server, the information generation source and the decoding circuit perform processing using independent system clocks. If each system clock refers to a common clock and a system clock that matches that clock cannot be generated, the data rate on the server side and the decryption rate on the client side are processed at different values. Plays back earlier or later, which causes a buffer overflow or underflow in the decoding circuit, and as a result, the video and audio presented to the user on the client side are temporarily stopped. It will be.
[0008]
For such a problem, a method of encapsulating data in a transport stream (hereinafter abbreviated as MPEG2-TS) in accordance with the MPEG standard has been proposed.
[0009]
In the transmission method using MPEG2-TS, which is also used in BS digital broadcasting, one time index called PCR (program clock reference) is inserted in the stream within at least 100 milliseconds.
[0010]
A client that has received this PCR generates a clock using a circuit called a PLL (phase lock loop) that generates a clock from the time of reception, the order of reception, and the value of the PCR. By using the same system clock as the information generation source, it is possible to receive, decode and present information.
[0011]
In order to generate a clock using an existing PLL circuit, the jitter (for example, see Non-Patent Document 1) of a packet received on the client side must be within several milliseconds. It can be used in networks, special ATM networks, and small networks.
[0012]
On the other hand, when using a network that goes through a plurality of external network devices such as routers during transmission, the clock cannot be generated even if a PLL circuit is used due to increased jitter. A method of generating a clock or a clock from a broadband digital communication network such as ISDN (for example, see Patent Document 1) has been proposed.
[0013]
However, this method has a problem that an asynchronous network such as an IP network having a large jitter must also have a synchronous network serving as a clock generation source such as ISDN at the same time.
[0014]
[Non-Patent Document 1]
Annex A of ATM Forum "Audio / Visual Multimedia Services: Video on Demand v1.1" af-saa-0049.001, March 1997
[Patent Document 1]
JP-A-8-251152
[0015]
[Problems to be solved by the invention]
As described above, there are the following problems in accordance with the prior art.
[0016]
That is, in the transmission method using MPEG2-TS, which is also used in BS digital broadcasting, one time index called PCR is inserted into the stream within at least 100 milliseconds.
[0017]
A client that has received this PCR generates a clock using a circuit called a PLL that generates a clock from the time of reception, the order of reception, and the value of the PCR, and uses this generated clock as an information source. Reception, decoding, and information presentation can be performed using the same system clock.
[0018]
However, in order to generate a clock using an existing PLL circuit, the jitter of a packet received on the client side must be within a few milliseconds, so a digital broadcasting network such as BS digital, a special ATM network, Although it can be used in a small-scale network, there is a problem that it cannot be used in a network that passes through a plurality of external network devices such as routers for transmission.
[0019]
On the other hand, when using a network that goes through multiple external network devices such as routers for transmission, a clock cannot be generated even if a PLL circuit is used. A method of generating a clock from a broadband digital communication network such as ISDN has been proposed.
[0020]
However, this method has a problem that an asynchronous network such as an IP network having a large jitter must also have a synchronous network serving as a clock generation source such as ISDN at the same time.
[0021]
The present invention has been made in view of such circumstances, and in an asynchronous network such as an IP network in which the transmission time of a packet between two points is not constant, a server sends request request data from a client in a stream transmission method. An object of the present invention is to provide a new stream distribution technique that can improve the decoding accuracy when the client receives the data and receives the data for decoding.
[0022]
[Means for Solving the Problems]
  The stream of the present inventionThe system reception system includes a stream relay device, a synchronization signal relay device, and a stream reception device that are connected to each other via a connection synchronization network.
  (1) Configuration of stream relay device
  The stream relay apparatus receives (a) an encoded stream to which a time index is generated that is generated by the stream distribution apparatus based on a clock used by the broadcast station from the stream distribution apparatus connected via the asynchronous network. And (b) transmitting means for transmitting the encoded stream received by the receiving means to the stream receiving device via the connection synchronization network.
  (2) Configuration of synchronization signal relay device
  The synchronization signal relay apparatus receives (a) a synchronization stream to which a broadcast station has added a time index generated based on a predetermined clock via a relay synchronization network provided separately from the connection synchronization network. Means, (b) shaping means for shaping the synchronization stream received by the receiving means into a form that can be received by the stream receiving device, and (c) receiving the synchronization stream shaped by the shaping means via the connection synchronization network. Transmitting means for transmitting to the apparatus.
  (3) Configuration of stream receiver
  The stream receiving device includes (a) a first receiving means for receiving a synchronizing stream from the synchronizing signal relay device via the connection synchronizing network, and (b) broadcasting from the synchronizing stream received by the first receiving means. Generating means for generating the clock used by the station, (c) second receiving means for receiving the encoded stream from the stream relay device via the connection synchronization network, and (d) the clock generated by the generating means. And a decoding means for decoding the encoded stream received by the second receiving means.
  When adopting this configuration, the receiving means included in the stream relay device is provided with a time index generated based on the clock generated from the synchronization stream received from the broadcasting station by the stream distribution device via the relay synchronization network. An added encoded stream may be received.
  In addition, when the broadcast station uses a standard clock, the receiving means included in the synchronization signal relay apparatus may receive a synchronization stream from a broadcast station different from the broadcast station used by the stream distribution apparatus.
  In addition, when the broadcasting station uses a standard clock, the receiving means included in the stream relay device may receive the encoded stream generated based on the standard clock generated by the stream distribution device from the stream distribution device. is there.
[0048]
  In the stream receiving system of the present invention configured as described above,When the relay device receives the synchronization stream from the broadcasting station, it converts the received synchronization stream into an IP packet, thereby shaping the received synchronization stream into a form that can be received by the stream reception device. Send.
  At this time, the synchronization signal relay device may transmit only the synchronization stream portion to which the time index is added, which is the stream portion required by the stream reception device.
  On the other hand, the stream relay device receives the encoded stream to which the time index generated by the stream distribution device based on the clock used by the broadcast station is received from the stream distribution device connected via the asynchronous network.
[0050]
  Upon receiving the IP packetized synchronization stream, a stream receiving deviceIs in sync signalWhen the synchronization stream is received from the relay device, the clock used by the broadcasting station is generated from the received synchronization stream. AndConnected via an asynchronous networkWhen receiving the reception target stream transmitted from the stream distribution apparatus and receiving the reception target stream, the reception target stream is decoded using the clock generated from the synchronization stream.
[0051]
  Thus, in the stream reception system of the present invention, by using the synchronization stream broadcast by the broadcast station, it is possible to share the clock among the broadcast station, the stream distribution device, and the stream reception device, thereby Since the stream distribution device and the stream reception device can perform encoding and decoding with the same clock, buffer overrun and underrun can be prevented, and video and audio Can be presented to the user without interruption.
  Moreover, in the stream distribution system of the present invention, since clock synchronization is realized using a synchronization stream broadcast by a broadcasting station, only a facility capable of receiving broadcasting from the broadcasting station is required, and a broadband digital communication network such as ISDN is required. Such as an atomic clock, because it can be realized without using a standard clock (a clock that can always obtain the same value regardless of where it is measured in the world). There is no need to prepare facilities.
  And in realizing this, the synchronization signalIf no relay device is provided, each stream receiver must be equipped with an antenna and other equipment for receiving the synchronization stream.Since the stream reception system of the present invention employs a configuration including a synchronization signal relay device,Only the relay device needs to be equipped with an antenna and other equipment for receiving the synchronization stream.During sync signalThe plurality of stream receiving devices connected to the relay device do not need to be provided with equipment such as an antenna for receiving the synchronization stream.
[0052]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail according to embodiments.
[0053]
As the network, there are an asynchronous network having a large jitter such as an IP network and a synchronous network having a small jitter such as a digital broadcasting network.
[0054]
In an asynchronous network with large jitter such as an IP network, (1) two hosts are connected via a plurality of network devices such as gateways, routers, repeaters, and hubs, and (2) packet transmission between the two hosts. The time required for this is not constant, and its jitter is much larger than 10 milliseconds.
[0055]
On the other hand, in a synchronous network such as a digital broadcasting network, (1) two hosts are directly connected via wire or wireless, and (2) the time required for packet transmission between the two hosts is almost constant. The jitter is within 10 milliseconds, and the clock can be extracted using a PLL when MPEG2-TS is transmitted.
[0056]
Here, even an asynchronous network such as an ATM may have these characteristics. Therefore, in the present invention, an ATM network having these characteristics is also treated as a special synchronous network.
[0057]
FIG. 1 illustrates a basic system configuration of the present invention.
[0058]
As shown in this figure, the present invention comprises a transmission server 1 that provides a video-on-demand service, a digital broadcasting station 2, and a plurality of clients 3. Each client 3 is on an asynchronous network 4. Are connected to a digital broadcast station 2 on a synchronous network 5.
[0059]
The transmission server 1 and the digital broadcasting station 2 have a transmission mechanism for transmitting a stream to which a time index is added using a predetermined clock (which may be a standard clock).
[0060]
Here, the standard clock means a clock that can always acquire the same value regardless of where it is measured in the world, and is a clock based on a standard time that can be acquired from a GPS or an atomic clock.
[0061]
On the other hand, the client 3 receives a stream from the digital broadcasting station 2 on the synchronous network 5 and generates a clock, and receives the stream from the transmission server 1 on the asynchronous network 4 and uses the generated clock. And a decryption mechanism.
[0062]
  〔I〕First technique related to the present invention
  Figure 2 shows theThe first technology related to Ming1 illustrates an example of a system configuration to be realized.
[0063]
  This figure2Shown inThe first technology related to the present inventionWhen realized, the outgoing server 1 is connected to the client 3 via the asynchronous network 4 and connected to the digital broadcast station 2 via the synchronous network 5 connecting the digital broadcast station 2 and the client 3. Will be.
[0064]
FIG. 3 shows an example of detailed device configurations of the transmission server 1, the digital broadcasting station 2, and the client 3 for realizing the system configuration shown in FIG.
[0065]
  The first technique related to the present invention shown in FIG.The digital broadcasting station 2 performs a process of broadcasting a synchronization stream to which a time index is added using a predetermined clock (a special stream need not be prepared and an encoded stream of a normal broadcast program may be used). Therefore, the transmission server 1 receives the broadcast of the synchronization stream, generates a clock used by the digital broadcast station 2, and uses the clock to generate a self-excited crystal oscillator. While performing the process of adjusting the clock to the clock, the stream to be provided to the client 3 is encoded, and a time index is added, and the stream is transmitted to the client 3 via the asynchronous network 4.
[0066]
On the other hand, the client 3 receives the synchronization stream broadcasted by the digital broadcast station 2, generates a clock used by the digital broadcast station 2, and then uses the clock to generate its own clock. While performing processing for adjusting the clock of the excited crystal oscillator to the clock, processing is performed so as to receive and decode the requested encoded stream transmitted from the transmission server 1.
[0067]
As described above, the transmission server 1 receives a stream from any one of the digital broadcasting stations 2 that broadcast a stream encoded using a predetermined clock and added with a time index, and the digital broadcast is transmitted from the stream. The clock used by the station 2 is generated, and the moving image data is encoded using the generated clock and stored, or processed so as to be transmitted to the client 3 as it is.
[0068]
The clock adjustment processing performed at this time is continuously performed while encoding and while transmitting a stream to the client 3.
[0069]
The client 3 generates a clock used by the digital broadcast station 2 from the synchronization stream received from the digital broadcast station 2, and uses the generated clock to transmit its own request transmitted from the transmission server 1. The encoded stream thus received is processed to be decoded.
[0070]
That is, as shown in the processing flow of FIG. 4, when the client 3 selects a channel that broadcasts a program to be a synchronization stream, the client 3 receives the stream from the selected channel and receives the clock from the received stream. Is extracted, and the process of matching the clock of the self-excited crystal oscillator that the user has with the extracted clock is entered, and the clock matching is continued.
[0071]
At this time, when a stream request request is issued from the user, the stream is requested to the originating server 1, and when there is a notification of the encoding rate from the originating server 1 in response to this request, it is received, While receiving the stream sent from the outgoing server 1, while extracting the stream from the outgoing server 1, the clock was extracted from the self-excited crystal oscillator that I had, and the extracted clock and received Using the encoding rate, the received stream is decoded and output to the monitor.
[0072]
  Like thisIn the first related technique of the present invention shown in FIG.Realizes sharing of a clock among the digital broadcasting station 2, the transmission server 1, and the client 3 by using a synchronization stream broadcast by the same digital broadcasting station 2, thereby enabling the same clock to be used. Since encoding and decoding are performed, buffer overrun and underrun can be prevented, so that video and audio can be presented to the user without interruption.
[0073]
Here, in order to decode the stream transmitted from the transmission server 1, the client 3 needs to specify the digital broadcasting station 2 that is broadcasting the synchronization stream received by the transmission server 1. .
[0074]
Therefore, the transmission server 1 informs the client 3 of the digital broadcasting station 2 that is broadcasting the synchronization stream in order to inform the client 3 of which synchronization stream to be broadcast by the digital broadcasting station 2 is received. In response to the notification of the information for specifying, the client 3 obtains information for specifying the digital broadcasting station 2 that broadcasts the synchronization stream from the transmission server 1, and based on the information. Thus, the synchronization stream received by the transmission server 1 can be received from the digital broadcasting station 2.
[0075]
When the transmission server 1 does not have such a notification function, the client 3 manages whether each digital broadcasting station 2 is broadcasting a stream for synchronization. By making an inquiry to the broadcast station 2, the digital broadcast station 2 that is broadcasting the stream used for synchronization is searched.
[0076]
When the system configuration shown in FIG. 2 is followed, since the transmission server 1 and the client 3 receive a stream from the common digital broadcasting station 2, the clock of the digital broadcasting station 2 is set to the standard clock. However, when the clock of the digital broadcast station 2 is set to the standard clock, the transmission server 1 is connected to the same digital broadcast station 2 as the digital broadcast station 2 to which the client 3 is connected. There is no need to be.
[0077]
In other words, when each digital broadcasting station 2 is set to the standard clock by receiving GPS or extracting the clock from the atomic clock, as shown in FIG. The digital broadcast station 2a connected to the digital broadcast station 2 to which the client 3 is connected is connected to the digital broadcast station 2a through a synchronization stream (a time index generated based on the standard clock is generated from the digital broadcast station 2a). It is possible to perform clock synchronization by receiving (added).
[0078]
FIG. 6 shows an example of detailed device configurations of the transmission server 1, the digital broadcast station 2, and the client 3 for realizing the system configuration shown in FIG.
[0079]
As shown in FIG. 6, the device configurations of the transmission server 1, the digital broadcasting station 2, and the client 3 are basically the same as those when the system configuration shown in FIG. 2 is used.
[0080]
Therefore, the processing when the system configuration shown in FIG. 5 is used is the same as the processing when the system configuration shown in FIG. 2 is used.
[0081]
That is, the digital broadcasting stations 2 and 2a encode using a standard clock, record a time index in a packet, generate a stream for synchronization, and broadcast the stream.
[0082]
In response to this, the client 3 sends a synchronization stream from any one of the digital broadcasting stations (the digital broadcasting station 2 in the case of FIG. 5) broadcasting the synchronization stream via the synchronization network 5. And generate a standard clock from the stream. Then, the client 3 synchronizes the clock of the self-excited crystal oscillator that the client 3 has with the standard clock. This self-excited crystal oscillator clock synchronization process is continuously performed while a stream is received from the transmission server 1 and decoded.
[0083]
On the other hand, the transmission server 1 receives a synchronization stream from any one of the digital broadcast stations broadcasting the synchronization stream (in the case of FIG. 5, the digital broadcast station 2a), and receives the standard clock from the stream. Is generated. Then, the transmission server 1 encodes the stream to be provided to the client 3 using the generated standard clock, and records the time index in the packet.
[0084]
In response to the processing of the transmission server 1, the client 3 receives the encoded and time-indexed stream from the transmission server 1 that provides the desired service together with information necessary for decoding including the encoding rate. Then, the decoding is started. At that time, decoding is performed using a standard clock obtained from the synchronization stream.
[0085]
In this way, even when the system configuration shown in FIG. 5 is used, it is possible to share the clock among the digital broadcasting station 2, the transmission server 1, and the client 3, and thereby encode with the same clock. Thus, the buffer overrun and underrun can be prevented, and the video and audio can be presented to the user without interruption.
[0086]
Here, when the system configuration shown in FIG. 5 is used, the transmission server 1 generates the standard clock from the synchronization stream broadcast by the digital broadcasting station 2a. However, as shown in FIG. The server 1 itself may be provided with a standard clock generation mechanism such as GPS.
[0087]
FIG. 8 shows an example of detailed device configurations of the transmission server 1, the digital broadcast station 2, and the client 3 for realizing the system configuration shown in FIG.
[0088]
As shown in this figure, when the transmission server 1 itself has a standard clock generation mechanism such as GPS, the transmission server 1 generates a standard clock from a synchronization stream broadcasted by a digital broadcasting station 2a or the like. There is no need to provide a mechanism for processing.
[0089]
  [B]Second technique related to the present invention
  In FIG.Second technology related to Ming1 illustrates an example of a system configuration to be realized.
[0090]
  thisThe second technique related to the present invention shown in FIG.A gateway 6 is provided.
[0091]
The gateway 6 is connected to the transmission server 1 via the asynchronous network 7, connected to the digital broadcasting station 2 via the synchronous network 9, and further connected to the client 3 via the synchronous network 8. Become.
[0092]
Here, the transmission server 1 is connected to the broadcasting station 2 via the synchronous network 9. Although not shown in FIG. 9, a plurality of clients 3 are connected to one gateway 6.
[0093]
  NaIn the second technique related to this invention,The provided synchronization network 8 is, for example, a small-scale network for connecting a plurality of clients 3 used in one house or the like.
[0094]
FIG. 10 illustrates an example of detailed apparatus configurations of the transmission server 1, the digital broadcasting station 2, the client 3, and the gateway 6 for realizing the system configuration illustrated in FIG.
[0095]
  The second technique related to the present invention shown in FIG.Since the digital broadcasting station 2 performs a process of broadcasting a synchronization stream to which a time index is added using a predetermined clock, the transmission server 1 receives the synchronization stream broadcast, and then Generate a clock used by the digital broadcasting station 2, and use the clock to encode the stream to be provided to the client 3 while processing the clock of its own self-excited crystal oscillator to the clock. At the same time, a time index is added and processed to be transmitted to the client 3 via the gateway 6 via the asynchronous network 7.
[0096]
On the other hand, the gateway 6 receives a synchronization stream broadcast by the digital broadcasting station 2, generates a clock used by the digital broadcasting station 2, and uses the clock to generate a self-excited crystal owned by itself. By performing the process of matching the clock of the oscillator to the clock, the jitter of the stream transmitted from the transmission server 1 is absorbed and transmitted to the client 3 at equal intervals.
[0097]
In response to the intervention of the gateway 6, the client 3 generates a clock from the stream transmitted from the transmission server 1 via the gateway 6 using the existing PLL circuit, and decodes the stream according to the clock. To process.
[0098]
As described above, the transmission server 1 receives a stream from any one of the digital broadcasting stations 2 that are broadcasting a stream encoded with a predetermined clock and added with a time index. The clock used by the broadcasting station 2 is generated, and the moving image data is encoded and stored using the generated clock, or is processed to be transmitted to the client 3 via the gateway 6 as it is.
[0099]
The clock adjustment processing performed at this time is continuously performed while encoding and while transmitting a stream to the client 3.
[0100]
Then, the gateway 6 generates a clock used by the digital broadcast station 2 from the synchronization stream received from the digital broadcast station 2 and uses the generated clock to transmit the client 3 transmitted from the transmission server 1. The transmission interval of the requested stream is adjusted to be equal, and processing is performed to transmit it to the client 3.
[0101]
Then, the client 3 receives the stream transmitted from the transmission server 1 in which the jitter is absorbed, and the client 3 uses the existing PLL circuit from the stream from the transmission server 1 transmitted via the gateway 6. A clock is generated and processed to decode the stream according to the clock.
[0102]
  SnowThat is, in the first technique related to the present invention shown in FIG.The client 3 receives the broadcast of the synchronization stream broadcasted by the digital broadcast station 2, generates a clock used by the digital broadcast station 2, and uses the clock to generate its own clock. While processing to match the clock of the excited crystal oscillator with the clock, processing to decode the encoded stream requested by the transmission server 1 is performed.The second technique related to the present invention shown in FIG.In the case of complying, the client 3 uses an existing PLL circuit to generate a clock from the stream from the originating server 1 transmitted via the gateway 6 and decode the stream according to the clock. Process it.
[0103]
  Follow this configurationThe second technique related to the present invention shown in FIG.According to this, by using the synchronization stream broadcast by the same digital broadcasting station 2, it is possible to share the clock among the digital broadcasting station 2, the transmission server 1, and the client 3, and thereby the same clock is used. Encoding and decoding are performed, so that buffer overruns and underruns can be prevented so that video and audio can be presented to the user without interruption. As long as it is realized, only the gateway 6 needs to be equipped with an antenna or the like for receiving the synchronization stream, and a plurality of clients 3 connected to the gateway 6 can be of the conventional configuration. .
[0104]
When the system configuration shown in FIG. 9 is followed, since the transmission server 1 and the gateway 6 receive the stream from the common digital broadcasting station 2, the clock of the digital broadcasting station 2 is set to the standard clock. However, when the clock of the digital broadcast station 2 is set to the standard clock, the transmission server 1 is connected to the same digital broadcast station 2 as the digital broadcast station 2 to which the gateway 6 is connected. There is no need to be.
[0105]
That is, when each digital broadcasting station 2 receives the GPS or extracts the clock from the atomic clock, etc., as shown in FIG. 11, as shown in FIG. Is connected to a digital broadcast station 2a different from the digital broadcast station 2 to which the gateway 6 is connected, and a synchronization stream (a time index generated based on a standard clock is generated from the digital broadcast station 2a). It is possible to perform clock synchronization by receiving (added).
[0106]
FIG. 12 illustrates an example of detailed apparatus configurations of the transmission server 1, the digital broadcasting station 2, the client 3, and the gateway 6 for realizing the system configuration illustrated in FIG.
[0107]
As shown in FIG. 12, the device configuration of the transmission server 1, the digital broadcasting station 2, the client 3, and the gateway 6 is basically the same as when the system configuration shown in FIG. 9 is used.
[0108]
Therefore, the processing when the system configuration shown in FIG. 11 is used is the same as the processing when the system configuration shown in FIG. 9 is used.
[0109]
That is, the digital broadcasting stations 2 and 2a encode using a standard clock, record a time index in a packet, generate a stream for synchronization, and broadcast the stream.
[0110]
In response to this, the gateway 6 receives the synchronization stream from any one of the digital broadcasting stations (the digital broadcasting station 2 in the case of FIG. 11) broadcasting the synchronization stream via the synchronization network 9. And generate a standard clock from the stream. Then, the gateway 6 synchronizes the clock of the self-excited crystal oscillator that it has with the standard clock. This self-excited crystal oscillator clock adjustment process is continuously performed while the stream is received from the transmission server 1.
[0111]
On the other hand, the transmission server 1 receives a synchronization stream from any one of the digital broadcast stations broadcasting the synchronization stream (in the case of FIG. 11, the digital broadcast station 2a), and receives the standard clock from the stream. Is generated. Then, the transmission server 1 encodes the stream to be provided to the client 3 using the generated standard clock, and records the time index in the packet.
[0112]
Then, the client 3 requests, via the gateway 6, the stream encoded as described above and attached with the time index to the originating server 1 that provides the desired stream.
[0113]
When a stream is transmitted from the originating server 1 in response to this request, the gateway 6 accumulates the stream in the buffer, and at the same time, at a certain rate from the buffer based on the received coding rate information. Is read out and transmitted to the client 3 as it is.
[0114]
In response to this, the client 3 extracts a standard clock from the stream received from the gateway 6 using a PLL circuit having a conventional configuration, and performs a decoding process according to the extracted standard clock.
[0115]
In this way, even when the system configuration shown in FIG. 11 is used, it is possible to share the clock among the digital broadcasting station 2, the transmission server 1, and the client 3, thereby encoding with the same clock. Thus, the buffer overrun and underrun can be prevented, and the video and audio can be presented to the user without interruption.
[0116]
Here, when the configuration shown in FIG. 11 is used, the transmission server 1 generates the standard clock from the synchronization stream broadcast by the digital broadcasting station 2a. However, as shown in FIG. The transmission server 1 itself may be provided with a standard clock generation mechanism such as GPS.
[0117]
FIG. 14 shows an example of detailed device configurations of the transmission server 1, the digital broadcast station 2, and the client 3 for realizing the system configuration shown in FIG.
[0118]
As shown in this figure, when the transmission server 1 itself has a standard clock generation mechanism such as GPS, the transmission server 1 generates a standard clock from a synchronization stream broadcasted by a digital broadcasting station 2a or the like. There is no need to provide a mechanism for processing.
[0119]
  [C]Of the present inventionExample embodiment
  FIG. 15 shows the present invention.The fruit of1 illustrates an example of a system configuration that realizes an embodiment.
[0120]
  This figure15As shown inIn fact,The embodiment is characterized by including a bridge 10.
[0121]
The bridge 10 is connected to the broadcasting station 2 via the synchronous network 9 and is connected to the client 3 via the synchronous network 8.
[0122]
  hereAnd in factAlso in the embodiment, a gateway 11 connected to the originating server 1 via the asynchronous network 7 and connected to the client 3 via the synchronous network 8 is provided.Is a second technique related to the present invention shown in FIG.Unlike the gateway 6 provided, it is transmitted from the outgoing server 1CodingOnly the process of relaying the stream and transmitting it to the client 3 is performed.
[0123]
  NaOh, realThe synchronization network 8 provided in the embodiment is, for example, a small-scale network for connecting a plurality of clients 3 used in one house or the like.
[0124]
FIG. 16 illustrates an example of detailed device configurations of the transmission server 1, the digital broadcasting station 2, the client 3, the gateway 11, and the bridge 10 for realizing the system configuration illustrated in FIG.
[0125]
In the present invention, the digital broadcasting station 2 performs a process of broadcasting a synchronization stream to which a time index is added using a predetermined clock. Therefore, the transmission server 1 receives the broadcast of the synchronization stream. Then, a clock used by the digital broadcasting station 2 is generated, and a stream to be provided to the client 3 while performing a process of matching the clock of the self-excited crystal oscillator possessed by the clock with the clock. Is encoded and a time index is added, and the time index is added to the client 3 via the gateway 11 via the asynchronous network 7.
[0126]
  On the other hand, when the bridge 10 receives a synchronization stream broadcast by the digital broadcasting station 2, the bridge 10 adds the IP header or the like to the MPEG2-TS packet of the digital broadcasting network, for example.ConversionThen, by transmitting to the client 3 via the synchronization network 8, processing is performed so that the client 3 can receive the synchronization stream.
[0127]
At this time, since the client 3 needs only the synchronization stream portion to which the time index is added, the bridge 10 may process to transmit only the synchronization stream portion to the client 3 in some cases.
[0128]
Under the intervention of the bridge 10, the client 3 receives the broadcast of the synchronization stream transmitted from the bridge 10, generates a clock used by the digital broadcast station 2, and uses the clock. While performing the process of matching the clock of the self-excited crystal oscillator that the user has with the clock, the encoded stream requested by the sender server 1 is decoded.
[0129]
As described above, the transmission server 1 receives a stream from any one of the digital broadcasting stations 2 that broadcast a stream encoded using a predetermined clock and added with a time index, and the digital broadcast is transmitted from the stream. The clock used by the station 2 is generated, and the moving image data is encoded and stored using the generated clock, or is processed to be transmitted to the client 3 via the gateway 11 as it is.
[0130]
The clock adjustment processing performed at this time is continuously performed while encoding and while transmitting a stream to the client 3.
[0131]
On the other hand, when the bridge 10 receives the synchronization stream broadcast by the digital broadcasting station 2 (which is notified from the client 3 for example which digital broadcasting station 2 is received) received by the transmission server 1, the bridge 10 receives the stream. By converting the packet into an IP packet and transmitting it to the client 3 via the synchronous network 8, processing is performed so that the client 3 can receive the synchronization stream.
[0132]
Then, the client 3 receives the synchronization stream broadcast transmitted from the bridge 10, generates a clock used by the digital broadcast station 2, and uses the clock to transmit the own stream. While performing the process of adjusting the clock of the excited crystal oscillator to the clock, the process is performed to decode the requested encoded stream transmitted from the transmission server 1.
[0133]
  SnowThat is, in the first technique related to the present invention shown in FIG.In order to comply, the client 3 receives the broadcast of the synchronization stream broadcasted by the digital broadcasting station 2, generates a clock used by the digital broadcasting station 2, and uses the clock to own the client 3 FIG. 15 shows the process of decoding the requested encoded stream transmitted from the transmission server 1 while performing the process of adjusting the clock of the self-excited crystal oscillator to the clock.RealWhen the embodiment 3 is followed, the client 3 receives the synchronization stream received by the bridge 10, generates a clock used by the digital broadcasting station 2, and uses the clock to own the client 3. While performing the process of adjusting the clock of the excited crystal oscillator to the clock, the process is performed to decode the requested encoded stream transmitted from the transmission server 1.
[0134]
  Follow this configurationActuallyAccording to the embodiment, by using a synchronization stream broadcast by the same digital broadcasting station 2, it is possible to share a clock among the digital broadcasting station 2, the transmission server 1, and the client 3, Since encoding and decoding are performed with the same clock, buffer overrun and underrun can be prevented so that video and audio can be presented to the user without interruption. It is sufficient that only the bridge 10 has a facility such as an antenna for receiving the synchronization stream, and that the client 3 does not need to be equipped with such an antenna. become.
[0135]
When the system configuration shown in FIG. 15 is followed, since the transmission server 1 and the client 3 receive a stream from the common digital broadcast station 2, the clock of the digital broadcast station 2 is set to the standard clock. However, when the clock of the digital broadcast station 2 is set to the standard clock, the transmission server 1 is connected to the same digital broadcast station 2 as the digital broadcast station 2 to which the client 3 is connected. There is no need to be.
[0136]
That is, when each digital broadcast station 2 is set to the standard clock by receiving GPS or extracting the clock from the atomic clock, as shown in FIG. The digital broadcast station 2a connected to the digital broadcast station 2 to which the client 3 is connected is connected to the digital broadcast station 2a through a synchronization stream (a time index generated based on the standard clock is generated from the digital broadcast station 2a). It is possible to perform clock synchronization by receiving (added).
[0137]
FIG. 18 illustrates an example of detailed device configurations of the transmission server 1, the digital broadcast station 2, the client 3, the gateway 11, and the bridge 10 for realizing the system configuration illustrated in FIG.
[0138]
As shown in FIG. 18, the device configuration of the transmission server 1, digital broadcasting station 2, client 3, gateway 11, and bridge 10 is basically the same as when the system configuration shown in FIG. 16 is used.
[0139]
Accordingly, the processing when the system configuration shown in FIG. 17 is used is the same as the processing when the system configuration shown in FIG. 15 is used.
[0140]
That is, the digital broadcasting stations 2 and 2a encode using a standard clock, record a time index in a packet, generate a stream for synchronization, and broadcast the stream.
[0141]
In response to this, the bridge 10 receives the synchronization stream from any one of the digital broadcasting stations (the digital broadcasting station 2 in the case of FIG. 17) broadcasting the synchronization stream via the synchronization network 9. The received stream is converted into an IP packet and transmitted to the client 3 via the synchronous network 8.
[0142]
In response to this, the client 3 receives a synchronization stream transmitted from the bridge 10 and generates a standard clock from the stream. Then, the client 3 synchronizes the clock of the self-excited crystal oscillator that the client 3 has with the standard clock. This self-excited crystal oscillator clock synchronization process is continuously performed while a stream is received from the transmission server 1 and decoded.
[0143]
On the other hand, the transmission server 1 receives a synchronization stream from any one of the digital broadcast stations broadcasting the synchronization stream (in the case of FIG. 17, the digital broadcast station 2a), and receives the standard clock from the stream. Is generated. Then, the transmission server 1 encodes the stream to be provided to the client 3 using the generated standard clock, and records the time index in the packet.
[0144]
Then, the client 3 requests, via the gateway 11, the stream that has been encoded as described above and attached with the time index to the originating server 1 that provides the desired stream.
[0145]
When a stream is transmitted from the originating server 1 in response to this request, the client 3 receives the encoded and time-indexed stream together with information necessary for decoding including the encoding rate. The decryption is started. At that time, decoding is performed using a standard clock obtained from the synchronization stream.
[0146]
In this way, even when the system configuration shown in FIG. 17 is used, it is possible to share the clock among the digital broadcasting station 2, the transmission server 1, and the client 3, and thereby the encoding is performed with the same clock. Thus, the buffer overrun and underrun can be prevented, and the video and audio can be presented to the user without interruption.
[0147]
Here, when the configuration shown in FIG. 17 is used, the transmission server 1 generates the standard clock from the synchronization stream broadcast by the digital broadcasting station 2a. However, as shown in FIG. The transmission server 1 itself may be provided with a standard clock generation mechanism such as GPS.
[0148]
FIG. 20 shows an example of detailed device configurations of the transmission server 1, the digital broadcast station 2, the client 3, the gateway 11, and the bridge 10 for realizing the system configuration shown in FIG.
[0149]
As shown in this figure, when the transmission server 1 itself has a standard clock generation mechanism such as GPS, the transmission server 1 generates a standard clock from a synchronization stream broadcasted by a digital broadcasting station 2a or the like. There is no need to provide a mechanism for processing.
[0150]
【The invention's effect】
As described above, in the present invention, when a real-time stream is distributed via a network, a clock used by a digital broadcasting station is generated by a client using the stream on the digital broadcasting network, and is decoded using the clock. By making it possible to accurately match the encoding rate and the decoding rate, buffer overruns and underruns can be prevented. As a result, even when receiving a video distribution service on an IP network for a long time, video and audio are not interrupted or stopped midway.
[0151]
In addition, by generating a clock by receiving a stream from the same digital broadcasting station, the transmission server and the client can realize that the clock of the transmission server and the client can be made the same without using a standard clock, This eliminates the need for expensive equipment to match the standard clock.
[0153]
  In order to achieve this, the present inventionA bridge is prepared to receive digital broadcasts and process the received stream as an IP packet and transfer it to the client.According to this configuration.Since only the bridges need to be equipped with receiving antennas, the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic system configuration of the present invention.
[Figure 2]The first technique related to the present invention isIt is a figure which shows an example of the system configuration | structure implement | achieved.
[Fig. 3]The first technique related to the present invention isIt is a figure which shows an example of the apparatus structure of each apparatus implement | achieved.
FIG. 4 is a processing flow executed by a client.
[Figure 5]The first technique related to the present invention isIt is a figure which shows another example of the system configuration | structure implement | achieved.
[Fig. 6]The first technique related to the present invention isIt is a figure which shows another example of the apparatus structure of each apparatus implement | achieved.
[Fig. 7]The first technique related to the present invention isIt is a figure which shows another example of the system configuration | structure implement | achieved.
[Fig. 8]The first technique related to the present invention isIt is a figure which shows another example of the apparatus structure of each apparatus implement | achieved.
FIG. 9The second technique related to the present inventionIt is a figure which shows an example of the system structure to implement | achieve.
FIG. 10The second technique related to the present inventionIt is a figure which shows an example of the apparatus structure of each apparatus implement | achieved.
FIG. 11The second technique related to the present inventionIt is a figure which shows another example of the system configuration | structure implement | achieved.
FIG.The second technique related to the present inventionIt is a figure which shows another example of the apparatus structure of each apparatus implement | achieved.
FIG. 13The second technique related to the present inventionIt is a figure which shows another example of the system configuration | structure implement | achieved.
FIG. 14The second technique related to the present inventionIt is a figure which shows another example of the apparatus structure of each apparatus implement | achieved.
FIG. 15Reality of the present inventionIt is a figure which shows an example of the system configuration which implement | achieves an example of embodiment.
FIG. 16Reality of the present inventionIt is a figure which shows an example of the apparatus structure of each apparatus which implement | achieves an example of embodiment.
FIG. 17Reality of the present inventionIt is a figure which shows another example of the system configuration which implement | achieves an example of embodiment.
FIG. 18Reality of the present inventionIt is a figure which shows another example of the apparatus structure of each apparatus which implement | achieves an embodiment.
FIG. 19Reality of the present inventionIt is a figure which shows another example of the system configuration which implement | achieves an example of embodiment.
FIG. 20Reality of the present inventionIt is a figure which shows another example of the apparatus structure of each apparatus which implement | achieves an embodiment.

Claims (5)

A stream reception system including a stream relay device, a synchronization signal relay device, and a stream reception device connected to each other via a connection synchronization network,
The stream relay device
Means for receiving, from the stream distribution apparatus connected via an asynchronous network, an encoded stream to which a time index generated based on a clock used by the broadcast station is transmitted by the stream distribution apparatus;
Means for transmitting the received encoded stream to the stream receiving device via the connection synchronization network;
The synchronous signal relay device is
Means for receiving, via a relay synchronization network provided separately from the connection synchronization network, a synchronization stream with a time index added by the broadcasting station based on a predetermined clock;
Means for shaping the received synchronization stream into a form that can be received by the stream receiving device;
Means for transmitting the shaped synchronization stream to the stream receiving device via the connection synchronization network;
The stream receiver is
Means for receiving a synchronization stream from the synchronization signal relay device via the connection synchronization network;
Means for generating a clock used by the broadcast station from the received synchronization stream;
Means for receiving an encoded stream from the stream relay device via the connection synchronization network;
Means for decoding the received encoded stream using the generated clock.
A stream receiving system. The stream receiving system according to claim 1,
The means for receiving the encoded stream included in the stream relay device adds a time index generated by the stream distribution device based on a clock generated from a synchronization stream received from a broadcasting station via the relay synchronization network. Received encoded stream
A stream receiving system. The stream receiving system according to claim 1,
The means for receiving the synchronization stream included in the synchronization signal relay apparatus receives the synchronization stream from a broadcast station different from the broadcast station used by the stream distribution apparatus when the broadcast station uses a standard clock.
A stream receiving system. The stream receiving system according to claim 1,
When the broadcast station uses a standard clock, the means for receiving the encoded stream included in the stream relay device is configured to distribute the encoded stream generated based on the standard clock generated by the stream distribution device. Receive from device
A stream receiving system. A stream reception method executed in a stream reception system including a stream relay device, a synchronization signal relay device, and a stream reception device connected to each other via a connection synchronization network,
The stream relay device receives an encoded stream to which a time index is generated based on a clock used by a broadcast station from the stream distribution device from the stream distribution device connected via an asynchronous network, and receives the received stream. The encoded stream is transmitted to the stream receiving device via the connection synchronization network,
The synchronization signal relay device receives a synchronization stream to which a time index is added generated by the broadcast station based on a predetermined clock via a relay synchronization network provided separately from the connection synchronization network. The received synchronization stream is shaped into a form that can be received by the stream receiving device, and the shaped synchronization stream is transmitted to the stream receiving device via the connection synchronization network,
The stream reception device receives a synchronization stream from the synchronization signal relay device via the connection synchronization network, generates a clock used by the broadcast station from the received synchronization stream, and connects the connection The encoded stream is received from the stream relay device via the synchronous network for decoding, and the received encoded stream is decoded using the generated clock.
And a stream receiving method.

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