JP2008016905A - Content transmission apparatus, content receiving apparatus, and content distribution method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content distribution apparatus with a light distribution load and providing a light network load by distributing a stream resulting from eliminating a video stream from a distributed content to a content receiving apparatus such as a speaker coping with only sound. <P>SOLUTION: Each of content receiving apparatuses includes a network I/F, a buffer means, a reproduction synchronizing means, and a partial TS reproducing means. The reproduction synchronizing means includes a PCR extract means, which sets a time stamp value attached to respective PCR packets to an initial value of a counter of the partial TS reproducing means on the opportunity of a "synchronous trigger" signal from the content receiving apparatus into which the PCR packet arrives latest among the apparatuses synchronizingly reproducing the packets. Since the partial TS reproducing means compares the time stamp with the count of the counter to execute partial TS reproduction, the timings for TS reproduction of each content receiving apparatus are synchronized with each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a network device and a content distribution method for transmitting or receiving video and audio content via a network, and particularly to a transmission format in which a stream of content to be distributed includes time alignment information.

Due to the penetration of the network environment into the home and the use of DTCP-IP (Digital Transmission Content Protection over Internet Protocol) as an output interface for digital broadcasting by the Japan Radio Industry Association as a digital broadcasting operation rule. In addition, it is expected that network devices compatible with IP (Internet Protocol) transmission in the home of digital broadcasting HD programs will be popularized. In the future, most AV (Audio Visual) devices are expected to be compatible with networks, and network-compatible speaker devices equipped with audio decoders are expected to appear.
In such an environment, in order not to waste network resources, the video / audio program content is divided into a video stream and an audio stream, the audio stream is delivered to the speakers, and the video stream is delivered to the display. A usage scene in which the content of a program is divided into video and audio and distributed to different devices can be considered.
However, since the IP network cannot guarantee the delivery timing, there is a risk that the audio and video will be played out of synchronization. Japanese Patent Application Laid-Open No. 2004-228561 provides a means for distributing a clock and a reference time to each device on the network, and each network device adjusts the clock synchronization and the time used as a reference for the reproduction time based on the reference time.

JP 2003-37585 A

In the prior art, broadcasting is performed from a device on the network that generates a reference time. However, it is not realistic to arrange a device or functional block only for time adjustment on the network. SUMMARY OF THE INVENTION An object of the present invention is to provide a system that corrects a deviation in stream reception timing of a video reception network device or an audio reception network device using reference time information included in a distribution content stream, and performs synchronous reproduction.
In the prior art, content is distributed from a content source to a speaker and a display, respectively, and consideration has not been given to the distribution load of the content distribution apparatus and the network load. In the present invention, a content distribution device that has a light distribution load on the content distribution device and a light network load is provided by distributing a stream obtained by deleting a video stream from the content to be distributed to a content reception device that supports only audio such as a speaker. For the purpose.

In order to achieve the above object, a content transmission apparatus for network distribution of content according to the present invention corresponds to a means for identifying and separating a video stream or an audio stream from a content stream constituting a program, and a distribution destination network apparatus. Means for acquiring the type of the stream, and configured to deliver a separated content stream obtained by separating a stream that is not supported by the delivery destination network device from the content stream constituting the program.
The content receiving apparatus according to the present invention includes a network I / F, buffer means, reproduction synchronization means, and partial TS reproduction means, and the reproduction synchronization means includes PCR extraction means, which is the latest PCR among the apparatuses for synchronous reproduction. In response to the “synchronization trigger” signal from the content receiving device when the packet arrives, the time stamp value added to each PCR packet is set to the initial value of the counter of the partial TS playback means, and the partial TS playback is performed. The means is configured to reproduce the partial TS by comparing the time stamp and the counter value. Thereby, the TS playback timing of each content receiving apparatus is synchronized.

  According to the present invention, it is possible to provide a system that corrects a deviation in stream reception timing of a video reception network device or an audio reception network device using reference time information included in a distribution content stream, and performs synchronous reproduction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Embodiment 1 of the present invention will be described below.

  FIG. 1 is a configuration diagram of a network system according to the first embodiment. The network devices in FIG. 1 are connected to each other via an IP (Internet Protocol) network. A content receiving device 2 distributes content to the network. Reference numerals 3 and 4 denote content receiving apparatuses that receive and reproduce content via a network. Reference numeral 3 denotes a display device having a function of reproducing a video stream, and reference numeral 4 denotes headphones having a function of reproducing an audio stream.

FIG. 2 shows an example of the configuration of the content transmission device 2. Reference numeral 201 denotes a partial transport stream generation means (hereinafter referred to as a partial TS generation means), which is an MPEG (Motion Picture Experts Group) in which a plurality of streams such as video and audio output from a digital tuner (not shown) are multiplexed. A process of removing TS packets not related to the program from the transport stream (TS) output is performed, and a partial TS is generated and output.
That is, when a certain channel is selected, the P M T (Program Map Table) of the channel is designated with the P I D (packet I D) of the video stream or the audio stream constituting the program of the channel. . Therefore, the header of the MPEG TS packet is analyzed, and TS packets having P ID not related to the program are removed.

Hereinafter, the partial TS generated by the partial TS generation unit 201 is referred to as a basic partial TS (220). Further, the PID of the video stream and audio stream constituting the channel is stored in the PID holding unit 206.
The stream separation unit 202 selects a partial TS obtained by removing a TS packet having a predetermined PID from a basic partial TS (220) or a TS having a predetermined PID as specified by the control unit (207). Generate. Further, the contents of the PMT are reorganized so that there is no contradiction between the configuration of the generated partial TS and the PMT, and the PMT of the basic partial TS (220) is replaced. The partial TS output from the stream separation unit 202 is called a separation partial TS (221) with respect to the basic partial TS (220).

The time stamp adding means 203 adds a time stamp to the separated partial TS (221) so that the content receiving apparatus can reproduce the time interval of TS packets that are corrupted by passing through IP communication. The time-stamped partial TS stream output from the time stamp adding unit 203 is distributed to the content receiving apparatus via the buffer unit 204 and the network I / F (205).
The stream separation unit 212, the time stamp addition unit 213, and the buffer unit 214 have the same functions as the video stream separation unit 202, the time stamp addition unit 203, and the buffer unit 204, respectively.

  The control unit 205 has a function of acquiring media format information that can be played back by the content receiver on the network. When the content receiving device that has requested the content cannot reproduce the video, the stream separating unit 202 is instructed to remove the packet having the PID of the video stream by referring to the information recorded in the PID holding unit 206. A method for realizing the function of acquiring media format information is not particularly limited here. For example, it is realized by a control point (CP) and a device method according to a DLNA (Digital Living Network Alliance) guideline (hereinafter referred to as DLNA guideline). it can.

FIG. 3 shows an example of the configuration of the content receiving devices 3 and 4. The network I / F 301 receives a content stream from the network. Further, the command generated by the reproduction synchronization means 302 is sent to the network and received. The content stream from the network is removed from the protocol header on the network and stored in the buffer means 302 as a time-stamped TS packet.
The TS packet with a time stamp stored in the buffer means 302 is reproduced by the 310 partial TS reproducing means to reproduce the time interval of the partial TS from the time stamp. A clock oscillator 303 supplies a clock to a counter 312 that generates a value for comparing the time stamps of the distributed TS packets.

  The time stamp extraction unit 311 compares the time stamp value of the received TS packet with the counter, and notifies the TS output control unit 310 when both values are equal. The TS output control means 310 reads the TS packet to be output from the buffer means, and outputs it to the TS I / F 304 as a partial TS that reproduces the time interval. The partial TS output to the TS I / F 304 is input to an MPEG decoder (not shown in the figure) and output to a display in the case of video, or to headphones in the case of audio. Regardless of the type of stream to be handled, that is, whether it is a video stream or an audio stream, the configuration shown in FIG. 3 is the same.

  The reproduction synchronization means 320 is a means for controlling the packet output to the TS I / F at the TS packet level to synchronize with the content receiving apparatus receiving the same program on the network. The synchronized playback management means 321 is a means for searching for a content receiving apparatus to be synchronized, recording information of the content receiving apparatus that is performing synchronization processing in the recording means 323, and distributing a synchronization trigger signal to the network. The processing flow of the operation will be described later. When the TS packet with time stamp stored in the received buffer means 302 receives a PCR packet or a packet specifying a program (for example, PMT), the information packet processing means 322 extracts the value and sends it to the synchronous reproduction management means 321. At the same time, it is stored in the storage means 323.

Here, the configuration of the partial TS will be briefly described with reference to an example of the partial transport stream in FIG. Each square in the figure is a TS packet with a 192-byte time stamp in which a 4-byte time stamp is added to a 188-byte TS packet. As shown in FIG. 4 (d), the bold square is a PMT (Program Association Table). P ID (packet ID) for identifying a TS packet including a reference value PCR (Program Clock Reference) packet for correctly reproducing the generation time of the video, audio stream, and TS constituting the program is specified. Yes.
A thin square is a video TS packet, a hatched square is an audio packet, and a thick broken line is a PCR packet. Other packets are omitted here.

Although the full TS packet in the state of receiving the digital broadcast has a fixed rate, the basic partial TS 220 output from the partial TS generation unit 201 is a partial that is obtained by removing only the packets unrelated to the program as shown in FIG. The TS includes information packets such as video and audio packets and PCR packets.
(B) is an audio partial TS. The signal rate of high-definition video is as high as 20 Mbps. Therefore, if only the audio stream is distributed to a content receiver that cannot reproduce the audio stream, network resources can be greatly saved. However, in a usage scene in which video is reproduced on the display device 3 and audio is reproduced on the headphones 4 with the system configuration as shown in FIG. 1, the video and audio distributed as different IP streams must be synchronized.

  In the present invention, the reference value PCR for correctly reproducing the generation time of the video, audio stream, and TS constituting the program is used for the synchronous reproduction of the video stream and the audio stream. Therefore, when the distribution destination does not have a video playback function, the control unit 207 of the content transmitting apparatus 2 leaves the audio packet and the information packet such as PCR as in (d), and removes only the video packet to the stream separation unit 212. Instruct.

Next, the processing of the reproduction synchronization means 320 for synchronously reproducing the content received between different content receiving apparatuses will be described with reference to the flowcharts of FIGS. 5, 6, 7, 8, and 9.
When the synchronized playback management unit 321 starts receiving content, it starts determining whether there is a partner to be synchronized (FIG. 5). The information packet processing means 323 extracts a TS packet for specifying a program, for example, a PMT packet from the received content, and broadcasts a “synchronous search notification” together with the received PMT value to the network (S501).

  When there is a response from the other network device to the “synchronous search notification”, information for identifying the device, for example, an IP address is stored in the storage unit 323 as the synchronous device information (S503). A response is waited for a predetermined time, for example, about 0.5 seconds (S504). If no synchronization device information is recorded, it is determined that there is no synchronization device, and a predetermined time, for example, is set so that broadcast signals are not frequently sent to the network. After one minute has passed (S506), the “synchronous search notification” is returned to the broadcast process.

  If it is determined in S505 that there is a synchronization device, the synchronization device information stored in the storage means in S503 is used as a parameter to send “synchronization device information” to all the synchronization devices stored in the storage means in S503 (S507). The synchronization determination process ends with its own state as “synchronous reception”. By receiving the “synchronization device information”, other content reception devices can recognize that there is another content reception device that must be synchronized and reproduced on the network.

  FIG. 6 is a processing flow of processing when the content receiving apparatus receives “synchronous search notification”. When the content receiving apparatus receives the “synchronous search notification” (S601), it acquires program information parameters for specifying the content to be synchronized from the “synchronous search notification”, and program information (PMT value etc.) of the content being received by itself. And determine whether the apparatus should be synchronized (S602). If the device is not to be synchronized, the process returns to waiting for reception of “synchronous search notification”. If the device is to be synchronized, information for identifying the device, for example, the IP address is stored in the storage unit 323 as the synchronization device information, and a response is transmitted to the transmission source of the “synchronous search notification”. It informs itself that it is a device to be synchronized (S602).

  Then, it waits for a predetermined time until the “synchronization device information” is transmitted from the transmission source of the “synchronization search notification” (S604, S605). If the “synchronization device information” is transmitted within a predetermined time, the information on the device included in the “synchronization device information”, the IP address, etc. are stored in the storage means 323 in order to start the synchronous reception of the content ( S606). Then, the own state is set to “synchronous reception”, and the process again returns to “synchronous search notification” reception waiting (S601). The reason for returning to S601 is to dynamically respond to changes and additions of content devices that are synchronized and played back, for example, when the sound is switched to speakers during synchronous viewing with the display and headphones.

FIG. 7 is a flowchart of synchronous playback processing of the content receiving apparatus.
When “synchronous reception is in progress”, the content receiving apparatus enters the synchronous reproduction process (S701), and detects the PCR reception from the information packet processing means 322 (S702). When the PCR is received, the information in the storage means is immediately referred to and it is confirmed whether or not all the “PCR reception notifications” of the same PCR value from other synchronization devices have been received (S703).
If it has not been received yet, that is, if it is not the last device that has received the PCR, it multicasts a “PCR reception notification” to all other synchronization devices (S704), and returns to S701. On the other hand, if the device itself is the last device that has received the PCR, then the multicast value is sent to all other synchronization devices using the PCR value as a parameter (S708), and its own time stamp counter 312 is set to the PCR value. initialize.

  When a “synchronization trigger” is received from another synchronization device (S710), the own time stamp counter 312 is initialized with the PCR value included in the parameter. The time stamp counter 312 is a counter that generates a reference time for the TS output control means 310 to reproduce the time interval of the partial TS and output it to the TS I / F 304. In the present invention, synchronized playback between different content receiving apparatuses is realized by adjusting the time of the reference counter using a “synchronization trigger”.

FIG. 8 is a flow of the synchronization end process.
When the synchronous reception of the content is to be terminated, the “synchronization disconnection notification” is multicast to the other content reception devices that are performing synchronous reproduction, and the synchronization device information and the program information (PMT) specifying the synchronous content are deleted from the storage unit 323. Then, the storage of the PMT and PCR storage means 323 extracted by the information packet processing means 322 is stopped. Further, the process is terminated with its own state set to “synchronous reception end”.

FIG. 9 is a processing flow when the “synchronization disconnection notification” is received.
The information of the content receiving device that has transmitted the “synchronization disconnection notification” is deleted from the storage unit 323 (S902), the storage unit 323 is referred to, and it is confirmed whether there is another content receiving device that is synchronously reproduced (S903). If it still exists, the process returns to waiting for reception of “synchronization disconnection notification” (S901), and if not, storage is stopped in the PMT and PCR storage means 323 extracted by the information packet processing means 322. Further, the process is terminated with its own state set to “synchronous reception end”. In this way, even if content devices to be synchronized and reproduced are individually detached, it is possible to respond dynamically without affecting the synchronization of the devices being synchronized and reproduced.
As described above, according to the present invention, the “synchronization trigger” is delivered and the time is adjusted in response to the arrival time of the PCR signal, so that the synchronous reproduction can be realized using the reference time information included in the stream.

  The present invention is effective for a network system in which the content of the same program is distributed from a single content transmission device to a plurality of content reception devices and played back in time.

1 is a network configuration according to the first embodiment. It is an example of a structure of a content transmitter. It is an example of a structure of a content receiver. It is an example of a partial transport stream. It is an example of the flowchart of the synchronous determination process in a content receiver. It is an example of the flowchart of the "synchronous search notification" process in a content receiver. It is an example of the flowchart of the reproduction | regeneration synchronous process in a content receiver. It is an example of the flowchart of the reproduction | regeneration synchronous completion | finish process in a content receiver. It is an example of the flowchart of a "synchronization leaving notification" process in the content receiving device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 IP network 2 Content transmission apparatus 3 Speaker system 4 Display apparatus 201 Partial TS production | generation means 202,212 Video / audio separation means 203,213 Time stamp addition means 204,214,302 Buffer means 220,222 Basic partial TS
221 and 223 separation partial TS
205, 301 Network I / F
303 Clock oscillator 304 TS I / F
310 Partial TS reproduction means 313 TS output control means 312 Counter 313 Time stamp extraction processing circuit 320 Reproduction synchronization means 321 Synchronous reproduction control means 322 Information packet processing means 323 Storage means

Claims (4)

A content transmission device for distributing content over a network,
Means for identifying and separating a video stream or an audio stream from a content stream constituting a program;
Means for acquiring the type of stream corresponding to the distribution destination network device,
A content transmission apparatus that distributes a separated content stream obtained by separating a stream that is not supported by the distribution destination network apparatus from a content stream that constitutes a program. A content receiving device for receiving content via a network,
Means for detecting connection / disconnection of other content receiving devices on the network;
A reference time extraction means for extracting a reference time packet included in the content stream;
Synchronous playback control means for detecting whether or not synchronized playback with the detected other content receiving apparatus is necessary and transmitting the synchronization timing to the other content receiving apparatus at the timing when the reference time extracting means extracts the reference time packet; A recording synchronization unit configured to record information for identifying the other content receiving device to be synchronized and reproduced,
A partial TS reproduction means comprising: a time stamp processing means for extracting a time stamp of content; and a counter for generating a comparison value of the time stamp;
Buffer means for temporarily holding content,
The time stamp value added to each reference time packet is set to the initial value of the counter of the partial TS playback means in response to the synchronization trigger signal from the content receiving apparatus in which the latest reference time packet has arrived. A content receiving apparatus, wherein the TS playback timing of each content receiving apparatus is synchronized.   3. The content receiving apparatus according to claim 2, wherein the reference time packet is a packet including an MPEG-TS PCR. A content distribution method in a content transmission apparatus for distributing content over a network,
Identifying and separating a video stream or audio stream from a content stream comprising a program;
Obtaining a stream type corresponding to the distribution destination network device;
Delivering a separated content stream obtained by separating a stream not supported by the delivery destination network device from the content stream constituting the program based on the acquired type. Delivery method.

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