JPH08149453A - Video server system - Google Patents

Abstract

PURPOSE: To make a constitution of a digital demodulation part simplify when digital compressed data is transmitted by using a digital modulation, in the video server system composed of a digital video server, a transmission line and a terminal. CONSTITUTION: Each terminal part is divided into each zone by a distance from each digital video server 113 and the number of the stages of the amplifier 107 through a transmission line. As for the frequency band of the modulation wave in a digital modulation part 104 in which a digitally multiplexed signal is inputted in the digital video server 113, a modulation is performed by using a high frequency band in the case of the transmission to the terminal part within a close zone. In the case of the transmission to the terminal part within a distant zone, the modulation is performed by using a low frequency band. Thus, the frequency band received by each terminal part is narrowed, and the automatic equalization circuit and the automatic amplitude circuit in the terminal part can be easily constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video server system used in a CATV system or the like.

[0002]

2. Description of the Related Art FIG. 8 shows a block diagram of a video server system in a conventional CATV or the like. In this system, the video server unit 310 and the plurality of terminal units are connected to the video transmission line 30.
8. It is configured to be connected via the control transmission path 111.
The video / audio signal output unit 301 receives an image / audio signal output request from the video control unit 306, and an analog modulation unit 302 in which required video / audio signals are designated.
Output to. One analog modulator modulates one video and audio signal. The analog modulator 302 has a fixed modulation carrier frequency, and performs AM modulation, for example, at that modulation frequency. Each analog modulator 302 is configured to perform modulation with a different unique modulation frequency carrier. The outputs of the plurality of analog modulation units 302 are mixed by the mixer unit 303 and transmitted via the video transmission line 308, for example, a coaxial cable. The modulated signal is received by, for example, one terminal unit 304 via the video transmission path 308 and the plurality of amplifiers 305. The video / audio signal output unit 301 and the analog modulation unit 302 are controlled by the video control unit 306. The video control unit 306 is the terminal unit 3
Control transmission line 11 for output request of video and audio signals from 04.
1. Received via the LAN interface unit 307,
The video / audio signal output unit 301 is instructed to output the requested video and audio signals, and the channel number of the modulated signal to be auditioned is given to the terminal unit 304 that requested the video and audio signal output. It is returned via the LAN interface unit 307 and the control transmission path 111.
The configuration of the terminal unit is shown in FIG. Upon receiving the video / audio viewing instruction requested by the user command from the command input section 208, the terminal control section 405 sends a video / audio signal output instruction to the video server section 310 via the LAN interface section 206 and the control transmission path 111. Send. When the LAN interface unit 206 receives the viewing channel number returned from the video server unit 310, it gives an instruction to the analog demodulation unit 401 to demodulate with the viewing channel number. Analog demodulator 40
1 demodulates the corresponding channel in the RF signal having the carrier frequency of the designated viewing channel number by, for example, AM demodulation, and outputs the demodulated signal to the separation unit 402. The separation unit 402 separates a video signal and an audio signal into a video output unit 2 respectively.
04 and the audio output unit 205. In this way, the video and audio signals that the user wants to listen to are provided.

[0003]

However, in the configuration of the conventional video server system described above, first, only one modulation signal can be transmitted to each analog channel, the frequency carrier of each modulation unit is fixed, and the video / audio signal output unit 301 is used. Since only one video signal and one audio signal are transmitted, one terminal requires one analog demodulation section and one separation section, respectively. Therefore, in the conventional configuration, for example, when performing a video-on-demand service in which the user wants to individually listen to the video and audio signals that he or she wants to audition individually, individual analog modulators and terminals for all the users are provided. There is a problem that the system scale and cost are large because an analog demodulation unit and a separation unit are required in each unit. Also, the analog demodulation unit 401 of the terminal unit 304 must be capable of receiving a wideband signal so that it can receive all video channels on the video transmission path 308. Actual video transmission line 308 and amplifier 305
Since the video signal via the video transmission line 308 has different distances and characteristics, the number of stages and frequency characteristics of the amplifier 305, and changes due to temperature and noise characteristics of the surrounding environment, circuits such as automatic amplitude adjustment and automatic equalizer are required. It was necessary and required hardware for it.

Further, in the ordinary time division multiplexing, the band of the signals to be multiplexed is fixed in advance,
For example, it is not possible to effectively use the entire band of the network by simultaneously transmitting signals of different bit rates, for example, video stream signals of MPEG1 and MPEG2 by variable-rate time division multiplexing.

It is an object of the present invention to easily realize moving picture transmission in a video-on-demand system which requires such variable rate real-time transmission.

[0006]

To achieve this object, the video server unit of the video server system of the present invention comprises a digital video / audio signal output unit, a video control unit, a zone table unit, a switch unit, and a plurality of digital multiplexing units. Conversion section, plural digital modulation sections, mixer section and L
It is composed of an AN interface part, and receives the video / audio selection input from the terminal part and time-division-multiplexes when transmitting the corresponding digital video and audio signals, and then the digital modulation part according to which zone the terminal part belongs to. Determines the bandwidth to be used for transmission.

[0007]

According to the present invention, the carrier frequency used for digital modulation is modulated and transmitted using a high frequency in a zone near the video server and a low frequency in a zone far from the video server.

Further, the digital video and audio signals to be multiplexed when performing digital multiplexing are multiplexed in a frame structure in which short fixed length cell information is one channel and a plurality of channels is one frame.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a video server system according to a first embodiment of the present invention. In FIG. 1, a digital video server unit 113 includes a digital video / audio signal output unit 101, a switch unit 102, a plurality of digital multiplexing units 103, a plurality of digital modulation units 104, a mixer unit 105, a LAN interface unit 109, and video control. It is composed of a unit 108 and a zone table unit 112, and digital video and audio signals are transmitted by the video transmission line 1.
10 and control signals communicate with a plurality of terminal units via the control transmission path 111. At this time, all the terminal units are connected to each other via the control transmission path 111 and perform bidirectional communication. For example, as such a control transmission line,
There are loop networks such as n Ring (IEEE802.5). As the transmission medium of the transmission line, for example, the video transmission line 110 may be a coaxial line, and the control transmission line 111 may be a twisted pair line. The configuration of the terminal unit is shown in FIG. A digital demodulation unit 201, a digital separation unit 202, a plurality of digital decoder units 203 and 210, a terminal control unit 207, a LAN interface unit 206, a plurality of video output units 204 and 211 and a plurality of audio output units 205 and 2.
12 and a plurality of command input units 208 and 209. In such a video server system, the digital video server unit 113 provides the necessary video and audio signals in response to a request from the terminal unit 106.
Consider a case of performing a video-on-demand service such as outputting to 06. Video on demand is a service that allows users to freely select and watch movies and music programs that they want to watch. Here, the video and audio services that the user listens to can be realized as individual services for the user who is using it, and for example, it can be paused while watching a movie and then played again later. It refers to those that realize completely independent services without affecting the services of users.

When the video / audio service number to be viewed is input from the command input unit 208 of the terminal unit 106, the terminal control unit 207 inputs it through the LAN interface unit 206 and the control transmission path 111 to the LAN interface unit of the digital video server unit 113. It is transmitted to the video control unit 108 via 109. The video control unit 108 determines the video and audio service numbers and gives the corresponding digital video and audio signal output command to the digital video and audio signal output unit 101. Further, the video control unit 108 is the zone table unit 11
2, it is determined which zone the requested terminal unit 106 belongs to. In this case, for example, the zone 2 is set. Next, the digital multiplexer 103 and the digital modulator 104, which are determined to output signals to the corresponding zone 2,
The digital video / audio signal output unit 10 to the corresponding digital multiplexing unit 103 and digital modulation unit 104.
A switching instruction is given to the switch unit 102 so that the digital video / audio signal from 1 is output. The digital video / audio signal output unit 101 outputs a designated digital video / audio signal, for example, a video stream signal compressed by MPEG to the switch unit 102. The video stream signal is input to one digital multiplexing unit 103 via the switch unit 102 that has already been switched. Here, a plurality of other video stream signals are multiplexed. FIG. 3 shows an example of the format of a frame to be multiplexed. Video stream signals of a plurality of digital channels, for example, 20 channels are multiplexed by time division multiplexing to form one frame format. One frame appears repeatedly with a constant time period.
A start of frame signal (hereinafter S
(Hereinafter referred to as OF), and thereafter, digital channels are sequentially time-division multiplexed as fixed-length digital data. The video stream signal is divided into corresponding channels in a frame and sequentially stored. The video control unit 108 instructs the digital multiplexing unit 103 which channel among the multiplexed channels should be used for multiplexing. The digital multiplexed signal is input to the digital modulation unit 104, multivalued digital modulation such as 64QAM is performed, and the video transmission line 110 is mixed with other digital modulation signals via the mixer unit 105.
And is transmitted to the terminal unit 106 via the amplifier 107. At this time, one of the modulated waves is modulated and transmitted using a band of 6 MHz, for example. The arrangement of each frequency band in the entire band of the transmission path is shown in FIG. Here, consider the frequency band allocation in the digital modulator. The frequency band assigned by each digital modulator is determined by the arrangement of each zone. That is, the digital modulator that performs transmission to the terminal unit arranged in the zone near the digital video server unit 113 allocates the frequency band to the channel of the higher frequency band out of the total modulation channels in the entire band of the transmission path. For example, when transmitting to the terminal unit 114 in zone 1, c in FIG.
Use h12. Conversely, the digital video server section 11
The digital modulation unit for transmitting to the terminal unit arranged in the zone far from 3 allocates the frequency band to the channel of the lower frequency band out of the total modulation channels in the entire band of the transmission path. For example, the terminal unit 115 in the zone 3
In the case of transmitting to ch.1, ch1 in FIG. 4 is used.

On the other hand, the video control unit 108 is a LAN
A channel number indicating which channel in the multiplexed frame the requested digital video and audio signals are arranged is transmitted to the terminal control unit 207 of the terminal unit 106 via the interface unit 109. The terminal control unit 207 gives the received channel number to the digital separating unit 202. Each modulated signal is, for example, 6 MH
It is arranged as a z-band modulated signal, and the digital demodulation unit in one terminal unit is configured to receive only a signal in one of the frequency bands. That is, the frequency carrier demodulated by the digital demodulation unit 201 is configured to detect only one frequency, and the circuit configuration is simplified to receive only the narrow band RF signal. The digital demodulation unit 201 demodulates and decodes a signal in a specific allocated frequency band, and outputs it as digital data to the digital separation unit 202. The digital separation unit 202 separates a digital channel signal having a channel number designated by the terminal control unit 207 in advance from the frame structure of FIG.
Output to. The digital decoder unit 203 is, for example, MP
The video and audio signals compressed by the EG are separated and decoded respectively, and the video output unit 204 and the audio output unit 205 are separated.
To a video signal and an audio signal, respectively. Also,
With respect to other video and audio viewing requests from the command input unit 209, the video signal is output to the video output unit 211 and the audio signal is output to the audio output unit 212 by similar control.

FIG. 5 is a block diagram of a video server system according to the second embodiment of the present invention. In the figure, a digital video server unit 713 includes a digital video / audio signal output unit 701, a switch unit 702, a plurality of digital multiplexing units 703, a plurality of digital modulation units 704, a mixer unit 705, a LAN interface unit 709, and video control. The digital video / audio signal communicates with a plurality of terminal units via the video transmission line 110 and the control signal via the control transmission line 111.
At this time, all the terminal units are connected to each other via the control transmission path 111 and perform bidirectional communication. For example, as such a control transmission line, Token Ring (IEEE)
There are loop networks such as 802.5). As a transmission medium of the transmission line, the video transmission line 110 is, for example, a coaxial line,
The control transmission line 111 may be a twisted pair line or the like.
The structure of the terminal unit is shown in FIG. Digital demodulation unit 801, digital separation unit 802, and a plurality of digital decoder units 80
3, 810, terminal control unit 807, LAN interface unit 806, and plural video output units 804, 811.
And a plurality of voice output units 805 and 812 and a plurality of command input units 808 and 809.

Consider a case where such a video server system provides a video-on-demand service in which the digital video server unit 713 outputs the necessary video and audio signals to one terminal unit 706 in response to a request from the terminal unit 706. Video on demand is a service that allows users to freely select and watch movies and music programs that they want to watch. Here, the video and audio services that the user listens to can be realized as individual services for the user who is using it, and for example, it can be paused while watching a movie and then played again later. It refers to those that realize completely independent services without affecting the services of users.

When a desired video or audio service number is input from the command input unit 808 of the terminal unit 706, the terminal control unit 807 inputs the same through the LAN interface unit 806 and the control transmission path 111 to the LAN interface unit of the digital video server unit 713. It is transmitted to the video control unit 708 via 709. The video control unit 708 determines the video and audio service numbers and gives the corresponding digital video and audio signal output command to the digital video and audio signal output unit 701. Also, the video control unit 708 is configured to output a signal to the corresponding terminal unit (in this case, the terminal unit 706), the digital multiplexing unit 703 and the digital modulation unit 7.
04 is specified, and a switching command is given to the switch unit 702 so that the digital video / audio signal from the digital video / audio signal output unit 701 is output to the corresponding digital multiplexing unit 703 and digital modulation unit 704. The digital video / audio signal output unit 701 is a designated digital video / audio signal, which is, for example, MPEG.
The video stream signal compressed by 1 to MPEG2 is output to the switch unit 702. The video stream signal is input to one digital multiplexing unit 703 via the switch unit 702 that has already been switched. Here, a plurality of other video stream signals are multiplexed. FIG. 7 shows an example of the format of the multiplexed frame. Video stream signals of a plurality of digital channels, for example, 20 channels are multiplexed by time division multiplexing as short fixed length cell information to form one frame format. One frame appears repeatedly with a constant time period.
A start of frame signal (hereinafter S
(Hereinafter referred to as OF), and thereafter, digital channels are sequentially time-division multiplexed as short fixed-length cell data including channel numbers. The channel number here is the terminal unit 706 that issued the request for viewing the video and audio signals.
Indicates the unique number of the channel of the signal transmitted to.

The video stream signal is sequentially divided and stored in the digital video and audio data areas following the channel number in each fixed length cell information. The number of cells used in one frame at this time is made variable depending on the band of the signal to be transmitted.
This is because the video control unit 708 is a digital video,
A signal output instruction is given to the audio signal output unit 701, and the number of cell information in one frame necessary for transmitting the bit rate of the digital video and audio signals is calculated in advance and given to the digital multiplexing unit 703. . In addition, the video control unit 708 instructs the digital multiplexing unit 703 a channel number indicating which channel in one frame of the multiplexed channels should be used as the cell information for multiplexing. At this time, the number of cell information is adjusted within a range in which the total bit rate of the plurality of digital video and audio signals from the switch unit 702 does not exceed the bit rate that the digital modulator 704 can transmit. This digital multiplexed signal is input to the digital modulation unit 704 to perform multi-valued digital modulation such as 64QAM, and together with other digital modulation signals, the mixer unit 705, the video transmission line 110, and the terminal unit via the amplifier 107. Sent to 706. At this time, one of the modulated waves is modulated and transmitted using a band of 6 MHz, for example. The arrangement of each frequency band in the entire band of the transmission path is shown in FIG.

On the other hand, the video control unit 708 is a LAN
A channel number indicating which channel in the multiplexed frame the requested digital video and audio signals are arranged is transmitted to the terminal control unit 807 of the terminal unit 706 via the interface unit 709. The terminal control unit 807 gives the received channel number to the digital separation unit 802. Each modulated signal is, for example, 6 MH
It is arranged as a z-band modulated signal, and the digital demodulation unit in one terminal unit is configured to receive only a signal in one of the frequency bands. That is, the frequency carrier demodulated by the digital demodulation unit 801 is configured to detect only one frequency, and the circuit configuration is simplified to receive only a narrow band RF signal. The digital demodulation unit 801 demodulates and decodes a signal in a specific allocated frequency band, and outputs it as digital data to the digital separation unit 802. The digital separation unit 802 separates the digital video and audio data of the cell information in the frame having the channel number designated in advance from the terminal control unit 807 from the frame structure of FIG. 7 and outputs it to the digital decoder unit 803. The digital decoder unit 803 separates and decodes video and audio signals compressed by, for example, MPEG1 and MPEG2, and outputs them as video signals and audio signals to the video output unit 804 and audio output unit 805, respectively. In addition, in response to the video and audio viewing requests from the other command input unit 809, the video signal is output to the video output unit 811 by similar control.
And a voice signal to the voice output unit 812.

Regarding the second embodiment of the present invention, the same effect can be obtained even if the terminal section 706 has one digital decoder section, one video output section, one audio output section, and one command input section. Needless to say.

[0019]

In the video server system which realizes such a video on demand, the digital video and audio signals to be transmitted are compressed and digitally demodulated as a multiplexed signal for transmission, thereby performing digital demodulation in the terminal section. Section, digital separation section can be shared, and 1
By configuring the demodulation carrier frequency in digital demodulation in one terminal unit to receive only one fixed channel, it is possible to realize a simple automatic equalizer and amplitude adjustment circuit in the digital demodulation unit. Hardware can be reduced, which is practically useful.

When the digital video and audio signals are multiplexed as cell information of a short fixed length having a channel number, for example, digital video and audio data having different transmission rates are dynamically multiplexed. Can be placed and managed as a frame. That is, by changing the number of cells used by one transmission channel in a fixed number of one frame, digital video and audio data of different transmission rates can be multiplexed by any combination.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a video server system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a terminal unit of the video server system according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a format of a time division multiplexed frame in the digital multiplexing unit of the video server system according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an arrangement of respective frequency bands in the entire band of the transmission line in the first and second embodiments of the present invention.

FIG. 5 is a configuration diagram of a video server system according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a terminal unit of a video server system according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a format of a time division multiplexed frame of short fixed length cell information in the digital multiplexing unit of the video server system according to the second embodiment of the present invention.

FIG. 8 is a block diagram of a video server system in a conventional example.

FIG. 9 is a block diagram of a terminal unit of a video server system in a conventional example.

[Explanation of symbols]

 101 digital video / audio signal output unit 102 switch unit 103 digital multiplexing unit 104 digital modulation unit 105 mixer unit 106, 114, 115 terminal unit 108 video control unit 109 LAN interface unit 110 video transmission line 111 control transmission line 112 zone table Section 113 digital video server section 201 digital demodulation section 202 digital separation section 203, 210 digital decoder section 204, 211 video output section 205, 212 audio output section 206 LAN interface section 207 terminal control section 208, 209 command input section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Maeda 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Kyoji Takeda, 1006 Kadoma, Kadoma, Osaka Pref.

Claims (5)

[Claims] 1. A digital video transmission system comprising a digital video server unit for outputting digital video and audio and a plurality of terminal units interconnected via a video transmission line and a control transmission line. A terminal control unit in the terminal unit receives a video or audio signal selection input from one command input unit, and uses this as a control signal from the LAN interface unit in the terminal unit via the control transmission path to the digital video server unit. L
When the video control unit receives it via the AN interface unit, the video control unit outputs the digital video and audio signals requested by the terminal unit from the digital video and audio signal output units in the digital video server unit. In addition to controlling the digital video and audio signal output section, it is determined from the contents of the zone table section in the digital video server section, which network zone the terminal section that requested the output of the digital video and audio signals belongs to and is requested. A video server system which outputs digital video and audio signals to a plurality of terminal units in a corresponding zone. 2. The video control section outputs signals to a digital multiplexing section and a digital modulation section in a specific digital video server section which is specified to output digital video and audio signals requested by the terminal section. For this purpose, switching control is performed for the switch unit in the digital video server unit, and the video control unit controls the digital multiplexing unit for digital video and audio from the switch unit on one time division channel in one multiplexed frame. The channel number of the corresponding time division channel is assigned to the corresponding digital multiplexing unit for arranging the signal, and the corresponding time division channel number is transmitted to the terminal control unit of the terminal unit via the control transmission line to perform the digital multiplexing. The digitizing unit is used to output a plurality of digital video and audio signals from the switch unit. Signals are time-division multiplexed by the digital multiplexing unit, the digital modulation unit corresponds to the zones in advance with a high frequency band in a zone close to the digital video server unit and a low frequency region in a distant zone. Using the digital modulation adjusted for transmission and modulation, the data is transmitted to the video transmission path through the mixer section in the digital video server section, received by the digital demodulation section of the terminal section, and time-division In the multiplexed frame, the digital video and audio signals of the channel designated by the channel number received in advance are separated by the digital separation unit in the terminal unit and correspond to the command input unit.
2. The video signals decoded by one of the digital decoder units in one of the terminal units are output to one video output unit, and the audio signal is output to one audio output unit.
Video server system described. 3. A digital video transmission system configured to connect a digital video server unit for outputting digital video and audio and a plurality of terminal units to each other via a video transmission line and a control transmission line. In the digital video server unit for outputting digital video and audio signals to the digital multiplexing unit and the digital modulation unit in the specific digital video server unit that is specified to output the generated digital video signal to the corresponding terminal unit. The video control unit controls switching of the switch unit in the digital video server unit, divides one digital video and audio signal into short fixed length cell information having a specific channel number, and divides this into one channel. Different digital video and audio signals as multiple channels The video control unit assigns the channel number to the digital multiplexing unit that time-division-multiplexes into the video stream, and the digital multiplexing unit receives the plurality of digital video and audio signals from the switch unit from the plurality of channels. A signal is arranged by time division multiplexing as one frame, the channel number is transmitted to the terminal control unit of the terminal unit via the LAN interface unit and the control transmission path, and the digital modulation unit performs the digital multiplexing. The signal from the digital part is digitally modulated, transmitted to the video transmission line through the mixer part in the digital video server part, received by the digital demodulation part in the terminal part, and time-division multiplexed. A plurality of cell information having a channel number designated by the previously received channel number in the encrypted frame. From the digital video and audio signals are separated by a digital separation unit in the terminal unit and decoded by one digital decoder unit in the terminal unit corresponding to the command input unit, and the video signal is one video output unit in the terminal unit. The video server system is characterized in that the audio signal is output to one audio output unit in the terminal unit. 4. The terminal unit is configured to have a plurality of sets, each set including a digital decoder unit, a video output unit, an audio output unit, and a command input unit.
Or the video server system described in 3. 5. The video server system according to claim 1, 2 or 3, wherein the digital video and audio signals from the digital video and audio signal output section are compressed digital signals.