JPH01168130A - Electric communication system with burst and continuous audio signal - Google Patents

Abstract

PURPOSE: To attain the interactive and wide-range service that is capable of an interaction by using a circuit which selects the video and audio frames in response to the corresponding addresses of both frames and attenuating the continuous audio signals in response to the reproduction of an audio burst. CONSTITUTION: A center equipment 11 is connected to plural terminals 12 via a 1st transmission medium 13 which transfers a reference TV frame and also via a 2nd transmission medium 14 which is capable of the simultaneous transmission/reception communication of control signals without requiring the large band width. The static images included in a video frame that is selected in response to the corresponding addresses of both video and audio frames are stored and reproduced, and the continuous audio signals are attenuated in response to the reproduction of an audio burst. As a result, an interactive (conversational) system is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to telecommunications, and more particularly to interactive telecommunications systems.

BACKGROUND OF THE INVENTION A number of telecommunication systems have been proposed and developed that allow users of terminals to request specific video information from remote repositories. Services possible with such a system include, but are not limited to, information exploration, retrieval,
Examples include commerce, reservations, and shopping.

In some systems, both the user request and the video information are sent over a single duplex medium, such as a telephone line.

An example of such a single duplex system is U.S. Patent No. 4.500.7.
No. 51 and No. 4.578.535.

In other systems, requests are sent over telephone lines and video information is sent over a higher bandwidth medium such as cable. Examples of such dual media systems are U.S. Pat.
I2-Electrotechnique/Electronica No. 4-1986, pages 35-39.

In the system of U.S. Pat. No. 3,746,780,
Users desiring service call a central facility with a code number. At the central facility, selected video information is retrieved from video discs or other storage means and sent as still television frames to users over cable or other media. Since many terminals are usually coupled to the same medium, each still frame contains a location number or address that is read by an address detector located at the terminal, and only frames with the same address as the terminal are accepted. The accepted frames can be stored digitally by the terminal and repeatedly displayed on a conventional television receiver.

[Problems to be Solved by the Invention] Examples of video information include menus, forms, data, text, and still images.

It would be desirable to have audio information such as music and voice accompanying the video, but this is not present in the systems described above.

A publication of N) (K (Japan Broadcasting Corporation) dated May 1978 describes a system for transmitting still images accompanied by program sound. Frames for multiple programs are time multiplexed. .Each video frame has a code that identifies which program it belongs to.The audio signals of all programs are digitally encoded and time-multiplexed onto lines within the audio frame.Video and audio Both frames are standard NTSC.The video frames are sent serially.
Each video frame is followed by two audio frames,
Each video frame carries analog video information corresponding to one program, while each audio frame carries digitized audio information corresponding to all programs.

The receiver captures and records video frames of the selected program for repeated display. Obviously, audio is converted to analog and played back when it is received, but analog video can be digitized and stored in solid-state memory. The NHK system is suitable for broadcasting multiple scheduled programs, but it is also suitable for broadcasting interactive programs where many users can access and interact with a program or service at different times. operation) is not optimal for broadband services.

SUMMARY OF THE INVENTION Briefly described, according to one aspect of the present invention, a telecommunications system for transmitting video and audio information over a transmission medium includes equipment and an addressable terminal. The facility also includes at least one apparatus for providing addressed video frames containing information corresponding to still images and for providing addressed audio frames containing information corresponding to audio bursts. Means are provided for providing an unaddressed signal containing information corresponding to two channels of consecutive audio. The addressed video frames, addressed audio frames, and unaddressed signals are coupled to the transmission medium and sent to the terminal. The addressable terminal includes means for detecting the addressed video frames, addressed audio frames, and unaddressed signals of the transmission medium in response to corresponding addresses of video frames and audio frames. A circuit for selecting a frame is provided.0 Apparatus is provided for storing still images contained by the selected video frame and for storing and reproducing audio bursts contained by the selected audio frame. It is being A circuit is provided for providing a continuous audio signal contained by said unaddressed signal.

A circuit is provided for attenuating the continuous audio signal in response to playing an audio burst.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A telecommunications system IO implementing the invention is shown in FIG. The central facility 11 has a first transmission medium 1 having sufficient bandwidth to carry standard television frames.
3 to a plurality of terminals 12. The first transmission medium 13 may be a cable, such as a CATV network; fiber optics, air, and other broadband media are also suitable. The central facility 11 and the terminals 12 are also coupled by a second transmission medium 14 that allows simultaneous transmission and reception of control signals without requiring large bandwidths. A subscriber switched telephone system is a satisfactory second transmission medium, and as an alternative to allowing low bit rate signals to be transmitted between equipment 11 and a particular terminal, the low bit rate signals are described above. It may also be transmitted over a broadband medium 13.

Central facility 11 provides video and audio picture information in response to subscriber requests. Video information can include text, pictures, etc. sent as a series of addressed video frames.
or represent still frames of other images, each still frame may be displayed for a few seconds on a television receiver or monitor connected to the terminal, and audio may be provided to accompany the video during this time. desirable.

This system supports two types of audio: continuous audio that may be played simultaneously and specific audio.
The continuous audio, preferably having , is sent on a real-time basis, for example in an audio channel. An example of continuous audio is background music (
The specific audio (background music), so called because it is specific to the displayed still frame, is an audio narration or instruction. 0 time compressed audio where the particular audio is intended only for one selected terminal at a time and is sent in time compressed bursts by addressed frames with the same address as the accompanying video frame Only one channel of is carried in an audio frame.

Both audio and video frames are in the same television format, such as NTSC. The same principles can be directly applied to other television systems such as PAL or SECAM.

In the NTSC system, each frame is 1/30 seconds long and consists of two fields of 262.5 horizontal scan lines each. The scan lines of the two fields are interlaced for a total of 525 lines per frame. Approximately 21 lines occur during a period called the vertical blanking interval (VBI), which is at least 1.33 milliseconds long. These lines do not appear on the television screen;
Approximately 483 lines of video remain in one frame.

The NTSC system is briefly described in "Federal Communications Commission, Public Notices" of December 17, 1953 and June 6, 1954.

When the NTSC standard was written, a minimum VBI of 1.33 milliseconds was required to scan back to the top of the picture tube between fields. U.S. Patent No. 3.493.674 and North American Broadcast Teletext, Subscription Engineering &
VB! Development, CBS Television, Newark, New Jersey, June 22, 1981. A scheme has been developed for transmitting auxiliary information into one or more lines of the .

According to the present invention, the address, mode code, successive audio channel selection code and error detection/correction code are
It is sent on one line in the BI, for example line 12. The structure of this line is such that the first 8 bits always represent the mode code and tag sequence number, the next 24 bits always represent the address, and the next 8 bits represent the consecutive audio channel selection codes. . The address correspondingly signals the addressed terminal that the addressed frame is to be accepted.

The mode code identifies this frame as video or audio and its sequence with respect to other frames so that the terminal can process it accordingly.

Audio frame information, which may be digital or analog, is sent in time-compressed bursts, allowing more than one second of audio to be carried by each l/30 second frame. The terminal stores the time-compressed audio frames and plays them at normal speed through the television receiver.

Central facility 11 consists of four basic subsystems. That is, a concentrator subsystem 15,
A server subsystem 16, a video subsystem 17, and a control and maintenance subsystem 18.

Each subsystem can be implemented on a commercially available general purpose computer and interconnected by a local area network. The software for each subsystem can be designed as a self-contained entity, and the subsystem interfacing interfaces conform to standard interprocessor protocols. This assumes a complete central facility system configuration in which each subsystem consists of a separate processor or group of processors; however, in smaller configurations one or more of these subsystems may be It can be implemented on one computer, yet still maintain a software interface that allows simple expansion to multi-computer configurations.

The control and maintenance subsystem 18 is responsible for providing control over the central facility and also for collecting statistics on the operation of the entire system.The control and maintenance subsystem 18 is necessary to carry out the present invention. Therefore, further explanation will be omitted. - The concentrator subsystem 15 is the ink face to the terminals for all control and communication purposes. This subsystem is accessed by a remote terminal on a second transmission medium 14, which may be a dial-up connection over a public telephone network or an R5232C direct terminal access interface for high efficiency control terminal activities. .

The server subsystem 16 acts as the overall controller of the session, using input from the terminals x2-b) via the concentrator subsystem 15 to access the appropriate database and send which video and audio frames to the user. It sends instructions to the concentrator subsystem 15 as to what to send.

Video subsystem 17, shown alone in FIG. 2, stores video and coded audio information frames and sends them to terminal 12 via CATV link 13. Video still frames are stored on an optical video disc unit 2o in standard NTSC composite baseband format.
is memorized. Approximately 54,000 still frames can be stored on each disk.

Since the seek time of a video disc unit is longer than desired, significantly more video disc units than the minimum number to accommodate all still frames are needed. The video disc unit 20 is AC (alternating current)
To provide a combined signal, a DC regenerator 21 is required before the non-blocking video matrix switch 22.

When a user requests a video still frame, central processor 23 identifies its location on an available video disc unit. After the unit reaches the requested rest frame, it notifies switch 22, which transfers the l frame to pulse insertion device 24. The inserted pulses come directly from the station synchronization mask. The frame is sent to channel processor 25, which sends one VBI
Insert address, mode code and error code using lines. The addressed frame is provided to the video input of CATV modulator 26.

The audio frames (more than one of which may be associated with a particular video frame) are pre-stored digitally on a Winchester-type magnetic disk 27 in an 8-bit PCM encoded format at a sampling rate of, for example, 16 KHz. A disk drive unit capable of processing approximately IG bytes can process 1000 minutes of audio at 124 Kb/s.

Time-compressed audio can also be stored in an analog format and transmitted as an analog signal.

Audio is compressed to store as much audio as possible in each frame. real time audio 1
More than a second is sent in each l/30 second frame depending on the form of compression.

After the transfer is complete, the central processor 23 identifies these audio frames, associates them with the selected video frames, and unloads (dumps) them from the correct address on the Winchester disk 27 to the buffer memory 2. The central processor 23 requests a corresponding number of black frames via the switch to accommodate the audio data. These black frames contain color bursts for clock recovery at the terminal, with each active line at black level. In the NTSC system, black is represented by a low signal level. Data is inserted by channel processor 25. The data bits are converted into pulses, and these pulses are first conditioned by a Nyquist filter to reduce inter-symbol interference and interference to the acoustic channel and to adjacent channels before they are aggregated into a Black-Threshold frame. conditioned to prevent the spread of energy.

Color subcarrier frequency 3.579545MHz 8
75 transmission bit rate (5,727272Mb/S)
can be used. The data clock has a period of 174.6 nanoseconds. Although this is the same bit rate as Teletext, and about the highest bit rate that can be performed by most CATV systems, the preferred formatting of the data and the method of clocking the incoming data is much more efficient and significantly different. are doing.

Referring again to Figure 4, for each line where data exists,
A flag bit in the form of a "1" bit is placed after the leading edge of the horizontal sync pulse, for example, 10.5 microseconds (60 data clock pulses). In the case of audio data, followed by 288 bits of data (ie 36 bytes), this totals □142272 bits/frame.

Referring to Figure 3, both audio and video frames have four lines within the vertical blanking period: address, mode (video or audio) and error code.
and reserved for future use. In the audio frame, lines 16-262 of field 1 and lines 279-525 of field 2 are used for audio data.

Referring again to FIG. 4, a black frame with audio data is switched into the video input of CATV channel modulator 26 for a period of one frame (approximately 1730 seconds). Video frames are also sent to the video input of CATV channel modulator 26. There is always a continuous stream of still frames, and black burst frames are switched in when no information frames are being sent.

Each channel modulator is selected to transmit over a single coaxial distribution system and a single coaxial cable system 13. - There can be over 100 active users typically sharing one channel for a set of projected traffic patterns. The video and audio frames of one program are time multiplexed with others on one CATV video channel and sent to a remote terminal. Continuous audio is sent on an audio channel.

Central facility 11 uses the BTSC multichannel television audio format to place continuous audio (eg, background music) on up to three separate audio channels 3° of the NTSC composite signal. The SAP (Second Audio Program) channel is used. The three possible channels are mono (L+R), stereo difference channel, and SAP channel. It is also possible to have a large number of separate and different background music channels available to the user.

The above-mentioned continuous audio and framed specific audio may occur simultaneously; when the video specific audio is played on the user terminal in real time, the continuous audio components, if present, are automatically is attenuated to The central processor 23 is controlled by a control signal inserted into the vertical blanking period line 12 by the channel processor 25 or by the concentrator subsystem 15.
control signals sent through the telephone loop 14 by the user terminal control the selection of consecutive audio channels (or silence) at the user terminal. Successive audio sources are connected to the same modulator 26 audio input, where the user may have the ability to mute them.

The audio input of the channel modulator 26 can be driven by individual SAP channel encoders 31 or by a single encoder using a suitable distribution unit 32.

Video and audio frames and continuous audio are distributed to the terminals through the CATV network 13.

“Referring to FIG. 5, terminal 12 consists of a set top module 33 and a remote keypad 34.

Set-top module connector panel (not shown)
Cable in = 75 ohm coaxial F connector, TV coax F 5 ohm coaxial F connector, telephone line = R
A variety of physical connectors are provided, including a J-11 telephone jack and an auxiliary RJ-11 telephone jack. ``Through these connectors, the terminal 12 is coupled to a CATV channel 13, a telephone loop 14, and a television receiver or monitor 35.

The set-top module 33 receives and processes video and audio frames for data communication to and from the central facility 11 and sent from the central facility, and provides them to the television receiver 35. The set-top module also includes a power supply and a controllable modem 36 as an interface to the telephone loop 14.

CATV tuner demodulator 38 receives selected NTSC channel signals over the CATV network. This composite signal includes video frames, digitally encoded audio frames, and BTSC encoded audio channels; CATV tuner demodulator 38 demodulates the incoming signal to baseband and separates the audio channels from the video and audio frames. .

Consecutive audio channels taken from the audio output of CATV tuner demodulator 38 are separated by low pass filter 39 and SAP channel decoder 40. They are fed to an analog switch 41 which is controlled by successive audio selection codes sent from the central facility 11 sent during the vertical blanking period of a frame. Six selection codes are drawn from that frame. Then, the switch 41 is controlled to select the desired continuous audio signal. In response to pressing the mute key on keypad 34,
The signal from the R receiver 65 is sent to the CPU 67 via the MUART 37.
energize one of the two control lines indicated by F. This opens the switch, disconnecting the continuous audio from the output of the switch 41, thereby disconnecting the continuous audio from the attenuator 42, thereby muting the continuous audio. By pressing the mute key again, the control signal to switch 41 is deactivated;
As a result, continuous audio is not muted on the Intel 8256 Multifunction Universal
MUART 37, which may be an asynchronous receiver transmitter LSI, provides a serial I10 interface to modem 36. Moreover, 2 of the parallel line indicated as F
One is used to control the mute and background audio selection switches of switch 41. The output of the selected channel of switch 41 is provided to attenuator 42 . This block is a programmable gain amplifier whose gain is reduced by approximately 12 dB when the control signal from audio controller 43 is activated. This control signal is generated by audio controller 43 when the last audio frame is stored in audio 50. The audio controller 43 can determine this state based on the data on line 12 of the VBI. As soon as the audio controller detects this condition, it energizes the control signal and begins playing the audio 50 content. audio 5
The digitized audio samples from 0 are converted to analog audio by a combination of audio D/A and LPF 51. This is a digital-to-analog converter and filter block. This audio is summed with the attenuated continuous audio in a summer 44. This is done to prevent continuous audio, e.g. background music, from drowning out video-specific stored audio, e.g. speech. The output of the zero summer 44 is fed to the audio input of the channel modulator 45. , the modulator 45 transmits it to the television receiver 3.
Supply to 5. Continuous audio is being played simultaneously with the stored still images.

Each video and coded audio frame received from the central facility 11 is line 1 of the vertical blanking interval (VBI).
2, a 3-byte terminal address, a 2-bit mode code, and a continuous audio channel selection code were added.

VBI processing circuit 46 detects line 12 and error detector 4
7. Address register 49, mode/tag register 48
and the actions of spare registers 74. mode/tag register 48 is strobed to accept and store a mode code bit;
Meanwhile, reserve register 74 is strobed to store successive audio selection code bits from the data on line 12. Error detector 47 indicates if any errors are detected in the data on line 12. VBI processing circuit 4
6 compares the contents of address register 49 with the address bits on line 12. A zero match condition indicates that the current frame should be captured by this terminal. line 1
At the end of step 2, if the addresses match and no transmission error was detected by error detector 47, CPU 6
7 is a decoder interface 68 and a system bus 66
Receive interrupts through. CPU 67 reads the contents of mode/tag register 48 and reserve register 74 through the CPU interface block. Based on the contents of reserve register 74, CPU 67 can select the appropriate consecutive audio channel in response to control signals from MUART 37. A mode code can have one or four meanings: These are: video frame; video frame, preceding audio stop; audio play end, initial frame; audio play end, successive frames.

Vertical and horizontal drivers are used to identify all frame lines by number.

Line 12 is read and the address and mode (video or audio) bits are sent to VBI processor 46, mode/tag register 48 and error detector 47. The address is correlated with the user address present in address register 49 and the mode bits are checked to determine the type of frame so that appropriate action is taken. Each frame transmitted from the central facility is numbered repeating in blocks of 64. This sequence of numbers is the 6 tag bits of the mode/tag register. These can be interrogated by the central facility to check the delivery of any particular still frame that has been recently transmitted.

If the address on line 12 can be correlated with the terminal ID, the frame is inserted into the appropriate storage depending on the mode (video or audio).

In the case of audio, they are stored in bursts (per line) to 5.7272 Mb and clocked into the audio RAM 50 line by line through the appropriate set of frames.

After the audio data segment is received, it is
D including AM50 to 7.5 Hz low pass filter
The music is played through the /A converter 51 at an appropriate speed (for example, 128 to b/8) until the end. The analog output from the D/A converter is sent to an acoustic summer 44. This adder 4
4 is connected to the audio input of channel 3 modulator 45. This analog output is summed with the selected consecutive audio channels which are attenuated until the sequence is complete.

The frames from the demodulator 38 are connected via a DC regenerator 52 to a color subcarrier (3.58 MHz) bandpass filter 53. Its output is sent to a color subcarrier regenerator chip 54. For this to work,
Must have a burst flag gate. To accomplish this, a sync pulse is extracted from the incoming video frame by a sync stripper 55, and the output from the 0 generator 56, which is fed to a sync pulse generator 56, is set to the horizontal drive, vertical drive, and color subcarrier burst flags. All clock frequencies for synchronization, including , are derived from the color subcarrier burst that is always present in the incoming still frame. In order for the synchronous generator 56 to operate,
Input (14,32M) I at 4 times the color subcarrier frequency
Z) is required. This is provided by phase-locked loop 57. The output of the regenerated color subcarrier frequency is fed into a phase locked loop 57 that locks to eight times the color subcarrier oscillator. From this oscillator 4
Twice as many color subcarriers are extracted.

The directly regenerated frames from the DC regenerator 52 are provided to a buffer that generates TTL logic levels from the bits of the raster. These levels are provided to a clock generator and data extraction circuit 59. This data extraction makes effective use of raster frames.

The leading edge of the horizontal sync pulse is too sloped to accurately synchronize the bit stream, so a bit sync circuit is used. Recall that the first bit on each data line is a ``1'' placed 10.5 microseconds (60 data clock pulses) after the leading edge of the horizontal sync pulse; this is called the flag bit. . The 8x color subcarrier source is connected to a clock 59, which is
Divide by 15 to generate a 174.6 nanosecond data clock pulse. The leading edge of the horizontal sync pulse is used to start counting using data clock 59. Referring to FIG. 4, 58 data clock pulses (10, 12
After counting (7 microseconds), the gate or time window is opened to the 8x color subcarrier clock (28.64 MHz) for a period of 5 data clock pulses (873 ng). These five data clock pulses are ANDed with the data bit stream, resulting in a leading '1'.
If present (eg, a flag bit), its position relative to the five data clock pulses is identified and used to precisely synchronize the data clock to the rest of the data on the line.

Referring to FIG. 5, a flash A/D converter 60A, part of a video coder 60, clocked at approximately 14.32 xlO' 8-bit samples/second, continuously provides data to an input register 61. However, until the strobe is received, it is memory panchromatic 2 (3,82M
b) If the mode register 48 recognizes the incoming frame as being addressed to a user terminal and is for video display, a strobe is sent to the video frame store. Memory panchromator 2 is then loaded from register 61 for exactly one frame period (approximately 1/30 seconds). It uses a 4x color subcarrier clock (14,32MH2) to
It is repeatedly and completely reproduced as a still frame via the A converter 60B. Since there is a jump in the phase of the color subcarrier between every other frame, this is corrected in the frame jump correction block 63.

Before being applied to the video input of modulator 45, the video signal is sent to character generator 64. This generator is used to insert characters as they are inserted from the user keypad 34. Characters are typically inserted near the bottom of the screen display.

This system provides interactive data retrieval and transactions. An infrared keypad 34 provided with the system has a sufficient number of keys (eg, 53) to interact with the system. These keys include alphanumeric keys and various special function keys for simplified, dedicated on/off operations, page forward, page backward, -time stop, purchase, and other functions.

Keypad 46 transmits PCM encoded IR commands to the set top module via infrared receiver 65. This keypad is the mechanism by which the user controls the set-top module and communicates with central facility 11 via telephone loop 14. These keys are used to control the terminal, central facility functions, and to enter transaction specific data by the user.

IR receiver 65 sends special coded IR pulses to 8080
It includes a decoder to convert it into a format convenient for insertion into the CPU bus 66.

Data communication with the central facility 11 is via the telephone exchange 30
This is done by a modem 36 which transfers asynchronous ASCII data at a rate of 0 or 1200 bps. modem 36
has an auto-dialing capability to automatically place calls to a central facility. LED indicator 74 is a data carrier detector.

The terminal is controlled by a microprocessor 67 coupled to a system bus 66. 8085 CPU can be used. MUART 36 is connected to system bus 66.

Decoder interface 68 is used as a buffer between path 66 and the circuitry associated with the data on line 12.

Address decoder 69 is adapted to 8085 bus 66. Program Farm Uniaba E F ROM 70
G: 1m is memorized. EEFROM71 is telephone loop 1
It is used to store information from the central facility 11 via 4. Examples of these are the terminal address, password, and display characters used before the connection is established.

EEFROM 71 also provides storage of representations and messages for display, and the terminal identification (serial number) and terminal type (serial number) for use in the logon process.
(version number) is also memorized. The messages stored in EEFROM include the following: That is: Call placed call completed Call attempt failure Video channel failure rvs Session terminated Call disconnected.

These pre-stored message data are stored in the central facility 1.
1 to the terminal via the telephone loop 14. The terminal 12 has the ability to receive ASCII text via the telephone line 14, or retrieve it from the EEFROM and switch it with the currently displayed video frame. The blank frame generated by the sync generator 56, with or without, allows only ASCII text to be displayed. Video character generator 64 generates characters for display on the screen.

When the terminal is in the off state, only the infrared receiver is energized. In this state, the set top module is completely transparent to the television signal. This transparent state is provided by switch 73, which provides the incoming signal to television receiver 35 with all set-top module components in the disconnected state.

When the terminal 12 is turned on, the locally stored representation is displayed on the screen and the terminal modem automatically dials the central facility 11. When concentrator subsystem 15 detects a power-up message (sent by terminal 12 when a carrier is detected on telephone loop 14),
Concentrator subsystem 15 then sends a message to the server to establish a new session.

In one mode of operation, to control use of the service only by the subscriber, the server subsystem 16 sends a logon form to the terminal 12 and the user ID and password entered by the subscriber are verified against the database. It will be done.

In the unlikely event that the user ID or password is invalid, an appropriate error message will be sent to server subsystem 16.
sent by. The user is acknowledged to have made two input errors, but the third one is also incorrect.

If so, the session is terminated by server subsystem 16 based on the assumption that access is being made by an unauthorized user. The carrier signal on telephone loop 14 is dropped and terminal 12 is disconnected from the system. Once a valid ID and password are received by server subsystem 16, a confirmation message is sent to concentrator subsystem 15, which sends a "begin session" message to video subsystem 17.

As part of the subscriber profile in the server subsystem's database is the CATV channel number to which the terminal is tuned, and this information is sent to the video subsystem 17 as part of the "begin session" message. Video subsystem 17 selects an initial video frame (associated with an audio frame, if necessary) from storage indicated by server subsystem 16. Video subsystem 17 selects an available time slot on the appropriate channel and sends the selected frame or frames. Each frame has a terminal address coded on line 12 of the VBI.

An "initiation response" message is sent from the video subsystem to the concentrator subsystem to complete the logon procedure.

After observing the initial screen (e.g. main menu),
The terminal user indicates his next request by one or more keystrokes on the remote keypad. These keystrokes are transmitted by telephone loop 14 and interpreted by concentrator subsystem 15. Concentrator subsystem 15 generates and sends video/audio processing (VAP) messages to server subsystem 16 . Server subsystem 16 uses this information to search its database to find the identifier of the information frame that satisfies the subscriber's request. This information is sent to the concentrator subsystem 1 in a two-part message.
The first part, called the page 0 control record, returned to 5 contains information regarding any prompts or cursor controls that must be sent to terminal 12 via telephone loop 14; this information is maintained by concentrator subsystem 15. The second part, called the page 0 display record, contains information about the frames to be sent (single frame or timed sequence, identifiers of all video and audio frames), which is sent to the video subsystem 17. Video subsystem 17 is PDR
accesses the video subsystem's database and retrieves the requested frames from storage using the C
The signals are sequentially transmitted to the terminals through the ATV link 13.

Processing of the subscriber's request continues until the log-off message is received by concentrator subsystem 15.
Continuing in the manner described above, upon receipt, concentrator subsystem 15 sends a detach message to both server subsystem 16 and video subsystem 17 in response. Video subsystem 17 sends appropriate information regarding the session to control and maintenance subsystem 18 and deallocates all data structures used in the session.

CAT for interconnecting the central facility 11 and the terminals 12
Using both V (or equivalent distribution system) and telephone loop 14 allows adding more complex interfaces to the system. One such application is customer service representative (CS).
R). If a subscriber decides in the middle of a session that he needs some assistance, he can use the standard telephone calling features or the services of the concentrator subsystem 15 to complete the connection. "On hold" and CS
A telephone connection can be made to R. The C3R (through the second terminal) can control the user's session, ie, what is sent to the terminal 12, while talking to the user through the telephone loop 14. When the negotiation is finished, the CSR disconnects and returns control to the user.

A preferred embodiment and what is believed to be the best mode of carrying out the invention have been described. However, other embodiments and variations and modifications will be apparent to those skilled in the art. Accordingly, the scope of the invention should be determined by the claims that follow.

4. A cloudy day FIG. 1 is a schematic block diagram of a telecommunications system implementing the present invention, FIG. 2 is a block diagram showing details of the video server subsystem of the central facility in FIG. 1, and FIG. 3 is a block diagram of the central facility in FIG. FIG. 4 is a diagram illustrating the waveforms of a bit synchronization system; FIG. 5 is a diagram illustrating the waveforms of a bit synchronization system; FIG. 2 is a block diagram of a terminal.

lO: Telecommunications System 11: Central Facility 12: Terminal 13: First Transmission Medium 14: Second Transmission Medium 15: Concentrator Subsystem 16: Server Subsystem 17: Video Subsystem 18: Control and Maintenance Subsystem 19 : Local area network (LAN) 20 : Video disk unit 21 : Direct current playback device 22 ; Non-blocking video matrix switch 23 : Central processor 24 : Pulse insertion device 25 : Channel processor 26 : CATV modulator 27 : Winchester-type magnetic disk 28 : Buffer memory 29 : Coupling device 30 : Audio channel 31 : SAP channel encoder 32 : Distribution unit 33 : Set-top module 34 : Remote keypad 35 : Television receiver or monitor/Ii+ UU+! +7

Claims (1)

[Claims] (1) A telecommunications system for transmitting video and a plurality of audio information in a transmission medium, the equipment comprising: equipment and addressable terminals, the equipment providing addressed video frames containing information corresponding to still images; means for providing an addressed audio frame containing information corresponding to an audio burst; and means for providing an unaddressed signal containing information corresponding to at least one channel of continuous audio. and means for coupling the addressed video frames, addressed audio frames, and unaddressed signals to the transmission medium, the addressable terminal comprising: means for coupling the addressed video frames, addressed audio frames, and unaddressed signals to the transmission medium; means for detecting unaddressed audio frames and unaddressed signals; means for selecting video frames and audio frames in response to corresponding addresses of the frames; and stills contained by the selected video frames; means for storing and reproducing images; means for storing and reproducing audio bursts contained by selected audio frames; and means for reproducing successive audio signals contained by said unaddressed signals. and means for attenuating the continuous audio signal in response to playing an audio burst.