MXPA96002660A - A guide to channels of a digital television system that has a lifetime - Google Patents

Abstract

The present invention relates to a television system for receiving a plurality of digitally encoded television programs wherein each of the digitally encoded television programs is associated with at least one of a plurality of digital data transmission channels, each of the digital data transmission channels has the ability to transmit at least one digitally encoded television program and at least one of the plurality of digital data transmission channels includes program data of television programs, the system that comprises: means responsive to the control signal for selecting a particular digital data transmission channel of the plurality of digital data transmission channels, and control means coupled with the selection means for generating the control signal; because: the programming data of television programs is ac They update at predetermined time intervals and comprise: a first data structure (MPG) that defines the relationship of each of the television programs with the respective ones of the plurality of digital data transmission channels, a second data structure (" LIFE PERIOD ") which indicates a period of time during which the defined relationships are valid, and a third data structure (" CHANGE OF NUMBER ") that indicates a change in the defined relationships, the means of control make the first Data structure (MPG) of the television program programming data is obtained and stored in the system when the second data structure ("LIFE PERIOD") indicates that the valid time period is less than a predetermined period of time or when the third data structure ("CHANGE OF NUMBER") indicates that the defined relationships have changed, the control means examine the third data structure ("CHANGE OF NUMBER") c more often than the second data structure ("LIFE PERIOD

Description

A GUIDE TO PN CHANNELS DIGITAL TELEVISION SYSTEM THAT HAS A USEFUL LIFE FIELD OF THE INVENTION This invention relates to the field of digital communications systems, and is described with reference to a digital satellite television system, but can also be applied to systems such as a digital cable system, digital terrestrial transmission system , or a digital communication system that uses telephone lines. The invention specifically concerns a method and apparatus for ensuring that television programming data, to generate on-screen displays to control the system, are current.

BACKGROUND OF THE INVENTION In a satellite television communication system, the satellite receives a signal representing audio, video or data information from a ground-based transmitter. The satellite amplifies and retransmits this signal to a plurality of receivers, located in the residences of consumers, via answering machines that operate at specified frequencies and have given bandwidths. Such a system includes an upstream transmission portion (from ground to satellite), a satellite reception and transmission unit in orbit above the earth, and a downstream connection portion (from satellite to ground) that includes a receiver located in the user's residence. The subject matter of the present invention concerns especially the downward connection receiving unit designed for relatively easy use by the user. The system of interest is designed to employ two satellites within a few degrees of each other in geosynchrony of Earth orbit stationed at an altitude of 35,887,702 kilometers, approximately over the state of Texas. With this arrangement, receivers located anywhere in the 48 contiguous states of the United States of America can receive signals from both satellites in the same parabolic antenna reflector without the need to replenish the parabolic reflector of the antenna. Each satellite transmits its signals with a respective polarization. The selection of a satellite for the reception of its signals is achieved in the receiving antenna by selecting those signals with the appropriate polarization. Each satellite includes sixteen answering machines to transmit signals to the parabolic reflector of the receiving antenna over a range of frequencies. Each answering machine is multiplexed in time to carry a plurality of television channels, (for example, from six to eight channels), substantially simultaneously. The satellite signals are transmitted in compressed and packaged form, and include television and auxiliary data signals. Because the system is capable of carrying as many as two hundred and fifty-six channels, the user must be provided with some method and apparatus for selecting television programs, which is easy to understand and operate. If we watch conventional VHF and UHF analog transmission television as a guide, we find that the solution provided in it is of very little help, for the following reasons. The channel number of a given television station corresponds to a fixed frequency band. In other words, channel 6 in the United States of North America is regulated to occupy the 82-88 MHz range. Most consumers who are not technicians do not understand the frequency assignments of the television transmission bands. Instead, they tune into a desired channel by entering their channel number into their receiver. Your receiver is programmed with the appropriate information to perform the required tuning for the desired channel by generating the band connection and the appropriate tuning commands, in response to the introduction of the channel number made by the user. It is possible for manufacturers to build a fixed channel-to-frequency number translation arrangement within each television receiver, only because the relationship between the channel number and the frequency band must conform to a transmission standard. In the United States of America, there is a terrestrial television programming guide system known as Starsigh that provides a channel guide display for selecting television channels at fixed transmission frequencies. Starsigh data is transmitted in the vertical range of television programs on some transmitters (usually public transmitting stations (PBS)), and is displayed in the form of a programming guide on the user's television screen. Unfortunately, there are three problems with the Starsigh system. First of all, it took several hours for a Starsigh receiver to load its channel guide data due to its transmission at a low data rate, so an observer will not be able to use its Starsigh system to tune into channels for at least In the second place, channel guidance information is not transmitted on all channels, so updating the guide requires tuning the channel of the public transmitting station, thus interrupting the use of the channel. from the observer of the receiver during the several hours it takes to reload the guide Thirdly, a user of Starsigh must choose a window in time of several hours, which occurs once every twenty-four hours, for the Starsigh receiver to load a updated copy of the channel guide It is important to mention that, the Starsigh unit can not detect unexpected changes in television programming if the Anal that is being watched at the moment does not carry signals from Starsigh, and most channels do not carry those signals. Thus, unexpected changes in television programming can not be handled within a reasonable time due to the failure of the system to detect those changes, and the restriction of loading the programming from a particular transmitting station during a predetermined time window.

SUMMARY OF THE INVENTION A television system for receiving a plurality of digitally encoded television programs includes an integrated receiver decoder (IRD) having circuits for selecting a particular digital data transmission channel among a plurality of digital data transmission channels that they contain a desired television program digitally encoded in response to a control signal, also including many of those transmission channels program data of television programs. The system also includes data entry circuits operable by the user to enter data, and a controller for generating the control signal mentioned above in response to the data entered by the user. The controller selects a virtual channel among a plurality of virtual channels in response to the data entered by the user, each virtual channel being subject to reassignment to a different one of the plurality of digital data transmission channels, defining the programming data of the digital channel. television programs the relationship of each of the television programs with the respec ones of the plurality of digital data transmission channels. Television programming is repeated several times a minute, and a code indicating its lifetime is repeated. The receiver acquires a new master program guide when it is determined that its current channel guide has expired. In order to adapt unexpected changes in programming, every few minutes the receiver checks a status byte to see if the master program guide has changed. Predetermining the exact number of minutes to be several times less than the lifetime of the program guide. If the status byte indicates that the program guide has changed, then a new program guide is read, without waiting for the current guide to expire. The status byte can be a version number for the program master guide, which is compared to the version number of the currently stored program master guide.

BRIEF DESCRIPTION OF THE DRAWING FIGURES 1 and 2 are illustrations of a typical data stream transmitted from an answering machine according to the invention. FIGURE 3 is an illustration of an on-screen display of a program guide according to the invention. FIGURE 4 is an illustration of the segmentation of the master program guide and special program guides according to the invention. FIGURES 5a and 5b are illustrations of program data structures according to the invention. FIGURE 6 is a block diagram of a satellite transmission / reception system according to the invention. FIGURE 7 is a block diagram of the integrated receiver decoder receiver unit. FIGURE 8 is a block diagram of a portion of the integrated receiver decoder receiver unit of FIGURES 6 and 7, in detail. FIGURE 9 is a flow chart showing a portion of the microcomputer control program of the integrated receiver decoder receiver unit.

DETAILED DESCRIPTION OF THE DRAWING In the system in question, the information necessary to select a given television program is not programmed in a fixed way inside each receiver but, on the contrary, it is loaded from the satellite continuously in each answering machine.

The television program selection information comprises a set of data known as the Master Program Guide (MPG), which refers to the titles of the programs, their start and end times, a virtual channel number that will be displayed to the user, and information assigning virtual channels to frequencies of the answering machines and for a position in the data stream multiplexed in time transmitted by the particular answering machine. In a system according to the invention which is, it is not possible to tune to any channel until the first master program guide is received from the satellite, because the receiver literally does not know where any channel is located, in terms of frequency and position (that is, time track of data) within the data stream of any answering machine. Conveniently, the system is fully flexible because any program can be allocated, or reassigned to any transmission time of the program master guide, for any answering machine or data time track, in a manner that is completely transparent to the user , who only sees the title of the program and the virtual »channel without change. The problem of changes in television programming is overcome because the master program guide is transmitted preferably to all the answering machines with the video, audio and auxiliary data of the television programs, and is repeated periodically, for example, every 2 seconds However, there is also a system in which only one or some of the answering machines carries the master program guide, because a quick tuner could be used to connect the answering machine that carries the program master guide, or a second tuner could be tuned to receive the data of the master program guide. The speed of the data to transmit a master program guide is approximately 100 kbits per second. The master program guide, once received, is kept in a memory unit in the receiver, and is updated periodically, for example every 30 minutes. The retention of the program master guide allows instantaneous selection of television programs because the necessary selection data is always available. The program master guide has a useful life (time within which your data is considered valid) of thirty minutes. A byte indicating the remaining lifetime of the program master guide is transmitted with each transmission of the guide itself (that is, approximately every two seconds). In addition to the thirty-minute service life of a master program guide, an "emergency guide" is available to provide a means to correct errors in the program guide, caused by operator error at the connection site, or caused by a sporting event that runs "overtime" (that is, beyond its scheduled time). A status byte of the program guide (ie, the "change number" byte) is checked repeatedly at the end of each five-minute interval to see if the content of the program master guide has already been received (but not stored) still) changed with respect to the content of the currently stored program master guide. If so, then the newly received program master guide is loaded into the memory for immediate use. Otherwise, the newly received program master guide is discarded. Here is an explanation of how a system of this type is implemented. As mentioned above, the system is capable of transmitting hundreds of programs. Each program can include many services. A service is defined herein as a program component, such as a video signal, an audio signal, a closed captioning signal, or other data, including executable computer programs, for an appropriate receiver. Each service of each program is identified by a Service Component Identifier (SCID). The information for the respective services is transmitted in packets of predetermined amounts of data (for example, 130 bytes) and each packet includes a service component identifier corresponding to the service. A representation of a typical data stream from one of the answering machines is shown in FIGURE 1, and a typical packet of that data stream is shown in FIGURE 2. In FIGURE 1, a row of boxes represents signal packets that they are components of a plurality of different television programs transmitted by a given answering machine. Packages with letters that have the same subscripts represent components of a single television program. For example, the package identified as Vx, A? and D1 # represent video, audio and data for the program 1. In the top row of the packet row, the respective components of a particular program are shown grouped together. However, it is not necessary to group the components of a particular program together, as indicated by the sequence of packages in the center of the row. Moreover, it is not required to place the packages of a row in any particular order. The row of packages shown in the lower part of FIGURE 1 represents three programs multiplexed in time, programs 1, 2 and 3, plus the packages that represent a program guide (packages D4). It is important to mention that the program guide data interrelates the program components and the virtual channels by virtue of the service component identifier. The respective packets are arranged to include a prefix and a payload as shown in FIGURE 2. The prefix in this example includes two 8-bit bytes that comprise five fields, four of which are 1-byte fields (P, BB , CF, CS) and a 12-bit field (service component identifier). The payload portion contains the actual information that will be received and processed. The example prefix includes a 1-bit priority field (P); a limit field of 1 bit (BB), which indicates the limits between the changes of significant signals; a 1-bit field (CF), which indicates whether the payload is entangled or not, - a 1-bit field (CS) that indicates which of two keys to unravel will be used to unravel a tangled payload; and a 12-bit service component identifier. The rest of the packet comprises the payload which may include parity bits of error code appended to the end of the payload data. A master program guide comprises packaged data formatted as defined above, and is assigned a specific service component identifier, such as 0000 0000 0001. A master program guide comprises four sequential, designated data blocks, SEGM, APGD , CSSM1 ... CSSMnseg, and PISM1 ... PISMnseg, which will be described later. A master program guide typically includes television programming for the next two hours, but may include programming for four, six, or eight hours depending on the size of the memory allocated to store it in the receiver. In addition to the master program guide, one or more special program guides (SPG) are also provided, which contain additional data, such as, for example, programming of television programs for the next eight hours. That is, the master guide retains all the information necessary to select television programs at the time, and the special guides contain information about future television programs. Special guides are loaded from the satellite as needed and are not retained in memory due to their large size. As shown in FIGURE 4, both the program master guide and the special program guides are divided into a plurality of segments or portions (from 0 to 15) with a "nseg" index indicating the current number of segments comprising the special guide. Each segment carries program information for one or more virtual channels that vary from 100 to 999. FIGURE 4 shows only an example assignment of virtual channels with respect to the segments, and other groupings can be made at the discretion of the operators in the center of connection upwards of the satellite. Each special guide segment includes two blocks of data in sequence, CSSM1 ... CSSMnseg, and PISM1 ... PISMnseg, which will also be described later. FIGURES 5a and 5b show structures of the system in question. Not all are relevant to the selection of the virtual channel and to update the master program guide. Only those portions that are relevant will be discussed. Referring to FIGS. 5a and 5b, the Segment Map block (SEGM) of the master program guide contains information about the division of the channel space into segments, and the number of segments. The Data Block of the Additional Program Guide (APGD) contains a program guide map that indicates which segments of the special program guide are active, and their location (that is, the particular answering machine that carries the segment), as well as the identifiers of the service components of the respective segments. The additional program guide data block contains information about the programs relating to the ratings and the subject of a particular television program. The additional program guide data block also includes a program guide map that associates special guide segments with the names of the virtual channels, the numbers of the virtual channels, and the respective content types.

The master guide and each special guide contain a block of Service Channel Segments Map (CSSM) and a Block of Program Information Segments Map (PISM) The Channel Segment Map describes virtual channels defining features such as channel name, acronym, channel number and type) that are in the corresponding segment. The Program Information Segments Map block contains connected lists of information about programs such as title, start time, duration, classification, and category, which are in each virtual channel described in the corresponding Channel Service Segments Map. . The relevant portions of the data structures shown in FIGURES 3, 4, 5a and 5b will be referred to in the following description of the program selection process. In order to understand the importance of maintaining a precise program master guide, it can help to describe how the program master guide is used to select a television program. Referring to FIGURE 3, a user selects a television program to be displayed by moving a cursor (via the operation of the direction control keys up, down, to the right, and to the left of a remote control), with with respect to a block of the screen display of the program guide containing the name of the desired program. The remote control unit is not shown for simplification. When a SELECT key on the remote control is pressed, the current position x and y of the cursor is evaluated to derive the virtual channel and program time information. As shown in FIGURE 4, and as mentioned above, the master program guide and special program guides are divided into segments (which can be as few as one segment or as many as 16). The lowest channel (100) is always assigned the first channel of the sec (0) Each segment contains channel and program information for a defined number of virtual channels. By deriving the virtual channel number from the position information of the X and Y cursor, the virtual channel number is used to indicate within the appropriate segment of the particular program guide (either a program master guide or a program guide). specials) to retrieve the specific channel information and program information. Specifically, the Channel Informancon Registers (Cl) in the Channel Service Segment Map have a fixed length of seventeen bytes and contain such items as the identification number of service components in use. (typically 2, audio and video), the answering machine of the channel (Chan Xpndr) the abbreviated name and channel number (that is, typically 4 characters), and a pointer within the information of the connected program. In order to have access to any specific Channel Information (Cl) it is only necessary to repeatedly add seventeen to a base value. Information about the program includes the start day and time of the program, the number of tracks of thirty minutes it occupies, the category of the theme (that is, drama, sports, comedy) and the classification of origin. Once the answering machine of the channel carrying a desired television program is tuned, the data packets containing the audio and video information for that program can be selected from the data stream received from the answering machine by examining the data packets the 12-bit code of the identifier of the appropriate service component. If the identifier of the service component of the data packet received at the time matches the identifier of the service component of the desired television program as listed in the program guide, then the data packet is directed to the processing sections of the program. appropriate data of the receiver. If the identifier of the service component of a particular package does not match the identifier of the service component of the desired television program as listed in the program guide, then the data packet is discarded. Referring again to the Segment Map (SEGM), of FIGURE 5a, there are included in the segment map two bytes of particular interest. The first is the byte of the useful life that is initially set at thirty minutes when a new master program guide is transmitted for the first time. Each transmission of that same master program guide will have a decrease in the useful life bytes by an amount equal to the delay time between the transmissions of that guide (typically, every two seconds). When the useful life byte reaches a value of zero (indicating that the stored master program guide currently has 30 minutes to live), then a new master program guide is acquired and stored for immediate use. The second byte of particular interest is the "number of change" byte. Each program master guide that has content that is different from the content of the stored program master guide will have a different number than the current master program guide stored at the time. This byte is the one that will be examined to determine if a change in unscheduled programming has occurred (that is, a change in television programming that occurred during the valid lifetime of the program master guide stored at the time). Detecting such an unexpected change requires the acquisition and storage of a new master program guide. At the end of each five-minute interval (although another period of time may be used) during the valid lifetime of the program master guide, the byte of "change number of a newly received guide will be examined to determine whether a guide has occurred. change in the master program guide, and if the newly received program master guide should be stored and used, or discarded, the "change number" byte may be a version number for the master program guide that is compared to the number of the version of the master program guide stored at the time A flow chart illustrating the portion of the control program for the receiver that is relevant to the update operation of the program master guide is shown in FIGURE 9. The routine of FIGURE 9 is introduced in step 900 and proceeds to step 910, where a check is made to see if the thirty minute life of the master program guide at Macenada at the moment has expired. If so, the program proceeds to step 920 for acquiring and storing a new master program guide, and then exits in step 990. If, in step 910, the lifetime of the program master guide stored at the time is not has expired, then the NO path is taken to step 930 where a check is made to see if five minutes have passed since the last time the byte of that change number was examined. If the five minute period has not elapsed, then the routine is left in step 990. If the five minute period has elapsed, then the byte of change number is read in step 940. In step 950, it is taken a determination as to whether the received program master guide has changed with respect to the program master guide stored at the time. If so, the program proceeds to step 920 to acquire and store a new master program guide, and then exit at step 990. If it is not, then the NO path to the exit is taken in step 990. Thus, In the normal course of events, the master program guide with new information is updated every thirty minutes. However, in the case of an unexpected change in the programming of the television programs, the receiver will correct his master program guide within a period of five minutes, because the master program guide includes programming data for all active virtual channels are transmitted on every transmission channel every two seconds, and because a new complete master program guide takes only two seconds to load. Now follows a brief description of the hardware of the system, suitable for implementing the invention described above. In FIGURE 6, a transmitter 601 processes a data signal from a source 614 (e.g., a television signal source) and transmits it to the satellite 613 that receives and retransmits the signal to the receiver 612. The transmitter 601 includes an encoder 602, a forward error modulator / corrector (FEO 603, and an uplink unit 604. The encoder 602 compresses and encodes signals from the source 614 according to a predetermined standard such as MPEG. an international standard developed by the Moving Picture Expert Group of the International Standards Organization for the coded representation of moving images and associated audio stored in a digital storage medium A coded signal from unit 602 is supplied to the modulator / corrector Forward Error (FEC) 603, which encodes the signal with error correction data, and the Quaternary Phase Change Key (QPSK) modul to the signal coded by a transporter. Both the coding of the convolution block and the Reed-Solomon (RS) are made in block 603. The uplink unit 604 transmits the compressed and encoded signal to satellite 613, which transmits the signal to a geographical reception area selected In this mode, satellite 613 operates in two ways, according to which it exchanges channel capacity for transmission energy, or transmission power for channel capacity. In the first mode, satellite 613 illustratively transmits sixteen channels at 120 watts each. In the second mode, satellite 613 transmits eight channels at 240 watts each.

The signal from satellite 613 is received by the parabolic antenna reflector 605 coupled to an input of a so-called top-set receiver 612 (ie, an interface device located on top of a television receiver). The receiver 612 includes a forward demodulator / error correction decoder (FEC) 607 for demodulating the signal and for decoding the error correction data, a microprocessor 606, which operates interactively with the forward demodulator / error correction unit 607 , and a transport unit 608 for transporting the signal to an appropriate decoder within the unit 609 depending on the content of the signal, ie, audio or video information. The transport unit 608 receives the corrected data packets from the unit 607 and checks the header of each packet to determine its address. The decoders in the 609 unit decode the signal and remove the added transport data, if used. An NTSC 610 Encoder encodes the decoded signal into a format suitable for use by the signal processing circuits in a standard 611 NTSC consumer television receiver. FIGURE 7 is a block diagram showing the components of the decoder-receiver system. receiver-integrated that includes the outdoor antenna parabolic reflector unit 7-5. The integrated receiver-decoder includes a block 707 that includes a tuner 734 and a demodulator unit 735 for tuning various television signals. The integrated decoder-receiver is under the control of a microcontroller 706, which also controls the interfaces between the integrated decoder-receiver and a telephone network via a 734 telephone modem, between the integrated decoder-receiver and a user via a connection IR 725 and between the receiver-integrated decoder and a television receiver via an MPEG decoder 723, a video encoder 721, and a radio frequency modulator 722, and finally, between the decoder-receiver-integrated unit and a user via a smart card interface and transport IC 708. The master program guide is stored, for example, in the buffer 709. Referring now to FIGURE 8, the scrambler / forward error correction unit 807 acquires', demodulates , and decodes the data signal that is received from the parabolic reflector of the antenna 805. This unit includes a tuner 834, a clav demodulator. and quaternary phase change 835, a Viterbi 836 convolution decoder, an 837 interleaver, and a Reed-Solomon (RS) 838 decoder, all of conventional design, arranged as shown.

The tuner 834 receives an input signal from the antenna parabolic reflector 805. Based on a user's channel selection, a control unit 806 (ie, a microprocessor) sends an < frequency signal to tuner 834. This signal causes tuner 834 to tune to the appropriate channel and convert the received signal into frequency in response to the signal of ^ the tuned frequency sent to tuner 834 from the microprocessor 806. An output signal is provided from the tuner 34 to the quaternary phase change key demodulator 835. The quaternary phase change key demodulator 835 is secured at (or synchronized with) the tuned channel, demodulates the modulated data signal, and generates an indicative signal of the quality of the demodulated signal. The demodulator 835 demodulates the modulated input data signal independent of the speed of the error correction code of the received data signal. The closed phase cycle circuit in the demodulator 835 synchronizes the operation of the demodulator 835 with the input signal using well-known techniques. The demodulator 835 generates a demodulator closing output control signal which indicates whether the demodulator 835 is synchronized or not with the input signal, and supplies this signal to a storage recorder in the microprocessor 806. A demodulated output data signal is provided from the unit 835 to the Viterbi decoder 836. The demodulator 835 also generates an output signal Signal Quality, which is indicative of the quality of the signal received from the satellite transmission, and refers to the signal-to-noise ratio of the received signal. Various sources of noise, as well as fading by rain, can deteriorate the quality of a received signal. A quaternary phase change key demodulator suitable for use as the 835 unit is commercially available from Hughes Network Systems of Germantown, Maryland (integrated circuit type No. 1016212), and from Comstream Corp., San Diego California (No. CD2000) . The decoder 836 uses a Viterbi algorithm to decode and correct bit errors in the demodulated signal from the unit 835. The decoder 836 includes internal networks, as is known, to synchronize its operation with the incoming demodulated signal in order to effectively decoding the demodulated signal. After the decoder 836 decodes and corrects errors of the demodulated data signal, the decoded data signal is supplied to an interleaver 837. The interleaver 837 restores the ordering of the data signal to its original sequence, and forms Reed-Solomon blocks (RS blocks), according to known techniques. To this end, deinterleaver 837 is based on an 8-bit synchronization word inserted by the encoder at the beginning of each Reed-Solomon block, thereby providing Reed-Solomon block synchronization. The de-interleaved signal is supplied to a Reed Solomon (RS) 838 decoder. The Reed-Solomon 838 decoder decodes the Reed-Solomon blocks and corrects byte errors within a block. A decoded signal is provided from the Viterbi decoder to the Reed-Solomon 838 decoder via the interleaver 837. If the decoder 36 uses the appropriate error correction decoding rate to decode the data signal, the interleaver 837 and the Reed Solomon 838 decoder will work normally. Thus, a multi-channel transmission system was shown and described which allocates television programs to answering machines and tracks multiplexed in time in the data stream of a given answering machine in a manner that is completely transparent to the user, who simply tunes into a program of desired television by selecting a virtual channel. Clearly, the key to the smooth operation of this system is the transmission of the master and special channel guides which refers to the channels of the answering machine and to the positions of the data of the programs in the data stream of the answering machine with respect to the numbers of virtual channels. The invention in question ensures that the stored program master guide data is current by recharging it every half hour, and verifying it every five minutes to see if the content of a newly received program master guide differs from the content of the master guide. of programs stored at the moment.

Claims (9)

1. CLAIMS 1. A television system for receiving a plurality of digitally encoded television programs, comprising: an element for selecting a particular digital data transmission channel among a plurality of digital data transmission channels containing the desired of the programs digitally encoded television in response to a control signal, also including at least one of those data transmission channels, programming data of the television programs; a data entry element operable by the user to enter data; a control element coupled to the selection element and the data entry element for generating the control signal in response to the data entered by the user, and - selecting the control element a virtual channel among a plurality of virtual channels in response to the data entered by the user, the data of the programming of the television programs defining the relationship of each of the television programs with the respective ones of the plurality of digital data transmission channels; including television program schedule data information having a first portion indicative of a period of time during which that television program schedule data is valid, and a second portion indicating a change of content; making that control element that the program data of television programs that are to be acquired and stored when the first portion of the information indicates that the period of time has expired, and causing the program data of television programs to be they will acquire and store when the second portion of the information indicates that the content has changed regardless of the expiration of the period of time.
2. 2. The television system of claim 1 wherein all the data transmission channels also include the programming data of the television programs.
3. 3. The television system of claim 1 wherein the first portion of the information conveys information indicative of the remaining time of a period of time during which the programming data of the television programs can be considered valid.
4. 4. The television system of claim 3, wherein the period of time during which the programming data of the television programs will be considered valid is thirty minutes.
5. The television system of claim 1 wherein the second portion of the information is a number indicative of a version of the programming data of the television programs.
6. 6. A television system for receiving a plurality of digitally encoded television programs, comprising: an element for selecting a particular data channel from one of a plurality of data channels in a plurality of transmission channels in response to a signal of control, including also at least one of the transmission channels, program data of television programs; a data entry element operable by the user to enter data; a control element coupled to the selection element and to the data entry element for generating the control signal in response to the data entered by the user; and the control element that selects a data channel in response to the data entered by the user, the program data of television programs defining the relationship of each of the television programs with the respective ones of the plurality of transmission channels. . including programming data of the television programs information having a first portion indicative of a period of time during which the 5 data of the programming of television programs are valid, and a second portion indicative of the change of content; making the control element that the programming data of the television programs are acquired and stored when the first portion of the information indicates that that period of time has expired, and making the data of the television program programming acquire and store when the first portion of the information indicates that the content has changed, 15 regardless of whether the time period has expired.
7. The television system of claim 6 wherein, all the data transmission channels also include the television program programming data.
8. 8. A method for receiving a plurality of 20 digitally encoded television programs, comprising the steps of: selecting a digital data transmission channel among a plurality of digital data transmission channels containing a desired one of the television programs digitally encoded in response to a control signal, also including at least one of the data transmission channels, television program schedule data; read a data entry element operable by the user to enter data; generate the control signal in response to the data entered by the user; and introducing television program schedule data including information that has a first portion indicative of a period of time during which television program schedule data is valid, and a second portion indicative of content change; controlling the control element for acquiring and storing the television program schedule data when the first portion of the information indicates that the time period has expired, and causing the television program programming data to be acquired and stored when the The first portion of the information indicates that the content has changed regardless of whether the time period has expired. The method of claim 8 wherein, all data transmission channels also include television program schedule data.