Abstract:
Disclosed is a method (and associated apparatus and software) to determine issuance intervals for like types of tables, respectively, in a digital television packet stream having a plurality of different types of tables that do not have issuance intervals set by a governing standard. Such a method comprises: setting issuance intervals for like ones of the non-governed tables, respectively, to be non-uniform. Such non-uniform issuance intervals can be determined as a function of at least one of an amount of time in the future to which the table corresponds and a degree of probable interest to a viewer. Further, such non-uniform issuance intervals can be weighted so that an issuance interval for a table corresponding to a time nearer the present is smaller than an issuance interval corresponding to a time further in the future.

Description:
CONTINUITY DATA  
       [0001]    This application claims priority upon U.S. Provisional Patent Application, Ser. No. 60/197,677, filed Apr. 17, 2000, the entirety of which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention is directed toward the field of digital television signal meta data generation, and more particularly to the non-uniform issuance of certain tables included within such meta data.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is known for a digital television (DTV) signal to include meta data representing information about the contents of the events, e.g., programs, movies, sports games, etc. contained in the DTV signal. For a terrestrially broadcast DTV signal, the American Television Standards Committee (ATSC) has promulgated the A/65 Standard that defines such meta data. The A/65 standard refers to such meta data as program and system information protocol (PSIP) data.  
           [0004]    The PSIP type of meta data is issued periodically. Data of greater importance in the meta data hierarchy is inserted into the DTV signal more frequently than data of lower importance.  
           [0005]    In general, in this art it is desired to maximize the amount of available bandwidth that can be allocated to the transmission of the DTV program content. Unfortunately, meta data consumes bandwidth that otherwise could be used to transmit the corresponding DTV program content. But such meta data is a prerequisite to an A/65 compliant DTV signal, hence it cannot be eliminated to recover bandwidth.  
           [0006]    It is a problem to reconcile the contradictory design criteria of maximizing bandwidth allocated to DTV program content and providing sufficient meta data to ensure compliance with the A/65 standard.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention is, in part, a solution to the problem of how to insert the least amount possible of meta data into the DTV signal and yet still achieve an A/65compliant DTV signal. In other words, the invention is, in part, a recognition that it is desirable to insert meta data into the DTV signal as infrequently as possible.  
           [0008]    The invention is, also in part, a recognition that: the A/65 standard establishes fixed frequencies of table output for some of the program and system information protocol (PSIP) data tables, e.g., such as the Master Guide Table (MGT), the Virtual Channel Table (VCT) and the System Time Table (STT), but not for some others; and such unfixed output intervals afford opportunities to lessen meta data output thereby reducing bandwidth consumption in the form of PSIP meta data without sacrificing compliance with the A/65 standard.  
           [0009]    The invention provides, in part, a method to determine issuance intervals for like types of tables, respectively, in a digital television packet stream having a plurality of different types of tables that do not have issuance intervals set by a governing standard. Such a method comprises: setting issuance intervals for like ones of the non-governed tables, respectively, to be non-uniform. Such non-uniform issuance intervals can be determined as a function of at least one of an amount of time in the future to which the table corresponds and a degree of probable interest to a viewer. Further, such non-uniform issuance intervals can be weighted so that an issuance interval for a table corresponding to a time nearer the present is smaller than an issuance interval corresponding to a time further in the future.  
           [0010]    Examples of meta data PSIP tables that can benefit from the method according to the invention include extended text tables (ETTs) and extended information tables (EITs).  
           [0011]    Each issuance interval between any two instances of an i th  table can be determined according to the following equation: 
           interval(i th  table)=root_time+(increment_time)*i 
           [0012]    where interval(i th  table) is the interval between any two instances of the i th  table, root_time is a predetermined interval for the table corresponding most closely in time to the present, increment_time is a non-zero scalar and i is a non-zero integer.  
           [0013]    The invention, also in part, provides a program and system information protocol (PSIP) generator to generate tables for a digital television system packet stream, the generator comprising: an interface to receive at least one issuance parameter for like tables that do not all have an issue interval assigned by a governing standard; and a non-uniform interval calculation unit to determine nonuniform issuance intervals for unassigned-interval-ones of said like tables based upon said at least one issuance parameter. Such a PSIP generator embodies the method according to the invention, e.g., as described herein.  
           [0014]    The invention, also in part, provides a processor-readable article of manufacture having embodied thereon software comprising a plurality of code segments to cause a processor to perform the method according to the invention.  
           [0015]    Advantages of the present invention will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus do not limit the present invention.  
         [0017]    [0017]FIG. 1 is a block diagram of a PSIP generator according to the invention in the context of typical inputs to it and outputs from it.  
         [0018]    [0018]FIG. 2 is an image of a dialog window within a screen of a graphical user interface (GUI) generated by the PSIP data generator according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    [0019]FIG. 1 is a block diagram of a program and system information protocol (PSIP) data generator according to the invention in the context of system  100  that can produce an American Television Standards Committee (ATSC), standard A/65, compliant digital television (DTV) signal. The system  100  of FIG. 1 includes: a PSIP generator  102  according to the invention; sources of data upon which the PSIP generator operates, such as a source  108  of listing service data, a source  110  of traffic system data and a source  112  of other data; a multiplexer  114  to incorporate the PSIP data from the PSIP generator  102  into an A/65-compliant DTV signal; and a source  116  of audio data, video data, etc.  
         [0020]    In FIG. 1, the PSIP generator  102  includes an interface unit  104  and a non-uniform interval calculation unit  106 .  
         [0021]    The PSIP generator  102  according to the invention can be implemented by adapting a well known PSIP generator according to the discussion herein. An example of a known PSIP generator is the PSIP BUILDER PRO brand of PSIP generator manufactured and sold by TRIVENI DIGITAL INC., the assignee of the invention. The PSIP BUILDER PRO itself is based upon a programmed PC having a Pentium type of processor using the MICROSOFT WINDOWS NT 4.0 operating system. The software can be written in the Java language. The other blocks of FIG. 1 correspond to known technology.  
         [0022]    In FIG. 1, the invention has been depicted in the context of a digital television broadcast such as a terrestrial broadcast, and more particularly one that is compliant with the American Television Standards Committee (ATSC), where each event is a program, and the schedule data is PSIP data. However, the invention is readily applicable to any television format, e.g., analog terrestrial, analog cable, digital cable, satellite, etc., for which an electronic schedule is maintained and corresponding data is sent to a receiver for the purpose of presenting an electronic program guide (EPG) to a viewer.  
         [0023]    The units  104  and  106  within the PSIP generator  102  do not necessarily correspond to discrete hardware units. Rather, the units  102  and  104  can represent functional units corresponding to program segments of the software that can embody the invention.  
         [0024]    The interface unit  104  can generate a graphical user interface (GUI) that operates to receive at least one issuance parameter for like PSIP tables (e.g., ETTs or ElTs) that do not all have an issue interval assigned by the A/65 standard. Such an interface will be described in more detail below with regard to FIG. 2. The nonuniform interval calculation unit  106  is operable to determine non-uniform issuance intervals for ones of the like PSIP tables that do not have an assigned interval, based upon the issuance parameter(s) received via the interface unit  104 .  
         [0025]    [0025]FIG. 2 is an example image of a dialog window  200  (a GUI) that can be generated by the interface unit  104  according to the invention. In FIG. 2, the dialog window  200  can include: a Cycle Time Settings tab  202 ; a Miscellaneous Settings tab  204 ; a FTP Periodic Update Controls tab  206 ; an “Apply Settings” button  226 ; a “Defaults” button  228 ; a “Refresh” button  230 ; and a “Close” button  232 . The position of the cursor can be indicated via the reverse highlighting  234 . The Cycle Time Settings tab  202  can include a “Cycle Times (in seconds) for ElTs:” region  208 , a “Cycle Times (in seconds) for PSIP Tables:” region  210 , a “Cycle Times (in seconds) for PSI Tables:” region  212  and a “Cycle Times (in seconds) for ETTs:”region  214 .  
         [0026]    In FIG. 2, the “Cycle Times (in seconds) for EITs:” region  208  of the dialog window  200  can include: a box  216  in which a user can enter a fixed interval for the EIT 0  table; a box  218  in which a user can enter an increment for the EIT k  table; and a box  220  in which a user can enter a maximum number of EIT tables that are to be sent. Usually, the number entered in box  220  will be far smaller than the maximum number of EIT tables permitted by the A/65 standard.  
         [0027]    Also, in FIG. 2, the “Cycle Times (in seconds) for ETTs:” region  214  can include: a box  222  in which a user can enter a fixed interval for the ETT o  table; and a box  224  in which a user can enter an increment for the ETT k  table.  
         [0028]    The non-uniform interval calculation unit  106  can receive the values in the boxes  216 ,  218 ,  220 ,  222  and  224  from the regions  208  and  214 , respectively, and use them to determine the non-uniform issuance intervals of, e.g., the EIT and ETT tables. Further discussion of the operation of the unit  106  is couched in a particular non-limiting example, for simplicity.  
         [0029]    The A/65 standard recommends a time interval for outputting the zeroith Event Information Table (EIT), i.e., EIT 0 , but provides no guidelines regarding EIT 1  through EIT 128 . For the Rating Region Table (RRT), the A/65 standard recommends a value only for the output frequency of RRT 1 . And no recommendation is made regarding the output frequencies of any of the Extended Text Tables (ETTs).  
         [0030]    Under the A/65 standard, it is left to the discretion of the operator of a PSIP data generation system to select the frequency of table output for the unmentioned tables. The operator could specify an entry for each group of tables, but that would be burdensome because it would require a total of over 500 entries. A simple solution to the problem of unspecified output frequencies would be to set each type of table to the same output frequency, but that creates a problem in that the guidelines for bandwidth specified by the A/65 standard would be exceeded.  
         [0031]    A further consideration to solve the problem, namely of how to insert the least amount possible of meta data into the DTV signal and yet still achieve an A/65compliant DTV signal, is: How closely in time to the present moment does each table relate? That is, table types such as the EIT describe event information up to two weeks into the future. A user of an electronic program guide that receives such table types will typically want to view event information concerning only the next 24-48 hours. Users typically do not look farther into the future than this because (at least in part) the event schedule information two weeks into the future is much more likely to change than is event schedule information concerning the next 24-48 hours, i.e., the farther into the future, the less reliable the event information becomes.  
         [0032]    Care must be exercised so as not to set the intervals to be too infrequent. This is because the DTV receiver can become stalled waiting for a table to arrive. If the DTV receiver is stalled for 0.5 seconds, a user might not notice or object if she did. But such a delay of, e.g., 4-5 seconds probably would be noticed by, and probably would annoy, the user. This reinforces the need to set short intervals for near term events because users are likely to want to display EPG information about them.  
         [0033]    Again, the invention, in part, provides an interface unit  104  that defines parameters that the non-uniform interval calculation unit  106  then can use to generate the time intervals between tables of the same type. Typically (but not necessarily) the function performed by the unit  106  will be linear, e.g., with a defined start interval (the root_time) and an increment interval (increment_time). For example, if the user desires EIT 0  to be output every half second (root_time) with each succeeding EIT i  to be output 0.25 seconds less frequently than the preceding EIT, namely EIT i-1 , the user would enter 0.5 seconds as the root_time in box  216  and 0.25 seconds as the increment time in box  218 . The function for each table EIT-i interval would then be:  
         [0034]    Time between any two instances of table i   
         =root_time+(increment_time * i) 
         =0.5 sec+(0.25 sec * i) 
         [0035]    For example, EIT 12  can be output every 0.5 sec+(0.25 sec * 12 )=3.5 seconds.  
         [0036]    A similar calculation for ETTs can be performed by the unit  106 .  
         [0037]    The invention has at least the following advantages: 1) it provides an easy way of entering the interval times for the tables: 2) it defines the interval times for like tables that are not all fixed to a constant interval; and 3) it provides an interval function that increases the interval for tables that represent information further out in time.  
         [0038]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.