# Patent

## Title
Differentiated PSIP table update interval technology

## Abstract

A method to optimize a bandwidth of a digital television (DTV) transport stream and to determine transmission cycles for tables to be transmitted as part of the DTV transport stream, the method including; setting transmission cycles for event information tables (EITs) to be transmitted in sequence according to the following condition: transmission cycle (EITi-1)<transmission cycle (EITi), for i=1 and 2, a time span covered by EITi-1 being prior to a time span covered by EITi, where the transmission cycle for the EIT0 is set narrower than the transmission cycle for the EIT1; setting a transmission cycle for an extended text table ETT3 containing program description information associated with one of the event information tables other than the EIT0 and the EIT1, where the transmission cycle of the ETT3 is greater than a sum of the transmission cycle of the EIT0 and the transmission cycle of the EIT1.

## Background
CONTINUITY DATA
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
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
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 Advanced 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.
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.
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.
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
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/65 compliant 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.
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.
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.
According to one embodiment, a method to optimize a bandwidth of a digital television (DTV) transport stream and to determine transmission cycles for tables to be transmitted as part of the DTV transport stream, the method comprising; setting transmission cycles for event information tables (EITs) to be transmitted in sequence according to the following condition: transmission cycle (EITi-1)<transmission cycle (EITi), for i=1 and 2, a time span covered by EITi-1 being prior to a time span covered by EITi, wherein the transmission cycle for the EIT0 is set narrower than the transmission cycle for the EIT1; setting a transmission cycle for an extended text table ETT3 containing program description information associated with one of the event information tables other than the EIT0 and the EIT1, wherein the transmission cycle of the ETT3 is greater than a sum of the transmission cycle of the EIT0 and the transmission cycle of the EIT1.
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.
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
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus do not limit the present invention.
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.
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
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 Advanced 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.
In FIG. 1, the PSIP generator 102 includes an interface unit 104 and a non-uniform interval calculation unit 106.
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 NT4.0operating system. The software can be written in the Java language. The other blocks of FIG. 1 correspond to known technology.
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 Advanced 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.
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.
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 no uniform 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.
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.
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 EIT0 table; a box 218 in which a user can enter an increment for the EITk 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.
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 ETTo table; and a box 224 in which a user can enter an increment for the ETTk table.
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.
The A/65 standard recommends a time interval for outputting the zeroed Event Information Table (EIT), i.e., EIT0, but provides no guidelines regarding EIT1 through EIT128. For the Rating Region Table (RRT), the A/65 standard recommends a value only for the output frequency of RRT1. And no recommendation is made regarding the output frequencies of any of the Extended Text Tables (ETTs).
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.
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/65 compliant 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.
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.
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 EIT0 to be output every half second (root_time) with each succeeding EITi to be output 0.25 seconds less frequently than the preceding EIT, namely EITi-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:
Time between any two instances of tablei

=root_time+(increment_time * i)

=0.5 sec+(0.25 sec * i)

For example, EIT12 can be output every 0.5 sec+(0.25 sec *12)=3.5 seconds.

A similar calculation for ETTs can be performed by the unit 106.
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.
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.

## Claims

1. A method to optimize a bandwidth of a digital television (DTV) transport stream and to determine transmission cycles for tables to be transmitted as part of the DTV transport stream, the method comprising:
setting transmission cycles for event information tables (EITs) to be transmitted in sequence according to the following condition:
transmission cycle (EITi-1) <transmission cycle (EITi), for i=1and 2, a time span covered by EITi-1 being prior to a time span covered by EITi, wherein the transmission cycle for the EIT0 is set narrower than the transmission cycle for the EIT1;
setting a transmission cycle for an extended text table ETT3 containing program description information associated with one of the event information tables other than the EIT0 and the EIT1, wherein the transmission cycle of the ETT3 is greater than a sum of the transmission cycle of the EIT0 and the transmission cycle of the EIT1.

2. A program and system information protocol (PSIP) generator to optimize a bandwidth of a digital television (DTV) packet stream and to generate tables to be transmitted as part of the DTV transport stream, the PSIP generator comprising:
a transmission cycle determination unit to set transmission cycles for a plurality of event information tables (EITs) to be transmitted in sequence according to the following condition:
transmission cycle (EITi-1) <transmission cycle (EITi) for i =1and 2, a time span covered by EITi-1 being prior to a time span covered by EITi, wherein the transmission cycle for the EIT0 is set narrower than the transmission cycle for the EIT1,
the transmission cycle determination unit to further set a transmission cycle for an extended text table ETT3 containing program description information associated with one of the EITs other than the EIT0 and the EIT1,
wherein the transmission cycle of the ETT3 is greater than a sum of the transmission cycle of the EIT0 and the transmission cycle of the EIT1.

3. A method of operating a digital television (DTV) receiver that receives and processes a DTV transport stream, the method comprising:
receiving in a DTV transport stream a sequence of event information tables (EITs) according to the following condition:
transmission cycle (EITi-1)<transmission cycle (EITi) for i =1and 2, wherein the transmission cycle for the EIT0 is set narrower than the transmission cycle for the EIT1; parsing EITs from the transport stream;
receiving in the DTV transport stream an extended text table ETT3 containing program description information associated with one of the event information table other than the EIT0 and the EIT1, wherein the transmission cycle of the ETT3 is greater than a sum of the transmission cycle of the EIT0 and the transmission cycle of the EIT1; and parsing the ETT3 from the DTV transport stream.

4. The method of claim 1, wherein the transmission cycle of the ETT3 corresponds to a transmission cycle of EIT3.

5. The PSIP generator of claim 2, wherein the transmission cycle of the ETT3 corresponds to a transmission cycle of EIT3.

6. The method of claim 3, wherein the transmission cycle of the ETT3 corresponds to a transmission cycle of EIT3.