Abstract:
A method and apparatus for adjusting an embedded portion of a television signal. The embedded portion is adjusted such that a downstream receiver effects no change on a displayed video upon decoding the adjusted embedded portion.

Description:
The present invention relates to the adjustment of embedded information in a television signal. More specifically, the invention relates to a method and apparatus for preventing conflicts when a television receiver and set top terminal are each capable of processing embedded information, e.g., line  21  video information, in the television signal. 
   BACKGROUND OF THE DISCLOSURE 
     FIG. 1  depicts a system level diagram of a television system  100 . A typical configuration of the television system  100  comprises a signal source  110 , a set top terminal  120  and a television receiver  130 . The signal source  110  provides a television signal, e.g., a National Television Standard Committee (NTSC) television signal or a high definition television (HDTV) signal, for use in the television system  100 . Examples of such video sources  110  may include an antenna for producing “over-the-air” television signals, a cable carrying cable television signals or a satellite receiver for generating satellite television signals. 
   The set top terminal  120  receives the television signal from the signal source  110 . If the received television signal is RF or IF, the set top terminal  120  may convert the video and audio portions of the received television signal into baseband signals. The set top terminal  120  processes the video and audio components of the television signal into a suitable format, e.g., NTSC format, for display on the television receiver  130 . Examples of set top terminals  120  may include a cable box, a video cassette recorder (VCR), or an Advanced Television Systems Committee (ATSC) legacy converter box. 
   The television receiver  130  processes the television signal, e.g., a NTSC signal, to display standard video and audio programmed content. Recent versions of the television receiver  130  may provide closed caption information pursuant to the Television Decoder Circuitry Act of 1990 and V-chip rating control pursuant to the Telecommunications Act of 1996. As such, the television receiver  130  may decode and display information embedded, e.g., line  21  information, in the television signal. In this case, the set top terminal  120  generally passes the television signal from the signal source  110  to the television receiver  130 . 
   However, the set top terminal  120  is also capable of decoding and processing the television signal for display on the television receiver  130 . This processing is normally performed where the television receiver  130  is a legacy television incapable of independently decoding embedded information in the television signal. In this case, only the set top terminal  120  may process embedded information used to provide closed captioning and filter video content. 
   A problem exists if both the set top terminal  120  and television receiver  130  decode and process the television signal for display. As the set top terminal  120  and television receiver may independently process embedded information for display, conflicts between the set top terminal  120  and television receiver  130  may arise. In one example, both the set top terminal  120  and television receiver  130  may provide separate closed caption displays over the displayed video. If the closed caption displays are not placed with identical positions and identical fonts from the set top terminal  120  and television receiver  130 , then these closed caption displays will overlap, thereby creating a confusing display. 
   In another example, the set top terminal  120  and television receiver  130  perform block or pass program content based on V-chip information. For example, a set top terminal  120  may pass or allow program content that is then blocked by a downstream television receiver  130 . Since only the display from the downstream television receiver  130 , i.e., the device blocking the program, is shown, the viewer loses feedback from the tuning device, i.e., the set top terminal  120 . Moreover, if the television system  100  comprises multiple set top terminals  120 , e.g., a cable box and a VCR, it would be difficult to determine which set top terminal  120  is actually blocking the program content. 
   In another example, the set top terminal  120 , e.g., a VCR, may record a program with a time index or timestamp typically embedded in line  21  of the television signal. As a downstream set top terminal  120  or television receiver  130  utilizes this timestamp to set a display clock. As such, when the television signal is played back at a later time, the playing device would provide erroneous time information. 
   Therefore, a need exists in the art for eliminating the display conflicts between the set top terminal and the television receiver. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the disadvantages associated with the prior art by providing a method and apparatus that adjusts the embedded portion of a received television signal. Specifically, the invention receives a television signal having an embedded portion, detects the embedded portion, and adjusts the embedded portion. The adjustment is performed such that a downstream receiver effects no change on a displayed video upon decoding the adjusted embedded portion. Such embedded information may comprise line  21  information such as closed captioning, V-chip rating or timestamp information. In one embodiment of the invention, a set top terminal may adjust the embedded portion such that a downstream television receiver may not affect changes to a displayed video. In this case, only the set top terminal may effect changes on the displayed video upon decoding the embedded portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
       FIG. 1  depicts a high level block diagram of a television system; 
       FIG. 2  depicts a block diagram of a set top terminal in the television system of  FIG. 1 ; 
       FIG. 3  depicts a flow diagram for implementing a processing routine of the present invention; 
       FIG. 4  depicts a portion of the processing routine in a first embodiment of the present invention; 
       FIG. 5  depicts a portion of the processing routine in a second embodiment of the present invention; and 
       FIG. 6  depicts a portion of the processing routine in a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   Although the present invention is described in the context of a television system comprising a receiver and set top terminal, the present invention also applies to any system having two or more receivers capable of processing embedded information in a signal. 
     FIG. 2  depicts a block diagram of a set top terminal  200  in the television system of FIG.  1 . The set top terminal  200  may comprise any terminal that receives a television signal via path  201 , processes the television signal and provides the processed television signal to a television via path  221 . An example of the set top terminal  200  is provided in U.S. patent application Ser. No. 08/950, 505, filed on Sep. 16, 1997, and entitled “Set Top Terminal for an Interactive Information Distribution System,” which is herein incorporated by reference in its entirety. 
   Specifically, the set top terminal  200  comprises a tuner  202 , a first switch  204 , a digital demodulator  206 , an analog demodulator  208 , a second switch  210 , a processor  212 , a memory  214 , input/output (I/O) circuits  218 , a National Television Standard Committee (NTSC) modulator  220 , and a decoder  222 . In one embodiment of the invention, the tuner  202  receives a radio frequency (RF) television signal from the signal source, e.g., an antenna, and downconverts the RF television signal into an intermediate frequency (IF) television signal. 
   The first switch  204  couples the IF television signal from the tuner  202  to either the digital demodulator  206  or the analog demodulator  208 , e.g., a NTSC demodulator. Namely, the first switch  204  routes the IF television signal to the proper demodulator. The digital demodulator  206  converts a digital IF television signal into a digital baseband television signal. Similarly, the analog demodulator  208  converts an analog IF television signal into an analog baseband television signal. The second switch  210  couples the digital or analog baseband television signal to the processor  212 . 
   The baseband television signal is coupled to the processor  212  and the decoder  222 . The processor  212  executes a software program to perform the required processing for overcoming the problems of the prior art. Specifically, the processor  212  executes a software program to implement a method  300  embodied in  FIG. 3  as described below. The software program is stored in memory  214 , e.g., read only memory (ROM), solid state memory, optical memory and the like. A viewer may use input/output (I/O) devices  216  to control features or settings, e.g., closed captioning, blockage of selected program content, of the set top terminal  200 . In the context of a television system  100 , the I/O device  216  may comprise an input device, e.g., a remote control, or an output device, e.g., a display device or monitor. The I/O circuits  218  provide an interface between the processor  212  and one or more I/O devices  216 . 
   Upon executing the software program, the processor  212  adjusts the embedded portion, e.g., the line  21  information, of the baseband television signal. In one embodiment of the invention, the closed captioning information may be removed from the line  21  information. In another embodiment, the V-chip rating may be removed or adjusted to a rating, e.g., a G rating, which is always passed by a downstream television  130 . The timestamp in the embedded information may be removed as well. The adjusted television signal is coupled to a NTSC modulator, where the adjusted baseband television signal is modulated into a NTSC television signal. This NTSC television signal is coupled to a downstream television receiver via path  221 . In this manner, the television receiver is prevented from processing the embedded portion of the television signal. As such, since only the set top terminal  200  processes the embedded portion of the television signal, the prior art problem is thereby eliminated. 
   In one embodiment of the invention, the processor  212  extracts the embedded portion of the baseband television signal. The decoder  222  decodes the extracted signal, e.g., the embedded portion of the baseband television signal, to generate graphics information, e.g., open caption information. The graphics information is applied to the NTSC modulator  220 , where an image having integrated graphics is created. The NTSC modulated television signal is transmitted to a downstream receiver, e.g., a television receiver. 
   The present invention may also be implemented as a program product for use with the television system  100 . The program(s) of the program product defines functions that can be contained on a variety of signal/bearing media, which include, but are not limited to, (i) information permanently stored on non-writable storage media, (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive); (ii) alterable information stored on writable storage media (e.g., floppy disks within a diskette drive or hard-disk drive); or (iii) information conveyed to a computer by a communications medium, such as through a computer or telephone network, including wireless communications. Such signal-bearing media, when carrying computer-readable instructions that direct the functions of the present invention, represent additional embodiments of the present invention. 
     FIG. 3  depicts flow diagram for implementing a method  300  of the present invention. The method  300  starts at step  302  and proceeds to receive the baseband television signal at step  304 . Prior conversions of the television signal, i.e., conversion to RF to IF to baseband, are performed in a standard manner and are not discussed within the context of this method  300 . 
   At step  306 , the method  300  determines whether to provide closed captioning. If closed caption is desired, then the method  300  proceeds to step  308 , where closed caption processing is performed. Step  308  is embodied in a method  400  in FIG.  4 . 
     FIG. 4  depicts a flow diagram of the method  400  to implement a first embodiment of the present invention. The method  400  proceeds to step  410 , where closed caption information is detected within the television signal. The closed caption information represents information that is embedded within the television signal, e.g., line  21  information of a NTSC television signal or line  22  of a Phase Alternate Line (PAL) television signal. Closed caption information is typically provided in analog television signals in accordance with EIA-608 (EIA: Electronic Industries Alliance) standard and provided in digital television signals, e.g., a HDTV signal, in accordance with EIA-708. 
   At step  420 , the method  400  reformats, e.g., removes, the portion of the television signal corresponding to the closed-caption information. In one embodiment of the invention, step  420  removes the closed caption information from the line  21  information of the NTSC television signal. In this matter, the television receiver or another downstream set top terminal can no longer process the closed caption information removed from the television signal. As such, only closed caption information from the set top terminal is displayed. Step  420  can also remove the closed caption information in a selective manner, i.e., the closed caption information can be always removed or only when the set top terminal is used to display closed caption information. 
   The method  400  proceeds to step  430 , where the set top terminal 200  applies the open captions, i.e., the embedded portion of the television signal that is decoded, to the video. More specifically, the detected closed caption information is extracted from the television signal, decoded into open caption graphics, and applied to the video. In this matter, the open caption is integrated into the video of the television signal and the embedded portion is reformatted. This television signal is sent downstream to a receiver, e.g., a television receiver. 
   Returning to  FIG. 3 , after performing closed caption processing at step  308 , the method  300  proceeds to step  310 . If closed captioning is not desired at step  306 , the method directly proceeds to step  310 . At step  310 , the method  300  determines whether to restrict program viewing. If program viewing is to be restricted, the method  300  proceeds step  312 , where V-chip processing is performed. Step  312  is embodied in a method  500  depicted in FIG.  5 . 
     FIG. 5  depicts a flow diagram of a method  500  to implement a second embodiment of the present invention. As with closed captioning information, V-chip rating information is typically provided in line  21  of the television signal. The V-chip ratings are generally provided in an NTSC television signal in accordance with, for example, EIA-744A. In an Advanced Television Systems Committee (ATSC) television signal, the V-chip rating information is provided in accordance to a Program and System Information Protocol (PSIP). 
   The method  600  starts at step  510 , where rating information streams are demultiplexed from the television signal. At step  520 , the V-chip rating information is detected from the television signal. The method  500  proceeds to step  530 , where the portion of the television signal corresponding to the V-chip rating information is reformatted, e.g., deleted or modified. After modifying the V-chip information, the method proceeds to provide a V-chip user interface on the display device. In one mode of operation, if a viewer desires to pass a particular rated program, the set top terminal would delete the V-chip information or modify the V-chip information to a general pass mode by modifying the V-chip information to a universally unblocked rating. In this case, the downstream receiver, e.g., a television receiver, is precluded from blocking the television program. That is, the set top terminal  200  controls the program viewability. 
   Returning to  FIG. 3 , after performing V-chip processing at step  312 , the method  300  proceeds to step  314 . If program viewing is not to be restricted at step  310 , the method  300  directly proceeds to step  314 . At step  314 , the method  300  determines whether to record program content having a time stamp or time index. If program content having timing information is to be recorded, the method  300  proceeds step  316 , where clock processing is performed. Step  316  is embodied in a method  600  depicted in FIG.  6 . 
     FIG. 6  depicts a flow diagram of a method  600  to implement a third embodiment of the present invention. The method  600  starts at step  610 , where timestamp information is detected in the television signal. Such information may be embedded in the line  21  information when a VCR records a program. At step  620 , the method  600  proceeds to remove the detected timestamp information. In this manner, a downstream device, e.g., a television receiver, is prevented from using this timestamp information in setting its display clock once the program is played back at a later time. 
   Returning to  FIG. 3 , after performing clock processing at step  316 , the method  300  proceeds to step  318 . If program content having timing information is not to be recorded, the method  300  directly proceeds to step  318 . At step  318 , the method  300  provides a signal, e.g., an adjusted NTSC television signal. Such a processed signal prevents the downstream television receiver from conflicting with information generated directly from the set top terminal  200 . 
   Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.