Patent Publication Number: US-2007118861-A1

Title: System and method for delivering graphics received through a cable television system to a digital television

Description:
BACKGROUND  
      Regular television, radio and other media broadcasts may be interrupted in the event of national or local emergencies so that authorities can disseminate information to the public. In the United States, a semi-automated system for interrupting broadcasts and transmitting emergency alerts is known as the Emergency Alert System (EAS) and is administered by the Federal Communications Commission. Other countries may have analogous systems, and the descriptions in this patent specification are applicable to such systems as well.  
      EAS emergency alerts that are broadcast via television and similar networks include not only an audible warning message but also digital information. In some cable television systems, the digital information causes the set-top box (STB) connected to the television to automatically tune to a different channel, where the EAS alert can be viewed.  
      In some instances, the digital information associated with an EAS alert can include codes for formatted graphics, such as a scrolling text box, for display on a television screen or similar device. While the regular broadcast content that a viewer watches on the television is encoded in accordance with either an analog video standard (e.g., NTSC) or a digital video standard (e.g., MPEG-2), EAS alerts and other such formatted graphics are generally encoded in accordance with non-video, graphics-oriented standards. (“MPEG” stands for Motion Picture Expert Group, the body that coordinated the design of the family of standards to which all current digital broadcasting moving images conform.) Also, in the case of a cable television system, such digital information is transmitted from the headend to subscribers via a channel that is separate from the channels carrying the regular broadcast content. This separate channel is commonly referred to as an out-of-band (OOB) channel to distinguish it from the broadcast content band (in-band) channels. In some cases, the separate channel used to carry EAS alerts can be a cable modem channel. In any case, the EAS alert is received by a subscriber&#39;s television, which is required to provide the alert to the subscriber in the proper format. If a subscriber has a set-top box (STB), the STB is required to provide the EAS alert to the television.  
      Most STB&#39;s in current use have the capability of inserting graphics into composite video, as is commonly done when an electronic program guide is to be displayed on the screen of a traditional analog television. Likewise, most STB&#39;s can insert the scrolling text or similar graphics characteristic of a received EAS alert into the composite video. A problem arises, however, if a subscriber is using a television connected to the STB not via a composite video connection but rather via a compressed digital connection, such as that conforming to the IEEE-1394 serial data bus interface standard. (This standard, promulgated by the Institute of Electrical and Electronics Engineers, is sometimes also referred to as FIREWIRE®, a name that Apple Computer, Inc., an early proponent of the IEEE-1394 standard, uses for its data buses that conform to the standard, and is sometimes also referred to as iLink, a name used by Sony Corporation.)  
      Digital televisions requiring compressed digital video are most commonly connected to an STB via an IEEE-1394 digital connection. Protocols have been developed for communicating formatted graphics information to a digital television via an IEEE-1394 asynchronous connection separately from the regular content information of the channel being watched, which is delivered to the digital television via an isochronous connection, but most digital televisions in current use do not support those asynchronous protocols. Furthermore, the STB cannot be made to compensate for this shortcoming of current digital televisions because most STB&#39;s in current use do not have the capability of simply inserting graphics into the compressed digital video the way they can with analog (e.g., composite) video or uncompressed digital video. Consequently, a subscriber typically cannot view an electronic program guide, an EAS alert, or any other information in the form of such formatted graphics on a digital television connected to an STB via an IEEE-1394 connection.  
      A limited solution to the problem has been suggested for use with subscribers whose digital televisions support the feature known as Analog-Digital Source Selection, set forth in the CEA-775 standard. (The Consumer Electronics Association, an American National Standards Association (ANSI) accredited body, develops standards for televisions and other consumer video and audio products.) When the STB detects an incoming EAS alert or user action that requires a graphical display, e.g., interactive guide, the STB commands such a television to switch its input source from the IEEE-1394 digital connection to the composite (analog) video connection. Most STB&#39;s include both an IEEE-1394 connection and a composite video connection on their rear connector panels, and both can be connected to the television if desired. The STB can then provide the EAS alert or graphical display to the television via the composite video connection. When the EAS alert or graphical display terminates, the STB switches back to the IEEE-1394 connection and continues providing the regular content. This solution is of limited use because most digital televisions in current use do not support the Analog-Digital Source Selection feature.  
      There are many thousands of STB&#39;s in the possession of digital cable television subscribers that do not have the capability of causing the digital televisions to properly display formatted graphics such as EAS alerts and electronic program guides (EPG&#39;s), and replacing subscribers&#39; STB&#39;s with newer versions having architectures specifically designed to handle formatted graphics via the IEEE-1394 connection would be costly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram of a system for delivering formatted graphics to a television over a digital interface.  
       FIG. 2  is a block diagram similar to  FIG. 1 , showing a portion of the system in further detail.  
       FIG. 3  is a flow diagram of a method for delivering emergency alert messages to a television over a digital interface. 
    
    
     DETAILED DESCRIPTION  
      In the following description, like reference numerals indicate like components to enhance the understanding of the invention through the description of the drawings. Also, although specific features, configurations, arrangements and steps are discussed below, it should be understood that such specificity is for illustrative purposes only. A person skilled in the relevant art will recognize that other features, configurations, arrangements and steps are useful without departing from the spirit and scope of the invention.  
      As illustrated in  FIG. 1 , a set-top box (STB)  10  connected to a cable television system (not shown) is configured to not only deliver regular television programming (content) to a digital television  12  but also to deliver formatted graphics to television  12  if, for example, an Emergency Alert System (EAS) alert or electronic programming guide (EPG) is to be displayed on television  12 . (The term “regular television programming” or “regular television content” is intended to refer to anything that a viewer would normally watch on a television, such as television shows and the like received from the cable television system (broadcaster) or read from a digital video disk (DVD) or similar source.) Television  12  is connected to STB  10  via a compressed digital connection such as that conforming to the IEEE-1394 standard. Television  12  does not itself have the capability of displaying formatted graphics, such as EAS alerts having a scrolling text format, received via its IEEE-1394 input. Rather, television  12  is only capable of displaying information encoded in the conventional manner in conformance with the MPEG-2 or similar digital video standard and delivered over IEEE-1394 via an isochronous connection.  
      As described in further detail below, STB  10  is configured to compensate for the above-described deficiency of television  12  and the IEEE-1394 standard. Specifically, STB  10  is configured to route video information received from the cable television system or network and regular television content information through separate paths to its IEEE-1394 output  14 . The regular television content signal is received through the input and central processing circuitry  16  of STB  10 , which demodulates it in the conventional manner and provides it to digital processing circuitry  18 . Digital processing circuitry  18  in turn provides a signal to television  12  via IEEE-1394 output  14  that is encoded in accordance with the MPEG-2 digital video standard or other suitable format capable of being decoded by television  12 . The regular television information is similarly received through input and central processing circuitry  16 , but is then routed through analog and graphics processing circuitry  20 , which produces a composite video signal and overlays/mixes any graphics (e.g. interactive guide, closed captioning, etc.). The composite video signal is routed through a conventional composite vide RCA cable  22  connected externally to STB  10  between its composite video output  24  and composite video input  26 . The cable television subscriber in possession of STB  10  can connect cable  22  as directed by the cable television company, or company personnel can connect it for the subscriber. Alternatively, in other embodiments of the invention, instead of an externally connected cable  22 , STB  10  can be modified internally with a jumper, switch or similar connection between composite video output  24  and composite video input  26 . In the illustrated embodiment, digital processing circuitry  18  receives the composite signal that loops back into STB  10  via cable  22 , digitizes it, encodes it in accordance with the MPEG-2 digital video standard or other suitable format capable of being decoded by television  12 , and provides it to television  12  via IEEE-1394 output  14 .  
      The solution described above makes use of composite video output  24  and composite video input  26  of STB  10 , which most subscribers who have digital televisions utilizing the IEEE-1394 interface typically leave unconnected to any external video equipment. STB  10  includes composite video output  24  so that subscribers who have analog televisions can connect them to STB  10 . Similarly, STB  10  includes composite video input  26  so that subscribers have the option of connecting video equipment that outputs analog (composite) video signals, such as an analog videocassette recorder (VCR), video camera, etc.  
      The architecture of STB  10  is shown in further detail in  FIG. 2 . It should be noted that this general architecture is typical of STB&#39;s (e.g., those produced by Motorola, Inc.) that have been in commercial use for several years. Nevertheless, STB  10  is designed to be firmware-configurable or programmable, such that the flow of data among the illustrated elements is dependent upon the manner in which STB  10  is configured or programmed. As known in the art, the cable system operator can transmit programming code from the headend (not shown for purposes of clarity) through the cable system or network to STB  10 , which stores the code in non-volatile random-access memory (NVRAM)  28  (e.g., FLASH memory) under control of a central processing unit (CPU)  30 . Accordingly, STB  10  can be programmed to configure it in the novel manner described herein. As described in further detail below with regard to the method that is performed, CPU  30  controls both the flow of data and the manner in which certain elements process or otherwise act upon the data. CPU  30  also processes the EAS messages and controls operation of the electronic program guide (EPG) and the conditional access (CA) features. Note that the combination of the programming code and NVRAM  28  or other data storage or transmission medium constitutes a “computer program product” as that term is used in patent claims.  
      In addition to NVRAM  28  and CPU  30 , input and central processing circuitry  16  includes user interface logic  32 , an in-band tuner  34 , an out-of-band (OOB) tuner  36 , a cable modem  38 , and various conventional modulators and demodulators  40 - 48 , namely, a vertical blanking interval (VBI) decoder  40 , an NTSC video demodulator  42 , a quadrature amplitude modulation (QAM) signal demodulator  44 , an OOB signal demodulator  46 , and an OOB signal modulator  48 , for decoding VBI-embedded data, demodulating NTSC video, demodulating digital video, and modulating and demodulating OOB signals, respectively. Working memory  50 , which can be random access memory (RAM), is also included for use by CPU  30 . Conditional access (CA) logic  52  is also included to ensure that only authorized digital content is displayed, in accordance with the well-known cable television feature known as conditional access. Modulators  40 - 48 , cable modem  38 , memories  28  and  50 , conditional access logic  52 , and CPU  30  are all in communication via a common PCI (Peripheral Component Interconnect) bus  54 .  
      Digital processing circuitry  18 , which is also in communication with CPU  30  via PCI bus  54 , includes digital video circuitry  56  that can perform decoding, decrypting, demultiplexing, pass-through, and other functions. Digital processing circuitry  18  is connected to the above-mentioned IEEE-1394 output  14  as well as to a digital visual interface (DVI) or High-bandwidth Digital Multimedia Interface (HDMI) output  58 . An MPEG-2 encoder  60  is included so that content received in analog format via the cable system or via composite video input  26  can be output in compressed digital format. In the case of analog content received via the cable system, an analog-to-digital converter  62  receives the demodulated video signal from NTSC demodulator  42  and provides it to digital video circuitry  56 .  
      Analog and graphics processing circuitry  20  includes NTSC video and graphics circuitry  64  that can receive demodulated analog video from NTSC demodulator  42 , decoded data from vertical blanking interval (VBI) decoder  40 , analog video, audio and data signals from digital video circuitry  56 , and a composite video signal from composite video input  26 . (Note that although the system is described for purposes of illustration in terms of the standards promulgated by the National Television System Committee (NTSC), the body charged with setting television standards in the United States, and bodies such as MPEG, the principles described herein can also be applied to televisions and STB&#39;s that conform to standards found in other regions of the world.) An analog-to-digital converter  66  is also included to receive a composite video signal from composite video input  26 , digitize it, and provide the resulting digital video signal to MPEG-2 encoder  60 . Analog and graphics processing circuitry  20  is in communication with CPU  30  via PCI bus  54 .  
      The flowchart of  FIG. 3  illustrates an exemplary method of operation for which STB  10  can be configured by downloading the corresponding program code as described above. As noted above, CPU  30  controls the overall process or method, including the routing of data among the elements illustrated in  FIG. 2  and the manner in which the controllable ones of those elements act upon the data.  
      Initially (i.e., before the method illustrated by the flowchart of  FIG. 3  is begun), STB  10  may be receiving regular content via the cable television system or other digital video source, e.g., a digital video recorder (DVR), and providing it in compressed digital format to television  12  via the IEEE 1394 interface  14 . The cable system, responding in the conventional manner to an EAS alert it receives via other pathways at the cable system headend (not shown), passes the alert on to subscribers with the intent of interrupting subscribers&#39; viewing of the regular content and substituting or overlaying onto the display of the regular content on the television with the EAS alert. For example, the EAS alert transmitted to subscribers may take the form of a digitally encoded message to scroll text (i.e., graphics) across the television screen, with the displayed text advising viewers of an emergency situation. The format for EAS alerts is defined in a government standard and is not relevant to the method and system described herein. Alternatively, the cable system may transmit an electronic program guide (EPG) in response to a viewer&#39;s request. In any event, for purposes of illustrating the present invention, what the cable system transmits includes formatted graphics.  
      At step  68 , STB  10  receives such an EAS alert or EPG from the cable television system. Referring back to  FIG. 2 , the alert can be received, in some instances, via OOB tuner  36 , or in other instances, via cable modem  38 . (Many STB&#39;s currently in use do not have a cable modem.) For purposes herein, it is assumed the received EAS alert or EPG includes formatted graphics (e.g., a scrolling text block) of the type that either the television  12  cannot by itself properly display if provided via IEEE-1394 connection  14  or the STB  10  cannot by itself properly deliver to the TV  12  via IEEE-1394 connection  14  (as an example, the STB does not support On-Screen Display over IEEE-1394 as defined in CEA-775-B). In instances in which it cannot be predetermined whether a received EAS alert will contain such formatted graphics, CPU  30  can test the received EAS alert to determine if it contains codes representing such formatted graphics. (Such a testing step is not shown in  FIG. 3  for purposes of clarity and furthermore, such testing is well-known to those familiar with the art of EAS.) If the EAS alert is found not to contain graphics codes, the EAS alert would be handled in an alternative, conventional manner, such as by causing STB  10  to force-tune to a details channel on which the EAS alert is being broadcast. (The delivery of information regarding the details channel and tuning to the details channel is well-known to those of skill in the art and therefore not described herein.) In such a case, it is not necessary to perform the remaining steps set forth below.  
      As illustrated by step  70 , regardless of whether CPU  30  tests for the presence of formatted graphics, it is desirable that CPU  30  determine whether the loop-through cable  22  has been installed, because without cable  22  installed, the method would result in the display of a black screen, which, from a viewer&#39;s perspective, may seemingly occur without explanation in the middle of watching something else. CPU  30  can do this in any suitable manner, such as by causing a video signal having identifiable characteristics (e.g., a suitable test pattern) to be output at composite video output  24  and testing what is received at composite video input  26  to see if it has the expected characteristics. If it is determined that no cable  22  is connected, the method terminates, the steps described below are not performed, and instead some other suitable action can be taken. Alternatively, CPU  30  can test for the connection of cable  22  by causing text to be output (i.e., displayed on television  12 ) that instructs the viewer to interact with user interface  32  in a prescribed manner, such as by pressing a button, if the user has connected cable  22 . Although such a test can be performed at essentially any point in the method, it is shown following step  68  for purposes of illustration. Also note that, although desirable, step  70  is not a necessary or required step in the method.  
      At step  72 , CPU  30  causes NTSC video and graphics circuitry  64  to mix/overlay the graphics in analog (composite) video format into the analog (composite) video signal representing the video content that is to be viewed during the duration of the EAS alert. The video content may be the content/channel the user was viewing prior to the reception of the EAS alert or EPG, or the video content may be a details channel tuned to by the STB  10 . The output of NTSC video and graphics circuitry  64  feeds composite video output  24 , which is connected via cable  22  to composite video input  26 . At step  74 , the signal that is accordingly received at composite video input  26  is routed through analog-to-digital converter  66  to digitize it and then through MPEG-2 encoder  60  to digitally encode it. (Note that the compressed video may be of other compression types, e.g. H.264, AVC, VC1, MPEG4, Windows Media, Quicktime, etc., where the compression type is supported by both the STB  10  and the TV  12 .) At step  76 , digital video circuitry  56  receives the resulting encoded digital video information and provides it to IEEE-1394 connection  14 .  
      The result of the above-described steps is that digital television  12  receives a compressed digital video signal from STB  10  via IEEE-1394 connection  14 , where the digital television is able to decode and display to the compressed digital video to the end user, where the compressed digital video contains the required graphics (e.g. EAS text scroll, EPG, etc.), which are now properly displayed to the end user. Formatted graphics, such as a scrolling text box, would appear superimposed over any regular broadcast content that may continue to be received via the STB&#39;s  10  video tuner front end  16 , due to the mixing function of NTSC video and graphics circuitry  64 . Although not shown in  FIG. 3  for purposes of clarity, when the graphical presentation session terminates, i.e., there are no more graphics to display, television  12  returns to displaying the regular content as it was prior to the event.  
      It will be apparent to those skilled in the art that various modifications and variations can be made to the above-described method and system without departing from the spirit or scope of the invention. Thus, it is intended that the present method and system cover all modifications and variations that come within the scope of one or more claims and their equivalents. With regard to the claims, no claim is intended to invoke the sixth paragraph of 35 U.S.C. Section 112 unless it includes the term “means for” followed by a participle.