Abstract:
An entertainment system includes a digital television connected to a number of audio/video input devices. The television and at least two of the input devices support analog legacy communication schemes. The television is adapted to uniquely identify the analog output channels from each of the input devices. Uniquely identifying the analog output channels from each input device enables the television to automatically select the correct device output from among the numerous possibilities. This automation relieves the user of having to manually select the correct analog channel.

Description:
This is a continuation application of U.S. patent application Ser. No. 09/978,478, filed Oct. 16, 2001 now U.S. Pat. No. 6,961,099, entitled METHOD AND APPARATUS FOR AUTOMATICALLY SWITCHING BETWEEN ANALOG AND DIGITAL INPUT SIGNALS, the contents of which are hereby incorporated by reference. 

   BACKGROUND 
   Typical home entertainment systems include a television, a VHS tape machine, and some type of set-top box (e.g., a cable box). Sophisticated systems might also include such components as a radio receiver, a CD player, a pair of speakers, a karaoke, and a DVD player. The possibility of adding and combining many disparate audio and video input sources requires that at least one of the interconnected components enable users to select from various input sources and to appropriately configure the desired audio/video output source. Unfortunately, finding the correct configuration of components to display a desired audio/video presentation often requires a viewer to employ a number of different remote-control devices and user interfaces to arrive at the correct combination of device configurations. Experienced users of such systems can attest to the difficulty of finding the appropriate settings for each case; less experienced users find the task even more exasperating. 
   In view of the above, there is a need to provide consumers with simplified systems of devices, and preferably systems that can be controlled using a single, simple user interface. The IEEE 1394 system architecture, also known as the “FireWire® System Architecture,” addresses this need. (“FireWire” is a registered trademark of Apple Computer.) FireWire®-compliant devices assign six-bit physical identifiers to each device connected to a FireWire® serial bus. The FireWire®-compliant devices then use these physical identifiers to uniquely identify themselves on the bus. Whenever a new device is added to the bus, an existing device is removed from the bus, or both, a bus reset initiates certain well-known bus recovery communications and functions in accordance with the FireWire® standard. The bus reset then repeats the process of uniquely identifying each device on the bus. 
   The ability to uniquely identify each device in a home entertainment system greatly reduces the complexity required to display a desired program. For example, if a viewer issues a command to a FireWire®-capable television (via an infrared remote control, for example) to play a video disk in a FireWire®-capable DVD player, then the television would automatically communicate with the appropriate player over the bus to receive and display the contents of the video disk. 
   Most consumers who might consider purchasing an advanced entertainment system already own one or more older “legacy” devices and may have content stored using a legacy format. For example, a consumer interested in purchasing a recent model digital television may have a VHS machine, a collection of analog VHS tape recordings, and a set-top box equipped to deliver analog broadcast programming. The consumer will not likely wish to part with some or all of these. It is therefore important for manufacturers of the latest consumer electronics to provide support for older “legacy” devices. 
     FIG. 1  (prior art) depicts a system  100  in which a digital television (DTV)  105  and digital VCR (DVCR)  110  communicate via a digital FireWire® channel  115  and, to support legacy VHS recordings, an analog channel  120 . Both digital television  105  and digital VCR  110  are assumed to communicate using the IEEE 1394a standard. In one example, the devices of system  100  communicate in accordance with EIA 775, which defines a specification for a baseband digital interface to a digital television using the IEEE 1394 standard. 
   DTV  105  includes a display  125 , a digital interface  130 , and a switch  135 . Interface  130  controls switch  135  to select between digital channel  115  and analog channel  120 . DVCR  110  conventionally includes a panel subunit  140  and a VCR subunit  145 . Panel subunit  140  communicates with digital interface  130  using the FireWire® standard, and VCR subunit  145  reads both analog and digital video recordings. VCR subunit  145  provides digital signals to DTV  105  via panel subunit  140  and digital channel  115 , and provides analog signal to DTV  105  via analog channel  120 . 
   In the absence of some sort of intelligent interface, the user of system  100  would have to know at any given moment whether the output of the DVCR  110  was an analog signal or a digital signal. The user would then have to instruct DTV  105  to select the appropriate analog or digital input. Requiring the user to make such decisions can be confusing, especially if DVCR  110  can play tapes that include both analog and digital information. 
   The FireWire® standard addresses this problem by providing an intelligent means of automatically switching between analog channel  120  and digital channel  115  without requiring user input. When switching between analog and digital outputs, DVCR  110  can issue a FireWire® standard “CONNECT” command over digital channel  115  to instruct digital interface  130  to issue the appropriate video-select command on port VS to switch  135 . The user is thus relieved from the burden of having to manually switch between video signals. FireWire®-compliant systems that employ the EIA 775 protocol issue a CONNECT command with an EIA 775 “descriptor” specifying the analog_input_plug_ID as the destination plug. 
     FIG. 2  depicts an entertainment system  200  in which a digital television  205  is connected to two audio/video devices  210  and  215 . In the depicted example, DTV  205  is a FireWire®-compliant digital television, and devices  210  and  215  are a FireWire®-compliant digital VCR and a FireWire®-compliant digital set-top box, respectively. All three devices include analog communication channels to support legacy communication. 
   DTV  205  includes an analog tuner  220 , some FireWire®-compliant digital interface circuitry  225 , a video selection circuit  230  controlled by a user interface  235 , a video processor  242  to interpret incoming video signals, and a display  244  for presenting the interpreted video signals to users (i.e., viewers). Video selection circuit  230  includes three analog video channels AV 0 -AV 2  connected to three respective analog input jacks  245 . Video selection circuit  230  also includes a digital video channel DV# that receives digital video signals from three digital communication jacks  250  via digital interface circuitry  225  and a FireWire® bus  255 . 
   User interface  235  receives commands from the control panel (not shown) on DTV  205  and via an infrared receiver  260  that receives infrared instructions from a remote control  265 . User interface  235  connects to video selection circuit  230  and issues video select commands VS as directed by the user. In some embodiments, selection circuit  230  enables DTV  205  to simultaneously display the contents of more than one video input to selection circuit  230 . For example, DTV  205  can simultaneously display a user interface and broadcast video from an analog or digital broadcast, and embodiments that support picture-in-picture (PIP) can simultaneously receive and display data from two analog channels, two digital channels, or one analog and one video channel. 
   Digital interface circuitry  225  communicates with devices  210  and  215  via digital video channels DV 1  and DV 2 . Because interface circuitry  225  and devices  210  and  215  are all FireWire® compliant, interface circuitry  225  can distinguish between devices  210  and  215 . User instructions received by user interface  235  can therefore be directed to the appropriate one of devices  210  and  215 , and digital interface circuitry  225  can direct digital video streams from devices  210  and  215  to video selection circuit  230 . Assuming, for example, that device  210  is a digital video recorder, a user can instruct DTV  205  to play videotape in device  210 . Such an instruction would cause user interface  235  to command video selection circuit  230  to select digital video input DV# and to issue a “play” instruction to device  210  via digital interface circuitry  225  and bus  255 . In this way, the user can specify the output of either device  210  or  215  with a simple command to DTV  205 . 
   A problem can arise when one of devices  210  or  215  provides an analog output signal on its respective analog video output AV. As noted above, the FireWire® standard allows compliant devices to issue a “CONNECT” command causing DTV  205  to switch to an analog input. However, DTV  205  has no way of telling which of analog input jacks  245  is connected to the requesting device. Thus, a request to switch the input of DTV  205  to one of analog input jacks  245  may cause DTV  205  to display the correct video, video from the wrong device, or nothing at all. For example, if device  210  issues a command to switch to an analog input while device  215  is also active, DTV  205  might display broadcast video from antenna  270  or the analog signal from device  215 . The user would then have to either physically swap analog input connectors to jacks  245  until the appropriate signal is displayed, or would have to employ user interface  235  to manipulate video selection circuit  230 . The user would then have to repeat this process from time to time, depending on the selected device and the analog input currently selected by circuit  230 . 
   Requiring the user to manually select the appropriate video input or rearrange physical connections can be confusing; indeed, this is part of the reason the FireWire® standard was adopted. Unfortunately, the unique identifiers used by FireWire®-compliant devices do not exist for analog signals. There is therefore a need for a way to uniquely identify a number of analog channels to relieve the user of the burden of manually selecting from among them. 
   SUMMARY 
   The present invention is directed to an entertainment system that includes a digital receiver (e.g., a digital television) and a number of analog/video sources, for example a digital VCR and a digital set-top box. The television and the sources each support at least one form of legacy communication standard, such as the analog National Television System Committee (NTSC) Standard, and are therefore connected to the receiver via both analog and digital communication channels. 
   In accordance with the invention, the receiver can be configured to uniquely identify the sources associated with each analog channel. Uniquely identifying the analog sources allows the receiver to issue digital commands to the source of analog signals without requiring the user to manually select from among analog sources. 
   The scope of the invention is defined by the claims, and not by this summary. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  (prior art) depicts a system  100  in which a digital television (DTV)  105  and digital VCR (DVCR)  110  communicate via a digital FireWire® channel  115  and, to support legacy VHS recordings, an analog channel  120 . 
       FIG. 2  depicts an entertainment system  200  in which a digital television  205  is connected to two audio/video devices  210  and  215 . 
       FIG. 3  depicts an entertainment system  300  in accordance with one embodiment of the invention. 
       FIG. 4  depicts a method  400  of filling in lookup table  335  to correctly correlate analog input channels with the sources of the associated analog input signals. 
     This specific graphical user interface—sometimes referred to as a “screen wizard”—presents a screen similar to screen  500  of  FIG. 5A . 
       FIGS. 5A and 5B  depict screens  500  and  510  of a graphical user interface with which users interact to automate the selection of analog input channels for digital devices adapted to support analog legacy communication. 
       FIG. 6  depicts an alternative interactive screen  600  with which users might interact to automate the selection of analog input channels for digital devices adapted to support analog legacy communication. 
       FIG. 7  depicts yet another interactive screen  700  with which users might interact to automate the selection of analog input channels for digital devices adapted to support analog legacy communication. 
   

   DETAILED DESCRIPTION 
     FIG. 3  depicts an entertainment system  300  in accordance with one embodiment of the invention. Some components of system  300  are similar to those of system  200  of  FIG. 2 , like-numbered elements being the same. System  300  includes a DTV  305  connected to analog and digital ports of a set-top box  310  and a digital VCR  315  via respective pairs of analog and digital video links, or channels. In accordance with the invention, DTV  305  is modified to uniquely identify analog input signals, relieving the user of having to manually select from among multiple analog input signals. 
   DTV  305  conventionally includes display  244 , video processor  242 , video selection circuit  230 , and user interface  235  like those described above in connection with DTV  205  of  FIG. 2 . Unlike DTV  205 , however, DTV  305  includes a modified digital interface  308  designed to seek and store information allowing DTV  305  to uniquely identify analog inputs from among the FireWire®-compliant devices connected to analog input jacks  245 . Digital interface  308  includes a lookup table  312  for storing this information. Digital interface  308  also includes a conventional digital video decoder  318 . 
   Digital interface  308  includes a 1394 (FireWire®) interface  315 , which in turn includes a number of FireWire® layers. These layers include a physical layer  320 , a link layer  325 , a transaction layer  330 , and an application layer  335 . In accordance with the depicted embodiment, application layer  335  is adapted to communicate with lookup table  312  as described below in connection with  FIG. 4 . For a detailed treatment of the IEEE 1394 standard, including the various layers of 1394 interface  315 , see “FireWire® System Architecture, Second Edition, IEEE 1394a,” by Don Anderson, copyright 1999 by MindShare, Inc., which is incorporated herein by reference. In one embodiment, the devices of system  300  communicate in accordance with the EIA 775 specification. For a detailed treatment of the EIA 775 specification, see the 29 Oct. 1998 “Draft EIA-775, DTV 1394 Interface Specification” (Document DEIA775Q) edited by Shazia Azhar, which is also incorporated herein by reference. 
   Set-top box  310  and digital VCR  315  conventionally include globally unique identifiers GUID 1  and GUID 2 , respectively, which serve to uniquely identify set-top box  310  and digital VCR  315  on bus  255 . 1394 interface circuitry  315  also includes a globally unique identifier, though this is not shown. 
   In accordance with the invention, lookup table (LUT)  312  correlates devices on bus  255  with associated analog channels connected to analog input jacks  245 . Lookup table  335  includes one entry for each of analog input jacks  245 , or three entries in the example. Lookup table  312  includes some conventional non-volatile memory for storing a unique identifier for each device connected to one of analog input jacks  245 . In the example, lookup table  312  includes a number of device fields to store the GUID and an optional numerical designation for the device model for each source connected to an analog input jack  245 . Lookup table  312  is shown partially filled, with GUID 1  of the set-top box in the device field associated with analog video input AV 1  and GUID 2  of the digital VCR in the device field associated with the one of jacks  245  associated with analog video input AV 2 . If the analog outputs from STB  310  and DVCR  315  to DTV  305  were reversed, then GUID 1  of the set-top box would instead be in the field associated with analog video input AV 2  and GUID 2  of the digital VCR would instead be in the field associated with the analog video input AV 1 . The manner of filling in the appropriate fields in lookup table  312  is described below in connection with  FIG. 4 . 
   The information in lookup table  312  allows DTV  305  to uniquely identify analog inputs from devices connected to bus  255 . For example, if a viewer, using remote control  265 , instructs DTV  305  to play an analog videotape in digital VCR  315 , then VCR  315  will issue a “CONNECT” command instructing digital interface circuitry  308  to select the analog output from digital VCR  315 . Interface  315  then, knowing the GUID and model of the device issuing the “connect” command from the presence of this information in the command header, refers to lookup table  312  to determine which analog video input corresponds to the requesting device. In the depicted example, lookup table  312  correlates GUID 2  of VCR  315  with analog video input AV 2 , so lookup table  312  returns plug identifier AV 2  in response to the query from application layer  335  of 1394 interface  315 . Application layer  335  thus issues a video-select command on port VS instructing video selection circuit  230  to select analog channel AV 2 . 
     FIG. 4  depicts a method  400  of filling in lookup table  312  to correctly correlate analog input channels with the sources of the associated analog input signals. Before lookup table  335  can correlate analog outputs with their respective devices, the unique identifiers (GUIDs) and model designations associated with those devices are entered into the appropriate fields in lookup table  312 . In accordance with the FireWire® standard, the GUIDs and model information are available in each device&#39;s configuration ROM. 
   Beginning at step  405 , a user plugs in a new piece of FireWire®-compliant hardware, such as a set-top box or digital VCR. The addition of the new hardware conventionally causes a bus reset, during which 1394 interface  315  acquires a list of devices on bus  255  (step  410 ). Next, interface  315  selects the first device on the list (step  415 ) and uses the GUID to determine whether an analog plug ID has been specified in lookup table  312  for the selected device (step  420 ). If a plug ID has already been specified for the selected device, interface  315  moves the process to decision  425  and determines whether to consider another device. If no plug ID has been specified for the selected device, interface  315  moves the process to decision  430 , in which interface  315  determines whether an analog plug ID is required for the specified device. Some FireWire®-compliant devices may not support analog legacy communications, and therefore will not require an analog plug. 
   If no plug ID is required, the process again moves to step  425 ; otherwise, interface  315  provides a graphical user interface to display  244  (step  435 ) seeking input from the user. This specific graphical user interface—sometimes referred to as a “screen wizard” or “autowizard”—presents a screen similar to screen  500  of  FIG. 5A . 
   Referring to  FIG. 5A , screen  500  includes a window  505  displaying video derived from whichever analog input channel is selected by video selection circuit  230  of  FIG. 3  (step  440 ). Screen  500  prompts the viewer to select either a “yes” icon or a “no” icon, depending upon whether window  505  displays the appropriate analog signal.  FIG. 4  depicts the user&#39;s decision as decision  445 . 
   If the answer is yes, then interface  315  fills in the field of lookup table  312  associated with the selected analog video input to map the GUID of the selected device to the appropriate analog plug ID. On the other hand, if the answer to decision  445  is no, then interface  315  determines whether there are additional analog input channels left to try (step  455 ). If so, interface  315  switches video selection circuit  230  to the next available analog input channel (step  465 ) and presents a screen similar to screen  510  of  FIG. 5B  to the user. 
   Referring to  FIG. 5B , screen  510  is like screen  500  of  FIG. 5A , except window  505  displays video selected from analog input channel AV 2 . The process of  FIG. 4  then returns to step  445  and continues until either the correct video input is found and mapped in lookup table  312  or there are no more analog input channels to try. In either case, the process moves to step  425 , in which interface  315  determines whether there is another listed device: if so, the next device is selected (step  460 ) and the process returns to step  420 ; otherwise, the set-up process is finished. 
   In an embodiment that employs the EIA 775 protocol for digital communications, the device seeking to have DTV  305  switch between analog and digit input channels issues a CONNECT command specifying “any available external plug” in the EIA-775 descriptor as the destination plug. DTV  305  then selects the correct connection based on the information in lookup table  312 . DTV  305  can thus automatically manage analog inputs from multiple digital products. 
     FIG. 6  depicts an alternative interactive screen  600  with which users might interact to automate the selection of analog input channels for digital devices adapted to support analog legacy communication. Screen  600  includes a source-identification field  605 , an analog input field  610 , and arrow icons  615 . Using the up and down arrows  615  associated with source-identification field  605 , users can select from among the list of devices generated after a bus reset. In the depicted example, a user has selected a Sony Set-Top box and is interested in assigning that box the appropriate analog video input. Analog input field  610  shows the user which analog input is currently selected, and a window  620  displays video from that source. Up and down arrows  615  associated with field  610  allow the user to select from among the available analog input channels. The user knows the settings are correct when window  620  displays the video from the selected device. The user then selects the “OK” button, and the settings from fields  605  and  610  are used to update lookup table  312  ( FIG. 3 ). This process can be repeated for any number of devices. Once finished, the user can select the “Exit” button to exit screen  600 . 
     FIG. 7  depicts an alternative interactive screen  700  with which users might interact to automate the selection of analog input channels for digital devices adapted to support analog legacy communication. Users may be confused about the source of a video presentation. If the source is misidentified, the entertainment system may incorrectly identify an analog input. For example, if the user erroneously believes an analog broadcast is the correct output from a VCR being set up in step  445  ( FIG. 4 ), the VCR&#39;s analog output will be incorrectly mapped in LUT  312  ( FIG. 3 ). Some embodiments avoid such potential problems. Instead of using just video content to confirm the input source, system DTV  305  might issue a command to the device for which an audio input channel is to be identified to get some special audio or visual effects. In the example of  FIG. 7 , DTV  305  issues an instruction to the selected device to power off and on, resulting in a visible disruption in the video from the displayed analog channel if the correct analog channel is selected. Screen  700  then asks the viewer whether the video switched off and on in place of step  445  of  FIG. 4 . The EIA 775 protocol defines a “POWER” command that can be used for this purpose. 
   While the present invention has been described in connection with specific embodiments, variations of these embodiments will be obvious to those of ordinary skill in the art. For example, while the foregoing examples involve both audio and video data, systems in accordance with the invention can be used in purely audio systems. Moreover, all or a portion of the interface and selection circuitry depicted herein as part of a digital television can be embodied in a separate component (e.g., a “set-top box”) separate from a television display. Therefore, the spirit and scope of the appended claims should not be limited to the foregoing description.