Patent Publication Number: US-2003226153-A1

Title: Method and apparatus for switching television channels

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to television channel switching, and more particularly to television channel switching in digital television. Even more particularly, the present invention relates to the relatively large amount of time required and the display of blank or otherwise non-program periods in the switching of channels in digital television.  
       [0002] Television (TV) viewers perceive seamless, rapid switching from one channel to another to be an important TV receiver characteristic, and have become accustomed to seamless, rapid switching from one channel to another in analog television. This type of channel switching is generally effected by pressing a “channel up” (“up” or “+”) or “channel down” (“down” or “−”) key on a control (such as a remote control) for a television.  
       [0003] With the high number of channels now available to viewers for viewing, searching serially (e.g., in ascending or descending numerical order) through multiple channels quickly becomes desirable, so that viewers can find their desired programming in an efficient manner, without referring to a channel guide/schedule. This practice is known, in popular vernacular, as “channel surfing.” Switching to another channel (either sequentially, or directly, i.e., “randomly”) to view alternate programming during, for example, commercials is also desirable for many viewers.  
       [0004] As the number of channels available to viewers increases, due for example to the introduction of technologies such as digital television (DTV), the desirability of seamless, rapid switching between channels increases.  
       [0005] Unfortunately, however, it is well known in the art that certain properties of digital television (DTV) make channel switching times, i.e., the periods between the selection and display of channels, longer than the channel switching times of traditional analog television, regardless of whether such channel switching is sequential or “random.” 
       [0006] The longer channel switching time is due to several factors involved with processing a digital television signal. The primary one being that in digital television there is a reference frame transmitted to the television (via, for example, a coaxial cable transmission line, or air channel, such as, for example, a satellite channel) generally only every 0.5 seconds. These reference frames are used to help digitally tune to a desired “channel” by acquiring a correct frequency and timing for the desired “channel.” As a result, in some cases, the viewer is presented with a blank or otherwise non-program screen (display) for 1 second or more when switching channels.  
       [0007] Thus, there is a need for systems and methods that provide for channel switching (including “channel surfing”) in, for example, digital television, with reduced or eliminated blank or otherwise non-program displays during channel switching, and furthermore with a reduced or zero time delay (during which a non-program display is presented to the viewer) required for the switching channels.  
       [0008] The present invention advantageously addresses the above and other needs.  
       SUMMARY OF THE INVENTION  
       [0009] The present invention addresses the above and other needs by providing a system and method for switching channels.  
       [0010] In one embodiment, the present invention can be characterized as a method in which a first channel is received by a first tuner, the first channel is displayed, a second channel is selected by a viewer, and the second channel is received by a second tuner while the first channel is being displayed.  
       [0011] In accordance with a variation of the one embodiment, the second tuner is, before the second channel is selected by the viewer, tuned to a next higher channel from first channel. In the event the second channel selected by the viewer is the next higher channel from the first channel, and after a prescribed time period for tuning of the second tuner to the second channel, the second channel can be immediately displayed upon being selected. In further accordance with this variation, once the second channel is selected by the viewer, the first tuner is, before a third channel is selected by the viewer, tuned to a next higher channel from the second channel. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012] The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:  
     [0013]FIG. 1 is a block diagram of a channel switching system in accordance with one embodiment of the present invention;  
     [0014]FIG. 2 is a block diagram of the channel switching system of FIG. 1 with one example of signal processing subsystems and interrelationships thereinbetween shown in detail;  
     [0015]FIG. 3 is a process flow chart showing a channel switching process of the channel switching system of FIG. 1 and FIG. 2;  
     [0016]FIG. 4A is a timeline showing switching between two tuners of the channel switching system of FIG. 1 and FIG. 2; and  
     [0017]FIG. 4B is a timeline showing switching of channels using one tuner of a prior art conventional channel switching system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0018] The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.  
     [0019] Referring to FIG. 1, shown is a block diagram of the channel switching system in accordance with one embodiment of the present invention. Shown is a first tuner  100 , a second tuner  105 , a microprocessor  250 , a selection switch  111  and a display screen  115 .  
     [0020] There is an RF television signal input  145  to the first and second tuners  100 ,  105  and a channel selection input  150  to the microprocessor  250 . The first and second tuners  100 ,  105  are coupled  120 ,  125  to the selection switch  111 . The tuners  100 ,  105  are also coupled to the microprocessor  250  individually through separate duplex communication lines  130 ,  135 , respectively. The microprocessor  250  and display screen  115  are coupled  136 ,  140  to the selection switch  111 .  
     [0021] The first tuner  100  and the second tuner  105  receive an RF television signal input  145 . The microprocessor  250  controls which channels are tuned by the tuners  100 ,  105  and which output  120 ,  125  from each tuner  100 ,  105  is selected by the selection switch  111 . The output  140  of the selection switch  111  (controlled by the microprocessor) is a television signal that is sent to the display screen  115  for display.  
     [0022] Referring next to FIG. 2, shown is a block diagram of the channel switching system of FIG. 1 with one example of signal processing subsystems and interrelationships thereinbetween shown in detail. Shown are two signal paths. Each of the two parallel signal paths is substantially identical (therefore the components thereof are commonly numbered, with callout numbers of the components of one path carrying the prime (“′”) indicator). In the interest of conciseness, only one of the two parallel signal paths is described hereinbelow, with the other of the two parallel signal paths being understood to be identical to the one of the two parallel signal paths, except as otherwise described or depicted. Each signal path includes a tuner  100 , demodulator  200 , a decryptor  210 , a demultiplexer  215 , and a video decompression module  220 . Also shown is a single microprocessor  250 , the selection switch  111  and display screen  115 . Within each signal path, the tuner  100 , demodulator  200 , decryptor  210 , demultiplexer  215  and decompression module  220  are individually coupled to the microprocessor  250  which is coupled  136  to the selection switch. Also, the tuner  100  is coupled to the demodulator  200  which is in turn coupled to the decryptor  210 . The decryptor  210  is coupled to the demultiplexer  215  which is in turn coupled to the decompression module  220 , and the decompression module  220  is coupled to the selection switch  111 .  
     [0023] As explained above, the first tuner  100  and the second tuner  105  receive an RF television signal input  145 . Two television programs are extracted from the television signal input  145  by two parallel signal paths depicted in FIG. 2. Each of the two parallel signal paths shown includes a demodulator  200 , a decryptor  210  a demultiplexer  215  and a decompression device  220 , as are known in the art. As the respective signals pass through these devices, the microprocessor  250  coordinates the signal processing to produce a demodulated, decrypted and demultiplexed program signal. The microprocessor  250  initiates and coordinates decompression of the video for each of the program signals. Once these signals are decompressed, the decompression devices  220 ,  220 ′ output these two signals  221 ,  221 ′ for selective display by the television display screen  115 .  
     [0024] These two television signals  221 ,  221 ′ are input to a selection switch  111  that is coupled  136  to the microprocessor  250  having a channel selection input  150  as in FIG. 1, described above. The selection switch  111  is controlled by the microprocessor  250  which takes into account the value of the channel selection input  150  and operates according to the channel switching process described below. The output  140  of the selection switch  111  is the television signal selected by the selection switch  111  to be sent to the display screen  115  for display.  
     [0025] Referring now additionally to FIG. 3, shown is the channel switching process flow of the channel switching system of FIG. 1 and FIG. 2. Shown are blocks that represent the steps and decisions made during the channel switching process. The arrows point in order to the next step or decision to be made in the process.  
     [0026] By way of operation, a current channel is viewed  300  on the display screen  115  by receiving a signal  140  through the selection switch  111  ultimately from either the first tuner  100  or the second tuner  105 , e.g., the first tuner  100  in this case. By default, the tuner through which the current channel is not being viewed, e.g., the second tuner  105  in this case, can be, for example, tuned  260  to the next highest available channel. This operation is controlled via the selection switch  111 . By way of further example, the tuner through which the current channel is not being viewed, e.g., the second tuner  105 , can be, for example, tuned to a channel selected as a function of one or more of the following: dwell time (i.e., the length of time during which the viewer has viewed the current channel); a preselected or programmatically determined (such as determined as a function of the viewer viewing habits, e.g., a statistical analysis of the most probable next channel to be selected by the viewer); time of day; day of week; a previously viewed channel (e.g., if the viewer selected the current channel sequentially or nonsequentially, such as from a numeric keypad). The channel selected may be alternatively or additionally determined as a function of a viewer&#39;s direction of sequentially tuning through channels, e.g., selecting a next higher channel for tuning by the tuner through which the current channel is not being viewed in the event the current channel was selected by pressing a “DOWN” button. The way in which the channel selected is determined, i.e., of what the channel selected is a function, may be automatically or manually adjusted as e.g., a function of user behavior or interaction.  
     [0027] When a channel selection is made  305 , it is communicated to the microprocessor  250  via the channel selection input  150 . If the second tuner  105  is already tuned to that channel  310 ,  312  (such as may be the case when the viewer is scrolling sequentially up through the channels), the microprocessor  250  communicates  136  to the selection switch  111  to immediately switch  325  the display screen  115  input  140  from the output  221  originating from the first tuner  100  to the output  221 ′ originating from the second tuner  105 , thus effecting the channel change (channel switching). As a result, the channel selection is immediately reflected on the display screen  115 .  
     [0028] If the second tuner  105  is not already tuned to that channel  311  the microprocessor  250  communicates the channel selection to the second tuner  105 . The second tuner  105  then tunes  315  to the channel (which, as mentioned above may take up to one second or more). Then, after the second tuner  105  acquires  320  the channel and any corresponding signal processing is completed, the selection switch  111  switches  325  the display screen  115  input  140  from the output  221  originating from the first tuner  100  to the output  221 ′ originating from the second tuner  105 , thus effecting the channel change. As a result, during the period it takes for the second tuner  105  to tune the channel  315 ,  320  the display screen  115  input  140  remains switched to the output  120  originating from the first tuner  100 , and thus the display screen  115  does not appear blank or otherwise reflect non-program displays. Alternative embodiments also exist where the switch to the new channel can take place even though the tuning and signal processing are not complete. This would be, for example, in the case described above where the second tuner  105  is not already tuned to the channel communicated through the channel selection input. In this case a blank or non-program screen is seen for a period of time until the tuning and signal processing are complete.  
     [0029] In either case, in preparation for a subsequent channel selection, the microprocessor  250  then communicates to the first tuner  100  to tune to a next higher channel  325  after the channel to which the second tuner  105  is tuned. When another channel selection is made  330 , the first tuner  100  will then tune to the desired channel  335 ,  341  (if not tuned already  340 ,  341  i.e., if the other channel is not the next higher channel). Then (in the present embodiment once the first tuner  100  has acquired  345  the desired channel, if necessary), the display screen  115  input  140  is switched  350  by the control module  110  to the output  120  originating from the first tuner  100 .  
     [0030] Referring next to FIG. 4A and FIG. 4B, shown in FIG. 4A is a timeline showing switching between two tuners of the channel switching system of FIG. 1 and FIG. 2. The state each is in at any given time is represented from left to right along the length of the horizontal line next to the name of the corresponding tuner. Shown in FIG. 4B is a timeline showing switching of channels using one tuner of a prior art conventional channel switching system. The state the tuner is in at any given time is represented from left to right along the length of the horizontal line.  
     [0031] As shown in FIG. 4A and FIG. 4B, the system and method of the present embodiment eliminates blank or otherwise non-program periods during channel switching, and reduces or eliminates the period between channel selection and display, i.e., reduces or eliminates the period required for channel switching (by “predicting” and “tuning to” a next channel, e.g., a next higher channel, with the tuner  100  or  105  to which the selection switch  111  is not switched).  
     [0032] As depicted in FIG. 4B, in conventional channel switching there is a blank or otherwise non-program period between selecting and displaying channels. This period results while the tuner (conventionally, a single tuner) tunes to and acquires the newly selected channel.  
     [0033]FIG. 4A shows that, in accordance with the present embodiment, while one tuner is tuning to a newly selected channel, a current channel is still being displayed using the other tuner, thus eliminating the blank or otherwise non-program period that would otherwise exist during channel switching.  
     [0034] Also, if the viewer selects a next highest available channel, say by scrolling up using a television remote control, the tuner through which the current program is not being viewed will, in accordance with one variation of the present embodiment, already be tuned to a next selected channel (i.e., next higher channel) and thus there will be no discernable switching time apparent to the viewer. This makes channel switching appear to the viewer to be virtually instantaneous (because the changing of the display from one channel to the next higher channel is nearly instantaneous).  
     [0035] While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.  
     [0036] For example, the embodiment and variation described above refer to tuning a first tuner to one channel for display, and tuning a second tuner to a next higher channel, so that in the event the user selects the next higher channel the change in the display from the one channel to the next higher channel can be nearly instantaneous. A further variation may include tuning the second tuner to a next lower channel in the event the viewer is “channel surfing” (sequentially tuning) down through channels, rather than sequentially up through channels, as assumed above.  
     [0037] Yet a further variation may include tuning the second tuner to a next higher/lower channel in a selected set of channels (channel group), such as, e.g., a news channel group.  
     [0038] And, yet another variation may include employing more sophisticated approaches and/or additional tuners to “predicting” a next channel to be selected, and then “tuning” to the next channel using the tuner  100  or  105 , or additional tuners, the output of which is not being displayed on the display screen  115 .