Abstract:
A method of implementing an RF passthrough for a digital network recorder, and a means for practicing the method, the method consists of the steps of: monitoring an output of a digital video decoder of a digital network recorder that continuously records an input television signal to a memory and continuously decodes and plays the input television signal having been recorded; and outputting the input television signal to a television, in the event an output video signal is not output from the digital video decoder, wherein the output video signal comprises the input television signal having been previously recorded and decoded. For example, the input television signal is passed through to the television during the booting up process or a failure of the digital network recorder.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to recorders for recording and playing an input television signal, and more specifically, the invention relates to digital network recorders that receive updates from a network and that records and plays an input television signal.  
         BACKGROUND OF THE INVENTION  
         [0002]    A television video recording unit (also known in the art as a digital hard disk video recorder or a digital network recorder) is a device which inputs a television signal, e.g. a television RF signal, continuously records the television signal and then outputs the television signal having been recorded to a television for the user to view. The input television signal may be received from an antenna system, a cable delivery system, or a satellite receiver, for example. Internally, the television recording unit includes a large hard disk drive for storing the television signal. The recording and playing feature is governed by an operating system stored on the hard drive. The operating system behaves as an operating system on a computer; thus, the digital network recorder combines the functionality of a personal computer (PC) with that of a video cassette recorder (VCR). Further included within the digital network recorder is encoder functionality for digitizing the input television signal (in the case of an analog input television signal), and encoding and compressing the signal for storage on the hard drive. Decoder functionality then decodes and decompresses the stored television signal and provides an output television signal (in either analog or digital format depending on the television type) to the television which is time shifted with respect to the input television signal by a short period of time depending on the speed of the digital network recorder, e.g., typically only a few seconds.  
           [0003]    Advantageously, since the live television RF signal is continuously being recorded, the user may actually pause, rewind, or replay the live television signal. The user can simply fast forward back to real time to catch up to the “live” television signal.  
           [0004]    Disadvantageously, since the digital network recorder is similar to a computer and requires an operating system, the operating system must “boot up” or initialize at power on. Thus, when the digital network recorder is powered on, the system must load the operating system from the hard drive into random access memory and ensure that all the necessary components of the digital network recorder are functioning before beginning to record the input television signal. Thus, while “booting up”, known digital network recorders can not supply an output television signal to the television.  
           [0005]    Unfortunately, this results in the television displaying a blank screen during the boot up process, or optionally, a screen display indicating that the digital network recorder is loading. Depending on the operating system, the boot up time may be from 1 to 5 minutes in duration. This delay from when the user powers on the digital network recorder until the user is able to view the television can be extremely irritating and frustrating to viewers. Television viewers are accustomed to powering on a television and immediately viewing programming, as is common to the majority of television delivery systems; thus, even a wait time of one minute may seem an eternity to the normal television viewer.  
           [0006]    Another problem common to digital network recorders is that if there is a crash in the hard drive of the recorder, the output television signal is interrupted such that no television signal is output to the television. Thus, the user may be unable to view any television signal in the event of a hard drive crash. Also, if the hard drive crash occurs during the boot up process, the user may be unaware of the crash and get frustrated waiting and waiting for the boot up process to finish (which will not happen in the event of a crash during boot up).  
           [0007]    The present invention advantageously addresses the above and other needs.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention advantageously addresses the needs above as well as other needs by providing an RF passthrough within the digital network recorder to pass the input television signal directly through to the television in the event that there is no video output from the digital network recorder.  
           [0009]    In one embodiment, the invention can be characterized as a method, and a means for practicing the method, the method including the steps of: monitoring an output of a digital video decoder of a digital network recorder that continuously records an input television signal to a memory and continuously decodes and plays the input television signal having been recorded; and outputting the input television signal to a television, in the event an output video signal is not output from the digital video decoder, wherein the output video signal comprises the input television signal having been previously recorded and decoded.  
           [0010]    In another embodiment, the invention can be characterized as an RF passthrough system for a digital network recorder including a memory for continuously storing an input television signal as digital data and a digital video decoder coupled to the memory for continuously retrieving the digital data, decoding the digital data and outputting an output video signal. The output video signal represents the input television signal and is to be output to a television coupled to the digital network recorder. The system also includes a switch for inputting the input television signal and the output video signal such that the switch outputs the input television signal in the event the output video signal is not input from the digital video decoder. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    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:  
         [0012]    [0012]FIG. 1 is a diagram of a system including a conventional digital network recorder for recording television signals and displaying on a television an indication that the digital network recorder is booting up;  
         [0013]    [0013]FIG. 2 is a functional block diagram of the conventional digital network recorder of FIG. 1;  
         [0014]    [0014]FIG. 3 is a functional block diagram of a digital network recorder incorporating an RF passthrough in accordance with one embodiment of the invention;  
         [0015]    [0015]FIG. 4 is an internal block diagram illustrating several components found within one variation of the conventional digital network recorder of FIG. 1;  
         [0016]    [0016]FIG. 5 is an internal block diagram of one embodiment of the digital network recorder of FIG. 3 in accordance with one embodiment of the invention; and  
         [0017]    [0017]FIG. 6 is a flowchart of the steps performed by the digital network recorder of FIGS. 3 and 5 in accordance with another embodiment of the invention.  
         [0018]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    The following description of the presently contemplated best mode of practicing the invention 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.  
         [0020]    Referring first to FIG. 1, a diagram is shown of a system  100  including a conventional digital network recorder for recording television signals and displaying on a television an indication that the digital network recorder is booting up. Shown is a digital network recorder  102 , a television  104 , a recorder remote control  106 , a television remote control  108 , an input television signal  110  (also referred to as the raw television signal), an output television signal  112 , a computer network  116  and a screen display  114 .  
         [0021]    The digital network recorder  102  is known in the art as a device which receives an input television signal  110 , e.g. a television RF signal, records the television signal  110  and then produces the output television signal  112  which is sent to the television  104 . The digital network recorder  102  is also referred to in the art as a network video recorder, a hard disk video recorder, or a digital personal video recorder. An example of such a device is the Sony Digital Network Recorder SVR-2000, commercially available from Sony Electronics Inc., of Park Ridge, N.J., which incorporates TiVO Service™ developed by TiVo, Inc. of Sunnyvale, Calif. Another example is the Panasonic PV-HS2000 Showstopper Hard Disk Recorder, commercially available from Matsushita Electronics Corporation of America headquartered in New Jersey, which uses Replay TV Service developed by RePlay TV, Inc., of Mountain View, Calif.  
         [0022]    The input television signal  110  may be received from an antenna system, a cable delivery system (e.g. cable modem or a cable set top box), or a satellite receiver, for example. Typically, the input television signal  110  is referred to as an RF input, since television signals are commonly modulated on a radio frequency (RF) carrier. Internally, the digital network recorder  102  includes a large hard disk drive (e.g. a 30 Gbyte hard disk) for storing the input television signal  110 . The recording and playing feature is governed by an operating system stored on the hard drive. The operating system behaves as an operating system on a computer; thus, the digital network recorder  102  combines the functionality of a PC with that of a VCR. For example, the Sony SVR-2000 utilizes a LINUX operating system, while the Panasonic PV-HS2000 utilizes a WINDOWS operating system. Further included within the television recording unit  102  is encoder functionality for digitizing the input television signal  110  (in the event the input television signal  110  is analog), encoding and compressing the input television signal  110  for storage on the hard drive. For example, the input television signal  110  is encoded using the motion picture experts group  2  standard (MPEG2) as known in the art. Decoder functionality then decodes and decompresses the stored data representing the input television signal  110  and provides an output television signal  112  (in either analog or digital format depending on the television type) to the television  104 .  
         [0023]    Thus, in effect, the digital network recorder buffers the input television signal. Advantageously, since the live input television signal  110  is continuously being recorded by the digital network recorder  102 , the user may actually pause the output television signal  112 , e.g. to answer a telephone or to use the restroom. Similarly, the user may rewind the television broadcast to watch a portion over again, e.g., to see a user created instant replay. The user can simply fast forward back to real time to catch up to the “live” input television signal  110 . It is noted that such digital network recorders are known in the art “time shifting devices” since the output television signal  112  is shifted in time about  1 - 2  seconds with respect to the input television signal  110  due to the continuous recording of the input television signal  110 .  
         [0024]    Additionally, the digital network recorder  102  is referred to as a network recorder, since the digital network recorder  102  includes a modem (not shown) for coupling the digital network recorder  102  to a computer network  116 , e.g., the Internet. This enables the digital network recorder  102  to receive updates and control information from services in the computer network  116  that manage the digital network recorder  102 . For example, the Sony SVR-2000 periodically dials into the TiVo Service server, which downloads programming schedules and other information to the digital network recorder. It is noted that this feature is well known and understood in the art.  
         [0025]    Disadvantageously, since the digital network recorder  102  is similar to a computer and requires an operating system, the operating system must “boot up” or initialize at power on. Thus, when the digital network recorder  102  is powered on, the operating system must be loaded from the hard drive into random access memory and ensure that all the necessary components of the digital network recorder  102  are functioning prior to being able to begin recording the input television signal  110 . In the context of the Sony SVR-2000, the “power on” which requires booting up occurs when power is supplied to the digital network recorder  102 , not when the user powers on and off the digital network recorder  102  with the recorder remote control  106 . However, it is noted that “power on” which requires booting up for other digital network recorders may occur at other times, e.g., while powering on the digital network recorder  102  with its remote control  106 . Additionally, the output television signal  112  is the signal retrieved from storage on the hard drive and decoded by the decoder. This output television signal  112  may be digital or analog depending on the television  104 . Thus, while “booting up”, conventional digital network recorders  102  do not supply the output television signal  112  to the television  104 .  
         [0026]    Unfortunately, this results in the television  104  displaying a blank screen during the boot up process, or optionally a screen display  114  indicating that the digital network recorder  102  is loading. Depending on the operating system, the boot up time may be from 1 to 5 minutes in duration. For example, digital network recorders  102  using a LINUX operating system take about 3-5 minutes to boot up, while a WINDOWS operating system takes about 1-2 minutes to boot up. This delay from when the user powers on the digital network recorder  102  until the user is able to view programming on the television  104  can be extremely irritating and frustrating to viewers. Television viewers are accustomed to powering on a television  104  and immediately viewing programming, as is common to the majority of television delivery systems (e.g. antenna, cable, and satellite); thus, even a wait time of one minute may seem an eternity to the normal television viewer.  
         [0027]    Furthermore, in digital network recorders  102  where power on requiring the boot-up process occurs when the user operates the remote control  106  on/off button, the problem of not being able to view the television signal during boot up occurs frequently. Most users are accustomed to powering on and off the television  104  with the same remote unit that changes the channels, adjusts the volume, etc., which is the recorder remote control  106  unit in this case, not the television remote control  108 . Thus, many users, while operating the digital network recorder  102  with the recorder remote control  106 , will accidentally hit the power button turning off the digital network recorder  102 , then use television remote control  108  to turn off the television  104 . This would be more likely with users not accustomed to operating the television  104  using other than the television remote control  108  supplied by the manufacturer, for example, users who do not have a cable set top box or a satellite receiver. Thus, unfortunately at power on, the user must endure the boot up process without being able to view the output television signal  112 .  
         [0028]    In digital network recorders  102 , such as the Sony SVR-2000, where powering on and off the digital network recorder via the recorder remote control  106  does not initiate the boot up process, the problem still exists. In this case, boot up is required when power is initially supplied to the digital network recorder  102  or power is removed and re-connected, either physically or with a switch. For example, the user will be unable to watch the television for several minutes when the user plugs the digital network recorder  102  into the power outlet. Furthermore, many users operate their the digital network recorder  102  with the use of a switched power supply, controlled by a switch on an electrical outlet strip or a light switch, for example. In these cases, the user will cause the power to be disconnected from the digital network recorder  102  such that during the re-connection (e.g., by activating the switch), the user must endure the boot up process before being able to watch television. As such, disadvantageously, the user must endure the boot up process without being able to watch the output television signal  112 .  
         [0029]    Another problem common to digital network recorders  102  is that if there is a crash in the hard drive of the digital network recorder  102 , the output television signal  112  is interrupted such that no television signal is output to the television  104 . Thus, the user may be unable to view any television signal in the event of a hard drive crash. Also, if the hard drive crash occurs during the boot up process, the user may be unaware of the crash and get frustrated waiting and waiting for the boot up process to finish (which does not happen in the event of a crash during boot up).  
         [0030]    Referring next to FIG. 2, a functional block diagram is shown of the conventional digital network recorder of FIG. 1. Shown is the input television signal  110  (also referred to as a raw input television signal  110 ), an analog to digital converter  202  (hereinafter referred to as the A/D converter  202 ), an encoder  204  (also referred to as a digital video encoder), a decoder  206  (also referred to as a digital video decoder), a memory  208 , and a digital to analog converter  210  (hereinafter referred to as the D/A converter  210 ).  
         [0031]    The input television signal  110  is input into the digital network recorder and is converted to digital format by the A/D converter  202 . It is noted that the A/D converter  202  may be unnecessary in embodiments in which the input television signal  110  is already in digital format, e.g., if the input television signal  110  is from an s-video or RCA input. Next, the digital signal is encoded at the encoder  204 . The encoder  204  encodes and compresses the input television signal  110  according to a coding scheme, such as the MPEG2 standard. The encoded and compressed digital data representing the input television signal  110  is then stored within the memory  208 . This memory  208  is conventionally a hard disk drive, e.g., a 30 Gbyte hard disk.  
         [0032]    As soon as the input televison signal is stored in memory, the decoder  206  continuously retrieves the stored data from memory  208  and decodes the stored data (e.g., using the MPEG2 standard) and forms a digital signal to be output to the television. If the television accepts only analog signals, then the D/A converter  210  converts the output television signal  112  to analog. Otherwise the D/A converter  210  is not used if the television is a digital television.  
         [0033]    As seen, when there is no output from the decoder  206 , there is no output television signal  112  to the television. This occurs while the operating system is booting up or when there is a hard drive crash, for example. Consequently, as described above, the viewer can not view any television.  
         [0034]    Referring next to FIG. 3, a functional block diagram is shown of a digital network recorder incorporating an RF passthrough in accordance with one embodiment of the invention. Shown is the input television signal  110  (also referred to as the raw input television signal  110 ), the A/D converter  202 , the encoder  204  (also referred to as a digital video encoder), the decoder  206  (also referred to as a digital video decoder), the memory  208 , the D/A converter  210 , a switch  302 , and the output television signal  112 .  
         [0035]    This embodiment of the invention includes the same basic functions as the digital network recorder of FIG. 2, but includes the addition of the switch  302  that inputs the output of the decoder  206  and the input television signal  110 . The switch  302  selects one of the two inputs as the output televison signal  112  to the television. Thus, the input television signal  110  is coupled to the A/D converter  202  and to the switch  302 . As such, the switch  302  is configured to automatically output the input television signal  110  as the output television signal  112  in the event there is no output from the decoder  206  received at the switch  302 . When there is an output from the decoder  206  and D/A converter  210 , the raw input television signal  110  is overwritten by the output of the decoder  206 .  
         [0036]    Advantageously, this solution covers the boot up scenario. For example, when booting up, the switch  302  is configured to by-pass all elements under the control of the operating system. The switch  302  detects no output at the decoder  206  and D/A converter  210 . When the system is fully booted up and the decoder  206  is functioning (i.e., producing a video output signal), then the switch  302  causes the recorded television signal (i.e., the video output of the decoder  206 ) to be the output television signal  112 .  
         [0037]    Likewise, in the event of a hard drive crash or other failure, the decoder  206  will not output a signal, and the switch  302  will cause the raw input television signal  110  to be the output television signal  112 . Thus, the switch  302  is configured to always output the raw input television signal  110  unless there is a video output at the decoder  206 .  
         [0038]    In one embodiment, the switch  302  is an embedded chip, such as an Erasable Programmable Read Only Memory (EPROM) chip, which will not lose its memory when the power is turned off. This EPROM will act as an on-off switch between the raw input television signal  110  and the output of the decoder  206 . The EPROM would be programmed to output the raw input television signal  110 , unless it detected an output video signal from the decoder  206 . Someone skilled in the art of programming could easily create the code for programming the EPROM to behave in this manner. For example, the switch  302  could be programmed to detect the first bit of output at the decoder  206  or simply detect the signal from the D/A converter  210  as it is received into the switch  302 , and then switch from the raw input television signal  110  to the recorded signal from the decoder  206 . Furthermore, the EPROM can be configured to output a pre-programmed message to inform the user that the system is loading, so that the user will understand that the features of the digital network recorder are not yet usable.  
         [0039]    In another embodiment, the switch  302  is embodied as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) such as used in conventional VCRs to provide RF switches between VCR outputs and television signals. Such RF switching MOSFETs are known in the art and commercially available, for example, Phillips Electronics Part No. BF1107, is an n-channel single gate MOSFET and would be suitable as the switch  302 .  
         [0040]    Thus, the switch  302  behaves similarly to the operation of VCRs in that when the user presses stop for the video cassette, the VCR player stops and the RF signal is passed directly through to the television. Similarly, when the decoder  206  of the digital network recorder is not outputting a recorded video signal, then the switch  302  outputs the raw input television signal  110 .  
         [0041]    In other embodiments, the switch  302  is not required; however, the RF passthrough is implemented in software by the operating system. In such embodiments, the input television signal  110  must be made coupleable to the output television signal  112 . However, in such embodiments, if there is a failure of the operating system, then the system will be unable to switch to the raw input television signal  110 ; thus, the viewer will not see any programming. The software embodiment is described further below.  
         [0042]    It is noted that the A/D converter  202  is optional depending on the system. For example, if the input television signal  110  is already digitized, then the A/D converter  202  is not required. Likewise, in some embodiments, the encoder  204  is not required where a digital input television signal is already in encoded and compressed according to the decoder  206  scheme of the digital network recorder. Additionally, in other embodiments, the D/A converter  208  is not required if the output television signal is to be digital for a digital television. The memory  208  preferably takes the form of a hard disk, but may be other types of digital memory storage, such as a memory stick, as known and produced by Sony Electronics, Inc., of Park Ridge, N.J.  
         [0043]    Referring next to FIG. 4, an internal block diagram illustrating several components found within one variation of the conventional digital network recorder of FIG. 1 is shown. Illustrated are the input television signal  110  including an s-video/RCA signal  406 , the encoder  204 , a media switch  402 , the decoder  206 , a hard drive  404  (also referred to as a hard disk  404  or generically as a memory  208 ), and the output television signal  112 . It is noted that there are many other internal components to the conventional digital network recorder; however, only the relevant components are shown. This is a similar internal configuration as found in the Sony SVR-2000 as described above.  
         [0044]    The s-video/RCA signal  406  of the input television signal  110  is input into the encoder  204  to be encoded according to the MPEG2 standard. Note that the s-video/RCA signal  406  is in digital format; thus, the A/D converter  202  is not needed. Next, the encoded signal is passed to the media switch  402 , which is coupled to the hard drive  404  and the decoder  206 . The media switch  402  outputs the output television signal  112  to the television.  
         [0045]    The media switch  402  is typically in the form of an application specific integrated circuit (ASIC) chip that acts as a gate or switch to control the flow of television signals therethrough. For example, as is common, the media switch  402  is open or closed depending on the whether the user has selected RF channel 2, 3, or 4. Such media switches  402  are well known in the art. The media switch  402  routes the encoded signal from the encoder  204  to be stored on the hard drive  404 . It is noted that in some digital delivery systems, such as via a satellite delivery system, the input signal may be already encoded according to the MPEG2 standard, or other suitable standard; thus, the encoder  204  is optional.  
         [0046]    Next, the decoder  206  retrieves the encoded stored data from the hard drive  404  via the media switch  400  and decodes the data using the same coding scheme, e.g., MPEG2. In one embodiment, the decoder  206  then converts the signal to analog, in the event the television is an analog television. Then, the decoder  206  outputs the decoded video signal via the media switch  402  as the output television signal  112 .  
         [0047]    It is noted that the television input signal  110  that is coupled to the encoder  204  in the Sony SVR-2000 is the signal received from s-video inputs and RCA inputs, i.e., the s-video/RCA signal  406 , to the digital network recorder, while the RF connectors are not used. S-video, RCA and RF connectors are well known in the art of video equipment.  
         [0048]    As stated above, when the digital network recorder is booting up, i.e. the operating system is being loaded from the hard drive into random access memory, the encoder  204 , the decoder  206  and the media switch  402  are not outputting an output television signal  112 ; thus, the user is unable to view any television signal. It is only after the operating system has loaded and verified the functionality of the digital network recorder that the internal loop of recording and then outputting the television signal to the television can begin. This results in the viewer having to endure several minutes of waiting to see the programming.  
         [0049]    Similarly, in the event of a hard drive crash or failure, the decoder  206  will cease to output the output television signal  112  and again, the viewer will be unable to view any television programming at the television. Thus, the output television signal will not reach the television, so that the viewer will not see anything on the television screen.  
         [0050]    Referring next to FIG. 5, an internal block diagram of one embodiment of the digital network recorder of FIG. 3 is shown in accordance with one embodiment of the invention. Illustrated are the television input signal  110  comprising the s-video/RCA signal  406  and an RF connector signal  502 , the encoder  204 , the media switch  402 , the decoder  206 , the hard drive  404 , the switch  302 , and the output television signal  112 . This embodiment of the invention differs from the system of FIG. 4 in that the switch  302  is coupled to the output of the media switch  402 . As such, the switch  302  inputs the output of the decoder  206  (via the media switch  402 ) and also the RF connector signal  502  of the input television signal  110 . The output of the switch  302  is the output television signal  112 , which is either the raw input television signal  110  (i.e., the signal in the RF connector signal  502 ) or the decoder  206  output. Thus, the input television signal  110  is coupled to both the encoder  204  (via the s-video/RCA signal  406  in digital format) and also to the switch  302  (via the RF connector signal  502  in analog format).  
         [0051]    The switch  302  is as described with reference to FIG. 3, in that it is configured to output the raw input television signal (i.e. the RF connector signal  502 ), unless there is an output from the decoder  206  (via the media switch  402 ). Advantageously, the RF connector signal  502  has not digitized, encoded, stored, or decoded at all. It is merely in the raw input television signal  110 . Thus, the raw input television signal  110  passes through the digital network recorder. In the event that there is an output at the decoder  206 , then the raw input television signal is overwritten by the output of the decoder  206 . Thus, when there is no output signal from the decoder, the output television signal is the raw input television signal and when there is an output at the encoder/decoder, then the output television signal is the output signal from the encoder/decoder which is continuously being recorded.  
         [0052]    Advantageously, as described with reference to FIG. 3, this system covers the boot up scenario as well as the hard drive crash scenario. Furthermore, as described above, the switch  302  may be embodied as an embedded chip which will retain its memory in the event of power loss, such as an EPROM chip. Alternatively, the switch  302  may be a MOSFET used for RF switching in VCRs and DVDs.  
         [0053]    In other embodiments, the switch  302  is not required; however, the passthrough is implemented in software by the operating system. For example, the operating system will instruct the media switch  402  to output the raw input television signal when the decoder  206  is not ready. In such embodiments, a non-encoded input television signal is coupled to the media switch  402 , instead of to the switch  302 . For example, the RF connector signal  502  is coupled to the media switch  402 . However, in such embodiments, if there is a failure of the operating system which would control the RF passthrough, then the media switch  402  will not be instructed to output the raw input television signal (i.e. the RF connector signal  502 ) and again, the viewer will not see any programming. Furthermore, in the boot up scenario, there will be some wait period for the operating system to load enough to be able to issue an instruction to media switch to pass the raw input television signal  110  through to the television. This embodiment could be used with the system of FIG. 2, although the software of the operating system would need to be altered. One skilled in the art of programming could easily create the proper software to cause the media switch  402  to output the raw input television  110  and then the recorded signal once the decoder  206  was ready. Additionally, the raw input television signal  110  should be coupled to the media switch  402 .  
         [0054]    Referring next to FIG. 6, a flowchart is shown of the steps performed by the digital network recorder of FIGS. 3 and 5 in accordance with another embodiment of the invention. Initially, the output of the video decoder is monitored (Step  602 ). For example, the switch  302  of FIGS. 3 and 5 will detect the presence of a signal output from the decoder  206  preferably by simply detecting when an output video signal from the video decoder is received at the switch (via the media switch or via the D/A converter). The switch can easily detect the first bit of an incoming digital signal or the presence of an analog signal (if the video output of the decoder has been converted back to analog) at the input to the switch. Alternatively, in other embodiments, the operating system monitors the output of the video decoder. Furthermore, the video decoder itself may be configured to send a notification to the switch and/or operating system that it is correctly outputting a video signal. If there is no output at the video decoder (Step  604 ), then the raw input television signal is output to the television (Step  606 ). Then, the system will continue to monitor the output of the video decoder (Step  602 ).  
         [0055]    If there is an output at the video decoder (Step  604 ), i.e. the digital network recorder has recorded and retrieved the recorded signal to be output to the television, then the output video signal from the video decoder is output to the television (Step  608 ). Note that the output video signal from the decoder is an audio/video signal representing the input television signal. The system then continues to monitor the output of the video decoder (Step  602 ) to see if there has been any changes.  
         [0056]    Advantageously, this covers the situation where the operating system is booting up, since the video decoder will not output a signal yet, the raw input television signal is passed through as the output television signal. When the operating system is fully loaded and the encoder/decoder loop is functioning, then the recorded output at the decoder is output as the output television signal. Likewise, if there is a crash in the hard drive or failure in the operating system, the decoder will cease to have an output and the raw input television signal will be output as the output television signal. Thus, the viewer will not have to endure several minutes of booting up every time the digital network recorder is powered up. Similarly, in the event of hard drive crash or software failure, the user will be able to view the raw input television signal.  
         [0057]    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.