Abstract:
A video system for presenting content from a content provider to a user includes a tuner to select a program from a plurality of programs. The tuner outputs the selected program at an analog output when the selected program is represented by an analog signal. An analog output port is coupled to the analog output of the tuner, and is configured to be connectable to a storage device to record the selected program represented by an analog signal. An analog signal processing circuit is coupled to the analog output of the tuner to receive the analog signal representing the selected program from the tuner and to generate a digital representation of the analog signal. A first interface module is configured to be connectable to the storage device to receive recorded programs from the storage device. An overlay module is coupled to the analog signal processing circuit and to the first interface module. The overlay module selectively overlays information to a program received from one of the analog signal processing circuit and the first interface module.

Description:
This application is a continuation-in-part of U.S. application Ser. No. 09/585,249, filed on May 31, 2000 now U.S. Pat. No. 6,442,328, and U.S. application Ser. No. 09/605,623, filed on Jun. 28, 2000 now U.S. Pat. No. 6,751,402. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to information storage and display systems utilizing rotating storage drives, and more particularly, to video recording systems that record video data streams. 
   2. Description of the Related Art 
   Digital video recorders provide the capability of concurrently recording incoming streaming video data using hard disk drive technology and playing back previously recorded video data. As currently available, a digital video recorder receives incoming streaming video data from the output interface of a standard set-top box configured to receive the broadcast signals from a multiple-service operator (MSO), such as a cable provider, and the output of the digital video recorder is transmitted directly to a display device, such as a television. Such standard set-top boxes typically have only one input interface and one output interface. In response to commands from the user, the digital video recorder transmits to the display device either the incoming streaming video data from the output of the set-top box or the previously recorded video data. 
   Because currently available digital video recorders receive their input from the standard output interfaces of currently available set-top boxes, such digital video recorders require numerous components which are duplicates of components already utilized by the set-top boxes. For example, in order to view digital broadcast channels using a standard television, a set-top box must convert the input digital broadcast channels into output video signals which conform to a standard format for composite video, such as the National Television Standards Committee (NTSC) standard. This standard output format is generated by various components in the set-top box, such as a transport demultiplexer (“DEMUX”), an MPEG decoder, and an NTSC encoder. Additionally, the output from the set-top box may contain information from an on-screen display module. This information may represent programming information. The information may also list specialty capabilities such as picture-in-picture, which the user can enable. A digital video recorder compatible with such a configuration must convert the NTSC composite video received from the set-top box back into digital form for storage, and then reconvert again to NTSC composite video to play back the stored video signals. Therefore, just as the set-top box did, the digital video recorder requires a transport DEMUX, an MPEG decoder, and an NTSC encoder, which effectively duplicate components and functions of the set-top box. 
   Similarly, currently available digital video recorders also include a standard input interface that receives the output from the set-top box, and a modem that is configured to receive electronic program guide information from the MSO. Both the input interface and the modem of the digital video recorder duplicate components or functions found in currently available set-top boxes. 
   There is, therefore, a need to provide the capabilities of currently available digital video recorders and set-top boxes, while also enabling the reduction of the redundancy of functions and components among these digital video recorders and set-top boxes. 
   SUMMARY OF THE INVENTION 
   The present invention may be regarded as a video system for presenting content from a content provider to a user. The video system includes a tuner to select a program from a plurality of programs, wherein the tuner outputs the selected program at an analog output when the selected program is represented by an analog signal. An analog output port is coupled to the analog output of the tuner, and is configured to be connectable to a storage device to record the selected program represented by an analog signal. An analog signal processing circuit is coupled to the analog output of the tuner to receive the analog signal representing the selected program from the tuner and to generate a digital representation of the analog signal. A first interface module is configured to be connectable to the storage device to receive recorded programs from the storage device. An overlay module is coupled to the analog signal processing circuit and to the first interface module. The overlay module selectively overlays information to a program received from one of the analog signal processing circuit and the first interface module. 
   The present invention may be further regarded as a method of presenting content from a content provider to a user. The method selects a program from a plurality of programs and outputs the selected program at an analog output if the selected program is represented by an analog signal. The method provides the analog signal that represents the selected program at an analog output port to which a storage device is connectable for recording the selected program on the storage device. Further, the method converts the analog signal to a digital representation of the analog signal. The method overlays information to a selected one of a program represented by the analog signal, and a recorded program retrievable from the storage device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically illustrates a digital video recorder in accordance with an embodiment of the present invention, the digital video recorder connectable to an auxiliary interface of a set-top box that provides a video data stream to a display device based on selection between recorded video signal received from the digital video recorder and a real-time video signal. 
       FIG. 2  schematically illustrates an exemplary embodiment of the present invention wherein the digital video recorder and set-top box are configured to be compatible with digital video programming. 
       FIG. 3  schematically illustrates an exemplary embodiment of the present invention wherein the digital video recorder and set-top box are configured to be compatible with analog video programming. 
       FIG. 4  is a flow diagram in accordance with an embodiment of the present invention, in which the digital video recorder is connectable to an auxiliary interface of a set-top box that provides a video data stream to a display device based on selection between recorded video signal received from the digital video recorder and a real-time video signal. 
       FIG. 5  schematically illustrates another embodiment of the present invention, in which the digital video recorder and the set-top box are configured to be compatible with analog video programming and digital video programming. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  schematically illustrates a digital video recorder  200  in accordance with an embodiment of the present invention. The digital video recorder  200  is connectable to a set-top box  100  that includes a video input interface  110  that receives a broadcast signal  102 , a video output interface  120  that provides an output video data stream  104  to a display device  300 . The set-top box  100  has at least one auxiliary interface  130  that supports connection of the digital video recorder  200  to the set-top box  100 , a microprocessor  140  that generates a command in response to user input  142  that initiates a playback interval, and a multiplexer  150  coupled to the video output interface  120  and the microprocessor  140 . The set-top box  100  is configured to (a) use the video input interface  110  to generate a real-time video signal  106 , (b) recognize connection of the digital video recorder  200  to the set-top box  100  and subsequently continuously provide the real-time video signal  106  to the digital video recorder  200 , and (c) receive a recorded video signal  108  from the digital video recorder  200  during the playback interval. The digital video recorder  200  comprises at least one recorder interface  210  for connecting the digital video recorder  200  to the auxiliary interface  130  of the set-top box  100 . The recorder interface  210  continuously receives the real-time video signal  106  from the set-top box  100  and provides the recorded video signal  108  to the set-top box  100  during the playback interval. The digital video recorder  200  further comprises a disk  220  and a video data stream manager  230 . In response to the real-time video signal  106 , the video data stream manager  230  provides a first video stream  222  to store a selected video segment on the disk  220 . In response to the command from the microprocessor  140 , the video data stream manager  230  receives a second video stream  223  based on the selected video segment stored on the disk  220  to generate the recorded video signal  108 . The multiplexer  150  of the set-top box  100  selects the real-time video signal  106  during a real-time interval and selects the recorded video signal  108  during the playback interval to generate the output video data stream  104  that is provided to the display device  300 . 
   In one embodiment of the present invention, the broadcast signal  102  is transmitted from a multiple-service operator, also known as an MSO. MSOs are video data service providers that supply video programming to multiple users. Examples of MSOs include, but are not limited to, cable television systems and satellite systems. Alternatively, the broadcast signal  102  can be received from UHF or VHF broadcast signals using an antenna. The broadcast signal  102  is typically in the form of analog rf signals containing video programming from multiple channels, and it may carry the video programming in analog or digital form. 
   In the preferred embodiment of the present invention, the microprocessor  140  of the set-top box  100  controls the operation of both the set-top box  100  and the digital video recorder  200  in response to user input  142  and electronic program guide information  144 . By communicating with the video data stream manager  230  of the digital video recorder  200 , the microprocessor  140  recognizes the connection of the digital video recorder  200  to the set-top box  100  and receives information regarding the first video stream  222  provided by the video stream manager  230  in response to the real-time video signal  106  to store the selected video segment on the disk  220 . The microprocessor  140  also commands the video data stream manager  230  to receive the second video stream  223  based on the selected video segment stored on the disk  220  during a playback interval initiated by the user input  142 . By communicating with the multiplexer  150  of the set-top box  100 , the microprocessor  140  determines whether the real-time video signal  106  or the recorded video signal  108  is used to generate the output video data stream  104  provided to the display device  300 . Times at which the real-time video signal  106  is used are denoted as real-time intervals, and times at which the recorded video signal  108  is used are denoted as playback intervals. 
   The user input  142  includes commands from the user to control various operation parameters of the set-top box  100  and the digital video recorder  200 , such as record, playback, and display commands. In certain embodiments, the user input  142  includes the user turning on the set-top box  100  or the digital video recorder  200 . Alternatively, the user input  142  is a playback command. The user input  142  is generated by the user using an appropriate communication technology, such as remote control devices or keypad devices. Persons skilled in the art are able to select an appropriate communication technology for the user to generate the user input  142 . 
   The electronic program guide information  144  contains information regarding the broadcast schedules from various broadcast channels. In the embodiment illustrated in  FIG. 1 , the electronic program guide information  144  is a database containing information regarding the broadcast schedules from various broadcast channels. This information is typically expressed in the form of a program grid with columns denoting the time periods, and with separate rows for each of the available broadcast channels. In one embodiment, the electronic program guide information  144  is communicated to the microprocessor  140  via a separate input channel (e.g., via a phone line connection). Alternatively, in other embodiments of the present invention, the electronic program guide information  144  is received from the broadcast signal  102 . In addition, the electronic program guide information  144  is temporarily stored in memory. The memory may be dedicated flash memory within the set-top box  100  or the digital video recorder  200 . The memory may also be a portion of the disk  220  of the digital video recorder  200 . Typically, the electronic program guide information  144  is communicated to the user by displaying it directly on the display device  300  being viewed by the user. The user may then provide appropriate user input  142  to the microprocessor  140 , which uses the electronic program guide information  144  to generate appropriate commands. Persons skilled in the art are able to select an appropriate configuration of the electronic program guide information  144  and the method of communicating its information to both the user and the microprocessor  140  compatible with the present invention. 
     FIG. 2  schematically illustrates one embodiment of the present invention compatible with a digital programming channel. Note that other embodiments of the present invention are compatible with analog programming channels, or both analog and digital programming channels. The video input interface  110  comprises a video tuner  112  that receives the broadcast signal  102 , a quadrature amplitude modulation (QAM) demodulator  113 , and a conditional access module  114 . In response to commands from the microprocessor  140  in response to the user input  142 , the video tuner  112  selects one transponder signal from the multiple transponder signals contained in the broadcast signal  102 , and transmits the selected transponder signal to the QAM demodulator  113 , which converts the analog rf signal into a digital signal. This digital signal corresponding to the selected transponder signal is a digitally-formatted video data stream compressed under an MPEG (Motion Pictures Experts Group) standard, such as MPEG-2 or MPEG-4, and is transmitted to the conditional access module  114 . In other alternative embodiments, the selected transponder signal is compressed with other compression standards, including but not limited to, wavelet compression, motion JPEG compression, and DV25 compression. This digital signal contains approximately six separate digital video channels, and the conditional access module  114  selects one of these digital video channels in response to commands from the microprocessor  140  in response to the user input  142 , and generates a compressed single program transport stream representation of the real-time video signal  106  that is transmitted to the multiplexer  150  and to the auxiliary interface  130 . 
   During a real-time interval, defined as times in which the user input  142  indicates that the user wants to view the broadcast signal  102  in real-time, the microprocessor  140  commands the multiplexer  150  to transmit the real-time video signal  106  from the conditional access module  114  to the video output interface  120 . In the preferred embodiment illustrated in  FIG. 2 , the video output interface  120  comprises a transport demultiplexer (“DEMUX”)/MPEG decoder  122 , an on-screen display (OSD) module  124  comprising a display multiplexer, and an NTSC encoder  126 . The transport DEMUX/MPEG decoder  122  sorts out and synchronizes the compressed single program transport stream representation of the real-time video signal  106  from the multiplexer  150 , discarding unneeded MPEG packets and generating a decompressed digital signal transmitted to the OSD module  124 . The OSD module  124  can mix text, graphics, or additional video images selected by its display multiplexer with the decompressed digital signal from the transport DEMUX/MPEG decoder  122  to generate digital signals containing electronic program guide information  144 , system status information, picture-in-picture, or other specialty displays requested by the user. The output video data stream  104  generated by the NTSC encoder  126  in response to the digital signal from the OSD module  124  is then transmitted to the display device  300 , typically a television. In other embodiments, the NTSC encoder  126  is replaced by an encoder compatible with another standard composite video format, including but not limited to, PAL or RGB. 
   Concurrently, the compressed single program transport stream representation of the real-time video signal  106  from the conditional access module  114  is also transmitted to the auxiliary interface  130 . The microprocessor  140  communicates with the video data stream manager  230  of the digital video recorder  200  via the auxiliary interface  130  and the recorder interface  210 . Upon recognizing connection of the digital video recorder  200  to the set-top box  100 , the microprocessor  140  commands the auxiliary interface  130  to continuously transmit the real-time video signal  106  to the recorder interface  210  of the digital video recorder  200 . 
   In the preferred embodiment illustrated in  FIG. 2 , the auxiliary interface  130  supports isochronous communication compatible with the IEEE 1394 standard, which is described in the “IEEE Std 1394-1995 IEEE Standard for a High Performance Serial Bus,” Aug. 30, 1996, which is incorporated by reference herein. The recorder interface  210  also supports isochronous communication compatible with the IEEE 1394 standard. In other embodiments, the auxiliary interface  130  and the recorder interface  210  also include asynchronous or synchronous communication capabilities to communicate various commands and information between the microprocessor  140  and the video data stream manager  230 . 
   In particular embodiments of the present invention, the auxiliary interface  130  and the recorder interface  210  include the capability to encrypt the real-time video signal  106  sent to the video data stream manager  230  to provide protection from unauthorized copying or transporting of stored video data by removing the digital video recorder  200  and reattaching it to a different set-top box  100 . Similarly, the auxiliary interface  130  and the recorder interface  210  advantageously include the capability to decrypt the recorded video signal  108  sent to the multiplexer  150  from the video data stream manager  230 . 
   In the preferred embodiment, the auxiliary interface  130  and the recorder interface  210  are compatible with DTLA (“Digital Transmission Licensing Administrator”) copying protection utilizing authentication key exchange. DTLA copy protection is a well-known copy protection system, compatible with the IEEE 1394 standard, and is described in “Digital Transmission Content Protection Specification Revision 1.0,” Mar. 17, 1999, which is incorporated by reference herein. By applying DTLA copy protection to the real-time video signal  106  and the recorded video signal  108  transmitted between the auxiliary interface  130  and the recorder interface  210 , the real-time video signal  106  and the recorded video signal  108  are protected from unauthorized copying. 
   Upon continuously receiving the real-time video signal  106  from the auxiliary interface  130 , the recorder interface  210  generates a single program transport stream representation of the real-time video signal  106 , which is transmitted to the video data stream manager  230 . The video data stream manager  230  provides a first video stream  222  in response to the real-time video signal  106  to store a selected video segment on the disk  220 . In the preferred embodiment of the present invention, the disk  220  is a component of a rotating storage drive (e.g., a hard disk drive) compatible with the IEEE 1394 standard. Alternatively, the disk  220  can be a component of a writable digital video disk (DVD) drive, or of a drive that utilizes another technology that provides writable non-volatile storage. 
   Upon receiving a playback command from the user input  142 , the microprocessor  140  transmits an appropriate playback command to the multiplexer  150  and to the video data stream manager  230 , thereby terminating the real-time interval, and initiating a playback interval. Processing of the incoming broadcast signal  102  and the recording of the real-time video signal  106  continue during the playback interval as they had during the real-time interval. In response to the playback command from the microprocessor  140 , the video data stream manager  230  receives a second video stream  223  based on the selected video segment previously stored on the disk  220 . The second video stream  223  is used by the video data stream manager  230  to generate a single program transport stream representation of the recorded video signal  108 , which is transmitted to the recorder interface  210 . The recorder interface  210  transmits the recorded video signal  108  to the multiplexer  150  via the auxiliary interface  130  of the set-top box  100 . 
   In response to the playback command from the microprocessor  140 , the multiplexer  150  transmits the recorded video signal  108  to the video output interface  120 . In response to the recorded video signal  108 , the video output interface  120  then transmits an output video data stream  104  to the display device, thereby permitting the user to view previously stored video images. In addition, by utilizing the auxiliary interface  130  and the recorder interface  210  to transfer data streams between the set-top box  100  and the digital video recorder  200 , the digital video recorder  200  does not require an additional video input interface capable of receiving the broadcast signal  102  or an additional video output interface capable of transmitting an output video data stream  104  directly to a display device  300 . Furthermore, by sharing the electronic program guide information  144  with the set-top box  100 , the digital video recorder  200  does not need a modem connected to the MSO to provide programming information. In this way, the redundancy of components and functions between the set-top box  100  and the digital video recorder  200  is reduced, thereby providing a more cost-effective alternative to currently available systems. 
     FIG. 3  schematically illustrates one embodiment of the present invention compatible with an analog programming channel. The video input interface  110  comprises a video tuner  112  that receives the broadcast signal  102  and comprises an analog descrambler  115 . In response to commands generated by the microprocessor  140  in response to the user input  142 , the video tuner  112  selects one broadcast channel from the multiple broadcast channels contained in the broadcast signal  102  and transmits the selected broadcast channel to the analog descrambler  115 . In response to the selected broadcast channel, the analog descrambler  115  generates a baseband composite video representation of the real-time video signal  106 . The analog descrambler  115  provides the capability to view broadcast channels which require descrambling (e.g., for premium channels which are only accessible by a user for an additional fee). Non-scrambled broadcast channels and non-accessible scrambled broadcast channels are transmitted through the analog descrambler  115  without descrambling. In embodiments where there is no need to descramble any of the broadcast channels, the analog descrambler  115  is not included in the set-top box  100 , and the video tuner  112  generates a baseband composite video representation of the real-time video signal  106 . The baseband composite video representation of the real-time video signal  106  generated by the analog descrambler  115  is transmitted to the auxiliary interface  130  and to a video digitizer  125  coupled to the OSD module  124  of the video output interface  120 . 
   The video digitizer  125  generates a digital representation of the real-time video signal  106  in response to the baseband composite video representation of the real-time video signal  106  from the analog descrambler  115 . The digital representation of the real-time video signal  106  is then transmitted to the OSD module  124 , which comprises a display multiplexer  151 . During a real-time interval (i.e., times in which the user wants to view the broadcast signal  102  in real-time), the microprocessor  140  commands the display multiplexer  151  of the OSD module  124  to transmit the real-time video signal  106  to the NTSC encoder  126 . In response to the real-time video signal  106 , the NTSC encoder  126  generates an output video data stream  104  which is transmitted to the display device  300 . 
   Concurrently, the baseband composite video representation of the real-time video signal  106  from the analog descrambler  115  is also transmitted to the auxiliary interface  130 . In the embodiment illustrated in  FIG. 3 , the at least one auxiliary interface  130  comprises an analog auxiliary interface  132  which receives the baseband composite video representation of the real-time video signal  106 . The at least one auxiliary interface  130  also comprises a digital auxiliary interface  134  that supports isochronous communication compatible with the IEEE 1394 standard and DTLA copy protection. Similarly, the at least one recorder interface  210  of the digital video recorder  200  comprises an analog recorder interface  212  and a digital recorder interface  214  that supports isochronous communication compatible with the IEEE 1394 standard and DTLA copy protection. 
   The analog auxiliary interface  132  continuously transmits the real-time video signal  106  via the analog recorder interface  212  to an MPEG encoder  216 . In response to the continuously received real-time video signal  106 , the MPEG encoder generates a single program transport stream representation of the real-time video signal  106 , which is transmitted to the video data stream manager  230 . In response to the real-time video signal  106 , the video data stream manager  230  provides a first video stream  222  to store a selected video segment on the disk  220 . 
   Upon receiving a playback command from the user input  142 , the microprocessor  140  transmits an appropriate playback command to the multiplexer  150 , to the display multiplexer  151 , and to the video data stream manager  230 , thereby terminating the real-time interval and initiating a playback interval. The processing of the incoming broadcast signal  102  and the recording of the real-time video signal  106  continue during the playback interval as they had during the real-time interval. In response to the playback command from the microprocessor  140 , the video data stream manager  230  receives a second video stream  223  based on the selected video segment previously stored on the disk  220 . The second video stream  223  is used by the video data stream manager  230  to generate a single program transport stream representation of the recorded video signal  108 , which is transmitted to the digital recorder interface  214 . The digital recorder interface  214  transmits the recorded video signal  108  to the multiplexer  150  via the digital auxiliary interface  134  of the set-top box  100 . 
   In response to the playback command from the microprocessor  140 , the multiplexer  150  transmits the recorded video signal  108  to the video output interface  120 . The video output interface  120  comprises the transport DEMUX/MPEG decoder  122 , the OSD module  124 , and the NTSC encoder  126 . In response to the playback command from the microprocessor  140 , the display multiplexer  151  of the OSD module  124  responds to the recorded video signal  108  from the transport DEMUX/MPEG decoder  122  in generating the output video data stream  104  transmitted to the display device  300 , thereby permitting the user to view previously stored video images. Note that in this particular embodiment, the display multiplexer  151  in the OSD module  124  of the video output interface  120  performs the actual selection between the real-time video signal  106  and the recorded video signal  108 . This preferred embodiment of the present invention reduces the redundancy of components and functions between the set-top box  100  and the digital video recorder  200 , thereby providing a more cost-effective alternative to currently available systems. 
     FIG. 4  is a flow diagram in accordance with an embodiment of the present invention, in which the digital video recorder  200  is connectable to an auxiliary interface  130  of a set-top box  100  that provides video data stream to a display device  300  based on selection between recorded video signal  108  received from the digital video recorder  200  and a real-time video signal  106 . The flow diagram is described with reference to the set-top box  100  and the digital video recorder  200  illustrated in  FIG. 1 . Persons skilled in the art are able to recognize that, while the flow diagram illustrates a particular embodiment with steps in a particular order, other embodiments with different orders of steps are also compatible with the present invention. 
   In a step  410 , the recorder interface  210  of the digital video recorder  200  is connected to the auxiliary interface  130  of the set-top box  100 . The set-top box includes the video input interface  110 , the video output interface  120 , the microprocessor  140  that generates a command in response to user input  142  that initiates a playback interval, and a multiplexer  150  coupled to the video output interface  120  and the microprocessor  140 . The digital video recorder  200  includes a disk  220  and a video data stream controller  230 . 
   In a step  420 , the connection of the digital video recorder  200  to the set-top box  100  is recognized by the microprocessor  140  through communications between the microprocessor  140  and the video data stream manager  230 . In the preferred embodiment of the present invention, this communication is asynchronous, and occurs via the auxiliary interface  130  and the recorder interface  210 . Alternatively, the microprocessor  140  and the video data stream manager  230  utilize synchronous communication. 
   In a step  430 , the real-time video signal  106  is generated in response to the broadcast signal  102 . The broadcast signal  102  is received by the video input interface  110  of the set-top box  100 . 
   In a step  440 , the real-time video signal  106  is continuously provided to the multiplexer  150  and to the video data stream manager  230  of the digital video recorder  200 . The real-time video signal  106  is continuously provided to the video data stream manager  230  via the auxiliary interface  130  and the recorder interface  210 . 
   In a step  450 , the first video stream  222  is provided to store the selected video segment on the disk  220 . The first video stream  222  is provided by the video data stream manager  230  in response to the real-time video signal  106 . 
   In a step  460 , the video data stream manager  230  receives the second video stream  223  in response to the command from the microprocessor  140 . The video data stream manager  230  receives the recorded video signal  108  in response to the second selected video stream  223 . The playback interval is signified by a command from the microprocessor  140  in response to the user input  142 . 
   In a step  470 , the recorded video signal  108  is provided to the multiplexer  150  via the recorder interface  210  and the auxiliary interface  130  during the playback interval. 
   In a step  480 , the multiplexer  150  selectively transmits the real-time video signal  106  during the real-time interval and selectively transmits the recorded video signal  108  during the playback interval. In a step  490 , the output video data stream  104  is transmitted to the display device  300 . The output video data stream  104  is generated by the video output interface  120  in response to the selectively transmitted video signal from the multiplexer  150 . 
     FIG. 5  schematically illustrates another embodiment of the present invention, in which the digital video recorder  200  and the set-top box  100  are configured to be compatible with analog video programming and digital video programming. The set top box  100  is connected to the digital video recorder  200  as described above. As the embodiment of  FIG. 3 , the set top box  100  includes the tuner  112 , the OSD module  124 , the video digitizer  125 , the transport DEMUX/MPEG decoder  122  and the NTSC encoder  126 . 
   The tuner  112  has an analog output  112 A for the analog signal and a digital output  112 B for a digital signal. The analog output  112 A is part of an analog branch that extends between the tuner  112  and the OSD module  124 . The digital output  112 B is part of a digital branch that extends between the tuner  112  and the OSD module  124 . 
   The analog branch includes the video digitizer  125 , which provides for analog signal processing, and an IF module  252 , wherein the IF module  252  is coupled to the analog output  112 A of the tuner  112 , to the video digitizer  125  via a connection  262  and to an analog output port  254  via a connection  264 . The IF module  252  transforms the analog signal received from the tuner  112  into the baseband. 
   The digital branch includes the QAM demodulator  113  (“QAM DEMOD”), the conditional access module  114  and the transport DEMUX/MPEG decoder  122 . The QAM demodulator  113  is connected to the digital output  112 B of the tuner  112  and to the conditional access module  114 . An output of the conditional access module  114  is connected to the transport DEMUX/MPEG decoder  122  and to the interface module  134 . The transport DEMUX/MPEG decoder  122  is connected to the OSD module  124 . A connection  260  connects the interface module  134  to an output of the conditional access module  114  and to an input of the transport DEMUX/MPEG decoder  122 . Further, a connection  256  connects the interface module  134  to the digital video recorder  200 . 
   The components of the digital branch process the digital signal received from the tuner  112  and either forward the digital signal to the digital video recorder  200  for recording a selected program or to the display device  300  connected to the set top box  100 . Further, the components of the digital branch process digital signals received from the digital video recorder  200  prior to forwarding the processed signals to the display device  300  during playing back a selected program. 
   The digital video recorder  200  connected to the set top box  100  includes a video digitizer  125 A, the MPEG encoder  216 , the video data stream manager  230  and the disk  220 . The video data stream manager  230  is further connected to an interface  250  which is in communication with the interface  134  via the connection  256 . The video digitizer  125 A receives the analog signal from the tuner  112  via the analog output port  254  and a connection  258 . The components of the digital video recorder  200  operate as described above. 
   In accordance with the present invention, the digital video recorder  200  is releasably connected to the set top box  100 . More particularly, the digital video recorder  200  is releasably connected to the analog output port  254  via the connection  258 , and to the interface  134  via the connection  256 . One advantage of the system is that the digital video recorder  200  receives the analog signal that represents a selected program from the tuner  112 , i.e., before any overlay information is added to the program. The digital video recorder  200 , therefore, records the program without the overlay information.