Abstract:
A digital television receiver comprises a receiving means having selectable first and second inputs. The first input receives a broadcast digital television signal and the second input receives a digital television signal from a reproduction apparatus, and generates a video signal for display. A generating means is coupled to the receiving means for generating a display message responsive to display message data derived from the selected input and combining the display message with said video signal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of application Ser. No. 09/029,807, filed May 29, 1998 now U.S. Pat. No. 7,321,717. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the display of digital video signals and in particular to coupling of reproduced digital video signals between equipment components. 
     BACKGROUND OF THE INVENTION 
     A digital video signal may be processed to form a bit stream having a reduced bit rate. Such processing for bit rate reduction may be implemented according to an MPEG compression method, and may be formatted, for example, with an MPEG compatible structure, such as that employed in a digital satellite system, for example DSS™ or the proposed Grand Alliance or GA terrestrial system. 
     A consumer video recorder may be adapted to provide recording capabilities for both analog signals and digitally encoded signals processed for example, for compatibility with an MPEG standard and having GA or DSS™ signal formats. The adapted consumer video recorder may be considered as two electronic systems within one box, sharing a recording mechanism, servo and control systems. A conventional analog recording method may be employed where an analog luminance signal component frequency modulates an RF carrier and an analog chrominance signal component amplitude modulates a second RF carrier. When reproduced, the two modulated signals are demodulated, combined and coupled out for video display. 
     During both record and replay operating modes, on-screen display messages may indicate operational status, warning conditions, tape duration, record time, time code etc., of the video recorder. These on-screen display messages or OSDs may be added to the analog video output signal to provide the user with recorder status information. 
     Digital recording may be achieved by using the consumer video recorder as a digital bit stream recorder/reproducer. The MPEG compatible bit stream, for example transport packets, may be recorded by reformatting the transport packets to facilitate recording and reproduction. For example, the transport packets may be buffered and error detection and correction data words computed and added. The bit stream with error correction added may be formatted into recording data blocks or sync blocks containing a predetermined number of bytes which may be accommodated in each recorded track. The sync block signal may be coded to render the signal more suitable for digital recording, for example, to remove any DC component, or provide spectral shaping of the recorded signal, such modulation may be produced by “code book” type encoding. In a playback mode the recording processes are effectively reversed, for example, the “code book” encoding is decoded, errors are detected and corrected and the sync block formatting is removed restoring the bit stream to the original MPEG like format. 
     Although system interconnection and control between a digital signal source and monitor display may be simplified by the use of a bi-directional data bus, any interconnection additional to that of an analog system may present the user with installation complexity and confusion. In addition, status or warning messages originating from the recording or reproducing device are required for on screen display during all operational modes. 
     U.S. Pat. No. 5,097,349, issued 17 Mar. 1992 to Pioneer, shows a system in which picture information is recorded as a subcode within audio information. The picture information may subsequently be displayed on an alpha-numeric display or a television display. 
     SUMMARY OF THE INVENTION 
     Recorder or player status, warnings or timer displays which, for reasons described above are absent during digital operating modes are advantageously provided by the following inventive arrangements. A digital television receiver comprises a receiving means having selectable first and second inputs. The first input receives a broadcast digital television signal and the second input receives a digital television signal from a reproduction apparatus, and generates a video signal for display. A generating means is coupled to the receiving means for generating a display message responsive to display message data derived from the selected input and combining the display message with said video signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts in block diagram form packetized signal sources coupled for decoding and display. 
         FIG. 2  shows an exemplary block diagram including various inventive embodiments. 
         FIG. 3  is an exemplary block diagram showing a simplified switch including various inventive embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A simplified consumer digital audio video system is illustrated in  FIG. 1 . Sources of packetized, compressed audio video and control data are shown coupled for decoding and display. A receiver, IRD  100  is depicted coupled to a receiving antenna  50 , however, a modulated signal may be provided from a cable distribution network (not shown). The modulated packetized signal is tuned, demodulated and a user determined program is separated within the block indicated as PACKET SOURCE  109 . An output of PACKET SOURCE  109  comprises a transport packet stream of audio video and control data which is MPEG decoded to produce audio and video signals by DECODER  117 . The output from DECODER  117  is coupled for monitoring by display  300 . Other sources of packetized signals are shown coupled with a dotted line as alternative data streams for MPEG decoding by decoder  117 . Thus DECODER  117  may be utilized to decode transport streams from external packet sources thereby reducing the cost of these other sources. For example, PACKET SOURCE  75  may represent a computer forming a packetized output signal. Such a signal may be derived from a computer memory, or may originate from an external source such as a computer network. Such a computer source may reproduce compressed audio video and control data from disk memory. In addition, PACKET SOURCE  75  may represent a digital video disk player such as, for example, a DVD format device. A further source of transport packets may be provided by a magnetic tape player recorder, PACKET SOURCE  200 , which may have a format in accordance with, for example, D-VHS or DVC standards. 
     A simplified consumer digital video receiver, recorder and display system is illustrated in the exemplary block diagram of  FIG. 2 . The system employs a digital video signal source, for example an integrated receiver decoder or IRD  100 , an audio video monitor display device  300  and a digital video cassette recorder  200 , for example employing a D-VHS or DVC format. In the illustrated system, a digital video representative signal is modulated on an RF carrier and received by an antenna  50 . Antenna  50  is coupled to an integrated receiver decoder IRD  100 . However, a modulated carrier may be delivered to receiver  100  by a cable distribution system (not shown). The integrated receiver decoder  100  is tuned to the RF carrier frequency and demodulates therefrom an MPEG compatible transport data stream modulation. 
     The transport data stream may be decoded to produce analog audio and video signals for immediate monitoring by audio video display  300 . The decoded output signals are represented by signals  101  and  104 , which are coupled between receiver, IRD  100  and display  300 . Cost considerations may dictate that digital recorder  200  does not include MPEG encoding and decoding. Hence digital recorder  200  functions as a bit stream recorder/player, to provide time shifting or program delay capability. The omission of MPEG processing and the degree of complexity required to facilitate non-standard speed replay capability, precludes image reproduction in SHUTTLE, SLOW MOTION or TRICK-PLAY modes. Thus in summary, receiver  100  couples an MPEG compatible packet stream to digital A/V bus  112  for recording by recorder  200 . Similarly a reproduced packet stream from recorder  200  is coupled back to the receiver for MPEG decoding, and audio/video generation. An additional consequence of omitting MPEG processing from the recorder is that status messages, in the form of on-screen display messages or OSDs, cannot be combined or added to the replay packetized bit stream. Thus the operational status of the recorder is not readily obvious to the user. 
     In addition, since recorder image data is only available during RECORD, PLAY and STOP modes, the user may be uncertain as to the responsiveness of the recorder following control commands. For example, transitioning from PLAY to REWIND may result in the replay image switching for example, to the input bit stream, a condition known as electronics to electronics or E to E, or for example, the replay image may disappear and be replaced by frozen frame derived by the IRD, or perhaps the moving image may be substituted by a colored field. Thus the user may not readily associate these visual display effects as indicia of recorder mode responsiveness. 
     The system illustrated in  FIG. 2 , shows a first inventive interconnection arrangement where a demodulated transport bit stream is coupled from receiver IRD  100  to recorder  200  via a bi-directional data bus  112 . The transport packet stream is coupled to the data bus via an interface port  110  and is received at recorder  200  by means of interface port  210 . The interface ports are controlled via a control data stream which is carried on a separate conductor included with data bus  112 . Control signals may be derived from user input by activation of control switches (not shown), or by user generated IR remote control commands. For example, a user may chose to monitor a digital audio video signal received by dish antenna  50 . The receiver may be selected by touch or via a remote control, for example IR. Receiver selection may result in the automatic monitoring the display selection, i.e. the display is automatically switched to monitor the MPEG decoded audio video outputs. The user may select a digital RECORD mode which results in coupling the received transport stream from IRD  100  via bus  112  to the recorder and initiating recording. Similarly selection of a digital recorder PLAY mode results in a replayed data stream being coupled via bus  112  for decoding by decoder  117  of receiver  100 . 
     The MPEG compatible, packetized signal is coupled to recorder  200  and processed for recording by block D. REC.  210 . A buffer memory is included in block D. REC.  210 , and buffers the data stream to establish a signal more suited for recording than the packetized signal comprising bursts of data with variable duration gaps. The buffered data stream is read from the buffer to form record format sync blocks which may be encoded with error detection/correction data words. The sync block formatted data stream may be modulated for recording as described, and coupled from recording block D. REC.  210  via a selector switch A 4 . Selector switches A 4  and A 5  are controlled responsive to the selected D-VCR operating mode. For example, in  FIG. 2  switches A 4  and A 5  are shown, for digital recording and reproduction, with switch contacts DR, digital record and DP digital playback coupling data streams to and from a rotating head assembly  250 . For analog operation, switches A 4  and A 5  assume the alternate position as indicated by AR, analog record and AP analog playback. The sync block formatted data stream from D. REC.  210  is coupled to rotating head assembly  250  for recording on a magnetic tape. 
     In a PLAY mode the recorded sync block formatted data stream is reproduced from the magnetic tape by heads positioned on assembly  250 . The recovered signal is demodulated by digital replay block D. Rep.  220 , to remove any recording channel modulation. The replay signal is then subject to error detection and correction by means of the data words inserted prior to recording. Following error correction, the sync block formatting is removed and the bit stream restored to have substantially the same the packet format as that coupled to the recorder for recording. The packet stream from block D. Rep.  220  is coupled to interface port  210  which, responsive to the recorder PLAY mode couples the packet stream to the bi-directional data bus  112  for MPEG decoding by decoder  117 . 
     Integrated receiver decoder  100  decodes the MPEG compatible packet stream and generates both video and audio output signals. For example,  FIG. 2  illustrates video and audio output signals  101  and  102  and a component video signal  104 , for example S-Video. However, these digitally reproduced video signals are without recorder status information usually provided by means of an on-screen display or OSD. 
     Receiver IRD  100 , shown in simplified form in  FIG. 2 , comprises a controller, CTRL.  115 , which provides overall control of the receiver, for example tuning, packet header control demultiplexing, bus interface control and selection of packet source for coupling to MPEG decoder  117 . In addition the receiver status, or operational mode, may be indicated by means of an on-screen display message added to the decoded video signals. Controller  115  may construct an on-screen display message or may read a predetermined stored message from memory block MEM.  510 . The on-screen display message or OSD is coupled to an OSD inserted or adder, block  520  where the message is formatted for analog video display and added or combined with the MPEG decoded video signal. The video with OSD signal is coupled out via output amplifier  118  for display by monitor display  300 . 
     In  FIG. 2  recorder player  200  includes an on-screen display generator, OSD. GEN.  270 , coupled to a control system CTRL  205 . In response to signals from the recorder control system  205 , OSD generator  270  generates status or warning messages appropriate to the operation condition. These messages are formatted as video signals for insertion or combination with an analog video signal in block, OSD. ADD  275 . Analog video signals are coupled to the on-screen display adder  275  from a video selector block SEL.  280 . 
     Selector  280  is controlled by control system  205  and provides selection capability between various analog signal sources. For example, switch A 1  provides analog input signal selection between a tuner derived signal, a baseband analog signal input and an MPEG decoded audio video output signal  102 . The output from switch A 1  is coupled for analog recording by block A. REC. 
     Selector switch A 3  of SEL  280  advantageously provides selection of signal coupling to on-screen display adder  275 . In  FIG. 2  switch A 3  is shown providing an inventive coupling of the video component of output signal  102  to the input of on-screen display adder  275 . Thus, recorder player  200  status messages generated, for example during playback, may be added to video signal component  102  decoded from the output transport packet stream. Thus the digitally derived MPEG decoded replay signal with on-screen messages added, signal  103 , may be viewed by display  300 . 
     During analog operation of recorder player  200 , switch A 3  couples an analog replay signal, shown as signal VHS, to on-screen display adder  275 . Thus during analog operation OSD messages are added to the analog replay video signal. When digital recording is selected, OSD messages may be advantageously added to the analog video signal  102  decoded from the reproduced bit stream. Thus, by means of this advantageous feedback connection recorder status messages are combined with the video component and output as analog signal  103 . 
     Switch A 2  of selector SEL.  280  advantageously provides a connection which bypasses on-screen display adder  275  and allows output signal  102  to be coupled directly to monitor display  300 . Thus the bypass action of switch A 2  allows viewing of decoded output signals and removes the possibility of signal degradation due to adder  275 . The bypass path A 2  may be automatically selected when the recorder is OFF, in a STAND BY mode, or when viewing a decoded, non-recorded “live” bit stream. To permit viewing of decoded non-recorded signals during analog recording, the bypass switch may be manually activated. The advantageous bypass connection obviates unnecessary analog recorder signal processing, for example via the E/E recorder path which inherently degrades the digitally derived signal  102 . In addition the advantageous bypass function may be facilitated, for example by mechanical contact, such that switch A 2  allows receiver IRD  100  to be connected to monitor display  300  without regard to the operational status of recorder  200 . 
     On-screen display generator  270  generates messages formatted with specific horizontal and vertical synchronizing timing such that when inserted into the video signal the message is displayed at a predetermined position on the display screen. However, when operating in the digital replay mode and employing the advantageous feedback connection discussed above, OSD messages may be advantageously generated with horizontal and vertical synchronizing timing which is different from that employed during analog recorder operation. This different horizontal and vertical synchronizing timing advantageously compensates for replay signal propagation and MPEG decoding delays encountered, for example, in receiver  100 . Thus, the use of different OSD synchronizing timing advantageously achieves substantially the same predetermined message position in either analog or digital recorder operation. 
     Processing and MPEG decoding time delays may amount to periods of multiple frames. A multiple frame delay, or temporal offset, will result in an OSD message preceding an actual reproduced visual event. This temporal offset, where the recorder OSD message precedes a reproduced event, may be revealed as a consequence of a user control command and the delayed appearance of the corresponding reproduced image effect. The temporal offset may represent a more significant problem when displaying a recorded time code signal or the recorder tape timer. For example, during tape replay specific events may be noted from an on-screen display of the recorder tape timer or an OSD of a recorded time code signal. The noted times allow for subsequent location of the selected events. However, should the noted times be used as edit points for electronic editing performed between recorders, the resultant edited scenes will precede those selected during previewing. The effect of the temporal offset between the message and the replay image may be advantageously eliminated by a delaying, message generation, message communication, OSD presentation or by modifying the tape timer/time code numbers or count. In recorder  200  a delay, depicted as DLY.  207 , may be selected by switches A 7  or A 8 . For example, when decoded video signal  102  is fed back for recorder OSD message insertion at block  275 , an OSD message command may be generated responsive to controller  205 . The message command signal CMD, from controller  205  is illustrated coupled to switch A 7  and delay DLY  207 . Switch A 7  is controlled responsive to the recording mode selected for recorder  200 , i.e. analog or digital. Switch A 7  is shown in the digital mode, and selects a delayed version of signal CMD from delay  207 . The delayed command signal results in the generation and insertion of an OSD message which is substantially coincident with decoded video signal. An alternative arrangement employs switch A 8  which may insert delay  207  into the output from the OSD generator  270 . In this arrangement switch A 7  is connected to the output of controller  205 . Switch A 8  may also be employed to delay coupling of signal CMD to bus  112  and IRD  100 . The temporal offset between the OSD message and the decoded replay image may also be corrected in receiver  100  by the introduction of a delay, for example as depicted by DLY.  116 , into either the memory accessing signal or the memory output signal. Synchronization of repay image and OSD may be achieved by various methods, for example, by means of a delay using a clocked data latch, shift register, monostable multivibrator, etc. A tape timer or time code OSD may be synchronized with the decoded image, for example during edit mode preview by arithmetic manipulation of the display numerals. Thus the selected image and associated display numerals may be entered to enable an electronic edit to be performed. During analog operation of recorder  200  the command signal CMD, from controller  205  is not delayed and switch A 7  couples directly to generator  270 . 
     In another inventive embodiment, on-screen display messages originated by recorder  200 , may advantageously utilize the on-screen display capability of receiver  100 . Recorder derived messages may be coupled via the control conductor of data bus  112  to receiver  100  for on-screen display insertion at block OSD  520  of  FIG. 2 . The recorder message data may be formatted as a text message by generator  270 , to which a tag or label is appended. The tagged text message shown as signal  271  is coupled to controller  115  of IRD  100  for separation from other control bus data. Following separation the text message is coupled for display formatting and video insertion by OSD  520 . The text message is generated responsive to OSD command signal CMD from controller  205 . As described earlier, signal CMD may be subject to delay at block  207 . However, the text message from block  270  may be delayed at an alternative point by switch A 7  insertion of delay  207 . 
     In a further inventive embodiment, receiver  100  includes a memory  510  which contains receiver on-screen display messages and OSD messages specific to recorder  200 . Recorder specific messages may be accessed responsive to recorder on-screen display command signal, CMD, which may be coupled via the control bus to controller  115 . In recorder  200  the on-screen display command signal CMD, is generated by controller  205  which in addition determines the message to be generated. Thus command signal CMD, may be advantageously coupled to receiver  100  to enable accessing and display formatting of recorder specific graphical messages stored in memory  510 . 
     In yet another inventive arrangement receiver  100  may adaptively select between the recorder text message or a receiver graphical message responsive to a recorder command. The selection between the recorder text or IRD graphical message display permits the interconnection of recorders and receivers of differing ages having different features and facilities. For example, an older receiver may be connected to a recently manufactured recorder thus, the receiver memory may not contain preprogrammed graphical messages to support recorder on-screen message presentation. Thus the receiver may display the simple text message generated by the recorder. Conversely, a more modern receiver may be preprogrammed with selections of graphical messages for a variety of products of various manufactured ages and these various graphical messages may be displayed in place of the recorder text message. Selection between simple text or graphical message is facilitated by the tag or label which is appended to the text message. For example, the tag or label may contain the command signal CMD which selects, and enables the required recorder specific message. In addition the label may provide sufficient data capacity to communicate recorder profile information relating to, for example, the date of recorder manufacture, model, version or revision level and serial number. When the text message with tag or label is received by controller  115 , the tag or label is interpreted which results in the selection of a recorder specific graphical message from IRD memory  510 . However, if the receiver memory is not preprogrammed with the specified recorder message or with a message specific to the recorder profile, the tag enables formatting and display of the appended simple text message. As described previously a delay element may be inserted to compensate for temporal and spatial displacement between the OSD message, text or graphical, and the replayed decoded image. 
       FIG. 3  illustrates the use of a reduced cost display, for example, as depicted as display  301 . To reduce the display cost the number of signal inputs may be limited to, for example, an RF input, a component video or S-video input and one audio video signal input. The advantageous selection and bypass capability of selector  280  of  FIG. 2 , permits display  301  to monitor recorded, and non-recorded material via a single A/V input.