Abstract: Aspects of a method and system for redundancy-based decoding of video content are provided. A bit sequence comprising video content may be decoded in a multilayer process based on a decoding algorithm and at least one physical constraint. The decoding algorithm may be based on the Viterbi algorithm. Whether the bit sequence comprises video content may be determined based on information provided by a portion of a packet header or by packet priority information necessary for enabling quality of service applications. The physical constraint may be based on border, DC component, and/or low frequency continuity between neighboring discrete cosine transform (DCT) blocks. The physical constraint may also be based on the consistency of video data coded by a variable length coding (VLC) operation. At least one physical constraint test may be performed on selected estimated video bit sequences to select a decoded output video bit sequence.

Abstract: Methods for embedding and reading identification codes from media signals use embedded code signals modulated with the auxiliary message. These embedded code signals convey hidden tracking codes in images, video, music and printed objects. The embedded code signals are embedded by varying characteristics of the signal. The identification code varies for different copies of a media signal and indexes distribution information such as point of sale information and ownership information.

Abstract: A system and method for receiving, processing, and storing electronic data transmitted in the vertical blanking interval of a video signal. The system provides a flexible mechanism for reading electronic data from video signals including those in National Television Systems Committee (NTSC) and Phase Alternation by Line (PAL) formats. Some implementations provide for receiving electronic programming guide data transmitted at a single byte rate or at multiple byte rates. The data is stored on a computer-readable medium such as a hardrive for further processing and use.

Abstract: The present invention relates generally to generating or otherwise providing reports associated with content (e.g., audio or video). One claim recites a method including: processing data representing audio or video content; based at least in part on derived information, obtaining data associated with the audio or video content; and providing a report to a client or remote location. The report including at least a portion of the data associated with the audio or video content. Audio content includes audio portions and video content includes video elements. The act of processing provides information derived from the data representing audio portions or the video elements. Of course, other combinations are provided and claimed as well.

Abstract: A random number or HDCP key is sent from a TV to a set back box (SBB) over a HDMI channel, and unless the SBB returns the same random number/key to the TV over a USB link, the TV will not communicate further with the SBB.

Abstract: A method that hides data inside video signals and transmits the video signals to a display device, the method includes detecting whether a signature signal is attached to a window frame, picking the signature signal from the window frame when detecting the signature signal is attached to the window frame, generating a control signal according to the signature signal, and acting correspondingly on the display device according to the control signal.

Abstract: An improved video processing method and system is disclosed wherein a parent video having at least one critical image element is utilized to produce tracking information on the critical image element, a child video is obtained, the tracking information is adjusted using factors such as the compression ratio of the child video and user inputs, and the critical image element is reconstructed onto the child video using the adjusted tracking information to produce a grandchild video for display.

Abstract: The presently claimed invention relates generally to monitoring and/or filtering video or audio data. In one implementation a method is provided including: obtaining data representing video or audio; analyzing the data representing video or audio for an in-band signal, the in-band signal encoded in data representing video picture elements or in data representing audio elements; looking for out-of-band data conveyed with the data representing video or audio; restricting or allowing distribution of the data representing video or audio based at least in part on a result of the act of analyzing and a result of the act of looking. In some implementations the in-band signal includes steganographic encoding or digital watermarking. Of course, other implementations and embodiments are provided.

Abstract: A display system for adjusting video parameters of a user-selected area is disclosed. The display system includes a level detector detecting a line pattern included in one of a plurality of image lines representative of a complete image being displayed, and a pattern receiver coupled to the level detector for receiving the detected pattern, where the received pattern includes a position indicator whose ends are vertically aligned with vertical edges of the user-selected area. In addition, the display system further includes a pixel counter coupled to the pattern receiver for measuring a set of horizontal positions of the indicator ends with respect to a reference point, a pattern analyzer calculating a set of horizontal positions of vertical edges of a video control area on the basis of the positions of the indicator ends, and a video preamplifier adjusting at least one of video parameters of the video control area.

Abstract: An apparatus and method for facilitating program changes. The apparatus and method include a controller for detecting a change program request and for outputting change event data when a change event is detected. A non-active video information replacement module is coupled to the controller for receiving non-active video information and the change event data. When the replacement module receives change event data, a clear code generator generates clear code data that replaces non-active video information, and the non-active video information replacement module generates modified non-active video information. The modified non-active video information is provided to an output stage, whereupon the clear code data resets a non-active video information field within a display device, thereby preventing the display of erroneous information by a display within the output stage. Thereupon, clear code data is synthetically inserted within non-active video information upon the occurrence of a change event.

Abstract: A terminal 13 for selectively receiving broadcast data in a transport stream 7 over a first network, the broadcast data including a series of bursts of associated data packets (B1), comprises a controller 16 and a receiver 19. The controller 16 is configured to extract information identifying a group of data packets from the data packets within a first burst, e.g. Packet Identifier (PID) PID1, PID2, calculate a burst length and burst interval for the series on the basis of the times at which data packets are received by the receiver and to calculate one or more instances of time ts at which one or more subsequent bursts in the series will be received based on the calculated burst length ts3 and/or burst interval t1. The receiver 19 is operated to selectively receiving the transport stream 7, e.g. by switching the receiver 19 between its on and off states, the receiver 19 being switched on at time is for a period equal to the burst length in order to receive subsequent data bursts in the series.

Abstract: A method of reinserting Vertical Blanking Interval (VBI) data in a digital video signal includes creating a gray scale palette in a an On Screen Display (OSD) memory; sizing a VBI area in an OSD memory; locating a VBI area in an OSD memory; generating a VBI luma waveform bitmap; and overlaying the VBI luma waveform bitmap in a DVB video bit stream according to the gray scale palette, size and location data stored in the OSD memory.

Abstract: The present invention provides a method and system for generating reference signals that, when correlated with synchronization code signals or other components of broadcast TV signals, yield minimal sidelobes, produce large main peaks, and have minimal couplings to high frequency noise and low frequency disturbance signals. The present invention also provides a method and system for accurate position determination utilizing broadcast TV signals by employing reference signals with improved correlation characteristics of minimal sidelobes, minimal coupling to high frequency noise, minimal coupling to low frequency disturbance signals and a maximal main correlation peak.

Abstract: An apparatus for embedding digital watermark information in an image, includes an image divider dividing the image into a plurality of partial images; and an embedder embedding in each of the partial images a digital watermark which indicates the digital watermark information. The digital watermark includes a plurality of watermark elements arranged in a sequence which is different for each of the partial images.

Abstract: An information processing apparatus has: an input unit for inputting image data and program information data, the program information data indicating information on a program including the image data; a display unit for displaying an image corresponding to the image data input from the input unit; and a control unit responsive to a change in a program including images displayed by the display unit for controlling the display unit to display the changed program and the images on the same screen.

Abstract: Video programs are identified by watermark data subliminally conveyed within the picture data. By reference to such program identification data, video recording devices can automatically identify desired programs, and respond accordingly. For example, if a desired television program is originally scheduled to air at 5:00 p.m., but is delayed until 5:10 due to a sporting event that exceeded its broadcast slot, a video recorder equipped with the disclosed technology can sense the delayed start, commence recording at 5:10, and continue recording until the (delayed) end of the program. The program identification can also identify the program's subject matter, allowing automated recording of programs that match a viewer's profile.

Abstract: The present invention relates generally to hiding a signal in video. One form of hiding is steganographic encoding.

Abstract: A tuner extracts a digital broadcasting wave on a channel tuned in to, and demodulates the extracted digital broadcasting wave, to output a transport stream. A demultiplexer acquires various types of data from the transport stream. A CPU performs channel search processing when the timing of execution previously set has arrived (e.g., 4:00 a.m. on Thursday every week), and performs processing for acquiring channel information included in the digital broadcasting wave and storing, when a new channel is found, for example, channel information related to the new channel in a non-volatile memory.

Abstract: A digital TV and a method of switching a channel automatically thereof provides a viewer with advance notice of an automatic channel switch using linkage descriptor information on HD broadcasting. Providing the viewer with notice of the switched channel reduces viewer confusion. The method includes the steps of determining whether a linkage descriptor is included in additional information regarding a broadcast program whether the broadcast program regardless of whether the broadcast program is selected by a viewer, checking the remaining time of the broadcast program if the linkage descriptor is included in the additional information, displaying a channel switch notice message on a screen, determining whether or not the broadcast program has ended, switching a channel of the broadcast program to a designated channel when the broadcast program ends, and displaying a channel switch confirmation message on the screen.

Abstract: Methods and apparatuses in which two or more types of attributes from an information stream are identified. Each of the identified attributes from the information stream is encoded. A time ordered indication is assigned with each of the identified attributes. Each of the identified attributes shares a common time reference measurement. A time ordered index of the identified attributes is generated.

Abstract: The present invention includes a teletext decoder extracting to decode the teletext information from an inputted video signal, a video processing unit extracting to process a pure video signal from the inputted video signal only, a teletext bypass unit converting the teletext information extracted from the inputted video signal to an analog video signal form, a first synthesizing unit synthesizing to output the pure video signal outputted from the video processing unit and the teletext information outputted from the teletext decoder, a second synthesizing unit synthesizing to output the pure video signal outputted from the video processing unit and the teletext information outputted from the teletext bypass unit, and a memory storing the processed video signal and the teletext information extracted from the inputted video signal.

Abstract: The object of the present invention is to improve the accuracy of channel estimation and increase downlink capacity when a base station transmits an individual channel using directional beams. The base station 10 according to the present invention comprises an individual channel transmitter 15 configured to transmit an individual channel into which pilot symbols are inserted; and an individual channel format creator 14 configured to create a format of the individual channel. The individual channel format creator 14 changes between a format of an individual channel which is to be transmitted using directional beams and a format of an individual channel which is to be transmitted using non-directional beams.

Abstract: A computerized audio or video signal control system controlled by an announcer and having a display of the available signal sources and scheduled events which can be activated, mixed, faded and cued by the announcer in the scheduled order or in an order the announcer desires. The control system provides the correlation between the displayed source or event name, the devices necessary to air the source or event and the routing necessary to air the event or source and then activates the proper devices to perform the task. The control system additionally logs the events actually activated in order.

Abstract: A video, audio and graphics system uses multiple transport processors to receive in-band and out-of-band MPEG Transport streams, to perform PID and section filtering as well as DVB and DES decryption and to de-multiplex them. The system processes the PES into digital audio, MPEG video and message data. The system is capable of decoding multiple MPEG SLICEs concurrently. Graphics windows are blended in parallel, and blended with video using alpha blending. During graphics processing, a single-port SRAM is used equivalently as a dual-port SRAM. The video may include both analog video, e.g., NTSC/PAL/SECAM/S-video, and digital video, e.g., MPEG-2 video in SDTV or HDTV format. The system has a reduced memory mode in which video images are reduced in half in horizontal direction only during decoding. The system is capable of receiving and processing digital audio signals such as MPEG Layer 1 and Layer 2 audio and Dolby AC-3 audio, as well as PCM audio signals. The system includes a memory controller.

Abstract: Various improvements to steganographic systems, and applications therefore, are disclosed. The improvements include facilitating scale and rotation registration for steganographic decoding by use of rotationally symmetric steganographically embedded patterns and subliminal digital graticules; improved techniques for decoding without access to unencoded originals; improving robustness of steganographic coding in motion pictures and/or in the presence of lossy compression/decompression; and representing data by patterned bit cells whose energy in the spatial domain facilitates decoding registration. Applications include enhanced-security financial transactions, counterfeit resistant identification cards, fraud deterrent systems for cellular telephony, covert modem channels in video transmissions, photo duplication kiosks with automatic copyright detection, and hotlinked image objects (e.g. with embedded URLs) for use on the internet.

Abstract: The present invention is directed to a recording device and method for recording digital data constituting a program on a disc-shaped recording medium using a specified minimum data length (CDA) unit that must be contiguous. Digital data constituting a first and second programs that are mutually different are alternately recorded on the disc-shaped recording medium using the specified data length (CDA) unit.

Abstract: An information processing apparatus supplies time information by a real-time-clock (RTC) that is corrected and a correction history is recorded. When a signal representing a correct-time indication is received, a correction processing section corrects a setting time provided from the RTC using the signal and a result of the correction is recorded into a log memory. When a signal representing a correct-time indication is not received or detected, the correction processing section records failure of correction of the setting time of the RTC into a log memory. The correction processing section is also capable of reading a history of correction information from the log memory and correcting the setting time provided by the RTC based on the correction history.

Abstract: A method for modulating one or more fields of video signal (18) with auxiliary signal (20) by use of an encoding improvement, the one or more fields having one or more sub-fields, the one or more sub-fields having a plurality of odd and even scan lines, the plurality of odd and even scan lines having a plurality of pixels, the plurality of pixels each having an intensity comprising obtaining on encoder (12) the video signal from signal source (10), selectively designating on encoder the plurality of odd and even scan lines as up lines or down lines for at least one of the one or more sub-fields for at least one of the one or more fields, calculating an amount of intensity adjustment for the pixels of the plurality of odd and even scan lines on encoder, and adding intensity to the up lines and subtracting intensity from the down lines according to the amount of intensity adjustment for the pixels of the scan lines of video signal on encoder.

Abstract: A method and system for extracting segments from a broadcast television signal uses a mean display attribute value of pixels of each successive frame of a video component of the signal to identify segment transitions. Elapsed times between the identified segment transitions are compared with expected durations of segments, in order to detect intervals that are likely to constitute segments. Groups of the detected intervals are subjected to tests to see if they are temporally arranged in an expected distribution typical of segments in broadcast signals. The mean display attribute values concurrent with each detected segment are then used to form a statistical profile for the segment. These statistical profiles may be used to identify re-broadcast segments. Further a stream of mean audio amplitudes is preferably used to supply further segment transitions, to improve segment detection, and to provide more statistical values.

Abstract: A language displaying apparatus for a digital TV and a method for the same notices all kinds of languages included in broadcasting signals and enables a user to recognize them and select the preferable language easily and accurately. To achieve this, the method according to the present invention comprises the steps of abstracting and storing all kinds of languages included in broadcasting signals, displaying the stored kinds of languages or outputting in the form of an audio and outputting the audio signals corresponding to the language selected by the user among the kinds of languages.

Abstract: An interactive television program guide is provided. The interactive television program guide provides a user with the opportunity to select a language for playing television programming and displaying program guide text. Television program audio in the desired language may be obtained from a SAP or digital audio track and played in the selected language. Television related information in the desired language may be obtained from a digital track. If television program audio or related information is not provided in the selected language, the program guide may use a default language. The program guide may coordinate program guide display screen text with languages available for television programs when the programs are broadcast to users.

Abstract: According to the present invention, there is provided a method, system and program storage device for displaying textual information associated with a defined video object in video data on a video display device, comprising: sampling a video object plane to determine whether the video object is in the video object plane for displaying the video object on the video display device; updating a location of the video object in the video object plane as the video object moves during display of the video data on the video display device; determining whether a pointing device is over the updated location of the video object; and displaying the textual information associated with the video object on the video display device for a predetermined period of time.

Abstract: Advertising is marked with a code in a way which makes it difficult to fool the system. The advertising is marked with a code at the time the advertising is produced. Then, when the advertising is broadcast, the code on the advertising is analyzed. Different security measures can be used, including producing the code in the closed captioning so that many different people can see the code, or comparing codes in one part of the signal with a code in another part of the signal. Measures are taken to prevent the code from being used to detect commercials. According to another part of this system, a paradigm for a clearinghouse is disclosed in which the user signs up with the clearinghouse, obtains a line of credit, and the advertiser, the agency, and the ad producer also subscribe to the service. When the ad is actually aired, the payment can be automatically transferred.

Abstract: The system for updating a clock in an electronic device, such as a personal computer, has a receiver system having an input for receiving a real time signal and having an output on which is provided digital information representative of the real time signal. An extraction module is operatively coupled to the receiver system, the extraction module extracting at least a current time value from the display data. An update module is operatively coupled to the extraction module, the update module updating the clock in the computer when the current time value of the digital information differs from a current value of the clock in the computer. In one embodiment a validating unit is operatively coupled between the extraction module and the update module. The validating unit compares channel identification data derived from the display data to time zone data in the computer, the time zone data being indicative of a time zone in which the computer is currently located.

Abstract: A display data packet contains identification information. A display unit communication system includes a control unit, a terminal adaptor to which a terminal adaptor ID is assigned and which is connected to the control unit, and a display unit to which a display unit ID is assigned and which is connected to the terminal adaptor in series and drives a display element according to the display data packet supplied from the control unit. The terminal adaptor receives a display data packet, the terminal adaptor ID of which agrees with that contained in the identification information, and transfers the display data packet to the display unit. The display unit receives the display data packet, the display unit ID of which agrees with that contained in the identification information, and drives the display element to display an image.

Abstract: A VSB communication system or transmitter for processing supplemental data packets with MPEG-II data packets includes a VSB supplemental data processor and a VSB transmission system. The VSB supplemental data processor includes a Reed-Solomon coder for coding the supplemental data to be transmitted, a null sequence inserter for inserting a null sequence to an interleaved supplemental data for generating a predefined sequence, a header inserter for inserting an MPEG header to the supplemental data having the null sequence inserted therein, a multiplexer for multiplexing an MPEG data coded with the supplemental data having the MPEG header added thereto in a preset multiplexing ratio and units. The output of the multiplexer is provided to an 8T-VSB transmission system for modulating a data field from the multiplexer and transmitting the modulated data field to a VSB reception system.

Abstract: The present invention provides methods, apparatus and systems for embedding and detecting an electronic watermark without requiring signals for geometric compensation. A particular embodiment uses a periodic pattern with repetition as an embedded pattern itself, which has information embedded as an electronic watermark, and observes the change of its period upon detection to calculate the scaling factor. When detecting the electronic watermark, the scaling factor of images is calculated from digital data that underwent the scaling processing, and then the processing to detect the electronic watermark is performed based on the obtained scaling factor.

Abstract: Viewing of a program at optimum image quality is realized. A correspondence table of combinations of MPEG video encoding parameters and image signal processing parameters is stored in a RAM. A CPU reads out from the RAM an image signal processing parameter corresponding to a combination of MPEG video encoding parameters supplied from a demultiplexer, and on the basis of the image signal processing parameter, controls image signal processing in an image signal processor.

Abstract: When a serial digital transfer interface transmission packet in which an interval of each line of a video frame comprises an area into which an end synchronizing code EAV is inserted, an area into which header data is inserted, an area into which a start synchronizing code SAV is inserted and a payload area into which data containing video data and/or audio data is inserted is transmitted, a transmission packet is generated by inserting frame sequence data for managing the phase of the audio data into the payload area at its audio item portion of a header area corresponding to an audio data block area into which the audio data is inserted and transmitted in the form of serial data. Also, a transmission packet is generated by inserting not only the frame sequence data but also data indicative of the number of audio samples contained in a frame indicated by the frame sequence data into an audio sample count area corresponding to the audio data block area and transmitted.

Abstract: A method of recording an encoded bit stream, said encoded bit stream representing a plurality of video objects comprising a sequence of cells together constituting a part of an MPEG2 Program Stream, on a disc like record carrier, such as an optical disc. The method comprises recording video objects comprising a sequence of contiguously recorded cells, each cell comprising a unique cell identification number within a video object, recording of a playback sequence of cells that defines a playable program chain of cells, wherein said sequence comprises references to the cell identification numbers and recording navigation data within said cells comprising said cell identification numbers.

Abstract: A method and apparatus by which digitized large frames of packets are sent between computer-based switches over a data network and central switch with greater efficiency than with existing digitized voice switching technology. Frame bundling combines the voice packets coming from different terminals into longer frames so that the number of frames and the overhead is reduced on the data network. Frame bundling may be done only with terminals that are connected to the same destination switch. The efficiency of this invention depends on the number of switches in the network and the amount of traffic between pair of switches. Payload switching then sets up one or more central nodes that are connected to several other switches. The central node disassembles the large frames into the packets and reassembles the packets into large combined frames. The disassembled and reassembled frames are sent to the destination switches from the central node.

Abstract: A broadcast data receiver (BDR) is provided and a method of using the BDR for the production of a pseudo stable reference control for the reliable generation of composite video signals. The BDR receives video, audio and/or auxiliary data from a broadcaster can stored a part of all of the data in storage means, typically in the form of a hard disk drive. When the BDR is deriving video data from the hard disk due to the BDR being disconnected from the signal feed from the broadcaster, the BDR uses a pseudo stable reference produced by deriving one or more values from stable frequency information embedded in incoming data. The pseudo stable reference is used to control the frequency of a VCXO in the BDR, thereby allowing accurate color sub-carrier frequency generation for the generation of a final video output.

Abstract: A video recording and reproducing apparatus is provided which is capable of, even if the number of elementary streams (ES) of bits of a program to be recorded is too large and all the elementary streams can hardly be recorded, carrying out a recording operation with ease substantially corresponding to the direction of the user. The apparatus allows an ES selector to identify the elementary streams of video data, audio data, and their relevant data video in the stream of bits received from its program selector and, when the number of the elementary streams is higher than a given setting, pick up elementary streams which satisfy the predetermined requirements while deleting the other elementary streams. The elementary streams are then recorded by a recorder/player in the apparatus. Even if the elementary streams of bits are not all recorded, the elementary streams which satisfy the predetermined requirements can readily be recorded.

Abstract: A system method and apparatus for selectively recording on a VCR cassette, those news items of interest to a particular subscriber includes selecting video news items in accordance with previously entered user selected key word criteria. An advance data stream representing the text of each upcoming broadcast news item is provided in advance of the video broadcast of that news item. The advance data stream is searched for a match with any of the key word criteria previously entered by the subscriber. If a match between the stored user selected key word criteria and the advance data stream is found, the subscriber's VCR is enabled at the appropriate later time to record the desired news item. The VCR cassette contains those news items of interest to the particular subscriber, which the subscriber may watch at, any convenient later time.

Abstract: A teletext program includes several teletext pages, with each teletext page being broadcast in the form of a set of data packets. A method for displaying a teletext program index on a television receiver screen includes receiving a teletext page which includes the set of data packets. The set of data packets includes first and second data packets. The first data packet includes at least one label referring to another teletext page, and the second data packet is associated with the first data packet and includes a page number associated with at least one label. The method includes decoding the first and second data packets to obtain at least one label and the associated page number, and at least one label and the associated page number are stored in a buffer memory.

Abstract: A video, audio and graphics system uses multiple transport processors to receive in-band and out-of-band MPEG Transport streams, to perform PID and section filtering as well as DVB and DES decryption and to de-multiplex them. The system processes the PES into digital audio, MPEG video and message data. The system is capable of decoding multiple MPEG SLICEs concurrently. Graphics windows are blended in parallel, and blended with video using alpha blending. During graphics processing, a single-port SRAM is used equivalently as a dual-port SRAM. The video may include both analog video, e.g., NTSC/PAL/SECAM/S-video, and digital video, e.g., MPEG-2 video in SDTV or HDTV format. The system has a reduced memory mode in which video images are reduced in half in horizontal direction only during decoding. The system is capable of receiving and processing digital audio signals such as MPEG Layer 1 and Layer 2 audio and Dolby AC-3 audio, as well as PCM audio signals. The system includes a memory controller.

Abstract: A reproduction route composed of a still image section and a motion image section is recorded on a recordable DVD. A drive device (93) reads picture data from the DVD-RAM. An MPEG decoder (95) decodes and displays the read picture data. By referring to cell information, the judgment is performed as to whether the read picture data belongs to the still image section or the motion image data. If the read picture data belongs to the still image section, the next picture data is read out after a predetermined wait time.

Abstract: Systems and methods are described for broadcasting interactive content without using triggers embedded in the broadcast content. When a viewer sees an item of interest while viewing a program, the viewer can initiate a request for information (RFI) about that item with a single button actuation. When the RFI is entered, a client device, such as a set-top box, detects the RFI and transmits RFI data to a server, including the channel viewed, a time stamp and—in at least one implementation—a system-defined amount of closed captioning data. The RFI data is cross-referenced with program time code information, programming guide information, program information and/or advertiser information to determine the context of the RFI, i.e. what the user saw that made the user enter the RFI. Information about the item is then sent to the viewer as a system message, an e-mail message, a post, or by way of any other delivery mode.

Abstract: A terminal for interactive telebroadcasting system comprising on the one hand a unit for adaptation to the physical telebroadcasting medium and on the other hand a control unit. The first unit comprises a receiver for receiving of a telebroadcast signal and for producing downstream information extracted from the signal, a transmission time based generator for generation of a transmission time base from the downstream information and a transmitter for transmission of a return signal, which are clocked as a function of the transmission time base. The second unit comprises a calculation unit having means of generating upstream information. The calculation unit is clocked as a function of the transmission time base.

Abstract: A method of and apparatus for identifying a signal transmitting source detects a switching of a signal on the reception side thereby to prevent a transmission error from occurring when a signal is switched. The apparatus for identifying a signal transmitting source comprises a transmitting source identifying code extracting circuit for extracting a transmitting source identifying code provided in a SDDI format header of a received signal, a preceding transmitting source identifying code holding circuit for detecting a change of the transmitting source identifying code, and a transmitting source identifying code comparing circuit for detecting a switching of a transmitted signal based on the transmitting source identifying code thus changed, thereby detecting a switching of the transmitting source.