Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
  • H04N7/087—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only
  • H04N7/088—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only the inserted signal being digital
  • H04N7/0882—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only the inserted signal being digital for the transmission of character code signals, e.g. for teletext
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
  • H04N7/087—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only
  • H04N7/088—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only the inserted signal being digital

Definitions

• the invention relates to a method and apparatus for transmitting a television signal.
• Transmission is herein not only understood to mean transmission from a television transmitter to one or more television receivers, but also local transmission from one apparatus to another (for example, in a television studio), or transmission from one circuit to another in a television receiver. Transmission is also understood to mean storage on storage media such as tapes, disks, etc.
• the invention also relates to a method and apparatus for receiving a television signal.
• a known television transmission method comprises the steps of sampling the luminance component Y of an analog television signal at a luminance sampling frequency and sampling the chrominance components U and V of the television signal at a chrominance sampling frequency.
• the sampling frequencies 13.5 MHz and 6.75 MHz, respectively, are often used.
• the samples are then transmitted in a format such as YUYV or YYUV. Usually, the samples are transmitted as digital words, but this is not essential to the invention.
• An analog television signal may also include auxiliary data signals such as teletext, VPS data for controlling videorecorders, closed caption data, and wide-screen signalling bits.
• Said data is transmitted in lines of the vertical blanking interval, the data signal waveform being shaped so as to fit within the bandwidth of the analog signal.
• the data signal is transmitted in the form of a luminance signal. Accordingly, in the prior art transmission system, the data signal will be sampled at the luminance frequency f usually 13.5 MHz. It has been found that reconstruction (data slicing, clock recovery) of the data from the data signal thus sampled is difficult and error-prone.
• the method of transmitting a television signal is characterized by the steps of sampling the luminance signal in data lines of the television signal at a luminance sampling frequency which is higher than the luminance sampling frequency in video lines so as to obtain additional luminance samples, and transmitting said additional luminance samples instead of chrominance samples.
• the invention is based on the recognition that the data signal does not comprise a chrominance component.
• the data signal can be transmitted at a considerably higher sampling rate, without increasing the overall transmission rate.
• the performance of the data slicing and clock recovery operation which is applied to the sampled data signal is thereby considerably improved.
• all chrominance sample periods are used for data signal transmission.
• the data signal can then be sampled at 27 MHz.
• Figs. 1 and 2 show arrangements for transmitting a television signal in accordance with the invention.
• Fig. 3 shows a time diagram for illustrating the operation of the arrangements which are shown in Figs. 1 and 2.
• Fig. 4 shows an arrangement for receiving a television signal in accordance with the invention.
• Fig. 5 shows a television receiver for digitally processing an analog input signal in accordance with a further aspect of the invention.
• Fig. l shows an arrangement for transmitting a television signal in accordance with the invention.
• the arrangement receives an analog RGB video signal and teletext data TXT.
• the RGB video signal is converted into an analog luminance component y and two chrominance components u and v by a conversion circuit 1.
• the teletext data is shaped by a waveform-shaping circuit 2.
• the conversion circuit 1 and waveform-shaping circuit 2 are well-known in the field of analog television transmission.
• the data signal d, luminance signal y and chrominance signals u and v are applied to respective sampling stages and A/D converters 3, 4, 5 and 6, respectively, which receive respective sampling frequencies from a clock-generating circuit 7.
• the digital luminance samples are denoted Y
• the digital chrominance samples are denoted U and V
• the data signal samples are denoted D.
• the samples are applied to a transmission formatting circuit 8 which also receives a Data Line signal DL which indicates whether the current television line is an active video line or a teletext line.
• teletext lines are selected lines of the video blanking interval, but this is not essential to the invention.
• the formatting circuit 8 is adapted to transfer video samples to the system's output as successive sequences YUYV during television lines for which DL is low, and to transfer data samples in the format DDDD during television lines for which DL is high.
• Fig.2 shows an alternative embodiment of the arrangement. It is now assumed that the arrangement receives an analog composite video signal CVBS which already includes a teletext signal in selected television lines.
• the signal is applied to a video processor 10 which splits the input signal into its luminance component y and chrominance components u and v. They are applied to respective sampling stages and A/D converters 11-13.
• Fig.3 shows a time diagram for illustrating the operation of the arrangements which are shown in Figs. 1 and 2.
• Waveforms B and C show the outputs of two successive divide-by-two stages in the clock generator circuit (not shown in Figs. 1 and 2).
• Waveform G denotes the output signal of the arrangement during video lines (DL is low) in the format YUYV.
• Waveform H denotes the output signal of the arrangement during teletext lines (DL is high) in the format YYYY (or DDDD in the notation which is used in Fig. l).
• Fig.4 shows an arrangement for receiving a television signal in accordance with the invention.
• the digital television signal is applied to both a video processing stage and a teletext-processing stage.
• a significant feature of the invention is that it is not necessary to first determine whether YUYV or YYYY sequences are being received, and to apply the signal to either a video processor or a teletext processor in response to said determination.
• the video-processing stage is adapted to process sequences of YUYV samples and comprises a demultiplexer 40 to split the input signal into Y-samples, U-samples and V-samples.
• the D/A converters 41-43 are applied to respective D/A converters 41-43 so as to obtain an analog luminance signal y and analog chrominance signals u and v which are applied to a conventional analog video processor 44.
• the video processor 44 may be a digital processing circuit. In that case, the D/A-conversion is done after said processing.
• the teletext- processing stage comprises a D/A converter 45 adapted to run at a sampling frequency of 27 MHz.
• the analog signal d is then applied to a conventional analog teletext decoder 46.
• the teletext decoder may be a digital decoder, which is understood to mean that the process of data slicing and clock regeneration is performed by digital signal processing. In that case, D/A converter 45 can be dispensed with.
• teletext is transmitted in the vertical flyback interval of a television signal.
• the teletext decoder can be arranged to decode data only in said interval.
• the invention also enables transmission of teletext in lines of the active video interval.
• the decoder shown in Fig.4 will automatically handle this operation mode, because the decoder receives all samples during all television lines.
• a code indicating the transmission of teletext in the active video interval may be transmitted.
• Fig.5 shows a television receiver for digitally processing an analog input signal in accordance with a further aspect of the invention. Because of the great resemblance with the arrangement shown in Fig.2, the same reference numerals are used.
• the television receiver receives an analog television signal CVBS and converts the video lines thereof into digital YUYV sequences and the data lines into YYYY sequences. Instead of transmitting the samples, the YUV samples are now applied to a digital video processor 48, whereas the Y samples are also applied to a digital teletext decoder.
• Conventional analog television receivers with digital processing circuits 48 and 49 have a fourth A/D converter for the teletext signal.
• this converter is dispensed with.
• transmission of teletext in a digital television format is disclosed.
• the video information is transmitted in the conventional YUYV format.
• the U and V sample periods are used to transmit additional luminance samples.
• teletext is transmitted in YYYY format, which in the CCIR 601 system corresponds to a 27 MHz sampling frequency. Teletext recovery is much more reliable.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Television Systems (AREA)
• Color Television Systems (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (1)

Family

ID=8224691

Family Applications (1)

Country Status (6)

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• 1997
  • 1997-12-04 EP EP97913366A patent/EP0883961A2/de not_active Withdrawn
  • 1997-12-04 KR KR1019980706192A patent/KR19990082459A/ko not_active Withdrawn
  • 1997-12-04 JP JP10526416A patent/JP2000505975A/ja active Pending
  • 1997-12-04 WO PCT/IB1997/001515 patent/WO1998026591A2/en not_active Ceased
  • 1997-12-04 CN CN97193605A patent/CN1215527A/zh active Pending
  • 1997-12-04 AU AU50655/98A patent/AU5065598A/en not_active Abandoned

Non-Patent Citations (1)

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