Method of playing back video records through television receiver operating at a different line standard
Color television signal having color-difference signals alternating between two carriers Patent #: 4188638
ApplicationNo. 06/042576 filed on 05/25/1979
US Classes:386/2, Drop-out correction348/454PAL to NTSC or vice versa
ExaminersPrimary: Konick, Bernard
Assistant: McElheny, Donald Jr.
Attorney, Agent or Firm
International ClassesH04N 9/79 (20060101)
H04N 9/85 (20060101)
H04N 9/82 (20060101)
Foreign Application Priority Data1978-06-08 DE
AbstractAn NTSC color television signal picked up from a disc recording is mixed in such a way as to provide one sideband having the chrominance carrier at the PAL standard frequency and another sideband at a higher frequency which can be stepped down in a second mixer to the PAL color-carrier frequency to provide a side band shifted 180° in phase with respect to the color signal provided by the lower sideband of the first mixer. The mixing frequencies are kept in step by utilizing a standard frequency generator at the PAL color-carrier frequency which controls the phase of a VCO supplying a first mixing frequency in a third mixer from the output of which the second harmonic of the difference frequency is selected as the mixing frequency for the second mixer. From the standard frequency output there are also derived the phase-shifted color burst pulses for identifying the two chrominance signals produced as they are alternately utilized for the output PAL signal. A delay of one line scanning period allows the use of the delayed and undelayed signals to give the effect of a comb filter for the luminance signals and for the chrominance signal, and the delay line is also used in connection with a video switch and disturbance detector to allow use of the last undisturbed line when an unusable line is detected. The playback speed is slightly reduced (cf. U.S. Pat. No. 4,148,077) for reproduction by a television receiver operating at the European line-scanning frequency.