TRANSMISSION PATH ERROR DETECTION/COMPENSATION CIRCUIT IN DIFFERENTIAL ENCODER/DECODER OF COLOR TV SIGNAL

摘要

PURPOSE:To eliminate color blurring caused by a phase jump of a subcarrier signal on a reproduction screen by replacing a digitally decoded output of a horizontal scanning line having errors with that of one line two scanning lines before of said line as it is. CONSTITUTION:In an error detection circuit 6 a parity calculated from a digital decoded output in a differential decoding circuit 4 is compared with that in a transmission path frame transmitted from a differential encoding circuit 2 through a transmission path 3. When the presence of a transmission path is judged, a switch 8 is switched to the side as shown in the dotted line, an output of two-line memory 7 is selected as an input of a D/A convertor 5, and a digitally decoded output of a horizontal scanning line having errors are replaced with that of one line two line before of the line having errors as it is. At the same time, switches 9 and 11 are switched to the side as the dotted line shows, and an output of the D/A convertor 5 is operated so that a jump between a phase of a subcarrier signal of the horizontal scanning line, which is replaced with the digitally decoded output before two scanning lines by a delay circuit 10 having a certain delay period, and a subcarrier signal of the scanning line just before said lines will not occur.