摘要 |
A time base corrector for retiming the chrominance and luminance components of a non-phased television picture signal from a PAL video tape recorder to local reference syncs. The time base corrector comprises digital storage means and an analogue-to-digital converter connected to an input of the storage means. A digital-to-analogue converter is connected to the output of the storage means. "Read" clock pulse generating means are connected with the digital-to-analogue converter and the storage means to trigger the same. A first phase comparator means is operative to compare local horizontal reference signals with horizontal pulses from a divider connected to the "Read" clock pulse means for controlling the output frequency of the same. Horizontal synchronizing pulse addition means are connected with the output of the digital-to-analogue converter for receiving the analogue signal from the digital-to-analogue converter and imparting thereto a horizontal synchronizing pulse in exact time relationship with the line frequency. Heterodyning means are connected between the input to the corrector and the analogue-to-digital converter. A second phase comparator means is operative to compare the color burst output of the digital-to-analogue converter with a local sub carrier reference signal and to control the heterodyning means. The heterodyning means imparts to said analogue-to-digital converter a chrominace component signal having a frequency controlled with reference both to the off tape horizontal synchronizing pulses and to the required sub carrier reference frequency.
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