View sda9257 datasheet:

Clock Sync Generator SDA 9257 Preliminary Data MOS IC Features All settings made by I2C Bus PLL lock-in behavior can be set to TV- or VCR mode Automatic clamping of CVBS input Provides all horizontal and vertical sync signals and clocks for operating PAMUX, analog color decoders, the A/D converters, PSND and Featurebox Free-running capability Frequency generator function possible with digitally P-DIP-28-1 adjustable frequency Lock-in function of the PLL on CVBS also possible with externally supplied 24-MHz or 27-MHz clock Multi-standard operation (50 Hz, 60 Hz; PAL, NTSC, SECAM) Vertical noise suppression and 50/60-Hz detection Serial digital output for actual frequency value and CVBS-black level Applications Memory based image improvement with analog color de