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Figure: Video source selection
Once the signal source is selected, a chroma filter calibration is performed. The
received color burst sub-carrier frequency is used for this. Correspondingly, the chroma
band pass filter for PAL/NTSC processing or the cloche filter for SECAM processing is
switched on. The selected luminance (Y) signal is supplied to the horizontal and vertical
synchronization circuit and to the luminance processing circuit. In the luminance-
processing block, the luminance signal goes to the chroma trap filter. This trap is
switched 'on' or 'off' depending on the color burst detection of the chroma calibration
circuit.
The group delay correction part can be switched between the BG and a flat group delay
characteristic. This has the advantage that in multi-standard receivers no compromise
has to be made for the choice of the SAW filter.
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