METHOD AND APPARATUS OF AUTOMATICALLY SELECTING AUDIO FORMAT FOR OUTPUT SIGNAL OF A TUNER IN A TELEVISION SYSTEM

In a method of automatically selecting audio format for output signal of a tuner, a SAW filter is configured to a bandwidth of 5.5 MHz for filtering IF signal so as to generate CVBS signal and SSIF signal. Then, band-pass filters are used to detect a back porch of the CVBS signal thereby determining whether signal amplitude at a center frequency of 4.43 MHz is greater than that at a center frequency of 3.58 MHz. Finally, a bandwidth of 4.5 MHz is assigned to the SAW filter for filtering the intermediate frequency signal to re-generate the CVBS signal when the amplitude at 4.43 MHz is smaller than that at 3.58 MHz. Further, a video decoder decodes the CVBS signal to determine a video format from NTSC, PAL-M, and PAL-N formats, and an audio decoder decodes the SSIF signal to determine an audio format from MN, BG, DK, and I formats.