The DirectShow TV tuning architecture is based on pre-defined frequency tables, and the TV Tuner filter (kstvtune.ax) has an internal list of frequency tables. Each frequency table contains a list of frequencies, and corresponds to the broadcast or cable frequencies for a given country/region. So, when you use the IAMTuner interface, it gets the channel frequency values from the internal frequency tables according to the selected country/ region and tunes the TV channels.-The DirectShow TV tuning architecture is b Ha'ased on pre-defined frequency tables, and the TV Tuner filter (kstvtune.ax) has an int ernal list of frequency tables. Each frequency table contains a list of frequencies, and corresponds to the broadcast or cable frequ encies for a given country / region. So, when you use the IAMTuner interface, it gets the channel frequency values from the in ternal frequency tables according to the selec ted country / region and tunes the TV channels.