Circuit for converting HDTV signals into conventional TV signals with the letter box mode

A high definition television signal conversion circuit using a letter box mode, comprising:

• analog/digital conversion means for converting a high definition television signal into a digital signal at a first sampling frequency;
• line decimation means for performing a vertical decimation of output data from said analog/digital conversion means according to a scanning mode to delete lines;
• horizontal filtering means having a number of horizontal filters equal to a number of an interpolation, for delaying sequentially output data from said line decimation means to perform a horizontal interpolation of the output data from said line decimation means;
• horizontal decimation means having a number of horizontal decimation units equal to the number of said horizontal filters, each horizontal decimation unit performing a horizontal decimation of output data from a corresponding one of said horizonal filters;
• memory means having a number of memories equal to the number of said decimation units, each memory storing output data from said horizontal decimation means in response to a first write clock and outputting the stored data in response to a first read clock, said first read clock being determined according to the scanning mode;
• and
• first digital/analog conversion means for converting output data from said first memory means into an analog signal at a second sampling frequency, said second sampling frequency being determined according to the scanning mode.