Abstract: Video coding stands gives out several coding methods for interlace signal. However, many kinds of macroblock division methods for motion estimation, which makes these methods very time-consuming and can′t be used actually. So an extended video encoder was designed, motion-adaptive de-interlacing was used to convert interlace signal into frame signal, then encoding frame signal with the fixed frame method. There are three steps for signal converting. Firstly, motion detection by utilizing four field signals with the same parity to get motion status of pixel, secondly, according to the motion status of pixel, use different filter to interpolate the pixel, thirdly, interlace interpolation field and current field to get progressive frame. The experimental result shows that it can get the same peak signal noise rate as MBAFF, but the encoding time is about 1/3 of other methods. What′s more, when displayed on progressive screen, it can solve the problem such as line crawling etc.