We are develpping a video processing unit. The unit has one CVBS video input and one CVBS output. We are using adv7181c video decoder and adv7393 video encoder. The video input source can be PAL or NTSC. The digital data from video decoder (YCbCr, 8 bits, 4:2:2, EAV/SAV) is connected to the appropriate digital input port of video encoder and the pixel clock output of the ADV7181 to the clock input of the ADV7393. We configured the ADV7181C video encoder according to the script ##SD CVBS## version 3.2 and the video decoder according to the table 65 in the datasheet. The analog video input and output are connected to the video monitor. The setup is working well when we are using the PAL video source (the video output quality is similar to video input quality) . When connecting NTSC video source the color of the video output became ustable. We have activated the color bar option on the video encoder and the color bar on the monitor was stable for PAL video source only. Then we disconnected the pixel clock from video encoder and connect a 27mhz clock generated by PLL of the FPGA. The color bar became stable for any video source. So the problem in the 27mhz clock from the video decoder when the source of video is NTSC. It seems that there is a problem in configuration of the video decoder. We appriciate any help.