Bottom Black bar problem(22lines) of ADV7179 Output

Hi,

I designed and made the video compressor and de-compressor system using ADV212.

I use the input and output video data format as ITU656(NTSC) to use commercial CCTV camera.

I have problem with the system because of the bottom black bar(22 lines) on the output video.

When I see the output video on PC captured by Matrox frame grabber, 22 lines in 480 lines are exist.

Although I checked every register setting of ADV212, ADV7179, I could not find why the black bar is exist in the output video.

Here is the vertical sync signal of ADV7179 (NTSC).

According to measured signal, last 11 lines of each field are looks like blank area.

Is there any body who solved same problem? ;(