A strange problem with my board

I designed a video board, which mainly include input video AD, video processor, output video DA.

When testing my design, the board running in video local loop. That is, use a DVD to output CVBS analog video signal to my board, and then video processor forward the data from AD directly to DA, and DA output CVBS analog signal to a TV for user's view.

In the process, I found that after the board powered up, the output video on TV, which supposed to be a motion video, is stillness. And if I short circuit anyone of digital output signals of AD to the groud in a few seconds, the video on TV will be normal.

I have been working on the problem several days, and it is really tough for me.

Added after 5 minutes:

And I have tested following items, but no one is the root of the problem.

1)the signal quality is good, power, clock is good
2)AD and DA timing is ok
3)whatever the video on TV is normal, AD outputs are correct
4) I changed an AD, with other parts all the same, and the system is correct
5) I changed a video processor, with other parts all the same, and the system is correct, too.

It seems that maybe, there are compatibility problem between the AD and video processor

Hi,

It may be because of ADC saturation problem.
You may have to use other ADC which is having more number of bits.

If you need more information, contact me.

Regards,
N.Muralidhara

It would help if you give the IC numbers. Do any of them require a reset. Many video decoders / encoders require set up data via an I2C bus. More info please