AnsweredAssumed Answered

ADV7188 First frame delay?

Question asked by AlexKates on Sep 27, 2010
Latest reply on Sep 28, 2010 by mattp

Hi, I'm doing video capture with the 7188 and a BF561, working with the EZ-Kit code for a model.

 

My application requires a general sync between some analog data capture and the video. I am sending in sample numbers to the BF at a 1 kHz rate. I want to associate the frame number with this sample number sent at the time the frame is being decoded. I would like to be within +/-1 frame of accuracy in this association. At 29.97 fps, that's obviously +/- 33.3ms or so.

 

What I'm finding is that the first frame isn't being associated with any samples between 0 and 333, as I would hope,  but more like > 66 ms or 99 ms..., ie, 0, 1, 2, or 3 frames off (I've not seen > 3 frames off). After the first frame, all of the others seem to be correct, but offset by the same number of samples as the first frame.

 

That is, if I look at the first frame, figure out how many samples it is off by, and apply that as an offset, all of the other frames would be fine.

 

So it looks like I am having a problem with latency on the first frame. Is this a sign of some misconfiguration of the 7188, or does it have a native latency? If it does, why is it variable, and what could I do to minimize or eliminate it?

 

Thanks,
Alex

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