Video Capture problem with DM642 " the frame shift ,losing some lines of video"

If the shifting is for a short time than it could be the video decoder resynchronizing to the new video stream, which can vary in time based on the quality of the input signal but should usually happen very quickly. 

If the shifting is lasting indefinitely than you are probably looking at a de-synchronization between the incoming digital stream from the video encoder and the EDMA transfers that are setup to service the video port.Essentially what could be happening is that the video ports are getting out of sync from the EDMA transfers that are servicing them, this can happen if the video is disconnected and reconnected such that the disconnect happens during the middle of a frame. The video port resynchronizes with the video decoder but the driver and DMA within the DM642 may not always catch this condition so they will act as if the middle of the frame is the start of a new frame.

If this condition can be detected than you can call a covr_recover() function within the driver to resynchronize the DMA to the video port, normally you would call this command with FVID_control(fvidChan, VPORT_CMD_COVR_RECOVER, NULL);, the actual API is discussed in SPRA918a. I believe the driver is already set up to call this if it detects a short field, however depending on how fast the connect/disconnect happens it may not trigger. In the past the best way to fix this is to have the video decoder send a signal upon connection of the video source to the DSP for an interrupt to send the recover command, since this command will cause a studder in the video it is usually not good to use a periodic call.

Note that this problem no longer exists in the newer media processors we offer (Davinci and beyond) because the video ports initiate their own transfers without using the EDMA peripheral.

Hi Bernie,

Our application use TVP5154A and ChA or CHB video source will switch very often.

We meet the same issue on DM642 now.

Shall we really need to  call "VID_control(fvidChan, VPORT_CMD_COVR_RECOVER, NULL)"  for over run events every frame?

Where can i find the newest DM642 video port driver?

Which is the best way we shall take action now?

Hi Bernie,

As posted above, we have the same kind of questions, do you guys still support the DM642 development? do you still fixed bug in your DM642 video driver?  

We have the same video sync problem as above people, but we did a lot of effort to correct it - using video decoder and DM642 video driver to detect video lost sync, and re-sync it, we do not have problem in connection and disconnection, but we still see there is times video is shifted in our application. we use DM642 for traffic intersection control, 4 video cameras are connected to the Video ports. some brand video comeras are doing better than others.  

My questions are  - does DM642 have the bility to lock in the video with the EDMA scheme? is the hardware problem or video driver problem. when video port get ITU-R BT 656 digital video, it has all the info for a video, start and end, why DM642 can not do a proper video sync? 

Thanks.

Hi  Rex Liao!

 I have tried lots of method,both on software and hardware.

Finally  i found the useful way is to switch CHA and CHB before video Capture AD,

User analog switch can solve this problem effectively!

 

hi，Li Dong.We have the same video sync problem as you, but how did you to correct it - using video decoder and DM642 video driver to detect video lost sync, and re-sync it?