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Switching CSI into Progressive bt.656 Mode

Question asked by Steve Green on Sep 10, 2012
Latest reply on May 30, 2018 by yan zhang

We have a composite video decoder chip (TW9912) that can produce either Interlaced or Progressive bt.656 video, fed into CSI0.

In our application we do this:

   fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;

   ioctl(Fd_v4l_camera, VIDIOC_S_FMT, &fmt)

 

... and this works great when the video chip is in Interlaced mode; there's a reasonable but interlaced picture.

 

Now if we change the video chip to Progressive mode and also do this:

   fmt.fmt.pix.field = V4L2_FIELD_NONE; // according to V4L2, this means Progressive

   ioctl(Fd_v4l_camera, VIDIOC_S_FMT, &fmt)

 

... this gives no picture at all, though we can see data entering the CSI port from the video chip. This is the only change we made to our app. The drivers give no error, and if we read back the fmt using VIDIOC_G_FMT we see the correct value for fmt.fmt.pix.field (it is value 1).

 

Could someone please advise what we must do to configure the iMX to interface with a Progressive bt.656 signal.

 

Many thanks

 

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