iMX7 CSI MIPI : Deinterlace/FBUF Stride Configuration

[dh29]

Linux Kernel: v4.9.11

In my on-going battle to get an AD7280M (csi-mipi) working on an i.MX7 I can now capture an image from a PAL camera feed. Stable picture, correct colors, picture is clear....BUT.... I have 2 copies of the image, one on top of the other.

I am guessing that this is due to the ADV7280M sending INTERLACED picture, and I am not set-up for this.

To de-interlace the two images, I have enabled CSI de-interlacing (CSI_CSICR18 bit2) but I don't understand what to set register CSI_CSIFBUF_PARA. 

The mx6s_capture.c driver configures FBUF_STRIDE to the image pixel width i.e. 720 for my PAL input of 720x576, but according to the iMX7's manual,  

it should be set to Width of Frame Buffer (in double words) - Width of Image (in double words).

This raises the question of how do I find the Width of Frame Buffer ??

I have seen post i.mx6ul CSI receive interlace ccir656 video issue  which asks the same question but without any conclusion:

[Please note the iMX7. For other CSI MIPI posts, on the (very) rare occasions I've had a reply from NXP-support-staff, they have quoted advice only relevant to the iMX6 with an IPU which uses a completely different driver framework].

[Yuri]

Hello,

FBUF_STRIDE should be set to two lines, since after finished one, say field 0,

line, the buffer point will jump two lines, skipping field 1 line.

 The embedded DMA has two parameters for data transfer: start address

(for line) and (line) length. CSI_CSIFBUF_PARA provides them.

Have a great day,
Yuri

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[dh29 · Accepted solution]

Hi Yuri,

I have a solution working now for both PROGRESSIVE and INTERLACED from the ADV7280M.

However, I don't agree with your advice of setting FBUF_STRIDE. I have to set FBUF_STRIDE to 0 (zero) for a correct image. If I use 720 (line width) or 1440 (2x line width) the image is incorrect (garbled).

[dh29]

Hi Yuri,

This does not agree with the documentation! Is the documentation therefore wrong??

From what you are saying:

• for progressive (non-interlaced) PAL (720x576), FBUF_STRIDE should be set to 720
• for interlaced PAL (2-fields of 720x288), FBUF_STRIDE should be set to 1440 (2 x 720)

And, I just ignore DEINTERLACE_STRIDE and leave it as 0 ??