Issue with colors on HDMI output on iMX6

[jeromebolduc]

Hi,

We have an issue with our i.MX6Q module where we are getting color problems when capturing video with a webcam using gstreamer and we render the result over HDMI.

On this snapshot, it was captured over HDMI using i.MX6Q. You can see my reddish face the orange color of the wall.

Here the snapshot taken on a webcam on my PC. My face is normal and wall is more accurate.

What do you think could explain the problem? We tried to change IPU quantization levels to fit 0-255 but it seems the IPU only works in limited mode, is that right?

We did a simple test to send a grayscale 0-255 over HDMI on the iMX6, here is the original picture:

Here is what we capture over HDMI:

We are missing the first 2x black steps and the last 2x white steps.

Is there an auto clipping? Is that would explain the reddish issue shown on the images above?

Any insight would be appreciated.

Regards,

Jérôme

[jeromebolduc]

Any update on how to change this parameter? My response seems to be deleted each time I post it?!

[jeromebolduc]

I would like to know how we can change live the quantization level (full and limited range) on the HDMI output. Is that possible?

[jeromebolduc]

Any update on this?

[jeromebolduc]

Do you know how to access SAT_MODE parameter through userspace?

[jeromebolduc]

Any help from NXP?

Jérôme

[jeromebolduc]

Any throughts on this? How to change SAT_MODE parameter at runtime?

Regards,
Jerome

[joanxie]

see this topic:

"https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/How-to-change-SAT-MODE-in-BT656-display-..."

[joanxie]

did you use your customized board, right? what bsp version do you use? and if you don't connect HDMI, save the capturing picture to the file, is it the color ok?

[jeromebolduc]

Yes, we tried our custom board. Using Variscite VAR-SOM-MX6. Also have the same results using their latest BSP Dunfell 5.4.142 and their development kit. I suspect an issue with IPU/G2D drivers.

If we are using a gstreamer pipeline and we decode this JPEG image and encode it again and save it to a file, gray scale is preserved. It has something to do with the IPU I suppose.

We found out that the HDMI output seems to be RGB limited in the AVI infoframe over HDMI and that the content is full-scale. 

Is there a way to tell the IPU to work in 16-235?

I tried to get an access to the IC Task parameters through an utility called memtool. Do you know if there is a way to access the SAT_MODE parameter?

Please let me know about your findings.

Regards,

Jerome

[joanxie]

pls refer to the enclosed csc sample code which can calculate the CSC matrix and updates in real time from given parameters(Brightness,Contrast,Saturation,Hue, and gamma).

[jeromebolduc]

Thanks, I am more interested in answering this question:

Do you know if there is a way to access the SAT_MODE parameter?

Regards,

Jerome

[jeromebolduc]

Any update on this?