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Visitor divya_123
Visitor
6,753 Views
Registered: ‎01-06-2016

Adding RGB to YCrCb IP and Chroma REsampler IP reduces CCM IP core performance

Hi,

I want to change the brightness of an image/video using XIlinx CCM IP core . For that I am  updating the CCM coefficient registers. I am using the input and output data format of CCM as RGB.

 

When I directly took the RGB output and connected to a display device , i was able to see brightness changes from dark to whitish. Actual case, our image data should be in YUV 4:2:0 format . So, I have used the following IP cores to convert RGB output of CCM to 4:2:0 .

          CCM -> RGB to YCrCb(4:4:4) + Chroma REsampler(4:4:4 to 4:2:0)

 

Now , when I tried to increase the brightness , it is not changing as expected . It is not becoming whitish for higher values of brightness . We need to have 20 steps of brightness variations. After 13th step not much change in brightness is observed.

 

Is adding the above IP cores to CCM IP core output , cause any impact on the output image quality? The above IP cores does format conversion only , right .

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1 Reply
Explorer
Explorer
6,707 Views
Registered: ‎11-25-2014

Re: Adding RGB to YCrCb IP and Chroma REsampler IP reduces CCM IP core performance

Adjusting brightness by changing CCM coefficients is very unusual. Brightess adjustment should be just a DC shift. Read this:

 

http://www.poynton.com/notes/brightness_and_contrast/

 

I work on video cameras. We handle brightness, contrast and gamma adjustments using look-up tables that are updated based on user inputs. Speaking of gamma, if you are processing raw images that have not been gamma-corrected, that will have a huge impact on the brightness of your images when displayed on a standard monitor. Make sure that is correct before adjusting brightness or contrast.