UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

cancel
Showing results for 
Search instead for 
Did you mean: 
Observer ego
Observer
802 Views
Registered: ‎05-02-2018

Chroma Resampler number of bits at the output

Jump to solution

Hi

I am using Vivado 2015.4 for video processing on Z7030 board. I have a camera output in YUV 422 format with 16 bits/pixel which I can display from a HDMI monitor. I would like to convert YUV 422 to YUV 420 to decrease the number of bits/pixel to 8 bits/pixel. However when I use the Chroma Resampler IP in Vivado the  number of bits at the output does  not change from 16 bits even though 420 uses less number of bits in comparison. How can I decrease the number of bits at the output of this conversion? Any alternative is also welcomed.

 

Regards,

Engin

Tags (1)
0 Kudos
1 Solution

Accepted Solutions
Highlighted
Moderator
Moderator
887 Views
Registered: ‎11-09-2015

Re: Chroma Resampler number of bits at the output

Jump to solution

Hi @ego,

 

If everything is clear for you, please kindly close the topic by marking a reply as accepted solution.

Thanks and Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
0 Kudos
4 Replies
Moderator
Moderator
742 Views
Registered: ‎11-09-2015

Re: Chroma Resampler number of bits at the output

Jump to solution

Hi @ego,

 

I think you are unclear on YCbCr422 and YCbCr420. There is no difference of bit width depending on the two.

 

For YCbCr422 you will send YCb - YCr on every line.

 

For YCbCr420, you will send the chroma information only 1/2 lines.

 

So for both clolor format you need 2*component width.

 

Check the figure 2-6 of the TPG Product Guide (PG103), it is two pixel per clock but it might help you understand the difference between the 2:

TPG.JPG

 

Hope that helps,

 

Regards,

 


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
0 Kudos
Observer ego
Observer
733 Views
Registered: ‎05-02-2018

Re: Chroma Resampler number of bits at the output

Jump to solution

Thanks for the detailed description Florent. Let me summarize what I understand from the YUV or YCbCr representation.

YUV 444 uses the same number of bits namely 8+8+8=24 for the Y, U and V fields respectively. YUV 422 decimates U and V fields and obtains Y0U0Y1V0 sequence by using 8+4+4=16 bits/pixel. This is a decimation in vertical lines. When decimation is employed in the horizontal lines we obtain YUV 420 with 8+4+0=12 bits/pixel . The decimation in U and V fields is possible  since human eye is less sensitive to these terms and does not sense the difference between the original and YUV 420 image. In fact your figures show that YUV420 has less number U and V terms compared to YUV422 and therefore should have less number of bits/pixel. As I have pointed in my original post, when I use the Chroma Resampler IP, the number of bits/pixel for YUV422 and YUV420 representations are the same and 16 bits/pixel. I expect to see a decrease in the number of bits since YUV420 uses less terms.

 

Regards

Engin

 

0 Kudos
Moderator
Moderator
717 Views
Registered: ‎11-09-2015

Re: Chroma Resampler number of bits at the output

Jump to solution

Hi @ego,

 

You are still not right.

 

With YCbCr444 you have 8+8+8=24 bits this is correct.

 

For YCbCr422 you have a horizontal decimation. So you will send half the chroma information so you will send Ycb then YCr then again YCb. So you wuill have 8+8 = 16 bits (and not 8+4+4 you are still sending the full value for the chroma).

 

Then for YCbCr420 you will have a vertical decimation. This means that for odd lines you wont send any chroma information for some pixels.

 

Thus YCbCr420 you will send less data per frame so the mean bit per pixel will decrease. But for even line, you are still sending the Y + a chroma value so it will still be 8 + 8 = 16 bits.

 

Hope that clarify. If not, you might want ot read some books about Chroma Subsampling


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
0 Kudos
Highlighted
Moderator
Moderator
888 Views
Registered: ‎11-09-2015

Re: Chroma Resampler number of bits at the output

Jump to solution

Hi @ego,

 

If everything is clear for you, please kindly close the topic by marking a reply as accepted solution.

Thanks and Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
0 Kudos