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skhaled
Visitor
Visitor
1,594 Views
Registered: ‎05-29-2018

Artifact when scaling down with VPSS

Hello

 

I am using  VPSS to scale down 720x1280 Video to variable size to drive LED screen panels, with 16bits color depth,

 

however I am getting colored artifacts on the LED screen see photo pls, these artifacts disappear when I enable VDMA but cause a decrease in the throughput and video slags, and I don't want to use VDMA anyway as consume lot of resources.

 

any idea what causes these colored artifact?

 

cheers

 

20180808_105607[1].jpg
vivado.PNG
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7 Replies
samk
Moderator
Moderator
1,547 Views
Registered: ‎10-04-2017

Hi @skhaled,

 

I assume you are talking about the line and black pixels? I am not sure what the original image looks like so it is hard to tell what is incorrect with this one.

 

However, based on your description it sounds like the VDMA is acting as a buffer which fixes a starving/overflow issue in your system.

 

I would check your throughput characteristics of you video pipe and make sure that when you are scaling that your throughput is correct. This check is done by making sure all slaves can handle the data that they are being sent and that all masters are providing a sufficient amount of data so that the video transmitter does not run out of data.

 

Regards,

Sam

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Xilinx Video Design Hub
samk
Moderator
Moderator
1,546 Views
Registered: ‎10-04-2017

@skhaled,

 

If this is not your issue, please post the original (correct) image. 

 

Regards,

Sam

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skhaled
Visitor
Visitor
1,531 Views
Registered: ‎05-29-2018

Hi Sam

 

the original video (see pic bellow) would look very smooth, the black dot are just dead leds the artifact is those RGB threads from top to bottom.

 

the point is that when I enable more features (resampler, vdma) these artifacts fade out and I get smooth colors,

 

is problem with delay between RGB channels?

 

cheers

 

20180810_154804[1].jpg
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samk
Moderator
Moderator
1,520 Views
Registered: ‎10-04-2017

Hi @skhaled,

 

Because you do not want to use the VDMA, I will not look at why it is slowing down your throughput.

 

Looking at the VPSS artifacts, which Algorithm are you selecting? Bilinear, Bicubic, or Polyphase?

 

2018-08-10 11_29_44-Xilinx Documentation Navigator 2017.2 -  http___www.xilinx.com_support_documenta.png

 

-Sam

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skhaled
Visitor
Visitor
1,468 Views
Registered: ‎05-29-2018

Hi Sam

I am using Polyphase algorithm with 12 taps

 

the algorithms give worse results.

 

thanks

scaller.PNG
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florentw
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Moderator
1,399 Views
Registered: ‎11-09-2015

HI @skhaled,

 

What is your input color space? Are you doing any color space conversion with the VPSS in addition to scaling?


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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florentw
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Registered: ‎11-09-2015

HI @skhaled,

 

Do you have any update?

If your question is answered or your issue is solved, please mark the response which helped as solution (click on the button "Accept as solution" below the reply)

If this is not solved/answered, please reply in the topic giving more information on your current status.

Best Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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