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478 Views
Registered: ‎02-13-2019

ADV7511 720p resolution tolerance

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Hi,

I have a general question regarding video resolution tolerance when driving monitors with the ADV7511 HDMI transmitter.

I have a design where I wish to output a camera image on a PC monitor using the ADV7511.

I have already succesfully driven a test image on to a monitor through the ADV7511 using a 720p VHDL test pattern that I generated so I know this works.

The camera driving the image I wish to display provides configuration allowing the user to select a desired output resolution. It claims to output 720p, however its 720p frame has a 356 pixel clock discrepancy from the timings I used when generating the video test pattern.

I can't drive the camera image straight into the ADV7511 as it requires formatting, so in the formatting part I attempt to remove 356pixels from the frame being sent to the ADV7511. I do this by reducing the HSYNC period by 1 clock for 356 HSYNC's, but the Samsung Monitor being used then displays a message :-

"Not Optimum Mode","Recommended mode XXXX by XXXX 60Hz" 

So my question is, is there any tolerance when sending for example a 720p video frame to a monitor, or does it have to be exact as I seem to be finding.

Many thanks in advance

G

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430 Views
Registered: ‎11-09-2015

Re: ADV7511 720p resolution tolerance

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Hi @gwilym_williams ,

The first thing you want to ask yourself is what 720p means in both cases. I know or the default setting of the video timing controller, 720p means 720p50 thus the resolution is 1280 x 720 @ 50Hz. The 50Hz is important. It is not mentioned specifically but this is because it is a common resolution.

Your camera might be sending 720p60 meaning 1280 x 720 @ 60Hz. And this might be the reason why you are seing a discrepency. If you look at the monitor output, it mentions 60Hz.

I would recommend you to read my video series 15 - Understanding Video Timing with the VTC IP to understand a bit more about video timing.

Then the second thing you want to look at is, does my monitor supports this resolution? You need to be aware that monitors might not be supporting all the resolution. Usually, you have an EDID in the monitor for the source to know what resolution is supported by the monitor. Some "custom" (out of the standard) might not work.

Finally, how did you find the "356 pixel clock discrepancy" between the timing? Where is the discrepency? During active pixel or during active periods? (again refer to my video series 15 for details about active and blanking periods).

The difference might be that one resolution is doing reduced blanking and not the other. But that does not mean that the timing is incorrect.


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

Re: ADV7511 720p resolution tolerance

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Hi @gwilym_williams ,

The first thing you want to ask yourself is what 720p means in both cases. I know or the default setting of the video timing controller, 720p means 720p50 thus the resolution is 1280 x 720 @ 50Hz. The 50Hz is important. It is not mentioned specifically but this is because it is a common resolution.

Your camera might be sending 720p60 meaning 1280 x 720 @ 60Hz. And this might be the reason why you are seing a discrepency. If you look at the monitor output, it mentions 60Hz.

I would recommend you to read my video series 15 - Understanding Video Timing with the VTC IP to understand a bit more about video timing.

Then the second thing you want to look at is, does my monitor supports this resolution? You need to be aware that monitors might not be supporting all the resolution. Usually, you have an EDID in the monitor for the source to know what resolution is supported by the monitor. Some "custom" (out of the standard) might not work.

Finally, how did you find the "356 pixel clock discrepancy" between the timing? Where is the discrepency? During active pixel or during active periods? (again refer to my video series 15 for details about active and blanking periods).

The difference might be that one resolution is doing reduced blanking and not the other. But that does not mean that the timing is incorrect.


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

Re: ADV7511 720p resolution tolerance

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Hi @gwilym_williams ,

Do you have any updates on this? Were you able to make any progress?

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

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

Thanks and Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
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398 Views
Registered: ‎02-13-2019

Re: ADV7511 720p resolution tolerance

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Hi @florentw 

 

thanks for the response.

The camera generates 720p @ 60Hz with a total pixel count per frame of 1235644.

My HDMI side video pattern generator generates 720p @ 60Hz with a total pixel count per frame of 1236000. This is where the 365 pixel discrepancy appears.

There's no way to modify the camera video timing to match those for the HDMI side, that's why I attempted to remove 1 pixel from 356 horizontal blanking periods, but the HDMI driven monitor would not display this output.

I've contacted the camera manufacturer to confirm that this is the case, I await their response.

 

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Moderator
Moderator
392 Views
Registered: ‎11-09-2015

Re: ADV7511 720p resolution tolerance

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Hi @gwilym_williams ,

You should be able to do a different timing for both input and output. Just store the frames in memory using a VDMA or frame buffer and then generate a correct timing with the VTC


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