New Display: 1920X720. How to config?


13 posts
by AshPowers » Fri May 12, 2017 11:38 pm
I've come across a small handfull of search results regarding the modification for custom defined resolutions/hdmi modes.. I just haven't come across the information I need to set this new display up properly.

I am new to the Pi (~4 weeks) and do not know what potential consequences may exist if I just start punching text into config files and seeing what happens.

The display I have is 1920X720 native resolution.

In 1920X1080, 50Hz mode, she displays just fine with the exception of the image being vertically stretched, which was expected. I've run it at lower resolution selections in the Raspberry Pi Configuration without any errors.. Obviously the image just isn't properly scaled to its true resolution.

What exactly needs to be done to the configuration of the RPi3 B v1.2 to enable it to function with this particular screen resolution?

Thanks!
-Ash
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by fruitoftheloom » Sat May 13, 2017 5:28 am
AshPowers wrote:I've come across a small handfull of search results regarding the modification for custom defined resolutions/hdmi modes.. I just haven't come across the information I need to set this new display up properly.

I am new to the Pi (~4 weeks) and do not know what potential consequences may exist if I just start punching text into config files and seeing what happens.

The display I have is 1920X720 native resolution.

In 1920X1080, 50Hz mode, she displays just fine with the exception of the image being vertically stretched, which was expected. I've run it at lower resolution selections in the Raspberry Pi Configuration without any errors.. Obviously the image just isn't properly scaled to its true resolution.

What exactly needs to be done to the configuration of the RPi3 B v1.2 to enable it to function with this particular screen resolution?

Thanks!
-Ash


Yes but how are you connecting to the Monitor ? .HDMi, VGA adaptor, HDMi to DVi, Composite ?

https://www.raspberrypi.org/documentati ... t/video.md
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by AshPowers » Sat May 13, 2017 9:13 pm
It is connected to the HDMI port, no adapters, just a cable to the display's controller board.
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by AshPowers » Sat May 13, 2017 9:55 pm
How can I configure a custom aspect ratio? It is not listed in the hdmi_cvt section of that page. I'm pretty certain this is a 8:3 AR.
Last edited by AshPowers on Sun May 14, 2017 8:10 pm, edited 1 time in total.
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by mahjongg » Sat May 13, 2017 10:47 pm
perhaps https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=5851&p=77547#p77547 will answer that, IF its at all possible.
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by AshPowers » Sun May 14, 2017 1:48 am
I have a pretty decent grasp of how the configuration and parameters used in the config.txt file works in relation to the video output, unfortunately I do not see an actual mode that covers 1920X720, a 24:9 (or 8:3) aspect ratio. This will need to be added in to drive this display properly.

Unfortunately there is no easy workaround for this problem on my end as my application uses pi3d and it is screwing up the scale of rotating sprite components. Circles look like wide ovals when running it in 1920X1440, for obvious reasons.

Gonna need some help on this one.
Last edited by AshPowers on Sun May 14, 2017 7:34 pm, edited 2 times in total.
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by AshPowers » Sun May 14, 2017 2:24 am
Also, when I check the tvservice for CEA and DMT modes, the correct 1920X720 resolution is not listed. It shows 1920X1080 as the "prefer" setting.

I presume that this information is coming from the controller of this display, and not from the HDMI controller in the RPi, correct?

I have tried using a custom resolution and when I run it in 1920X720 resolution, the lower ~20mm of this 12.3" display is a fuzzy static.

I'm thinking that this controller that came with the display is not properly programmed for this display. It appears that the controller is designed for use with a 1920X1080 display and simply does not know what to do when you send it HDMI data on a 1920X720 format.

Is that a safe assumption to make? It looks like the RPi is doing what it is supposed to, although it would be more assuring if it were to also have the 24:9 (8:3) aspect ratio as a selection number for defining custom resolutions. I dont know what the consequence of that not being there has on what I am seeing.
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by AshPowers » Wed May 17, 2017 9:24 pm
OK, I have taken a video of what I am seeing on the display. As the video shows, the Pi says it is running 1920X720 but there is the lower ~20mm or so that has this static. There is actual desktop behind that static as when I drag the mouse below that top edge and further down, as I move the mouse back up, it takes a moment for the mouse cursor to reappear.

https://www.youtube.com/watch?v=3Ks_BaIPlXY

In config.txt,
overscan is off
framebuffers are set to 1920 and 720
force_hotplug is off
group = 2
CVT = 1920 720 60
mode = 87
drive = 2

I have tried 50Hz, 75Hz as well and same issue. 120Hz causes it to change to 1920X1080 for some odd reason.
1920X1080 works and it does not have the static, but it causes the screen to compress vertically and circles look like wide ovals.

I dont know if it is a problem with the display or a problem with the RPi, so I have no where to start.
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by fruitoftheloom » Thu May 18, 2017 5:08 am
AshPowers wrote:OK, I have taken a video of what I am seeing on the display. As the video shows, the Pi says it is running 1920X720 but there is the lower ~20mm or so that has this static. There is actual desktop behind that static as when I drag the mouse below that top edge and further down, as I move the mouse back up, it takes a moment for the mouse cursor to reappear.

https://www.youtube.com/watch?v=3Ks_BaIPlXY

In config.txt,
overscan is off
framebuffers are set to 1920 and 720
force_hotplug is off
group = 2
CVT = 1920 720 60
mode = 87
drive = 2

I have tried 50Hz, 75Hz as well and same issue. 120Hz causes it to change to 1920X1080 for some odd reason.
1920X1080 works and it does not have the static, but it causes the screen to compress vertically and circles look like wide ovals.

I dont know if it is a problem with the display or a problem with the RPi, so I have no where to start.


It would appear the screen uses a Controller Board, therefore it is quite feasible that the Raspberry Pi is actually receiving the correct information. It is the actual Controller Board which is not calibrated correctly.
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by MaxK1 » Thu May 18, 2017 11:33 am
Any links to the display/controller?
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by AshPowers » Thu May 18, 2017 6:05 pm
fruitoftheloom wrote:
AshPowers wrote:OK, I have taken a video of what I am seeing on the display. As the video shows, the Pi says it is running 1920X720 but there is the lower ~20mm or so that has this static. There is actual desktop behind that static as when I drag the mouse below that top edge and further down, as I move the mouse back up, it takes a moment for the mouse cursor to reappear.

https://www.youtube.com/watch?v=3Ks_BaIPlXY

In config.txt,
overscan is off
framebuffers are set to 1920 and 720
force_hotplug is off
group = 2
CVT = 1920 720 60
mode = 87
drive = 2

I have tried 50Hz, 75Hz as well and same issue. 120Hz causes it to change to 1920X1080 for some odd reason.
1920X1080 works and it does not have the static, but it causes the screen to compress vertically and circles look like wide ovals.

I dont know if it is a problem with the display or a problem with the RPi, so I have no where to start.


It would appear the screen uses a Controller Board, therefore it is quite feasible that the Raspberry Pi is actually receiving the correct information. It is the actual Controller Board which is not calibrated correctly.


Yes, the display has its own controller board. When I use the tvservice -m for CEA and DMT modes, the controller does NOT report back that it has a 1920X720 display mode. If I am not mistaken, tvservice is requesting data from the LCD's controller for the available modes it will support. It appears to me that the controller just does not support that resolution although both were purchased together.

Can someone confirm that tvservice is in fact, polling the controller for its available modes or is tvservice only reporting the modes that the RPi's video output will support?
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by AshPowers » Thu May 18, 2017 7:59 pm
More digging into this I have found that tvservice does, in fact, poll the LCD's display controller for its available modes.

I also attached this display to my Dell Inspiron laptop and configured the Intel Graphics to run it at 1920X720, 60Hz, CEA timing, and it does the same exact thing.

Two possibilities here: 1) Because the controller does not have an entry for the 1920X720 resolution, it does not know how to handle running that resolution.
2) There is a different problem with the controller.

I have run the display at higher resolutions so I doubt it is a memory issue with the memory on the controller board.
I just dont know enough about these display controllers to put my finger on what the problem is and my supplier for the display seems to be more lost than I am, LOL.
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by fruitoftheloom » Thu May 18, 2017 8:09 pm
AshPowers wrote:More digging into this I have found that tvservice does, in fact, poll the LCD's display controller for its available modes.

I also attached this display to my Dell Inspiron laptop and configured the Intel Graphics to run it at 1920X720, 60Hz, CEA timing, and it does the same exact thing.

Two possibilities here: 1) Because the controller does not have an entry for the 1920X720 resolution, it does not know how to handle running that resolution.
2) There is a different problem with the controller.

I have run the display at higher resolutions so I doubt it is a memory issue with the memory on the controller board.
I just dont know enough about these display controllers to put my finger on what the problem is and my supplier for the display seems to be more lost than I am, LOL.


AFAIAA the controller board has a HDMi input chipset which should send the EDID information to the Raspberry Pi HDMi chipset and that appears from the information provided correct.

It is the controller board circuitry which converts the HDMi input to the screen output, whatever that may be.....

Therefore I would presume the controller board has a programmable eeprom ( lvds boards do so ).
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