AnsweredAssumed Answered

ADV7842 VGA video format shift

Question asked by jbolduc01 on Oct 23, 2015
Latest reply on Jan 5, 2016 by Krishnavinod.k


We have a problem with the ADV7842 VGA input formats.


First, connected to a MS Surface Pro 3 via direct VGA connection through mini-DisplayPort to VGA adapter (tested both Apple mini-DisplayPort to VGA adapter and MS Surface VGA adapter):

- resolutions offered are 1920x1200, 1680x1050, 1440x900, 1280x800 (recommended), 1024x768.

- all work well and image looks as expected.


Next, connected a Macbook Pro 13" (retina), model MacbookPro11,1, directly through an Apple mini-DisplayPort to VGA adapter (tried three different adapters to verify adapter was good):

- resolutions offered are 1080p, 1080i, 720p, 1280x800 (default), 1280x768. 

- 720p, 1280x800, and 1280x768 work well and image looks as expected.

- 1080i option gives a solid black screen.

- 1080p option gives an image with significant shift to the right, with the right edge of the screen cut off (see image below)


Finally, I used the same Surface Pro 3 and MacbookPro11,1, but connected through an Extron EDID 101V.  The Extron has separate EDID settings for each of 14 different resolutions. I would set to a resolution, connect the cable to the laptop, and see how the signal looks.  (On the Mac, you have to be careful to select the "Best for Extron" radio button for each test. It sometimes switches off that.)  Here are the results:


Unless noted otherwise, results were the same for the Macbook Pro 13" (retina) and the MS Surface Pro.


800x600 - great

1024x768 - great

1280x720 - great

1280x768 - a little shifted to left, with some image lost on left of screen. but mostly usable (see image below)


1280x800 - shifted to right significant amount, right edge cut off. (see image below)


1280x1024 - great

1360x768 - great

1366x768 - very small shift to left, with some image lost on left of screen. usable (see image below)


1400x1050 - flickering distortion lines in image, and very small shift to left, with some image lost on left of screen (see image below)


1440x900 - solid black (no image)

1600x1200 - PC: great, Mac: stretched, with flickering distortion lines in image. This is the only one that seems to be different between the PC and Mac tested. (see image below)


1680x1050 - solid black (no image)

1920x1080 - great

1920x1200 - great


Do you have any ideas why we get the shift and the flickering from some sources? Is this related to EDID. I have attached the EDID used in these testings.


Can we correct the shift by the ADV registers?