Unexpected, short-lived grabbed frame resolution change for DVI2USB3.0

dvi2usb-30

#1

Dear Epiphan Community Forum,

Sometimes for 1-2 seconds the resolution of my grabbed frame changes from the normal 1360x768 to 1024x768 for no apparent reason when using DVI2USB3.0 with the latest firmware.

Has anyone encountered such a problem and knows how to prevent it from happening?

Thank & best regards
Dave


#2

I assume this is a VGA signal? This is likely the signal being detected and interpreted differently over time, VGA signals due to being analog have some room for interpretation there. If you are capturing 1360x768 make sure that under Capture -> Configure Device on the Adjustments tab that the “Prefer wide VGA mode” box is checked and click OK.


#3

Thank you for the explanation and advice @AdamFrame. The signal is indeed VGA. Will the suggested setting work if I am grabbing frames via a custom software using vga2usb,jar, or do I need to set something via FrmGrab API (perhaps via FrmGrab_SetGrabParams) in my program ?


#4

The setting within the Capture Tool application will indeed still work!


#5

Brilliant! After reading the documentation (a pretty useful thing to do from time to time :smiley:), it seems that GRAB_PREFER_WIDE_MODE can do the magic via the API as well.
I will test the setting and get back in case I’m still encountering some analogue ambiguity!


#6

Sounds good, and yes you can set this via API also, for testing it might be faster to just use the setting in the Capture Tool application. But up to you!


#7

Hi @AdamFrame,

I set the grab_flags of GrabParameters to GRAB_PREFER_WIDE_MODE, but at times the resolution still comes off wrong. My only guess is it’s due to grab_flags_mask that determines “which bits from grab_flags are used”, as per the source code comment. grab_flags_mask is set to the default value of 983040 (or 11110000000000000000 in binary). Is grab_flags going to be correctly interpreted with the mentioned grab_flags_mask?

Thanks,
Dave


#8

Can you perform some testing in the Capture Tool application? Trying to fix the problem here first will be faster and easier than attempting to implement changes in code that we are not yet sure will alleviate the problem.


#9

I just realised that I can use an HDMI port, so the problem is solved. Embarrasing :grinning: Digital wins this time! Thanks for the help @AdamFrame! Epiphan is amazing.