Author Topic: HDMI scrolling effect at high resolution - any ideas?  (Read 785 times)

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Offline Ale2.0Topic starter

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HDMI scrolling effect at high resolution - any ideas?
« on: April 04, 2020, 09:36:17 pm »
Hello dear community!

I am currently building up a new FPV setup for my drone.  For this I also use a HDMI to AV converter which works great at 480p but i get a scrolling like effect (Video, zipped). It gets better if I lay down a finger on the connector but not perfect (only if I truly touch the contacts) .

As I have no real clue of the HDMI standard I don't know of I could force 480p by hardware?

Fyi the source is a GoPro Hero 7 Black which outputs 1080p if not filming and during filming 480p. As far I have researched there's no way to enforce 480p output.

So if someone has an idea how to change this let me know!  :)

Thanks beforehand and greetings from Switzerland
Ale
 

Offline amyk

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Re: HDMI scrolling effect at high resolution - any ideas?
« Reply #1 on: April 04, 2020, 09:37:56 pm »
Loss of vertical sync.
 

Offline Ale2.0Topic starter

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Re: HDMI scrolling effect at high resolution - any ideas?
« Reply #2 on: April 04, 2020, 09:39:40 pm »
Yeah I thought this is a thing is there any way to fix this?  Thanks anyway!
 

Offline Ale2.0Topic starter

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Re: HDMI scrolling effect at high resolution - any ideas?
« Reply #3 on: April 04, 2020, 10:17:38 pm »
I now also reflowed some pins at the connector but it did not help
Actually if I press on the contacts I can get it nearly perfect but iI Don't know what I am adding. Maybe some resistance,  capacitance? I tried connecting some pins with a 1Mohm resistor which only had an effect on one pin which has a solid 3.2V on it according to my oscilloscope. I also reflowed this pin.  No clue what's going on...   |O

Edit: I also tried shielding everything with some tinfoil. Had no effect.
 

Offline Ale2.0Topic starter

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Re: HDMI scrolling effect at high resolution - any ideas?
« Reply #4 on: April 05, 2020, 08:25:46 pm »
UPDATE:
As touching the pins was the only indicator for help I tried different resistors to short some pins. Dirty but seems to be a way. I could identify one pin which is affecting it. Oscilloscope tells me it's a 3.2v stable. Anyway may investigate more later. If I connect it with one MOhm to the pin beside it, it's getting better. The lower I get with the resistance the better it gets. At a value of 510 Ohms it almost disappeared.  :wtf:

I think I'll solder this resistor down but to be honest it's not really satisfying me as I have no clue what it's affecting etc.  I think 510 is still a relatively high resistor, especially with only 3.2 V applied.

What do you think about this?  Is it somehow making sense to anyone?

Picture: The two pins I am talking of marked with black points. It's  a micro HDMI, but I can't get any Theory around with the pinout either.

Thanks for any explanation :phew:
 


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