shmups.system11.org

Shmups Forum
 
* FAQ    * Search
 * Register  * Login 
It is currently Wed Jun 28, 2017 3:40 pm View unanswered posts
View active topics



Post new topic Reply to topic  [ 8 posts ] 
Author Message
 Post subject: HDMI to VGA adaptr issues [720p]
PostPosted: Mon Mar 20, 2017 11:00 am 



Joined: 19 Mar 2017
Posts: 6
I currently have a HDMI to VGA adapter plugged into my video card's HDMI port. It is outputting a 1360x768 signal to a HDTV with a matching resolution. As it is 1:1 pixel mapped the desktop and text etc looks exactly as it should (flawless) and I am very happy with it bar one thing - I have to undervolt my video card or I get a very faint ripple or wave type effect which appears when playing games. Now I suspect that this has something to do with inherent shortcoming in analog VGA signals (read interference) but it still confuses me because I assumed the HDMI port was sending a clean digital signal to the VGA adapter (but why is the issue only present when gaming?). Not being the type of person that can let something like this go I ended up buying 3 completely different VGA adapters in an attempt to isolate the issue. Someone has suggested they mighht be passive adapters rather than active adapters, but how the hell do I tell? All I know is that they are all in-line adapters that don't require an external power supply. Would anyone be able to explain what I'm seeing or recommend a HDMI to VGA adapter that handles things differently to the ones I'm already using or have another suggestion... something bizarre like buying a new PSU?


Last edited by strayan on Tue Mar 21, 2017 1:07 am, edited 1 time in total.

Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Mon Mar 20, 2017 2:03 pm 


User avatar

Joined: 06 Oct 2015
Posts: 1716
Location: Canada
There is no such thing as a passive HDMI to VGA adapter. You'd need to have a DP++ compatible DisplayPort output, and then you could have a passive DisplayPort to VGA adapter, but not HDMI.


Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Tue Mar 21, 2017 12:58 am 



Joined: 19 Mar 2017
Posts: 6
Guspaz wrote:
There is no such thing as a passive HDMI to VGA adapter. You'd need to have a DP++ compatible DisplayPort output, and then you could have a passive DisplayPort to VGA adapter, but not HDMI.


I did not know about DP++. I will give that a shot.

Any idea where the EMI is coming from or how to address it?


Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Tue Mar 21, 2017 4:03 pm 


User avatar

Joined: 20 Dec 2016
Posts: 27
It might be of help if you would list what converters you have tried.

If the devices you were using don't have a separate power cable they will take the power through the HDMI cable. So the graphic card will supply the converter with power.

I also recently went shopping for such a converter. And pretty much all of the ones I found came with some sort of power cable, most use USB cables. In most cases it should work without a power cable. But that's not the proper way.


Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Tue Mar 21, 2017 4:47 pm 


User avatar

Joined: 06 Oct 2015
Posts: 1716
Location: Canada
HDMI is only required to provide a minescule amount of power (55 milliamps at 5 volts), so if an active converter will work on bus power alone is a crapshoot: the answer is yes only if the HDMI device provides far more power than it is required to.


Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Wed Mar 22, 2017 8:55 am 



Joined: 19 Mar 2017
Posts: 6
Nekoi wrote:
It might be of help if you would list what converters you have tried.


Sure:

https://www.amazon.com/Ableconn-HDMI2VG ... 783&sr=1-1

https://www.amazon.com/UGREEN-Adapter-C ... ugreen+vga

https://www.aliexpress.com/item/Male-to ... .57.7WC6Jx

Guspaz wrote:
HDMI is only required to provide a minescule amount of power (55 milliamps at 5 volts), so if an active converter will work on bus power alone is a crapshoot: the answer is yes only if the HDMI device provides far more power than it is required to.


Is there any way to disable power over HDMI?

Maybe I should try fibre optic hdmi cable: https://www.kogan.com/au/buy/unitek-15m ... ed-unitek/

Tempted to try optical cables but I read that some optical cables still have copper wire running along it for power: https://www.amazon.com/Optical-Cables-C ... OJRF6K#Ask


Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Wed Mar 22, 2017 2:23 pm 


User avatar

Joined: 06 Oct 2015
Posts: 1716
Location: Canada
Most devices that need more power than most HDMI devices produce have a supplemental power input (usually in the form of a mini or micro USB jack), using that will cause it to draw power over USB instead of HDMI. Some devices are designed to work within the power that HDMI does provide: Monoprice's optical HDMI cables are designed to work with 250 mW, which is within what HDMI is required to provide.

A 1.5 meter long fibre optic HDMI cable is laughably useless, so I'm going to assume that is intended to be a 15m cable. Either way, that's overpriced: Monoprice will sell you a 100m long fibre optic HDMI cable for US$135, and that appears to be a 15m cable for AU$115 (US$88). So it's not very cost effective, although I don't know what the equivalent to Monoprice is in Australia. Here in Canada, we have local distributors like PrimeCables who carry most Monoprice products by having stuff shipped to them in bulk as freight, presumably there is some equivalent in Australia.

Fibre optic video cables are only useful if you need to run a cable longer than copper is practical, and you're still within the realm of much cheaper ultra-slim HDMI cables at 3m or less. I don't see any point in a fibre optic HDMI cable below maybe 20m (where active HDMI cables top out), and there are cheaper solutions involving cat6/cat6a cable for long distance runs below 100m.

Of course, in your situation, you're looking to use the cable as an optoisolator. I'm speculating, but I don't think that would make a difference: if your HDMI port is putting out dirty power, you're still going to be using that power to convert the signal to optical. I would imagine that they don't have copper running that long down the cable, they probably draw power at both the sink and the source.

The UGREEN adapter you bought supports external power via USB. Try using an external power supply with it to see if that makes a difference.


Top
 Offline Profile  
 
 Post subject: Re: HDMI to VGA adaptr issues [720p]
PostPosted: Tue Apr 04, 2017 4:03 am 



Joined: 19 Mar 2017
Posts: 6
Guspaz wrote:
You'd need to have a DP++ compatible DisplayPort output, and then you could have a passive DisplayPort to VGA adapter, but not HDMI.


Thanks, this solved the issue!


Top
 Offline Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC


Who is online

Users browsing this forum: aconbere, SuperDeadite and 12 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Space Pilot 3K template by Jakob Persson
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group