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PC resolution, HDMI lag

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Old 09-05-2010, 02:30 PM   #1
What is HD?
 

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Default PC resolution, HDMI lag

Hello, complete noob here.

Was looking at a Loewe TV yesterday and as we currently have a media PC connected to our current TV by VGA (and optical to the amp) then we took the laptop along to check on the quality of the VGA picture.

When plugged in with the VGA the max screen resolution that the graphics card gave as a choice was 768 x 1360 (or something like that) even though the TV screen is 1080 x 1920 (laptop will do 1200 x 1920). Am I to understand from this that certain 1080 TVs do not allow 1080 with all connections. This is seems most confusing.

Then tried it with the HDMI which seemed to allow the 1080 x 1920 setting but the was a lag - move the mouse and the pointer was a bit behind. Not a huge problem but still a big surprise - again this seemed confusing. Should this happen?

If anyone fully understands how HD TVs work with PCs or maybe knows of a list of what resolutions you get from what inputs on which TVs would help make this all seem a bit l clearer. I read somewhere that the VGA size depends on the 'native resolution' of the screen. Why would this not be 1080 x 1920?

Thanks
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Old 09-05-2010, 02:38 PM   #2
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Yes some TV manufactures will limit the resolution available to be input on the VGA port, I believe this is because you can copy protect data over HDMI (HDCP) but not over VGA so they don't want people be able to output full HD (1080P) that isn't copy protected. You could either look for a different TV or stick with HDMI, tho I am not sure of the reason for the lag. My HTPC is connected via HDMI and so has my laptop been with no lag.
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Old 09-05-2010, 02:45 PM   #3
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I'd try a different HDTV. None of mine lag either.

Last edited by rbinck; 09-05-2010 at 06:01 PM. Reason: Fixed
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Old 09-06-2010, 12:22 AM   #4
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Wow - the TV now checks if you're watching genuine stuff. I am surprised. It doesn't seem to make sense that the manufacturer would limit the VGA resolution input because of this though does it? If I had a Blu Ray drive on my PC then I could not watch it in 1080 because the TV is trying to prevent pirate copies being viewed? Our media PC only has VGA out, (the HDMI used in the shop was off our laptop - won't be using the laptop with the TV at home- just took it to the shop try stuff out). Maybe a new graphics card with HDMI would work better. However it would be useful know now if the lag we experienced is down to the PC/graphics card or the TV.

Is it common for 1080 TVs to not allow 1080 through the VGA connection? Or am I looking at TV which is the exception rather than the norm? I cannot seem to find on the internet any specs for any brand of TV that state what resolution you get through VGA - even in the details for the the Loewe TV it does not mention the VGA resolution. This does seem a bit misleading if it is often less than the actual resolution of the screen.

Also, I appreciate I could look at other TVs. I was wondering if anyone could shed some light on the whole lag problem (and VGA problem) in fairly untechy terms so that I understand what is going on. Now I have started to look into all this I would rather understand what is going on and so make an informed purchase choice - also, once I want to know something I want to know which is why I've joined this forum and asked the question. However, if I can't find out then I will look at other TVs so thanks for the advice
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Old 09-06-2010, 08:56 AM   #5
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First the TV does not do the checking, the PC does. Basically through HDMI the source device (PC in this case) will request a HDCP verification from the TV. If it gets a validation that it is connected to a display device rather than some type of device capable of capture, it will allow the HD video to be output.

Now when the output is VGA, or other analog output, the source device will default to some non-HD resolution. With Blu-ray players this would be 480p.

Now it is true that most HDTVs will not allow 1920x1080p/60 through their analog inputs be it VGA or component, but a few will. I have Westinghouse LVM series monitors that will. But most will allow 1920x1080i/30 through their analog inputs. The problem here is most laptops will not output interlaced video like true media PCs will. I use 1920x1080i/30 on my media center PC because I use my whole house distribution system that is limited to 1080i video.

Is your TV the exception? No, I'd say it is the norm as only a few HDTVs or monitors will accept a 1920x1080p/60 input through the analog connections.

Now to the PC being able to output HD video through the analog outputs. I use an LG combination HD DVD/Blu-ray drive that came with their version of PowerDVD v7 and it will output HD video through both the VGA and component outputs. My media PC has both VGA and component outputs as well as HDMI. As I understand the newer versions of PowerDVD will not, like v10. Since I haven't updated mine past v8, I'm not completely sure about that. There was some talk about the newer versions being forced to downconvert through the analog outputs like the players have to, but that I don't know of either.

The reason for the downconversion through analog ports and HDCP requirements is because the motion picture industry got congress to pass a law making it illegal to sell equipment in the USA that does not comply with HDCP. There is an analog exemption that they are trying to close though.

Thus I have given up on Blu-ray discs for the most parts and record my HD media via my Hauppauge 1212 HD-PVR Video Capture device which allows me to order a pay for view movie and record it while I watch it. The resulting file is not as good as Blu-ray, but is as good as broadcast HD.

Video lag is due to the video processors in the TV. All TVs have them, but some are better than others. Also some TVs have the ability to turn off most of the video processors. There are two types of video processors, serial and parallel. Parallel processors are fast, serial processors are slow because the video must pass from one to the next through up to four stages and each stage has a small amount of time the processor takes. You can think of water through a pipe. Say you inject a dye in the source. On a long pipe it takes some time for the dye to show up.

Most LCDs have some lag due to the video processors they choose compared to most plasmas. It does take some shopping and research to find a HDTV that is low on lag. Lag in TV watching is somewhat unimportant as long as the audio and video have the same delay, but gaming is where the lag comes into play.

Last edited by rbinck; 09-06-2010 at 09:01 AM. Reason: spelling
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Old 09-08-2010, 11:21 AM   #6
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Right, thanks for that info. Let me just make sure I get it.

The pc knows what the TV was because it called it a Loewe TV when we went to change the resolution of the display. So it will do the HDMI OK as it knows it's a TV. But if it knows it a TV then why would it limit the resolution through the VGA. Or is this a slightly seperate matter? If the PC thinks it's not outputting to a display it will reduce the resolution of the HDMI. The VGA resolution is less just because of the design and capabilities of the TV? Not sure from your info if the VGA reduced resolution is because of the PC analogue output or because of the TV?

And - I'm not in the USA, I'm in England so would such things still apply?

I noticed that the TV had a 'gaming mode' setting. As the TV will also be having and Xbox 360 and a PS3 put through it then maybe gaming mode cuts out the processing that the TV normally does so there is no lag. The TV is 200Hz and apparently works out the 3 missing frames (for us PAL 50Hz people), which I find quite astonishing. Is this really what the TV does? How does this work with your NTSC 60Hz?

The 360 will also do VGA out but I've heard there might be an issue if it tries to output at 720 if the screen is not 720 as it's native resolution.

I think the Sky box also has something to adjust the audio.

So - Sky box in on HDMI, 360 and PS3 in on HDMI with gaming mode on - this will use up the 3 HDMI inputs. Then the PC in on the VGA at 768 x 1360. BUT, if we want the PC to be 1080 then will need another HDMI input. Could always see if there's something that lets you put 2 HDMIs into 1.
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Old 09-08-2010, 12:54 PM   #7
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The TV will give information to the PC, but only through the HDMI connection. As you suspected, the analog is another matter. Most likely the PC video card will not allow 1920x1080 on the analog output. You may be able to get some software that will allow modification of your video driver, but where you are, I don't know.
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