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5 posts

Wannabe Geek

#60481 26-Apr-2010 20:03
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In general, do HDTVs sleep/standby on loss of signal from an HDMI source (ie. as a computer monitor would)?

Thinking of buying a Panasonic TH-L37G1037" LCD TV but notice that it doesn't do this. Are there other makes/models, with this feature that I should consider?

Many Thanks

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722 posts

Ultimate Geek

  #323808 27-Apr-2010 18:28
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My Samsung 32" doesn't. A right pain as it leaves a "no signal" dialogue box, as well as one indicating input source. The only work-around I have found is using an option inside Mediaportal config that totally shuts down the screen after a set time.

Typical of manufacturers: don't want to know about connecting to a computer & make it hard as hell to find info regarding the matter. Take trying to find out if a make was able to do 1:1 pixel mapping a while back.

Silverstone LC14 HTPC Case/Intel E4600 CPU/GA-EP35-DS3 MOBO/Asus EN9500GT graphics/2GB RAM/total 2TB HDD space/HVR-2200 & 2X 150MCE tuner cards/LG GGC-H20L BD Drive/MCE2005/Mediaportal/TVServer 1.1.0Final/LG 55"3D LED-TV/Denon AVR-1803 receiver/X1 projector

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Wannabe Geek

  #324799 29-Apr-2010 15:50
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Thanks for the feedback 1gkar.


10574 posts

Uber Geek

  #326929 5-May-2010 14:58
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I've got related problems with HDTV or monitor connected to laptop via HDMI, HDMI->DVI, or VGA.

It seems that normally (on most desktops) there's still a signal sent by the computer to the screen even when the computer is in "sleep" mode, so that the monitor knows that it's connected and it's sleep time, not just unplugged from the device.
It further seems that with some laptops, and presumably as some battery-saving mode, once the OS tells the system to go to sleep, some clever person decided that the best option to save battery is to completely power down the graphics card. With two laptops here, one with an ATI card, the other with integrated intel graphics, behaviour is more or less the same. After the OS sends the system message to sleep, 5 seconds later the graphics is shut down. So once this happens, the TV or display "wakes up" to report that there's no (VGA/DVI/HDMI) connected. Nasty, because the monitor back-lighting is forced to switch back on to display the message, defeating the power and backlight saving advantage of sleep mode.
Via the win API - you can programatically send the system monitor the "sleep" message (WM_SYSCOMMAND, SC_MONITORPOWER, 2) to test things. Nice - but that doesn't work either except on a "proper" PC where some signal is maintained out of the video card. It just does the same and wakes up once power to graphics is cut. No - you can't loop the program to tell it to stay asleep at intervals of a few seconds - try it at your peril as you'll be working in the dark staring at a screen with a "no signal" message until you can shut the program down or reboot. (How do I know this? Don't ask)

I have the feeling that a hardware hack is needed. There's a common voltage on one pin of HDMI/VGA/DVI. If that could be hacked in to, then the monitor/TV could probably be tricked into thinking it's still connected and stay asleep until it's really time to wake up. (this again sent by via system command built in to windows or other OS api)
At a guess it's pin 18 on HDMI, pin 14 on DVI, pin 9 on VGA, all +5v "power to monitor" - a few hundred milliamps max . I guess that can be grabbed from a spare USB port, you'd cut the connection at the PC end of the cable, splice in the +5v to go to the monitor, and bob's your uncle, unless smoke starts coming out of something somewhere...
Could someone please try this for me...

10574 posts

Uber Geek

  #329659 13-May-2010 09:57
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Fred99: I've got related problems with HDTV or monitor connected to laptop via HDMI, HDMI->DVI, or VGA.

Problem solved.  This laptop was running Vista OEM Home premium with latest/current Toshiba drivers (ATI 2600 mobile card).  It never worked properly for video out, either HDMI or VGA, with VGA proper suspend/sleep function did not work, with HDMI as well as that, only standard HD resolutions (720, 1080) were supported (ie it would not work when forced to 1680x1050, 1920 x 1200 etc) Also via HDMI to my HDTV, refresh rates were limited to 24p or 30i, and if forced above this, it would fail and revert to 720p resolution.

Solution was to upgrade to Win 7.  The default win 7 graphics drivers support suspend via both HDMI and VGA, non-hd resolutions now work via HDMI _> DVI cable to monitor, refresh rate connected to TV at 1920x1080 is 59 or 60Hz non-interlaced.

I assumed that with an OEM install on a Toshiba system with custom OEM hardware support, they'd have at least got the graphics drivers right.

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