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JetPilot

How can I avoid the Blue screen / No video problem in LCD monitors ?

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Most LCD monitors go to a blue screen whenever the video is interrupted even for a split second, and it usually takes them a couple seconds to come back. Has anyone come up with a way into fooling a monitor that there is always a valid video signal when the wireless cuts out for a split second ??? A solution to this would open up many new devices for FPV use.

Thanks,

Mike

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This is a theroy rather than a proven way foward...

I think that most monitors monitor the sync pulse and this is the key to them staying on (computer monitor is clasic esample) when the sync disapears the monitor starts the shutdown / loss of signal process.

This can be reasonably simple to prove. Take a monitor that uses RGB + Sync... remove one at a time the r...g...b and look for the black screen... or take away the sync and see the blue screen...

I remember the device that generated sync pulses was a ZNA134 or later a ZNA234 this could be locked to the incoming sync so that it free runs in the event of signal loss then at the point of signal return you would at worse get a frame roll as it sync'd should help cut down the ammount of time its off beacause of lost signal and hopfully prevent teh blue screen of death...! I dont know if they are available now but it could be replicated with a micro...

Steve

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Hi Mike, I have been trying to find an answer to this one for some time, I even had a go at talking Mr RC-CAM into having a go but failed. I have had some luck with using a MAX LOS chip to switch to a signal from an old board camera when the signal was lost but it was pot luck if the sync pulses matched.

As Steve says we need the sync pulses locked to the input signal then to take over while these are lost.

I would like to get the problem solved so I could use my fussy MPEG2 recorder as its much better quality video than my Archos can deliver.

Terry

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As Steve says we need the sync pulses locked to the input signal then to take over while these are lost.

Why not use the Aiptek MPVR trick that was discussed months ago? Bench tests showed it could flywheel the missing syncs. My gut feeling is that it would work, but I have no way to test it since I don't own any of the recorders you folks are using.

http://www.rc-cam.co...dpost__p__23008

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Why not use the Aiptek MPVR trick that was discussed months ago? Bench tests showed it could flywheel the missing syncs. My gut feeling is that it would work, but I have no way to test it since I don't own any of the recorders you folks are using.

http://www.rc-cam.co...dpost__p__23008

MR RC-Cam,

The aiptek solution may work, but that just makes setup that much harder, and I have enough equipment that adding another camera that I have to turn on, set, and get working at every power up is not practical. Whatever I find, I want it to work as soon as power is put into with, without me having to go through a bunch of menus.

You stated before that no one would want to pay 150 dollars for the solution to this problem. I can tell you from dealing with this problem over the years, I would gladly pay 200 dollars or more for a device that would fix this, so would a lot of other people that have posted on RC Groups asking for a solution. I think you dont realize how big of a problem this is for the FPV world... Its not just for Video Recorders that we need this fix, there are a huge number of LCD monitors and televisions that we can not use because of this problem. For those wanting to get the most beautiful and detailed picture for FPV, a monitor is way better than goggles. Having flown a lot with both, and just about every goggle out there, the flat panel monitor is so much better than even the most expensive goggles.

Do you think that one of the small time base correctors like this would work ???

http://cgi.ebay.co.uk/Video-Time-Base-Corrector-Synchronizer-Color-Corrector_W0QQitemZ350256045255QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item518ce31cc7&_trksid=p3286.c0.m14#shId

Or the AVT-8710 http://www.bhphotovideo.com/c/product/276891-REG/AV_Toolbox_AVT_8710_AVT_8710_Multi_Standard_Time_Base.html

Mike

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The characteristics you need are not a default feature of a common timebase corrector. So, the only way to know if those two products will help you is to try them.

I haven't had any free time for months, so I don't have any custom solutions to offer at this time.

- Thomas

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I must have been lucky then, as over maybe 10 different monitors or so that I've had over the years, only one had such a problem... I'd just say change monitor, and get a good one. Of course if you go with cheapo ebay Chinese ones there are risks, but the "decent" ones I've had would all have a feature in the menu to enable/disable the blue screen.

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I was unable to find an Aiptek unit for a reasonable cost in the UK and also would rather have a no fuss little box that just gets on with it. I would pay up to £75 if I could get one, I paid £150 for a time base corrector that dose not cure the fault a few years back.

Terry

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Kilrah,

Even the most expensive monitors have the " Blue Screen of Death ". I have a very nice, expensive car screen that I want to use because of its exceptional brightness in the sun, so I need to solve this... My sharp 37 inch flat panel monitr is the same way, not cheap and not something I want to change out over this issue. This " Feature " is becomming universal on all monitors, so as we go to LED monitors etc. We will need to solve this problem if we want to use modern video equipment. More and more people will need something that fixes this as time goes on.

Terry,

What Time base corrector did you try ??? Did it help your video at all ?

MR RCam,

Thanks for the info you did give. We cant expect one person to come up with custom solutions for all our problems, even you deserve a life sometimes :) But I hope someone does, because if its at a resonalbe price, they will sell lots of these devices now and even more in the future as all video equipment starts to have this feature.

Mike

Edited by JetPilot

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As if it would ever be worth the effort, but as the Oracle is so reasonably-priced and works so well, I'd be happy with an 'Oracle Plus': includes the option of switching in a blank screen (or display saying 'No Sync', or something else) if neither of the two inputs have a sync signal.

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I'd be happy with an 'Oracle Plus': includes the option of switching in a blank screen (or display saying 'No Sync', or something else) if neither of the two inputs have a sync signal.

That is exactly something I have in mind. Truth be told, I have spent some design time on this issue and I'm not so sure curing blue screen issues will be as easy as it seems. For example, a catch-all cure would be quite complicated (gen-locked video frame buffer). So, the trick is to find a practical workaround that can be produced by us techie mortals.

If there was some useful data on what specific conditions are required before the blue screen kicks in, then it would save considerable design time. No doubt the little details will vary, depending on the monitor or DVR that is used. At this point, the poor fellow that solves this will need access to a variety of video monitors/DVRs to test. To make it more difficult, it is not possible to record the video signal at the time of the blue screen detection (the recording device will alter things), so that trick is just not one that will help.

It would be ideal if FPV'ers found an affordable commercially produced consumer device that would eliminate a custom solution. The Aiptek MPVR is one idea that has been mentioned. On monitors that have a built-in RF tuner, another trick would be to use a RF modulator instead of the composite inputs. Or, maybe install a dummy camera onto a lower priority input of the Philips video switcher that I saw discussed at rcgroups. Beyond that, one of the mentioned timebase correctors might have the extra required functions to do the job.

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What about a slightly different approach to this problem then. There has to be a chip that is sensing the video, and switching it off and replacing it with blue when it does not see video. If I knew which chip did this, I could just jump the video directly to its output so that it would never switch off. I read a post on RC Groups where a guy fed video directly to his TV by bypassing the tuner and feeding video directly to its output in the LCD screen. Anyone have any idea what this cursed chip would look like, or how to find it in the TV ?

Terry,

The Time Base Corrector is something I am still looking at. How did yours behave, what results did you get with it ? I am not looking to record right now, I have that covered, but I do need something that would work for my monitors, so it does not have to be as perfect as it would for your recorder. On the TV, if the signal breaks up, it will come back...

PS RC Cam,

My guess is that the LCD monitors would just look for video sync pulses, I cant immagine that they would get super complicated about colors etc when its so easy just to cut the video when the pulses are lost, and start it again when valid video sync pulses are there. Just a guess, but its much easier, work good ( for them ), and is cheaper that way.

Mike

Edited by JetPilot

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There has to be a chip that is sensing the video, and switching it off and replacing it with blue when it does not see video.

In a modern design, features like blue screen are not handled by a single function component. Instead, it is just an integrated feature buried inside a big chunk of silicon that does a huge variety of things. Invoking the blue screen is handled by firmware that has qualified the video and decided it is time to generate the blue screen. In other words, it is a software controlled feature.

My guess is that the LCD monitors would just look for video sync pulses,

I expect that it only needs to see proper syncs too. But, wireless video will experience many episodes of missing syncs that your eyes never recognize. So, just when do we have to jump in? How many syncs must be missing before blue screen is enabled? Which sync pulses (vertical or Horizontal or both)? No doubt the exact answers will vary, depending on the different monitor and DVR designs that are out there.

This is a long way of saying that if we use a simple sync substitution method, and jump in too soon, then the overall video quality may be worse. If we do it too late, well it will be too late. The fellow that solves this with a custom design will certainly learn the answers to these questions.

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I have been thinking about this and did a little research

http://www.atv-projects.com/50p_SPG.html

This is a litle generator that can be used to prove either way whether the sync is the 'keep alive' signal that blocks the blue screen and if so then there should be a way of remodeling the code on this chip to sync to an incoming sync pulse on one of the spare pins. Ok it may meen using a chip that can run at 8Mhz to make the timing work but its entirly posible to use a little micro to generate a phase locked sync signal and at worse you will see a frame roll as it locks this may be preferable to the 'blue screen'

Steve

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That little chip is more than a sync generator. It provides all the essential elements of a composite video signal. It basically creates black video fields. So for sure, it will prevent blue screen if you directly connect a monitor to it. That is the easy part. :)

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Mike,

Im not sure if it would cure your blue screen but I think it may. Have a look at this old test video, it shows the colour bars (sometimes black and white due to the recorder) from the TBC when the video is lost.

http://www.vimeo.com/852414

Terry

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This datasheet discusses some of the issues around loss of signal - although I note they are defining one of the possible inputs equivalent to "no signal" as... a blue screen!

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That little chip is more than a sync generator. It provides all the essential elements of a composite video signal.

Ok i understand that so move it from a 508 to a 629 or similar that has a capture module. Sample an incoming video signal using the frame pulse and interval with the capture module and hold off the rest of the code until it senses a frame period too long or loss . Then it could replace the signal seamlessly using an analouge switch. After it it sees the return of the frame pulse and period (one or two whole frames 40mS) then it can switch back to the incoming video signal.

The circuit is quite simple. Feed the composite video into the comparator useing a low reference voltage (so it only grabs the frame sync) and feed this out from the comparator into the capture module. This is alternatly configured to measure the frame pulse width and period. if all is ok you get a green light and the video switch is held towards the normal video input. in event that either the frame pulse is to long / short then the value comiing back from the capture module not match a good pulse and this would start the sync generator and at the same time flick the selection switch from normal to artifical thus keeping the dispaly alive for a frame or two whilst the normal signal restores.

The capture is interupt driven so the frame measure is late by the int latency period of say 10uS (or 2 lines) and this isnt normally a problem as the replacement signal isnt normally generated. In the event that the replacement signal is present then the INT is disabled except in the frame sync pulse where it firstly measures the period of the incoming sync to determine its presence prior to switch back to normal when it measures width and period.

Probable result using this method is a black screen for the duration of the missing sync +1 frame and then restore to normal with a dirty lock (frame roll or slide)

Sorry for the rambling but i can see a soulition but at the moment no time to code it...

Steve

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Everyone,

Thanks so much for all the advice and answers to this question, now I have just one more question, what is the meaning of life ???

Hahah, OK, it seems that terry has the closest thing to a solution that I can find, which is a Time Base Corrector. The one in your Link Terry looks like an exact copy of the AVT-8710 , which is what I just bought. Your test video looked pretty good, the point at which it went to color bars being generated was reasonable, with almost no usable video anyways. It appears that this would keep my Monitor happy, but only one way to find out. I will let everyone know what my results are when it gets here and I get it hooked up :)

Mike

Edited by JetPilot

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It appears that this would keep my Monitor happy, but only one way to find out.

Now we are talking! My gut feeling is that it will reduce the number of blue screen hits. The ideal box would stop them altogether.

I'm also trying to get an evaluation unit of a similar consumer TBC box. So, maybe between the two units the holy grail will be identified.

now I have just one more question, what is the meaning of life ???

The answer is 42.

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The one in your Link Terry looks like an exact copy of the AVT-8710 , which is what I just bought.

Hopefully the one you ordered is working for you. The TBC box I received does not have the behavior you need, so I essentially struck out.

It had a lot going for it. For example, you mentioned you did not want to have to set it up for each use. So rather than "soft" push buttons (which could reset at each power up), this one has slide switches to set up operation. See photo below.

It converts between video formats just fine. However, it does not provide simulated syncs upon loss of video. So, it just is not appropriate for your special needs.

Here is a full description from one that was sold on eBay: Click Me.

Long story short, take this one off the list of candidates.

post-2-125504151783_thumb.jpg

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I got the AVT-8710 Time base corrector to fix my " Blue Screen " problem and it works GREAT :D The time base corrector keeps the video from tearing when the signal starts to get bad, and when the signal is finally lost, generates a color bar pattern instantly keeping a monitor from going into " Blue Screen Mode " and prevents recorders from shutting off. The beautiful thing is, the AVT-8710 is designed to fix really bad video, so it will not go to the color bar mode until the video signal is totally gone ! In other words, it will not take away any video that you could fly by, and it helps video that is trying to tear itself.

Its a bit expensive at 210 dollars, but well worth the price for uses. Now I can use any modern video equipment or recorder I chose without fear of shutting down !!! Problem solved :)

Mike

post-2644-125554388613_thumb.gif

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