Go Down

Topic: Help coming up with Anti-BLUESCREEN device (Read 4760 times) previous topic - next topic

Grumpy_Mike

If you don't use the idea of switching video sources you need to syncronise the blank video source with the real video source. That is the sync pulses must be exactly in phase. This is a difficult thing to do and impossible on an arduino because these pulses must remain in phase even when the signal that syncronised them is gone. This would involve a complex phase locked loop and is not something that could be simply described in a forum post. It would be quite an involved design. Google the term genlock this reffers to a circuit that locks video sources together but requires your video source to be able to accept a syncronising oscillator input.
What form is this video in? Composite or RGBS or som other form. This is important for any solution.

MatCat

I can't take not possible as an answer because there are devices that already do so, granted they are processing the video before output and if that is how it can be done then there must be a way to do it!

funkyguy4000

He didn't say it was flat out impossible.  I said it was impossible on the arduino.  The other platforms probably aren't using the arduino as the brains. 



What form is this video in? Composite or RGBS or som other form. This is important for any solution.
Accelerate to 88 miles per hour.

kg4wsv

#18
Sep 20, 2012, 04:55 pm Last Edit: Sep 20, 2012, 04:57 pm by kg4wsv Reason: 1
The MAX7456 video overlay IC can generate a sync signal - I've used it as a display driver, with no input at all.  It has some modes for detecting sync in the input, too. Of course, it's for NTSC/PAL, not sure what resolution you are using.

As others have pointed out, it won't magically make a weak signal appear.  Sounds like you need better gain at the receive station; maybe an amplifier or directional antenna.

-j

Docedison

The problem with Genlock is that it requires the original information's synch signal and there is no (to the best of my knowledge as I date from the tube and early non digital systems information contained withing a video line to regenerate the synch information when it is lost and the data it was encoded with unless you can store a lot of lines of video or count them to try and detirmine the frame synch that way, either way it does exceed the limitations of this forum because of the nature of the task and it's inherent complexity... IMO

Doc
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Grumpy_Mike

Quote
I can't take not possible as an answer because there are devices that already do so

So buy one then!
I never said it was not possible, what I said is that you don't have the skill to design one and you can't afford me to do it for you.
You appere to not understand the difference between the function of a unit and how that function is acheaved.
Sorry I am out of here, and I have never said that before on this forum.

Docedison

#21
Sep 21, 2012, 04:07 am Last Edit: Sep 22, 2012, 04:53 pm by Docedison Reason: 1
There are those that don't know enough to be able to hear "NO" as a reasonable answer... and the OP wanted PAL too. I think did he truly understand why the "Pixelation" happens he might realize that the GENLOCK information isn't there and without it is vaguely like reading semaphores in a tornado.

Doc

{edit Doc}
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

MatCat

I don't quite understand the attitude everyone has on this forum... I fully realize that if the original video gets corrupted to the point of static that the data is gone, but at the same time every older tv can show static, as well as many other devices such as my dvd player, there are also other devices such as various dvrs capable of outputting the video feed static and all. There was someone else who used lm1881 to detect loss of sync then use the arduino to generate them back plus a resistor to lower the noise below the sync signal. There must be a chip that can process the video and output it back which is why I asked in here... Everyone on this forum likes to point out skill levels which is the entire point of a forum like this, to expand upon ones knowledge and share it with others. If a $10 device can do it there is no reason it cannot be produced diy style.

MatCat

Btw all signals involved are analog, I don't get pixelation more like tearing, rolling, and such when signal gets crappy :-), also someone asked the connector type (not sure why it matters...), but rca composite.

Docedison

The ATTITUDE EVERYONE HAS ON THIS FORUM IS FIRST TO TRY TO UNDERSTAND THE LIMITATIONS OF THE HARDWARE WE USE AND YOU WERE TOLD SEVERAL TIMES THAT WHAT YOU WANTED TO DO WAS WELL BEYOND THE CAPABILITIES OF AN ARDUINO AND YET YOU PERSISTED... NOW YOU SOUND LIKE SOME KID'S LITTLE BROTHER... YOU STILL DON'T UNDERSTAND NOT FOR AN ARDUINO SO I THOUGHT I MIGHT SPELL IT OUT FOR YOU... JUST IN CASE YOU HAVE TROUBLE READING TOO

DOCEDISON
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

MatCat

Hrm...  All caps locks?  You know that is the forum equivalent of screaming?  I never once insisted the arduino by itself could do it, as my OP clearly states I asked what chips could be used to do this, I never asked how to do it with just the arduino...  the arduino's only function would be to MICROCONTROL the necessary circuitry, not BE the circuitry.

A lot of people on here have much more vast knowledge of IC's then I do, eventually someone will come up with a workable solution, instead of insisting it cannot be done... Perhaps I will have to use an ARM chip, I don't really want to though an ARM chip would probably be powerful enough to actually do the needed processing... but I am fairly sure there are chips out there dedicated to processing video, that the arduino could happily control.

Riva

http://www.decadenet.com/products/index.html
Maybe you could use something like this, just don't bother to overlay any text. Not sure if it will re-generate the full video signal if no background is available or it expects a signal to genlock on to.
Maybe you could use an LM1881 to supply sync info to an arduino and if it stops supplying a sync output (no video?) then get the arduino to clamp and stamp sync signals on this feed to stop the TV blue screen (What model is it as you can turn off the blue screen on some models)

Docedison

#27
Sep 22, 2012, 04:45 pm Last Edit: Sep 22, 2012, 04:54 pm by Docedison Reason: 1
Yes I do realize that my caps lock key was pressed, I PRESSED IT, sometimes I LIKE to scREAM people.
    Put very simply the synch information is sent or generated on EVERY LINE of video information, there are 525 of them for a single frame of video and there are 60 frames per second. What the OP wanted to do was regenerate the "Lost" video when there is no line or frame synch. The real problem is that when synch is lost so is the video because the video is sent between the synch information. There is a great deal more lost than that as well Studio or originating COLOR synch is lost as well because it is a part of the frame synch period. 8 cycles of 3.58 MHz color "Burst" information is there on the "Back Porch" of the synch pulse... so is the "BLACK LEVEL" or the absolute reference for the LUMINANCE level of the video signal and there are no readily possible solutions to that process that an Arduino is capable of. For those with an "Inquiring Mind" I took the liberty of attaching a data sheet for the aforementioned "LM1881" in of itself it Should be enough... Material..
This is the short answer:
Without the synch information everything else is lost because the synch information is the "Wrapper" for all the rest of the "composite" video signal information. The issue is, that the OP was told several times that what he wanted to do was not readily possible with an Arduino and unfortunately the reasons for the NO answer are beyond the education level of the OP. MY son once said to me... "Daddy Why can't I Fly to the Moon"" and I said "it's too far away" He then said "New York is far away and I can Fly there...". Had the OP the simple theoretical knowledge of NTSC television, He wouldn't have asked the question because the answer is inherent in the knowledge of the medium used to transport the information...

Docedison

This was one of several "answers" that the OP chose to ignore:

Quote

There are those that don't know enough to be able to hear "NO" as a reasonable answer... and the OP wanted PAL too. I think did he truly understand why the "Pixelation" happens he might realize that the GENLOCK information isn't there and without it is vaguely like reading semaphores in a tornado.

Doc
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Riva

Many years ago I wrote a PIC program to count frame outputs from the LM1881 connected to reference output on a Sony VTR and also read and decode the RS422 deck control between the VTR and an Avid. This was needed because sometimes the Sony digibeta cameras would not lace up correctly to the last frame from standby and skip one or two frames in timecode. The Avid would not detect anything less than 6 frames as a timecode break and just keep recording. Editors were finding the ingested material could progressively loose lip-sync the more start/stops there were on the tape that Avid failed to detect. The PIC could detect single frame drops and then force the Avid to detect the dropout and then start the mark, pre-roll & record just beyond the break.
I just wondered if using the LM1881 you could easily detect when video is present/missing and then maybe use something like http://arduino.cc/playground/Main/TVout to keep the signal alive (so the TV does not turn off after a short time?). As there is no signal (when it's lost) then there should be no need to worry about correct colour and audio sub carriers, just create your own monochrome with correct porches and syncs as I assume the linked program does.

MatCat

See the idea is not to re-create the video itself, that is impossible.  Here I will give you a good example...

http://www.youtube.com/watch?v=KXTy1PGn3_8

If you watch that video you will see lot's of video glitch (This is one of my flights), every time that video glitches the current DVR I use will completely STOP recording, and on a lot of devices would blue screen every time it glitched, as you can see the video never really GOES OUT, it just glitches, sometimes fuzzes out and in, the real problem here is 2 fold, one is that my current DVR will STOP recording when this happens, the second is when a display bluescreens it could stay blue for seconds, even though the video feed itself is still technically not that bad, just a matter of a quick few microseconds of sync loss.

The recording device I was using for that video obviously doesn't care about loss of sync so much, as a matter of fact there are many moments you see rolling, tearing, etc because sync data is not there but it STILL shows it.

My idea is to atleast preserve as much as possible of the incoming video signal, this isn't like hooking up a VCR where the video signal is either good or it's not, this is an airplane flying in the air, with broadcast video signal.  A bird flying between the plane and my ground station can cause a video glitch, but even then most glitches are very momentary, and in those moments sync pulses needed to be generated to prevent bluescreening, even if they aren't fully SYNCEd to the original video perfectly, the idea is to still have some resemblance of the picture, when you are flying an airplane a mile + away from yourself, and your video goes out you can't see to fly (Well I have autopilot too but that is besides the point :)), and even a second of bluescreen can be disaster.

I hope I clarified myself enough on this.

Go Up