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Old February 6th, 2011, 11:49 AM   #1
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no frame delay switcher

Loking to build a HD multi camera recording system. What I've found, with SD or HD is, switchers have a frame delay that when making a cut switch to another camrea a small fraction of freeze or slight glitch happens.

What switchers allow a camera change without this issue?

Bob
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Old February 6th, 2011, 12:32 PM   #2
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No frame delay

All switchers have frame delay at least at affordable price leveles, you would need to search the higher end line (over 100k) to start seeing no delays.

The delays in most switchers are about 5 frames.what are you doing that could possibly be affected by these 5 frames? The delay's are from the camera to the monitor.

I use a software mixer for sports and talking heads. (for delayed tv broadcasting) avtake.com

There are other but this to me has the feel of a real mixer among other things

Ric
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Old February 6th, 2011, 05:59 PM   #3
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could be some kind of time-base-corrector or delay line the switcher is using to get a clean cut... or for that matter (more likely), lack of a TBC causing a glitch when your deck or monitor has to resynch to the new signal.

you might try gen-locking all your sources if possible.
if that's not an option, then a TBC will surely be needed... that tends to be tricky and expensive stuff, and more so with HD sources.
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Old February 7th, 2011, 07:53 PM   #4
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no frame delay switcher

The only no delay swithchers are software based using either fire wire conectors ot hd/sdi through decklink cards. The only other way of eliminating the glitch is to swicth from preview. in other words no disolves or effects. Put the next camerain on preview and then click program. You can also try a tricaster by newtek its a solid combination of hardware and sofftware. they have a new hd model that accepts up to 8 cameras via hd/sdi.

I would highly recomend a software based mixer they are efficient if you work with 4 or less cameras. You can insert clips, graphics titles... all for less than 5k. no tbc or other equpiment needed.

ric
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Old February 7th, 2011, 08:27 PM   #5
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Bob
What switchers are you having problems with? I've not noticed any frame delay on the boards I'm using. This includes the Grass Valley Indigo Switcher, DataVideo SE-800, an old Panasonic MX50a and an old Tricaster.
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Old February 8th, 2011, 10:38 AM   #6
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framd delay

Let me correct my self all swithers have frame delay including the software ones. This should present no problem. but this is different from the glitch you say you see. and that will happen in all mixers unless corrected by tbc . This tbc can be internal or external. Even the datavideo-800 has a 1/6 delay in video when using dv and somewhat less when using s video. Hd video shoud give you about a 6 frame delay in any system.

rycar_m



Quote:
Originally Posted by Ric Marrty View Post
The only no delay swithchers are software based using either fire wire conectors ot hd/sdi through decklink cards. The only other way of eliminating the glitch is to swicth from preview. in other words no disolves or effects. Put the next camerain on preview and then click program. You can also try a tricaster by newtek its a solid combination of hardware and sofftware. they have a new hd model that accepts up to 8 cameras via hd/sdi.

I would highly recomend a software based mixer they are efficient if you work with 4 or less cameras. You can insert clips, graphics titles... all for less than 5k. no tbc or other equpiment needed.

ric

Last edited by Ric Marrty; February 8th, 2011 at 10:48 AM. Reason: mor info
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Old February 8th, 2011, 11:14 AM   #7
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Quote:
Originally Posted by Ric Marrty View Post
Hd video shoud give you about a 6 frame delay in any system.
rycar_m
ouch : (

....
unless of course all your cameras are locked to the same sync...
then a very barebones, analogue switching system could suffice...
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Old February 8th, 2011, 06:10 PM   #8
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Frame delay

I disagree all swicthers have delay the least is about 2-3 frame but this requires a lot of highend hardware or if you go anolog and use s video or composite. You have to understand that the as fast as it is it has travel from where the camera is. The delay is the time it takes from where ever the camera is to the preview monitor.

May I ask what are you doing that this becomes an inconvinience? i do boxing and voleyball no problem with 5 frame relay at 720x480 digital through firewire.

ric

Last edited by Ric Marrty; February 8th, 2011 at 06:15 PM. Reason: add
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Old February 8th, 2011, 08:11 PM   #9
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Uhh - since the speed of propagation of a signal in a wire is in the ballpark of 4000 miles in a 30th of a second = 1 frame, I doubt the delay has anything to do with the distance from camera to monitor - unless the camera is somewhere in outer space.

The amount of time it takes a switcher to decide to do something and actually make the switch on the other hand would be in the range of a few frames..

Besides, just what delay are we talking about - the delay from hitting the "Switch" button until the new signal appears or a delay between the end of one stream and the beginning of the next? I would think that if you threw enough $$$ and hardware at the problem you could make a system that didn't have any delay between the output of two sources but there would still be a delay from the time someone hit the button.
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Old February 8th, 2011, 08:48 PM   #10
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Frame the delay

That plus the time it takes to process the signal causes the delay, also depends on how you input. if done through firewire it has more delay. Also it depends on the quality of the wire and connectors. so just because a signal can theoriticaly travel at the speed of light you have to take in consideration the materias right down to the silicon, If you use expensive, exotic metals like gold you can probobly cut down to near zero but then that 20 dolar fw card could cost you a couple of thousand dollars and ad this to the whole circuitry we are talking of big bucks.
It all adds up just like pennies in a jar. Only the big guys can afford such equipment but they still make compromises. How much are a few microsecounds worth vs the cost? thats the equation.

These systems will always have delays. but they are so small that imop they are inconsequential

We are talking about 5 frames 1/6 of a secound or 0.166666 micro seconds .I am sure that most will never mis those frames . You miss more by winking.

The delay between switching one camera to another is all about the human hand because the sigal if synced should have very little delay.

Now sync issues is another problem.

ric

Last edited by Ric Marrty; February 8th, 2011 at 09:03 PM. Reason: info plus
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Old February 9th, 2011, 01:45 AM   #11
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Umm - I think you meant 166,666.666....... micro seconds.

However, I'm really just teasing - the point is that as we've both said, distance has no appreciable effect, it's all the processing delay in the switchers or other electronic processing that takes all the time.

But I think there is also an issue of whether the delay we're talking about is the time it takes to actually switch after pushing the button, or the interruption/gap/whatever or whatever in the video stream, which can be minimized by running two or more (hopefully already synced/genlocked) signals into parallel buffers so that there would be no hiccup in the output stream.

Whether a delay of one or 5 frames is noticeable, I think, is really a question about the visual effect of a (small) interruption in the actual output stream. I know a single black frame is noticeable and I have seen cases where a single repeated frame can be noticed as a little "bump" or "stutter" in the video if you're watching critically. So I guess it depends on the material.
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Old February 9th, 2011, 08:26 AM   #12
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the delay is really just from DSP.

from the time you operate the switch to the time you see a result on your display, there really doesn't need to be any delay, unless there's more DSP in between. i think that for aesthetic reasons, a cut made in the middle of a frame should probably be delayed until the beginning of the next frame to keep it seemless.
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