HD video switcher Delay on My LED

[Mike Jeffs]

How much of a delay are you talking?

I have used ex3 on many occasions pertty sure that isn’t your problem. I haven’t used the blackmagic switcher but you say it doesn’t have a dely when sending the signal one way, but that their is a delay when sending it through converters, my guess would be the converters or the LCD itself.

We run a large 15,000 seat performace space and there is a small delay with our video projectors but it is slight enough that its mostly un noticeable the only thing we have to do is delay the audio a few milliseconds to conpensate.

Mike Jeffs
Video Coordinator
BYU-Idaho

[Jim Brown]

I understand your frustration as we have been there, done that many times. A couple of things from our experiences. The EX1/3 will introduce no more that 1 frame of delay. The ATEM is about a line of delay if the sources are genlocked, which you cannot do with the EX series camera so that adds another frame for the frame synch in the switcher. You now have 2 frames of delay.

The display device is normally the biggest culprit depending on manufacturer, display rate and intermediate devices. If you are using baluns to route via cat5/6 cable their delay is minimal (one line or so). If the cable device is changing the resolution then add at least a frame. Most projectors add from 2 to 6 frames of delay. You can minimize that if you are sending in the native resolution of the display device. ie it is not doing a conversion itself. If your display is 720p and you are sending 1080i the resolution is being converted. If it is 1080p and you are sending other than 1920×1080 then a conversion is occurring. The ATEM is either 720p or 1080i so if it is a 1080p display a conversion is occurring.

The delays are cumulative so if you add a frame from the camera, a frame from the switcher, and two from the display then you are at 4 frames of delay. It takes a very focused professional to see anything less than 4 or 5 frames of delay. At 7 frames everyone can see it. Each frame of delay is 33ms. You can delay the audio up to about 66ms before you have unacceptable levels of echo. The speaker or performer will notice even 33ms but most of the time they are listening through monitors which you do not delay.

We evaluate equipment based on the following test. We use a very noisy relay to power a light bulb. (incandescent). We take a camcorder and record turning on and off the light and capture the sound of the switch. Take that to your editing software and you can see the light coming on in a frame of video and look for the spike in the audio for the switch noise. Note the difference. Use your EX3 and you will get a baseline of the difference in the camera. Then introduce the switcher to a fast reacting display. We use an old analog crt for this. The ATEM outputs a composite video signal and will give you a worst case result as it must convert the HD to SD. Video record looking at the display and take that footage and do the same thing. You now have the delay of the switcher plus this display device. Then video record the same thing with your led display and evaluate.

We normally find the projector or the flat screen is the culprit. Flat screens (both LCD and LED) are notoriously slow devices. Most of them are cost reduced and that conversion processing is the cheapest manufacturers can find and it does not matter with most applications. Projectors are the same way, but we have noticed that EIKI typically has the fastest processors. EIKI are Sanyo projectors with their electronics and we use EIKI, so take this info with a grain of salt if you wish. The key is to drive the display device with its native resolution where possible.

Hope this helps. It is a real issue which no manufacturer wants to discuss, much less disclose in their technical specs.

Jim Brown
M&M ProductionsUSA

[Timothy Chew]

one expert said
we need to change 1 thing

EX3 to higher end camera or Blackmagic to Panasonic

Do u guys think this work

Tim

[Mike Jeffs]

Again I ask how much of a delay are you getting, (ballpark?)

Like Jim said the EX3 and the Black Magic are probably only introducing a couple of frames MAX of delay. I think you are going to spend more money switching out your cameras and Switcher then you would finding out which piece in your infrastructure is add the most delay and finding a replacement for that. I could be wrong, but i’m of the philosophy of trouble shooting to the point you know what excatly is happing instead of blindly trying to throw money at a probelm when your not sure thats the culprate.

The more info you give us the more we can help you.

Mike Jeffs
Video Coordinator
BYU-Idaho

[Jim Brown]

I would not exchange anything until I ran some tests as I described. I hate to make blanket statements but as a general rule I have found that Panasonic switchers add more delay than the Black Magic. Again, it depends on what the switcher is doing and is there resolution conversion, or interlace to progressive scan conversion, or …

If I were betting with what I know I would point to at the LED display. They are notorious for delay and it can be several frames. Tell us what kind of display you have. A way to test is to connect your camera directly to the display (you may have to use an sdi to hdmi converter) and evaluate. If you notice latency it is in the display. (A converter is negligible in terms of latency. Typically they would be one line (1/525th of a frame). The EX3 is also very minimal (1 frame or less) coming out the SDI port.

You did not say whether you are connecting this via SDI (digital) or you are using the analog SD interfaces (composite or component). That could make a huge difference, especially in the display.

Jim Brown
M&M ProductionsUSA

[Timothy Chew]

thanks for your reply

THE Led We are using is sony 46nx720 and Heran 46z57

our crew make some test
( if connect to Normal LCD like PC monitor HDMI ) there is no delay ( may be less

BUt Even if we connect short cable from cam to LED ,… there is a delay

For the How much delay still need to test it out ( but u can see it with your naked eye there is a delay

( do this mean that LED is not suitable for live )or switcher also

Tim

[Bruce Wheaton]

Be very careful on your tests. Your techs won’t be able to tell the difference between ‘no delay’ and delay within 100 milliseconds or so. The brain just fixes A/V sync below that – it’s a feature!

So your testing may actually be 3 frames delay versus 4 frames delay, and it won’t look like ‘a bit more delay’, it will appear to suddenly be quite a bit off.

The main cause of latency for you is probably de-interlacing. Any time you go from an interlaced to progressive display, such as in a display device, or a DVE in a switcher, 1.5 frames is a usual minimum.

Have you tried 720p, if you’re using 1080i right now?

For testing – make a video with a clear frame indicator. I have one knocking around somewhere with a white stripe that rolls past some frame markers – 5 or so, I recall. Feed that to a monitor. Shoot the monitor with a camera and feed the camera through your signal chain right to your display. If you can frame it to see the ‘original’ monitor and the post-processing monitor or display, you end up with a video you can pause and examine.

Bruce

Regards,

Bruce Wheaton
http://www.synchromeshDDR.com

[Timothy Chew]

I just want the delay to be unseen will do

By the way I saw people using

https://www.youtube.com/watch?v=M2FRt3YwYkU

( using HDMI ) or SDI .. I think is HDMI
And there is a projector ( live )

Why dont there feel the delay ..

———————————————

And for Latency problem

We also setup a Vidblaster Demo with osprey 460e
Any one try it before

I also suffer latency On SD signal

Any sure …

( I am doing live feed also )

Tim