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Re: HD video switcher Delay on My LED

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Jim BrownRe: HD video switcher Delay on My LED
by on Feb 26, 2012 at 12:54:44 pm

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 1920x1080 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


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