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Old February 12th, 2011, 11:12 AM   #1
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Delay/latency of video from HDMI feed

I am testing out a couple of Marshall monitors with my Nikon D3s via HDMI input. There is a delay in the image on the monitor compared with reality. So, if someone is speaking, their lips move on the monitor after their words actually come out. I'm using a 3 foot HDMI cable.

Is this the nature of all HDMI output? just from the Nikon? something that I can overcome with a different brand of monitor? a better HDMI cable?

Thanks for all advice on this.
Steve Kimmel is offline   Reply With Quote
Old February 12th, 2011, 08:12 PM   #2
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Hi, Steve................

If you think of it this way:

Reality is captured one frame/ field at a time, read serially off the sensor into a processor, then out again into memory where it's held in parallel bytes, then it's read out again, serialized to pump down the HDMI cable to the screen where it's re-assembled into parallel bytes to display, then fired to the LCD drivers in the screen.

Meanwhile, back at the ranch, reality has done what it does and moved on, so by the time all the previous palaver gives you a picture, it's lagging behind reality.

Is this the nature of all HDMI output?

Yes. It's only visible when reality and the picture are viewed at the same time.

just from the Nikon?

Some cameras will be faster than others due to sheer processing grunt and other factors.


something that I can overcome with a different brand of monitor?

All monitors vary in their processing power/ lcd switch rate to some extent, but I don't think you'd notice it by eye.


a better HDMI cable?

It's a serial digital signal going down the cable. It either makes sense to the receiving electronics or it doesn't. If it makes sense, you get a picture. If it doesn't, you get black. The quality or length of the cable makes no difference, it either works or it doesn't, there is no gracefull degradation in digital.

The length of the cable is irrelevant as the signal is travelling at just below the speed of light, so to get a 1 second delay due to the cable it would need to be somewhere North of 180,000 miles long, which I'm pretty sure the HDMI spec doesn't support.

You have raised an interesting point though.

Do any of the manufacturers quote HDMI delay in their camera specs?

I can't ever remember seeing it. Maybe they should?

On the other hand, does it really matter in the real world if there is a delay?

The other thing to consider is, does the signal from any other possible O/P from the camera, component etc lag as well? By the same amount?

I simply don't know, but have a feeling it must lag due to the same reasons as HDMI, at least in part.


CS
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Old February 12th, 2011, 08:43 PM   #3
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Wow, that's an incredibly helpful response. Thank you very much Chris!

I think that as I use it more I'll get used to it.

Would be interesting to see lag times in specs of monitors!
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Old February 21st, 2011, 04:45 PM   #4
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Re: Hi, Steve................

If DVINFO had a "Like" button I'd click it right now for this elegant explanation and comment.

Quote:
Originally Posted by Chris Soucy View Post
If you think of it this way...
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