Hi,

My system is quite similar in specifications, except for that graphics card, where I use a ATI 7850 and my MB is a Gigabyte Sniper

The vMix is configured for output using the 4th channel from the Decklink Quad as well as the HDMI output from the ATI card.

I found the following results:
When using the internal graphics of my MB for the application screen , the delay on the Quad output is approx. 0,3-0,4 seconds, so between 8 and 9 frames on PAL input.

I found improvement when using only the ATI card for the application (On DVI) AND the output using the HDMI connection and then the latency dropped to about 4-5 frames (0,2 sec.). In the BIOS I disabled the use of the internal graphics.
The Decklink Out was still a bit slower between 5-6 frames.(0,25sec)

I measured this by placing the iPhone in front a lower corner of the LCD screen and then recording this with the EX-3,with the feedback that it will create: you can make a whole string of iPhones with the stopwatch running on the screen. Record this for some seconds and then playback and pause. You can easily see and count the "round-trip duration"

But we have to take into account that even the output of the EX-3 as well as the input of an HD-screen might introduce a small delay, probably 1 frame or less but it still adds up in the whole chain. HDMI to SDI converters can also have their own delay.
According to Martin, the Decklink might also buffer 1 or 2 frames before sending it out again, which might explain the small increase compared to the HDMI output.


All in all I think that Martin's claim of approx. 2 frames delay introduced by vMix could be correct:
EX-3: 1 frame
vMix: 2 frames
HDMI-SDI: 1 frame
LCD: 1 frame

Total 5 frames...... That seems to me the minimum possible, but I love to hear about other's improvements.

Oh, this is only the video delay, I have not research the audio yet.

Rob

I tested the low latency option today with the newest software release and found that there is indeed a slight improvement in the total delay.
When the low latency setting is selected and the program restarted I found a total delay of approx. 0.17 seconds, that translates to 4.25 frames on 25P, while in the normal mode it is 0.2 seconds = 5 frames @ 25P.
With al the conversions going on from SDI-in to SDI-out I think that is perfect.

we still have to take all the other steps into account:
Camera EX-3: 1 frame
vMix: 1 to 1.25 frames
converter HDMI-SDI: 1 frame
LCD screen: 1 frame

So I think overall delay cannot be much less then 4 frames ( 16 millisec) from origin to display.

I am quite impressed!

Now if only I had a job for this machine.....

Rob

I have exactly the same problem with latency.
However my measurements are different (measured at 30fps).

The camera(Sony NX30)adds 2 frames of delay, the vMix another 4-5 frames. Capturing without audio reduces delay by 1 frame. Adding Blackmagic SDI external output adds another 3-4 frames. All together 10 frames or more, I got variable results.

HDMI to SDI converter only adds a few lines of delay, as there is no real conversion, uncompressed video is just repackaged.

I could live with 6-7 frames of delay, but once BM output kicks in with 3-4 frames or more it is just too much. I tried to use DVI output from graphic card but the video quality is not good enough (vertical tearing). It looks much better on the SDI output. Maybe is time for a switcher control, as Egriswold suggests.

Would it be feasible to consider adding a slight delay effect to the actual audio at the live event?
Not so much that the audience would notice, but enough to lessen the gap between the audio and video feeds?