[ANSWERED / TICKET] Problem of delay in live video

RégieTheatreP8

My live video is delayed with the live sound.

I use a Panasonic XC H920 camera (resolution 1080p50) connected by HDMI cable (hdmi high speed ethernet) to my PC computer, through a HDMI USB adaptator (HDMI capture to USB 3.0 from full hd resolution 1920*1080 30p to 4k 30p).

Then detected in live capture setting as usb camera with resolution 1920*1080p

My computer is I7 4th core 3.6ghz with 16 go of RAM memory.
My graphic card is NVIDIA Geforce GTX 750Ti

Then I send through 2x 10m HDMI cables joined with a repeater to a sony video projector VPL CX235 resolution full HD 1920x1080

Why do I have a sound delay with the images of my video ?

My Video is delayed of 1/4 second approximately.

Where is the problem ?

I use Isadora 2.6.1

liminal_andy

@régietheatrep8 there are a lot of variables in your chain but my first guess is that you have mismatched frame rates on several devices. Start by getting everything to run at 30FPS (progressive). See how that changes things.

craigw

Hello,

Unfortunately delay or (system latency) is in everything digital, even the most expensive broadcast facilities have the same type of problems.

Cameras have 1-3 lines of latency (not much), the HDMI to USB adapter will have latency because it's converting the signal, the computer processing the signal will add latency and the projector will also have latency (1-3 frames).

The main two areas to start with are the computer (biggest, fastest, best you can buy) and the HDMI to USB converter.

Even with the best equipment you may only be able to cut your time in half.

Also since Time and Frequency are an inverse of each other, the higher frequency the less latency. So 50hz, 60hz or even 120hz when possible.

RégieTheatreP8

@liminal_andy thanks for your answer and sorry for the delay but the reply button on the forum doesn't seem to work on my PC.

We have put all in 30fps or 25fps, but no changes, By the way the camera sends only 1920*1080 (50p) not less !

not solve unfortunately !

RégieTheatreP8

@craigw You mean I cannot separate sound from the video and get it by microphones ? Do I have to use the camera microphone only ?

But how can you not hear the physical voices on stage, behind a screen, with the digital voices captured by the camera, and not delayed ?

It seems we have a technical problem unsolved, first we accept the latency (all digital) but we don't have to hear the physical voices on stage or we hear the voice by microphones and accept the video latency ?

I don't remember I had this problem with DV cameras with composite and BNC cables, why ?

craigw

@régietheatrep8 Since I don't know your show I can only guess.

It's time for testing the video path.

Step 1- Plug the camera directly into the projector HDMI to HDMI (No Computer), point the camera at yourself and make sure you can see the projector. Then move around in front of the camera to see if there is any latency from that direct feed. If you see a little set, the camera Rez to 1080p50 or 1080i50 (or whatever your native Rez is). The projectors Rez should follow the input Rez, the projector to match it. If you see too what seems like too much latency check it with a different camera to compare. This will be your latency starting point.

Step 2 - Add the computer back in. Make sure all of its settings (Input capture also) are 1080p50 or 1080i50. At this point you're probably right back at where you started.:(

Now it's time to do some workarounds for the video, no one likes workarounds.

Adding equipment to put the camera directly into the projector so you're bypassing the computer when timing is critical (may not work for your show). This would be adding an External Video Switcher and other possible equipment. Or what I have to do most of the time because it's easy and fast, it's splitting the difference, you said 1/4 of a sec. which is 250ms, I delay the audio 112ms.

As far as mic audio routing, I rarely go through the computer, Mics go through an audio board and set any delays there.

Minimizing the video delay and working around it is all I've been able to do.

Juriaan

Hi there,
I was wondering or you found a proper solution, if not feel free to open a new support ticket at https://support.troikatronix.c... so that our technical team can assist further.

Thanks!