Blackmagic Forum

Do the 20x20 or 40x40 Videohubs introduce any fixed delays while routing? Trying to chase down an A/V sync issue with our ATEM 2 M/E and URSA Broadcast cameras with X32 Rack as a mixer and wanted to trace all potential sources of delays in the system.

create video with video blink and audio beep .. record it , and check delay in computer video editor ..

Video hub have invisible delay .. ATEM have 1 frame delay video to audio (when usinganalog audio inputs) ..

Thanks Roman for the info on the imperceptible delays introduced by the hub and the test scenario to help isolate the delays.

One other question, are there any known fixed delays introduced by the URSA Broadcast cameras?

I dont know .. We use 3 URSA Broadcast Cameras in Studio and have not problems with delays ..

Ursa Broadcast is within 1 frame from lens to output!

Videohubs only reclock the signal.. This delay is on bit nivo and is as non existing..

Atem will take 1 frame of delay. 2 if you have DVE / Supersource active.

Thanks Daniel for the info on the latency of the URSA Broadcast.

So far, I've found out these fixed latencies in our system:

• ATEM (1 frame w/o DVE, 2 frames w/DVE)
• URSA Broadcast < 1 frame
• VideoHub < 1 microsecond
• X32 .83 milliseconds
• AES 50 run 62.5 microseconds
• Dante Audio capture 10 milliseconds
• Dante network traffic 125 microseconds

Variable delays that I'm trying to quantify still, these seem to be where our problems lie

• iMac Headphones out to the X32 [have not be able to determine the delays in the Mac Core Audio drivers but we're seeing about 2 frames delay-66ms]. Anyone know a source that has latency info for Mac audio drivers?
• ProPresenter 7. Preliminary results are that audio is delay ~1 frame 33ms over a Decklink 8K Pro
• H.264 Pro Recorder 100-300 milliseconds. This device has a huge delay and then drifts. Problem report threads have existed on these forums for years without any particular answers. We don't use it real time but for our archives.
• Sony PXW-Z150. 3 frames delay ~100ms at 29.97fps.

Linden deCarmo wrote:Thanks Daniel for the info on the latency of the URSA Broadcast.

So far, I've found out these fixed latencies in our system:

• ATEM (1 frame w/o DVE, 2 frames w/DVE)
• URSA Broadcast < 1 frame
• VideoHub < 1 microsecond
• X32 .83 milliseconds
• AES 50 run 62.5 microseconds
• Dante Audio capture 10 milliseconds
• Dante network traffic 125 microseconds

Variable delays that I'm trying to quantify still, these seem to be where our problems lie

• iMac Headphones out to the X32 [have not be able to determine the delays in the Mac Core Audio drivers but we're seeing about 2 frames delay-66ms]. Anyone know a source that has latency info for Mac audio drivers?
• H.264 Pro Recorder 100-300 milliseconds. This device has a huge delay and then drifts. Problem report threads have existed on these forums for years without any particular answers. We don't use it real time but for our archives.

I suppose you're not using a sync signal in the chain, this should significantly reduce the delay, for instance the atem needs one frame (+1 for the dve) only if it needs to use the frame synchronizers

Raphaël Jacquot wrote:I suppose you're not using a sync signal in the chain, this should significantly reduce the delay, for instance the atem needs one frame (+1 for the dve) only if it needs to use the frame synchronizers

We've identified adding a frame sync signal as a work item. However, I don't think that will help with the two biggest issues (H.264 Pro Recorder Delay and iMac Headphones Audio out).

Longer term, we intend to migrate from the Headphones out to Dante, but I want to quantify the problem as is before we change anything.

I forgot to list the Sony PXW-Z150 as a problem. We have mostly URSA Broadcasts, but we also have a Sony PXW-Z150. It is at least 3 frames delayed compared to the URSA Broadcasts. We're on the latest firmware revision. However, I see comments on this forum that when the SDI output is used, Sony cameras shouldn't have significant delays. Anyone else have experience with this model and potential latency workarounds?

Linden deCarmo wrote:Thanks Daniel for the info on the latency of the URSA Broadcast.

So far, I've found out these fixed latencies in our system:

• ATEM (1 frame w/o DVE, 2 frames w/DVE)
• URSA Broadcast < 1 frame
• VideoHub < 1 microsecond
• X32 .83 milliseconds
• AES 50 run 62.5 microseconds
• Dante Audio capture 10 milliseconds
• Dante network traffic 125 microseconds

Variable delays that I'm trying to quantify still, these seem to be where our problems lie

• iMac Headphones out to the X32 [have not be able to determine the delays in the Mac Core Audio drivers but we're seeing about 2 frames delay-66ms]. Anyone know a source that has latency info for Mac audio drivers?
• ProPresenter 7. Preliminary results are that audio is delay ~1 frame 33ms over a Decklink 8K Pro
• H.264 Pro Recorder 100-300 milliseconds. This device has a huge delay and then drifts. Problem report threads have existed on these forums for years without any particular answers. We don't use it real time but for our archives.
• Sony PXW-Z150. 3 frames delay ~100ms at 29.97fps.

In your URSA Broadcast you need to set your timing to about -10 lines before your program sync. This can save you a full frame through the system. By pre-timing the incoming program sync your camera signal will arrive before the next frame sync of the switcher. If you don’t put any inverse delay, your sync arrives after the switcher sync and has to wait for the next one, creating an extra frame of delay.

David Hutchinson wrote:In your URSA Broadcast you need to set your timing to about -10 lines before your program sync. This can save you a full frame through the system. By pre-timing the incoming program sync your camera signal will arrive before the next frame sync of the switcher. If you don’t put any inverse delay, your sync arrives after the switcher sync and has to wait for the next one, creating an extra frame of delay.

good to know that setting exists... if only I had the budget for ursa broadcast