Audio ahead of Video

Questions about ATEM Switchers, Camera Converter and everything live!
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courtney

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Audio ahead of Video

PostTue May 01, 2018 8:40 pm

Hi there,

I have a Canon XF205 which is connected to a BlackMagic ATEM1 ME 4K Production Switcher via SDI. I then have SDI going out to two LED domestic TV's from the Auxiliaries. The TV's have BlackMagic SDI to HDMI converters and then HDMI into the TV's. The picture is great however the audio is miles ahead of the video.

The audio however is coming through our Auditorium sound from radio mics into an Allen & Heath desk. Is there a way to fix this latency issue?

Thanks
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Denny Smith

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Re: Audio ahead of Video

PostWed May 02, 2018 2:14 am

Video processing takes longer than the separate audio board/processing, so it is ahead of the video. You need to delay the audio in you sound board/desk to match the processed video.
Cheers
Denny Smith
SHA Productions
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Asgeir Hustad

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Re: Audio ahead of Video

PostWed May 02, 2018 3:58 am

If your audio is embedded via XLR inputs on THE CAMERA, it will be in sync. If it is embedded via XLR Inputs on the switcher, it will need to be delayed.
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courtney

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Re: Audio ahead of Video

PostWed May 02, 2018 8:56 am

Hi guys!

Thanks so much for getting back to me on this.
Would we then need to install a delay device in conjunction with the Allen & Heath desk to delay the microphone audio yes? I have heard about Bheringer Sharks. Is this the right kind of thing?

Wouldn't that then look a little strange with people sat in the first front few rows when the speaker is speaking but the audio is slightly delayed through the front of house or wouldn't they even notice?

Thanks for all your help
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Asgeir Hustad

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Re: Audio ahead of Video

PostWed May 02, 2018 4:06 pm

Generally, you won't delay the audio to the speakers in the room. Your audio mixer will almost definitely have some form of sends on it, separate outputs that have selectable tapping points. If it's a digital desk, you can probably set the delay directly on that output, internally in the mixer.

If it's an analog desk or a low-end digital desk, you can send that output to a delay-capable device and then into the video switcher. Haven't really got any to recommend, though, as we do this in our audio mixer.
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courtney

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Re: Audio ahead of Video

PostWed May 02, 2018 8:59 pm

Hey Asgeir, and all

Again thanks for figuring this out with me!

So our desk is a pretty good Allen & Heath one so I would imagine it has this built in so I have asked the audio techs to take a look into it. However, the issue I have is that the TV's don't emit sound, the sound people hear comes through the separate audio rig in the building if that makes sense?

Thanks
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courtney

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Re: Audio ahead of Video

PostThu May 03, 2018 7:39 am

Hi guys,

Thanks for all your help!
Not sure if I have explained exactly what I mean here...

So the audio that comes out the front system which is sent from a wireless microphone into an Allen & Heath digital desk and then out to the fronts is what needs to be matched to the tv's.

The tv's don't output any sound however the visual on the screen of the same speaker speaking is behind the audio they hear if that makes sense? So we don't send any audio feeds to the tv's only visual and it's that live visual that is out of sync with the audio that's coming through the speaker system?

Sorry for not being clearer.
Thanks again
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Denny Smith

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Re: Audio ahead of Video

PostThu May 03, 2018 4:23 pm

So, you need to delay the audio in your sound system to match the video feed to the TV monitors.
That said, can the audience see the sepaker/performer directly? If so, delaying the audio will put the performers out of sync visually, like in a small venue setting. In a large arena setting, yiu can not see the spear/performers lips anyway, so this should not be an issue either for a small amount of delay.
Cheers
Denny Smith
SHA Productions
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courtney

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Re: Audio ahead of Video

PostSat May 12, 2018 10:14 am

Hi guys,
Unfortunately we cant delay the audio as the audience would notice this. So we would then have the same problem but flipped in the sense that the Screens will be showing it in time but the audik rig would be out of time wit the speaker.

Someone said if I send the signal from the camera (a canon xf205) as i59.94 that might help. I have set up the camera to do that however when i change the output in the Atem 1 m/e to set the video standard to match i cant get a signal out. Any ideas why?
Thanms
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Thomas Seewald

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Re: Audio ahead of Video

PostFri May 18, 2018 7:22 pm

Having live monitors/projectors visible for any audience in the same room with the actor, you wil allways have the problem, that the displayed image (!) is not in sync with the real scene. The image is behind the reality. This is, where the audio-issue is coming from, because it is normally in sync with live scene.

You have the following possibilities:

1) Keep audio in sync to the real scene (no delay) and so before displayed image. Good for the actor, but maybe confusing the audience when looking primary to the monitors instead of looking to the real scene and a viewer of a recorded or broadcasted video.

2) delay the audio, that it fit to the monitors. Good for the audience, but you drive the actors crazy, because the hear themselves with a delay. This may (!) work (but is a pain) with talking people, but is absolutely no go for musicans / singers...

3) Feed the audio without delay into the room and delay audio for broadcast and record. (Only record is no problem, because you can solve this issue in post-production).

I think, the last way is the right one. Keep in mind, that (depending on the framerate) every 14m the sound is delayed for one frame because of the light speed is faster than the sound speed. I also think, that the audience near the real scene will prefer, looking direct to it instead of looking to the monitor/projection and for people far away, sound and image have less relative delay.

And a second point. You have several points, where the video delay comes from. First from the camera, second from vision mixer. Its output is the reference, when recording and broadcasting. And after this the additional delay behind at the live monitor/projection. This is, what is noticed by the live audience.

By the way: Take a look to big live projections in TV shows from realy big broadcasters with realy good and expensive stuff. They allways are behind the real scene and the audio fits th te scene, not to the projection ;-)

P.S. The trick with feeding the audio into a camera may work, when the camera really delay audio. But it only would solve the problem for recording and broadcasting, not for the live audience....(This would be the described situation 2.)
thos-berlin - Thomas S e e w a l d
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Brett Casadonte

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Re: Audio ahead of Video

PostSat May 19, 2018 12:48 am

courtney wrote:Hi there,

I have a Canon XF205 which is connected to a BlackMagic ATEM1 ME 4K Production Switcher via SDI. I then have SDI going out to two LED domestic TV's from the Auxiliaries. The TV's have BlackMagic SDI to HDMI converters and then HDMI into the TV's. The picture is great however the audio is miles ahead of the video.

The audio however is coming through our Auditorium sound from radio mics into an Allen & Heath desk. Is there a way to fix this latency issue?

Thanks


Welcome to the battle against the laws of physics!

To best understand where your latency is coming from, you need to examine your entire video chain. I'm not familiar with the Canon XF205, but that is one place to start. You'll want to do some research to understand how many frames of latency there are on the camera when its sends out its video signal. Since it has SDI, chances are it is low, but that is not a guarantee (the URSA mini cameras when they first came out had about 4 frames of latency on the SDI output if I remember correctly).

Next, you'll want to check the devices that the video signal goes in to. If your camera is connected directly to your ATEM, then there will likely be a single frame of delay for the resynchronization that occurs on the switcher. Next, you'll want to look at where you're sending your signal to. Since you're sending out of the Auxes directly to the TV, there probably isn't any delay there, so look at the TV. TV's, particularly older LED / LCD / Plasma display or ones with inexpensive digital signal processing are notorious for creating frames of delay when processing video signals.

So when you look at your entire video chain, add up all the frames of delay across it, and then you'll see what is creating your audio / video sync issue.

The next challenge is what to do about it.

In an iMag (short for image MAGnification) situation like you're describing where you have a camera that is capturing a live performer on stage and projecting them to a large screen for people to see, having audio / video sync issues are common. The best way to resolve them is to eliminate the frame delays in your video chain, because trying to dial in delay in a live environment is not only challenging for talent (because they hear what they are saying over the PA after they say it, very distracting) but it can also cause feedback (because the microphone is picking up with the the live performer is saying, after they say it, and then amplifying that to create an 'echo'). So it really isn't feasible to try and add audio delay to correct sync with iMag. The only real approach to dealing with it is addressing the latency in your video chain.
Brett Casadonte
Founder and Techinical Director - GlobeStream Media
http://www.globestreammedia.com
Live Production: on-location and REMI using LiveU
ATEM 2 M/E, 1 M/E, TV Studio Pro 4k, BM URSA Broadcast, & Studio/Micro Studio Cameras
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Peter Benson

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Re: Audio ahead of Video

PostSat May 19, 2018 1:58 am

You have latency generated within every digital video device you've got in tbe chain -- including camera, switcher, HDTV, and who knows what else.

Latency in that scenario is additive, and cannot be resolved in large mrasure except by strategically delaying the audio signal -- but where you do so in the signal chain is critical (perhaps it's not good to make the correction, for example, even via the video switcher's menu, if it posesses that capability -- but some consumer HD and 4K televisions even sport Audio Delay feature, that's menu accessible. Check that option out, and/or purchase a black box that performs such a delay for you).

Now, in a large oresentation space such as a church auditorium, concert hall, conference room, etc., a helpful trick to minimize the tension such latency arouses in your audience is to ensure your presenter is not standing directly "beneath" or "beside" the viewing screen(s) from the majoity of your audience's point of view -- that's an additional, practical benefit for the Stage Left/Stage Right dual-[projector] screen setups found in many large venues in worship centers and the like.

BUT WHAT ABOUT TACKLING THE MAGNAMINOUS ADDITIVE LATENCY CAUSED MORESO BY THE CHEAPEST QUALITY VIDEO DEVICES IN THE VIDEO SIGNAL CHAIN?

It would serve you well to minimize the use of unnecessary digital "enhancement" techniques you might have running in any of those digital video sources, video processors and display devices.

For example, within the camera, adding to the latency generated by analogue to digital conversion to SDI, you might investigate whether you've got image stabilization switched on. If so, shut it off -- and look for other possible latency-generating culprits you can do without.

Check Blackmagic Design's catalogue for MiniConverter accessories that might be equipped to aid you further, in wisely, i.e., strategically aligning audio and video signals where needed most, after you've taken remedial steps suggested above.

I hope you find this read useful.
Cheers!
Peter

courtney wrote:Hi there,

I have a Canon XF205 which is connected to a BlackMagic ATEM1 ME 4K Production Switcher via SDI. I then have SDI going out to two LED domestic TV's from the Auxiliaries. The TV's have BlackMagic SDI to HDMI converters and then HDMI into the TV's. The picture is great however the audio is miles ahead of the video.

The audio however is coming through our Auditorium sound from radio mics into an Allen & Heath desk. Is there a way to fix this latency issue?

Thanks


RS 14.3.0.014 | MiniMonitor | DTV 10.9.7 | Win64 8.1 | ASUS ROG G751JL, Intel i7HQ, 24GB, 1TB HDD, 500GB EVO 850 SSD, GTX965M | Mackie MCU Pro | Softube Console 1 | Shuttle Pro 2
DTV 10.9.7 > Kingston SD5000T > MiniMonitor > Bravia | Samsung U28D590 | DRS 14.3.0.014 | Win8.1 x64 | ASUS G751JL, i7-4720HQ, 24GB | GTX965M | 1TB HDD, 500GB EVO 850 SSD | MCU Pro | Softube Console 1 Mkii | Shuttle Pro 2
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Peter Benson

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Re: Audio ahead of Video

PostSat May 19, 2018 8:48 am

Properly managed audio engineering may prove effective in mitigating against feedback in situations where audio delay us carefully employed.
Brett Casadonte wrote:
courtney wrote:Hi there,

I have a Canon XF205 which is connected to a BlackMagic ATEM1 ME 4K Production Switcher via SDI. I then have SDI going out to two LED domestic TV's from the Auxiliaries. The TV's have BlackMagic SDI to HDMI converters and then HDMI into the TV's. The picture is great however the audio is miles ahead of the video.

The audio however is coming through our Auditorium sound from radio mics into an Allen & Heath desk. Is there a way to fix this latency issue?

Thanks


Welcome to the battle against the laws of physics!

To best understand where your latency is coming from, you need to examine your entire video chain. I'm not familiar with the Canon XF205, but that is one place to start. You'll want to do some research to understand how many frames of latency there are on the camera when its sends out its video signal. Since it has SDI, chances are it is low, but that is not a guarantee (the URSA mini cameras when they first came out had about 4 frames of latency on the SDI output if I remember correctly).

Next, you'll want to check the devices that the video signal goes in to. If your camera is connected directly to your ATEM, then there will likely be a single frame of delay for the resynchronization that occurs on the switcher. Next, you'll want to look at where you're sending your signal to. Since you're sending out of the Auxes directly to the TV, there probably isn't any delay there, so look at the TV. TV's, particularly older LED / LCD / Plasma display or ones with inexpensive digital signal processing are notorious for creating frames of delay when processing video signals.

So when you look at your entire video chain, add up all the frames of delay across it, and then you'll see what is creating your audio / video sync issue.

The next challenge is what to do about it.

In an iMag (short for image MAGnification) situation like you're describing where you have a camera that is capturing a live performer on stage and projecting them to a large screen for people to see, having audio / video sync issues are common. The best way to resolve them is to eliminate the frame delays in your video chain, because trying to dial in delay in a live environment is not only challenging for talent (because they hear what they are saying over the PA after they say it, very distracting) but it can also cause feedback (because the microphone is picking up with the the live performer is saying, after they say it, and then amplifying that to create an 'echo'). So it really isn't feasible to try and add audio delay to correct sync with iMag. The only real approach to dealing with it is addressing the latency in your video chain.


RS 14.3.0.014 | MiniMonitor | DTV 10.9.7 | Win64 8.1 | ASUS ROG G751JL, Intel i7HQ, 24GB, 1TB HDD, 500GB EVO 850 SSD, GTX965M | Mackie MCU Pro | Softube Console 1 | Shuttle Pro 2
DTV 10.9.7 > Kingston SD5000T > MiniMonitor > Bravia | Samsung U28D590 | DRS 14.3.0.014 | Win8.1 x64 | ASUS G751JL, i7-4720HQ, 24GB | GTX965M | 1TB HDD, 500GB EVO 850 SSD | MCU Pro | Softube Console 1 Mkii | Shuttle Pro 2

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