Audio 6 frames ahead of video

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Kit Laughlin

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Audio 6 frames ahead of video

PostTue Oct 17, 2017 6:34 am

Bedding the new ATEM Television Studio HD down; last step was to record tests.

1080p/29.97, set both in ATEM and Media Express. I am recording to very fast Thunderbolt SSDs. I am driving the setup with a fast MacBook Pro.

[Edit] Audio setup details:

Rode lav to Filmmaker transmitter > receiver > Behringer Ultragain 100 Tube amp > XLR to XLR in the back of the ATEM.

When I play back the footage in ME, I can see the sync problem.

When I bring this footage into FCPX, the audio is six frames in advance of the vision. [Edit] In today's tests, 5 frames ahead; I am not worried about one frame differences in the tests.

Any suggestions? TIA, KL
Last edited by Kit Laughlin on Fri Oct 20, 2017 6:28 am, edited 1 time in total.
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear
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Jack Fairley

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Re: Recording to SSD via UltraStudio Mini, audio 6 frames sl

PostTue Oct 17, 2017 8:34 am

Is the audio in sync if you monitor the ATEM output?
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Kit Laughlin

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Re: Recording to SSD via UltraStudio Mini, audio 6 frames sl

PostTue Oct 17, 2017 9:13 am

Yes, it is; well, that's how I recall it. I will check and report back. Thanks.
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear
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Kit Laughlin

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Re: Recording to SSD via UltraStudio Mini, audio 6 frames sl

PostWed Oct 18, 2017 7:13 am

So: duplicated the test, and audio is out of sync in the multi-display, the same amount it is out both in replay in Media Express and FCPX. I am able to count the frames in FCPX: audio is around 4.5 frames early today. Definitely was 6 frames early yesterday.

An aside: is there a recommended order in which to power BM decks/recorders/etc. up in? Most worrying for me is this variation: in five recordings today, audio 4.5 frames early; in eight recordings made yesterday, exact same setup and settings, audio 6 frames early.

I ask because the ME preferences window did not show the same options when I powered the system up tonight at first; there was no dropdown in the Media Express pref. window as there is now (only choice was record in native resolution). So, with the ATEM connected, I disconnected the USMini Recorder; when I plugged it back in, all standard preference options displayed.

Any suggestions?
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear
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Kit Laughlin

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Re: Audio 6 frames ahead of video; problem solved

PostSat Oct 28, 2017 12:11 am

I bought a Behringer FBD 100, which has a settable audio delay feature (designed for getting distant speakers at outdoor events in sync with front of house); settings go from 0.1ms all the way up to 2500ms.

I have put this in the circuit with the Behringer Ultragain Tube MIC100 pre., and dialled in 145ms on the FBD100, and audio and vision are in perfect sync, and there is no sync drift over the 10 minute test recordings I have done; I will do a 30' one and report back.

Apparently around the internet this slow processing of HDMI-out video in consumer and prosumer stills cameras that output video is well known.

I am surprised that the ATEM does not have a hardware or software audio delay as part of its feature set.

Delaying the audio seems to be the only solution.
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear
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Asgeir Hustad

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Re: Audio 6 frames ahead of video

PostSat Oct 28, 2017 7:49 pm

This should not really come as a surprise - practically every forum where an ATEM is mentioned, the fact that you generally need to delay the audio is not far behind. :D

There is a very logical reason for this as well - audio which is coming in from the SDI-ports is fine, and locked to the correct frame of video already. But audio coming in through the XLR ports does not have any such sync information, so it is embedded in the stream "as it comes". As the video processing chain takes a lot longer from the image is captured by the camera than the audio does, the audio WILL need to be delayed if it doesn't enter via a camera, which then does this syncing.

Audio has a general maximum latency of a few milliseconds from the artist makes the sound until it has to be out of the speakers and in-ear monitors, so the technology is designed for this speed. Video is designed to be transmitted in frames, which are generally consisting of 1/50s periods of image data. Unless you gen-lock your cameras, this needs to be synced later-on, and you need to wait at least until the start of every frame to do this. There are also general delays in both cameras (especially consumer / semi-pro ones), effects and mixers that means that video is somewhat behind the real thing, and always will be.

In real life, practically ANY digital audio mixer has this functionality built in, so there is no point adding it to the video mixer. Do it there, or get a box, like the DEQ2496, if you need to do it yourself and don't have an audio mixer.
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Kit Laughlin

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Re: Audio 6 frames ahead of video

PostSun Oct 29, 2017 4:51 am

Asgeir, hindsight is 20/20, as they say.

I did ask both BM and the dealer whether the setup (which I detailed to them without the FBD100) would work as is, and both assured me it would; this is not a problem, but tying as much money into a decent deck as the switcher seems a bit lop sided to me. Let me explain.

The majority of people using the ATEM TV HD unit will be connecting consumer cams that have this finite delay in processing. Making that common knowledge in the advertising of the ATEM makes sense to me. I am an ex-network director (in the days of SD) so am familiar with genlocking, but this is not part of the consumer-prosumer world (and the cameras we are using are primarily stills cameras that can record video to cards) so most people will not be considering this delay.

And thanks for your explanation. I posted here mainly to give other inexperienced users a heads-up. Cheers, KL
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear
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Thomas Seewald

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Re: Audio 6 frames ahead of video

PostSun Oct 29, 2017 6:41 am

Genlock only would reduce the video delay one(at maximum) frame. It gives a technical frame for one image - the current. So you will come from 6 frames to 5....Most of delay also comes from the signal processing inside the cunsumer cameras. They are not designed to send a realtime singnal to their outputs. The output is made for review/replay. Professional cameras are designed to output in realtime. So there are two ways.
1.) Use professional cameras for no noticeable delay
2.) Use consumer or semipro cameras and add audio delay (I dont know, if cameras can delay their audio for matching wit the video out. I think no). So use a audio delay from audio mixing console or an external effect unit)

I remember a steup, where audio was sent delayed from mixing console to tricaster. So not only a BM problem.

Knowing that delays are caused in camera processing, I would suggest not to mix different camera types (when showing the same object). Very important when showing music, less important at sports.
Last edited by Thomas Seewald on Sun Oct 29, 2017 5:39 pm, edited 1 time in total.
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Kit Laughlin

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Re: Audio 6 frames ahead of video

PostSun Oct 29, 2017 7:58 am

Thomas, agree completely. For this reason I bought three Panasonic GX85s. May have to buy one more. A LOT less expensive than buying professional cameras, and there is no discernible difference in image quality for programs that are viewed on tablets or phones. Thank you.
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear
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Andrew Martin

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Re: Audio 6 frames ahead of video

PostSun Oct 29, 2017 3:41 pm

Kit Laughlin wrote:Asgeir, hindsight is 20/20, as they say.

I did ask both BM and the dealer whether the setup (which I detailed to them without the FBD100) would work as is, and both assured me it would; this is not a problem, but tying as much money into a decent deck as the switcher seems a bit lop sided to me. Let me explain.

KL


I guess BMs reply might of been from a viewpoint that youll have the atems audio mixer allowing the audio to be captured in camera and so sync to each frame of video and so any processing in camera of feeding back to the atem for processing would see both in check. It's usually only when you have a different audio path from the video path that this sync issue occurs.. one work around would of been to feed audio from your audio board into a cameras mic input and so syncing as if captured from in camera and setting ur atems audio mixer to grab audio from only that solo camera source.

A.
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Thomas Seewald

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Re: Audio 6 frames ahead of video

PostSun Oct 29, 2017 5:37 pm

Different signal paths inside ATEM can't cause delay more than one (at models with DVE depending on its usage two in maximum) frames.
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Kit Laughlin

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Re: Audio 6 frames ahead of video

PostSun Oct 29, 2017 7:45 pm

Andrew, I did describe my setup (second system sound into the ATEM) and that I was not capturing sound and vision via HDMI–SDI. That was the point at which the need for audio delay would have been helpful, especially if it is a well-known problem.
Regards, Kit Laughlin::www.StretchTherapy.net::BodyPress Productions
ATEM Television Studio HD, UltraStudio Mini-Recorder, 3 x Panasonic GX85s, too much sound gear

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