Gradual Audio De-sync with Blackmagic ATEM Mini

[bmc1313]

Hello, and thanks in advance for any advice.

I am conducting a weekly multicamera stream with a Blackmagic ATEM Mini being fed to OBS and then to Facebook Live. We have 2-3 cameras going into the ATEM, which then goes to a 2018 MBP via Thunderbolt 3.

The first week we did this, we had our sound mixer going directly into the ATEM and we discovered nearly a 1-second audio delay through the entire show. The second week, we plugged the mixer into the XLRs on one of the cameras, and thought we had solved the problem. However, after reviewing the stream on Facebook, we found that it gradually went out of sync over the course of the event. It was locked in at the start and periodically throughout the 20 minute presentation, it would drift up to .5 seconds off before snapping back to synced. Maybe happened a half dozen times over the course of the event.

We do have OBS recording the stream on the side - could that be causing issues? I haven't had an opportunity to review that stream to see if the desync is happening there as well, but it's definitely happening on Facebook.

This is definitely uncharted territory for me. Appreciate any insight! Thanks!

 

[bmc1313]

We had another one of these productions last night. For the Video Input settings in OBS we were previously using a custom setup at 1080p. Last night I changed it to a preset and chose the best available, 720p. No sync issues that we're aware of. So while this solution solves the sync, it would be great to be able to output at 1080p which is the signal the ATEM is spitting out. Any ideas what other settings we could adjust to solve the desync but keep it at 1080p? Thanks.

 

[studio-ubik]

Hello !
I have the same sync problem. I'm using an ATEM mini pro to mix 3 cameras, then into OBS to convert the signal from 1080p to 720p and for recording the stream. I'm then using OBS virtual camera to send the stream to Gotowebinar, the platform my customer wants to stream with, which can't take 1080p signal.

So I'm not using OBS to stream in this case, I'm just using it to convert the signal and to record. However, the recordings I made with OBS gradually go out of sync (couldn't check the actual stream but I checked the gotowebinar recording and it's also out of sync). Since it's a long program (over 2 hours), the drift gets really bad. I've read on these forums about switching "use device timestamp" on or off, but apparently this doesn't always solve the problem.

bmc1313, how do you explain that switching to 720p solved the sync issue ? Anyone else has an explanation for this sync problem?

 

[Lukesssssss]

Hi All, I had same problem. In my case the solution was to downgrade software to 8.4. Mini Atem start to be unstable after upgrade to 8.5 and 8.5.1 with OBS and LiveStudio with a lot of crash of Windows. The procedure is very simple: uninstall Atem Software 8.5, restapc, install 8.4 versione and upgrade Mini Atem Firmware. Now I'm having a streaming started 2h ago. Yestyerday after 1h audio start to be unstable whre I had to add 250ms in audio trasmission during the live.
I hope this comment can help a lot of us :-)

 

[Moonlight Productions]

Hi Everyone. Have a similar situation. Using an ATEM mini pro to switch 3 cameras and video ad rolls into OBS for streaming a football game. Used OBS in order to rescale the stream to 720p as required by the streaming service, and to bring in instant replay feeds (2) via NDI. Computer (i7 laptop) using Windows 10 running OBS 26.0.2. Audio via the 3 camera HDMI feeds, as well as commentator audio from a external mixer connect to the mic1 input of the ATEM. Prior testing (2 10 minute test streams) was successful. Stream started well during the game but started losing sync about 30-40 minutes in. By halftime the audio was about 4-5 seconds behind the video. Didn’t want to stop the stream because we may have lost the handle on it from the streaming service. By the end of the game the delay was about 8-9 seconds.

This isn’t visible in any way from OBS. The audio mixer meters are all in sync with the incoming audio/video. The only way we noticed it was watching the game stream. Needless to say, this was a mess.

Made the following changes back at the shop: 1. Changed the audio input source from Atem Mini to Audio Input Capture (Microphone Blackmagic Design). Checked the Use Device Timestamps box on the audio source. Re-ran a 1 hour test by using the same camera, audio mixer and mics as used in the game to record a 1 hour video playing on an ipad. This stayed in sync for the entire hour. Not sure if recording vs streaming presents the same problem or not. If this stays in sync on a recording would it likely stay in sync on a live stream?

Have not tested on a live stream since we probably have been fired for the problems with the last game.