Question / Help Help with Audio Sync

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Thad Davidson

New Member
First of all, I would consider myself a novice with this, so your patience is greatly appreciated!

I am trying to live stream to Facebook and am having difficulty getting the audio to sync with the video. I have a Canon HF G20 camcorder, and the audio is coming into the camera through it's mic input from a mixer. All of this is then being output via HDMI to a Blackmagic Decklink recorder card on my PC. From what I understand, the camcorder outputs a 59.94i framerate so I have made sure that the settings of OBS match this everywhere that I can find. I have a delay set on the video and a delay on the audio to try and force a sync and once I got that synced up in testing and thought I was good to go; however, the next time I went to stream it was out of sync again. I've also noticed that even if I start out in sync, over time it will go out of sync. I have a suspicion that its a framerate issue, but I have no idea how to resolve it. In OBS, the only audio and video I have setup is the audio and video coming in from the camera and I have buffering turned off on the camera source (was a tip I saw in trying to resolve this).

Any thoughts on things I can try? Is it normal to be out of sync the next time you want to stream?

Thanks for any and all help!
 
Fenrir

Fenrir

Forum Admin
Just to clarify what I'm seeing here...

All the audio is coming in through the Decklink cards, correct? If the desync is happening somewhere in the card itself, I'm not sure that there will be anything we can do on the OBS side to help.
 
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Thad Davidson

New Member
Yes, that is correct. Are you thinking that I maybe split the audio from the mixer and feed it directly into the PC as a mic in? I can try that. I fiddled around with the settings last night and noticed a couple of things I didn't have setup correctly for streaming to Facebook Live including the keyframe interval. Not sure if that'd mess with the delay or not? I also corrected the Audio Sample Rate and Bit Rate. From there I had my wife help me test the video and audio delay for me and I finally landed on a 180 millisecond video delay and then added about 1 1/2 seconds to the audio delay, so 270 milliseconds, and it seemed to be ok. What I won't know for sure is when it has streamed for a couple of hours - we'll see if it gets out of sync again.
 
Fenrir

Fenrir

Forum Admin
No, I'm saying that the Decklink card should be handling the sync of the audio internally. There is likely a performance problem happening if the internal sync on those cards is drifting.

It's very, very unusual for those cards to have that kind of desync. Can you do a test in their software and check the resulting sync from a video recorded there? You might have a faulty card.
 
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Thad Davidson

New Member
Fenrir, thank you for your ongoing assistance, greatly appreciate it! After doing some more fiddling with the settings and thinking I got it right, over time it desynced again. I don't always have the time to troubleshoot, so what I am going to do is order an Elgato HD60 Pro and go from there. Hoping that a better card may solve the issue.
 
Fenrir

Fenrir

Forum Admin
The good news is that we did identify a few minor desync conditions, that have been corrected. If you can hold off until the next release (should be relatively soon, but don't want to give an exact date) or are willing to try a test build, might be better than replacing the card completely.

Elgato cards are notorious for having poor DirectShow drivers, which cause a host of issues with OBS.
 
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Thad Davidson

New Member
Oh, good to know, thank you! Just out of curiosity, what capture card would you recommend that works well with OBS? I had just read that the Elgato is an awesome capture card, but what I didn't know was what you shared with me. I just want to try and get this to working as I've been trying to figure it out for over a month. I don't want to throw in the towel as I like the simplicity of your software and what it does and is easy to train folks on what to do, but that is about where I'm at because I don't know what else to try; hence, wanted to try a different capture card.
 
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Thad Davidson

New Member
Fenrir, wanted to tell you that I saw the release at the end of October and read the release notes that the program had been updated to fix an issue with the Blackmagic Decklink Recorder driver. I finally had a chance to install that update and tested it this past Sunday and everything was in sync. Thank you so much for listening to me and providing a solution so quickly!
 
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