Audio randomly getting out of sync during a recording session.

[Larry-Boy]

Hello! First time on the forum, we’re having a randomly occurring issue where mid-recording, the audio will get out of sync. The audio mixer shows it during the session as well. Everything’s up-to-date. Is there a particular setting that might fix this issue??

Here’s the setup:
-PC is running Windows 11
-video capture device is an internal capture card
-outputting the final video mix from OBS to a hardware encoder that we stream from(full screen projector program).
-audio input capture from soundboard > interface > PC
-We record in OBS at a Target Bitrate of 16000 with a key frame interval of 2
-Constant Bitrate is enabled
-Recording Format is .mp4
-Encoder is H264/AVC Encoder (AMD)
-Audio encoder is FFmpeg AAC
-Audio bitrate is 128

All suggestions / advice is appreciated and welcomed!

Thank you!

 

[polarbearonfire]

I am having a similar issue. I am digitizing old home videos. If I don't restart OBS in between each recording, then a lot of my videos end up being out of sync with the audio. I don't know if it could be an OBS setting, but I have all filters turned off and the issue still occurs. Very terrible.

 

[Lawrence_SoCal]

1. don't ignore pinned post in this forum about posting your OBS Studio log (when asking for help/support)
2. real time video encoding is computationally demanding. Do not simply expect it to work, especially on older hardware, or with {default} OS settings leaving lots of resources committed to background tasks, etc).
3. Chance of being random is very close to ZERO
4. Original poster - why are your ignoring the BIG RED warning about NOT recording to MP4 format?
5. CBR is for Streaming.. Typically you want CPQ for Recording

Then the obvious of what are you doing for real-time hardware resource utilization monitoring? if nothing, then you are doing the equivalent of driving car blindfolded.

As for settings to address audio - hard to tell without knowing your EXACT audio setup (incl physical path) and settings.
Basic item - check OBS log and make sure no audio sampling rate mismatch, which tends to cause issue more often with under-powered hardware (but is not a good setup regardless, especially on Windows OS).

PolarBear - that sounds like an overwhelmed (under-powered) computer. though it could be a bunch of different things (largely OS related, but you could have set some OBS settings that don't work well with your computer).
- Make sure Operating System optimized for what you are doing (stopping unnecessary background tasks, turning off eye candy, etc). Then make sure you have enough RAM.

OBS Studio is free, open-source software. It is very powerful, flexible, etc. What is expected of the user is to RTFM. OBS Studio has a decent learning curve. There is for pay software that is much more approachable. but that won't help if hardware under-powered or operating system not running smoothly

 

[Larry-Boy]

Gonna ignore some of the extremely kind remarks, but I’ll remember to post the log next time. First time using the forums and we were in the middle of a recording session and I was trying to find a solution as quickly as possible.

But I’ve been using OBS for years now and yes it’s very powerful and has a lot to it. Still learning new things about it everyday it seems, but I have learned a lot of things that work, and a lot of things that don’t. And this particular setup has had yet to fail me for years now.

With all that being said, we’ve since upgraded systems (using a Mac Studio with a lot more RAM) and it’s been working fine so it probably was just a RAM issue or something. If not, I’m thinking this particular PC we were using must’ve had some kind of faulty or outdated equipment in it so Lawrence was probably right about that.

It might not have been literally random but it was consistently inconsistent as to when it would go out of sync. We record for upwards of three hours straight for a video and sometimes it happened, sometimes it didn’t. No distinct pattern that we could find.

Also the YELLOW warning about .mp4 (at least when I first used OBS) just simply warned that if there was ever a power failure or something it would delete the footage. Not really a scare of mine since we have backup recordings on other systems. But we’ve never once had any issue recording in mp4.

 

[Lawrence_SoCal]

The Recording format warning was in Red in older versions, didn't realize color had changed
MP4 is not a Recording safe format...period.. ANY number of glitches, even small ones (not just a big one like computer crash with power outage), can render the video unrecoverable [without clean Recording over marker/details at end of MP4 file, its near useless]. Instead, Record to MKV (which doesn't have that issue), then if you require MP4, let OBS Studio remux once Recording completed. My 1hr plus recordings (~11GB), on a NVME SSD, takes about 15-20 seconds to remux (change file wrapper from MKV to MP4, doesn't change actual video at all... the time taken is simply that required to create a copy of the Recording file).

A system that was working for years, but recently had issue... likely either an OS change/update (with MS copying Apple and adding auto-start background processes) and/or an app change (or addition) that added background load. I'd suspect in your case an Operating System background process that pushed system into overload, and that caused a/v sync to drift... but lots of other, related, possibilities as well