Help with Audio Desync specifically on .mkv format recordings.

MapleCryptid

New Member
Hey all! Firstly, I apologize for not having the logs for this specific issue. I discovered it once taking the recordings into Corel Video Studio, and when going through the appdata, the date of the batch recording is no longer listed, possibly due to updating OBS.

I'm having a strange issue with audio desync, but specifically with .mkv files. I've been recording an LP series via OBS. I use a 3.5mm connection mic and an Elgato HD60. OBS is set to record at 60p, the game is running at 30 if that's relevant. Video encode is NVIDIA NVENC H.264. Audio encode is FFmpeg AAC. Encoder rate control is CBR with 12K bitrate. Audio bitrate is 160 across all tracks, 48 kHz sample rate. When recording, I'm never hitting more than 15-20% CPU Usage.

Onto the issue at hand:
When recording, audio monitoring through OBS is totally in-sync. I don't have any set audio delay on any sources.
The recording output is into .mkv so I can maintain all audio tracks, including the master mix as well as the isolations for the mic and game audio. OBS automatically remuxes the recording into mp4. Strangely, the mp4 remux does not have the audio delay issue that the mkv container does. As a result, I can utilize this backup for the recordings I've already done, though admittedly with lower quality audio than I was hoping for. (I wanted to use the isolated tracks in order to use the audio ducking and other effects). To demonstrate how bad the delay is though, on the first recording when I ripped the audio via FFmpeg to get the game and mic isolations, the files had a longer duration than the video file!

I feel totally at a loss here. Admittedly, I'm completely self-taught, so I'm sure there's a setting somewhere causing this issue. But in all of my searching, I can't seem to find a straight answer. Can anyone point me to either a resource, or what settings I should be looking at to fix this for future recording sessions? I would be forever grateful.

Thanks y'all!
 
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