Audio drift between Elgato CamLink 4K capture and camera footage over long recordings

[angeloruggieridj]

Hi everyone,

I’ve noticed a persistent audio drift issue when recording with OBS Studio (on macOS) using an Elgato CamLink 4K. Here’s my setup:

• Camera recording directly to SD card, 50 fps, 48 kHz audio
• OBS capturing the same camera via CamLink, also 50 fps, 48 kHz audio
• OBS recording format: MKV (tried remuxing to MOV)
• Editing in Final Cut Pro

Even though both streams are nominally 50 fps and 48 kHz, when I overlay the camera footage and OBS recording in Final Cut, I see the audio drifting by about 0.5 seconds over an hour of recording.

I’ve checked the files with ffprobe and found:

• Video fps: both 50 fps
• OBS video time_base: 1/90000
• Camera video time_base: 1/180000
• Audio durations slightly different (by a few milliseconds over long recordings)

Attempts to fix this with ffmpeg (-fflags +genpts, -vsync cfr, resample audio, remux to MOV) don’t solve the drift.

It looks like the issue comes from slightly different clocks between OBS (AVFoundation/macOS) and the camera, even when using the same frame rate and audio sample rate.

Has anyone experienced something similar with Elgato CamLink 4K or other capture devices? Any reliable way to get long recordings perfectly synchronized with external camera footage?

Thanks in advance for any insights!