Question / Help OBS went out of sound&picture synce during live broadcast


New Member
I was filming a facebook live broadcast of a conference last week. All tests before the broadcast were fine, including an on camera speech test, recorded by OBS to the computer.
At the live broadcast, which I also recorded by the OBS to a computer file - everything seemed to be fine, but when I firtst checked the MP4 file the OBS recorded - I realized that the sound and picture were out of sync all the time.

Why did it happen, and how can I prevent this from happening ever again?

My hardware:
- Elgato cam link HDMI to USB 3 captue device
- HP laptop, model: 15-dw0xxx
intel core i7-8565u CPU 1.80Ghz 1.99Ghz
16GB of RAM
Windows 10 64bit
Resolution: 720p 30fps
Recording bit rate was 3900 (same as the internet conncetion data rate - the internet at this location was wery fast)
Recording to the computer started after the broadcast begen, due to a delay of the conference