"Favor audio sync when playing Variable Frame Rate (VFR) media"

rgr wrote on 6/27/2024, 12:25 PM

Does anyone know what exactly this option does?

My video:
Frame rate mode : Variable
Frame rate : 50.000 FPS
Minimum frame rate : 42.553 FPS
Maximum frame rate : 60.606 FPS
(but in reality it is almost perfect 50fps)

I put them into the video together with the video processed by Avisynth+LibavideoSource(fpsnum=50)+Vdub (i.e. CFR 50fps).

And so:
1. With the option OFF I found one duplicate frame (there are probably more), and the video with VFR is a few frames longer (i.e. there are probably more duplicates). Generally there should not be such a difference, rather max 1 frame.
2. With the option ON, both videos are perfectly synchronized (at least that's what I see),

Regardless of this, I have the audio shifted by 2 frames at the very beginning (original mp4 VFR vs Avisynth+LibaAudioSource+VDub).

Comments

Todd-AO wrote on 6/28/2024, 12:25 AM

What I'd like to know is what is the negative of having it turned on, if any.

This video about a missing frame says the solution is to turn the GPU decoder off which is true, however it was later suggested to turn on "Favor audio sync when playing Variable Frame Rate (VFR) media", and that also fixed the missing frame problem.