[FFmpeg-user] Audio delayed with DeckLink

[Marton Balint]

On Thu, 13 Oct 2016, PSPunch wrote:

> Hi,
>
> On Win7 x64, Capturing SDI from DeckLink Duo 2.
>
> When encoding with FFmpeg, audio seems to be about 100ms later than 
> video. Is there a known solution to this, or is there a way to delay 
> video by roughly 100ms?

I tested the DeckLink drivers on Linux, and they very often fail to 
provide proper timestamps for the audio and video they produce, there is 
also a noticable clock skew after a few hours if you use their video 
clock, and they also skip frames (different number of audio and video 
frames) in the event of a signal loss.

To work around this problem, there are the audio_pts and video_pts 
options, so you can customize where you want your timestamps to come 
from. In my experience, wallclock is the only thing that works 
reliably, so I typically use these options:

-vsync 1
-video_pts wallclock
-audio_pts wallclock
-af aresample=async=1

Regards,
Marton