[FFmpeg-user] Video and Audio is off-sync on Decklink SDI output

Bouke / VideoToolShed bouke at videotoolshed.com
Thu Mar 2 17:32:38 EET 2017

> On 22 Feb 2017, at 23:32, Tung Tran <tung.tran at v247.com> wrote:
> Dear all
> I am testing to setup a decoder with ffmpeg, take live stream in
> (RTMP/HLS,.) and output to Decklink SDI.
> Its working but I have the issue of audio and video is off-sync on decklink
> SDI output, I tried to play around with vf setpts and af asetpts but
> couldnt make video/audio to sync.

Perhaps unrelated, but on my system, depending on the state of my machine (Eg if I have run Avid MC before), the output of my decklink is out of sync on known good sync input.
(No matter the player, it seems a Decklink driver issue.)
So you might want to test output with a known good local input file. (While looking / listening to Decklink output.)

> Any input will be very appreciated.
> Here is my command so far
> * ffmpeg -i rtmp://something  -vf "setpts=PTS-STARTPTS" -af
> "asetpts=PTS-STARTPTS" -f decklink -pix_fmt uyvy422  "DeckLink SDI" *
> Video and audio of input rtmp is synced on VLC or other software.
> ---
> Best regards,
> *Tung Tran*
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