Decklink Output Audio Drift

dmdb

New Member
I've had a good look through the forums here, Reddit as well but so far have not found a solution to this.

I am using OBS with a Blackmagic Duo 2 SDI card, using outputs only using the Decklink support built in to OBS. We are not streaming or recording within OBS, only using the Decklink output. Our sources are normally all browser sources, but for the purposes of testing this issue I have been using a local sync test pattern as a media source on loop which is a download from this Youtube video: https://www.youtube.com/watch?v=bCPEidaVzQU

We are normally using four separate instances of OBS, all running from their own directories in portable mode, however, if I run one instance, the issue is still present. We are encountering audio drift if we leave this sync test pattern (or our normal sources) running, if we leave it running over a period of 12 hours then there are 10 or more frames of audio delay on the outputs(measured by playing back frame by frame on an EVS). We see the following sort of line in the log and the delay does seem to correspond to these values:

13:25:54.566: adding 21 milliseconds of audio buffering, total audio buffering is now 21 milliseconds (source: Media Source)

Most of the results I have found when searching for this issue refer to hardware overutilisation. Running Task manager we never see the CPU or GPU go higher than 50%, there is plenty of RAM spare etc so this does not appear as we see it to be the case but happy to accept suggestions to the contrary. If there was a constant number of frames delay we could deal with that but the drift is an issue. The amount of drift is arbitrary and I have been able to replicate this behaviour on a second identical machine.

I've attached a log file taken today from one of the OBS instances where there's a few lines shown, I have the instances running overnight as a fresh soak test with the only difference being that they are running with administrative rights as I found a suggestion that this can help with GPU access. This is running a fresh release of OBS from Github but we have experienced the same issue with the current release as well, hence trying a more up to date build to see if it made any difference.

Just wondering if anyone has encountered the same, or can offer any suggestions?
 

Attachments

  • 2021-03-24 13-25-53.txt
    6.2 KB · Views: 57

peterjdej

New Member
We are using OBS for NarrowCasting and want to do this through an Atem switcher. First we tried it with NDI output and a Magewell NDI to SDI converter. That gave an audio issue. Audio was out of sync (known problem, reported at NDI plugin github). Other NDI sources (like Vmix) does not have that issue. Now we tried the Decklink mini monitor PCI card, directly connected at the Atem switcher. That gives the same issue as described above. After a fresh start of OBS, audio is in sync with video, but after a while it is running out of sync.
 

Hoggins!

New Member
Experiencing the exact same problem right now on a live session (no output encoding, just Decklink output). Any hint?
 

movingwater

New Member
Experienced the same today with my UltraStudio HD mini. I'm on macOS and if I output the sound direkt to the UltraStudio the sound is more or less in sync. But if I output it through OBS with the blackhole virtual audio device sound is off almost a 1sec (30fps). Sound is behind 1 sec.
 

dmemphis

Member
Experiencing similar audio sync issue on a decklink mini monitor card, playing a list of files with "VLC video source". I was suspecting it to be VLC, but now I suspect it is OBS based on what I see here. This is a critical problem for us now.
 

Attachments

  • 2022-01-08 11-06-34.txt
    8.3 KB · Views: 37

video2go

New Member
Hi,
I am using RPI4 to play SRT streams to my old ATEM TV Switcher (1080i50) from HDMI. Having Blackmagic Decklink mini monitor I wanted to use OBS and Decklink out to HDMI to my ATEM TV Studio but there is a huge audio drift so all my program had asynchronous problems.
Any workarounds?
 

lindenkron

Member
Hi,
I am using RPI4 to play SRT streams to my old ATEM TV Switcher (1080i50) from HDMI. Having Blackmagic Decklink mini monitor I wanted to use OBS and Decklink out to HDMI to my ATEM TV Studio but there is a huge audio drift so all my program had asynchronous problems.
Any workarounds?

Am also experiencing major issues with this. It appears there's no solid solutions neither NDI nor SDI (Decklink) that does not come with audio sync complications.

Originally we used NDI and ran into drifting audio syncs, with buffering showing up in the logs as well. Then we've gone and purchased Decklinks for direct PC to PC SDI connection only to find that it's awfully out of sync as well. Having gone through every settings a multitude of time, I keep coming back it to simply being an OBS issue.

Worst part is that it seems to randomly work at times (no delay) then suddenly we're back to 1~ sec delay on video, and audio lagging behind by a whole second. Tragic having purchased hardware and then it turns out it's software issues :(
 

HSX

New Member
Hi !

The only thing I found to solve the problem at the moment is to use an audio embedder (Like the Audio to SDI blackmagic ones) to have both the audio & video sync. I didn't find any software solutions at the moment. Since it's only the audio that drifts but not the video it works perfectly.

Typically what I do is plug the Focusrite Line Outputs into the Audio Embedder along with the Decklink SDI Output.
Have been running a test for two days with a high GPU & CPU use and there's still no audio drift so it seems to work.

I'm still hoping for a fix but it works !
 

Gabriel Nogales

New Member
I've had a good look through the forums here, Reddit as well but so far have not found a solution to this.

I am using OBS with a Blackmagic Duo 2 SDI card, using outputs only using the Decklink support built in to OBS. We are not streaming or recording within OBS, only using the Decklink output. Our sources are normally all browser sources, but for the purposes of testing this issue I have been using a local sync test pattern as a media source on loop which is a download from this Youtube video: https://www.youtube.com/watch?v=bCPEidaVzQU

We are normally using four separate instances of OBS, all running from their own directories in portable mode, however, if I run one instance, the issue is still present. We are encountering audio drift if we leave this sync test pattern (or our normal sources) running, if we leave it running over a period of 12 hours then there are 10 or more frames of audio delay on the outputs(measured by playing back frame by frame on an EVS). We see the following sort of line in the log and the delay does seem to correspond to these values:



Most of the results I have found when searching for this issue refer to hardware overutilisation. Running Task manager we never see the CPU or GPU go higher than 50%, there is plenty of RAM spare etc so this does not appear as we see it to be the case but happy to accept suggestions to the contrary. If there was a constant number of frames delay we could deal with that but the drift is an issue. The amount of drift is arbitrary and I have been able to replicate this behaviour on a second identical machine.

I've attached a log file taken today from one of the OBS instances where there's a few lines shown, I have the instances running overnight as a fresh soak test with the only difference being that they are running with administrative rights as I found a suggestion that this can help with GPU access. This is running a fresh release of OBS from Github but we have experienced the same issue with the current release as well, hence trying a more up to date build to see if it made any difference.

Just wondering if anyone has encountered the same, or can offer any suggestions?
I have the same problem, I see you had it quite a while ago. Did you manage to solve it?
 
Top