Audio Time Lag - newbie here

[MartynP]

Hi and thanks in anticipation for any help I receive from this post.

I am a total newbie to OBS and of recording my own videos on computer from an external stream so apologies for being a bit slow at this.

I am seeking to record an HDMI source onto my desktop via an HDMI>USB capture device. Al seems to be working correctly with one exception - I have an unacceptable time lag between video and audio ... probably a full second if not more. I have tried messing with the lag settings in the audio settings of OBS and also on the box supplying the data stream but am defeated and I wonder if any guru here is able and kind enough to point me in the correct direction.

Log file > log file here

 

[AaronD]

If the video is early, you can do one of these on the video source:

If the audio is early, you can do this on the audio source:

Keep in mind though, that a cheap HDMI -> USB adapter might be a moving target. You could have it perfect, reboot, and have the same settings be wrong again.

I found that out with 4 of them on the same rig: the cameras were never in sync with each other, and always off by different amounts each time. Replaced them with a single 4-input card on PCIe, and not only are they all in sync now, but the required audio delay from a separate USB line-in went from about 500ms with variation to about 300ms steady.

 

[MartynP]

If the video is early, you can do one of these on the video source:
View attachment 93222
If the audio is early, you can do this on the audio source:
View attachment 93223
Keep in mind though, that a cheap HDMI -> USB adapter might be a moving target. You could have it perfect, reboot, and have the same settings be wrong again.

I found that out with 4 of them on the same rig: the cameras were never in sync with each other, and always off by different amounts each time. Replaced them with a single 4-input card on PCIe, and not only are they all in sync now, but the required audio delay from a separate USB line-in went from about 500ms with variation to about 300ms steady.

HUGE thanks for this which seems to have resolved my issue, for the time being at least. I will confess to buying the (almost) cheapest USB connecting device I could just to find out if it would do the job I wanted. So if I were to want RELIABLE and idiot-proof, what interface would you recommend.

Martyn

 

[AaronD]

So if I were to want RELIABLE and idiot-proof, what interface would you recommend.

For what it's worth, I tried the BlackMagic name brand first, and both I and support couldn't get it to work. Sent it back to Amazon for a refund. It could have been a dud card, but such it was.

My second try, worked:
Cards:

ACASIS PCIe Capture Card

Acasis PCIe capture card supports multiple HD resolutions (such as 4K60Hz), bringing crystal-clear visual effects to the audience. It also supports quad HDMI or SDI simultaneous input, allowing you to flexibly adjust between different camera angles or input devices. Solve your professional video...

www.acasis.com

Drivers:

ACASIS CAPTURE CARD DRIVERS

PCIE CAPTURE CARD AC-4HDMI (Quad HDMI-1080P60).zip AC-4SDI (Quad SDI-1080P60).zip AC-4HDMI PLUS (Quad HDMI-1080P60).zip AC-4SDI PLUS (Quad SDI-1080P60).zip AC-VS2583 (2 HDMI-4K60).zip AC-VS2584 (1HDMI+1SDI-1080P60).zip AC-VS007 (Dual HDMI-1080P60).zip AC-VS014 (2HDMI+2SDI-1080P60).zip AC-VS049...

www.acasis.com

Interestingly enough, their Linux driver comes as source code, and instructions for how to build it on your machine. The instructions "just work", so that's not a problem; I just found it interesting. I guess that's one way to guarantee compatibility on the zoo of Linux systems!

I got the 4-SDI-Input version, and that's all it does. No config: it "just works". I suspect that the others have a similar mentality.
(3 of my inputs were already SDI, and converted to a 3-inch HDMI jumper to feed the USB adapters; the remaining one was easy enough to convert from HDMI to a 3-foot SDI jumper)

The BlackMagic one tried to be a more flexible version of its predecessor, and ended up being a configuration mess that (I suspect) doesn't even have the option for 4 inputs. I told the support rep about that, along with a short lesson in Combinatorics (what's even possible, given what settings there are and how they work), and he said he'd pass it on. Also said something about making a new card from scratch...