Audio lagging

jrhooker

Hi all,

I'm having some issues with audio lagging.

I'm exporting video out from Premiere Pro and it looks great in quicktime, but when I bring it into Isadora the audio and video are no longer synced.

I'm running a brand new Mac Studio with NOTHING on it, so I can't imagine its a processing problem. But I'm sort of at a loss.

Isadora 4.1.3 (ARM) with a Apple M3 Ultra running Tahoe 26 and 96 GB memory.

Anybody have any suggestions about what's going wrong here.

Thanks,

Jake

Skulpture

@jrhooker what video file type and codec?

Woland

@jrhooker

Try exporting it as each of the following:

hap.mov
h264.mp4
apr.mov

jrhooker

Thanks @Skulpture and @Woland

After exporting several different file and codec combos, I realized that it was actually (maybe) a lag in my hdmi extender, which is old and not HDBaseT. I don't do a lot of this kind of content, so the lag was just much more evident...close ups of actors faces so the audio and video were just out of sync because of the lag.

Or at least that's my current theory. I ordered some new HDBaseT extenders and I'm hoping that will solve the problem. But I am using QT/Hap Alpha for the record.

Thanks, as always!

Jake

DusX

@jrhooker said:

that's my current theory

Can you run a test without the adapters, just a direct connection to a Display?

Skulpture

@jrhooker said:

Thanks @Skulpture and @Woland

After exporting several different file and codec combos, I realized that it was actually (maybe) a lag in my hdmi extender, which is old and not HDBaseT. I don't do a lot of this kind of content, so the lag was just much more evident...close ups of actors faces so the audio and video were just out of sync because of the lag.

Or at least that's my current theory. I ordered some new HDBaseT extenders and I'm hoping that will solve the problem. But I am using QT/Hap Alpha for the record.

Thanks, as always!

Jake

Hmmm I am not so sure. HDBaseT is marketed as zero latency. Unless the hardware is faulty or there are other factors we aren't aware of. Let us know how you get on.

jrhooker

@skulpture @woland Hello!

May back in March I asked for help, and you offered it and then I dropped it.

I won't get in the weeds why I left it and now I'm back with the same issue, but this is just a massively big project that I'm a bit over my head on (which is nothing unusual, hence my maybe varied panicked posts).

First -- just a blanket thanks for how much you two, in particular, have helped me over the years...and also the rest of the community. I never seem to get good enough at any of this to pay it forward and help anybody else out, alas.

In any case, it does sort of seem like I'm having an export issue that is causing a lag in Izzy. My files look great in both Premier and Quicktime after export. I'm exporting ProRes 4444 16 bit with alpha channel, because I need alpha. I know they're big files, but codecs are confounding to me...I never really know what I'm doing to be honest.

Could ProRes be the wrong file type and causeing the lag, which seems to be about 6 frames. Big enough to easily see where mouths and speaking aren't synced.

Thanks in advance for your generosity and help.

Jake

BvG73

@jrhooker

Hi Jake,

A steady offset of x frames points away from the codec. A codec that's too heavy usually causes stutter, dropped frames or sync that drifts further apart over time. A constant delay usually comes from somewhere in the playback chain. At 25–30 fps, 6 frames is roughly 200–240 ms. That's typical for a projector or TV doing image processing (keystone, warping, scaling, motion smoothing), an extender with a scaler, or an audio path with DSP or network delay.

Some things to check:

Which one is late, the audio or the video? Your thread title says audio lags, but the extender theory assumes the video is late.if that’s the case, using a device like a Lindy lipsync corrector is a fix. Simple little box, used it in similar situations.
Play the same file in QuickTime through the same projector and the same speakers. If it's out of sync there too, the file and Isadora are fine and the problem is the chain. Playing the file on your desktop monitor with the Mac speakers doesn't test that.
Is the offset constant, or does it grow during the clip? If it grows, check for a frame rate or sample rate mismatch (e.g. a 23.976 sequence, or 44.1 vs 48 kHz audio).
How does your audio get to the speakers? HDMI to the projector, a digital mixer with DSP, Dante, Bluetooth? Each adds its own delay.
Put the projector in game or low-latency mode if available and turn off keystone and image enhancement. And do @DusX's test: connect directly to a display without the extender ir converters

Codec primer

Container vs codec: .mov or .mp4 is the box. The codec (ProRes, HAP, H.264) is how the pictures inside are compressed.
HAP / HAP Alpha / HAP Q: decoded on the GPU. Big files, but very light on the CPU and great for scrubbing, looping and layering.
ProRes 422 / 422 HQ: high quality and edit-friendly, but no alpha.
ProRes 4444: the ProRes version that carries alpha. You don't need 16-bit for the alpha: ProRes 4444 stores alpha losslessly up to 16 bits regardless,"8-bpc + Alpha" in Premiere gives you transparency just fine and is plenty for playback.
H.264 / H.265 (.mp4): small files, but heavier to decode and less smooth for scrubbing or looping. No alpha, except HEVC with alpha on Mac.

Rule of thumb: stutter or drift means the codec or decode is struggling. A steady offset means latency somewhere in the display or audio chain.

Hope this helps narrowing it down,

Best!