Audio interface dropout


Dropout (stuttering) occurs when playing video (hap codec) with vdmx.

I am using Loopback / Behringer xr18 / imac pro big sur / b8.8.0.5.

Send from vdmx to loopback, go through xr18 and then back to loopback and output to capture board and speakers.

If you set Chrome and video player under the same conditions as above, there is no problem (refer to the image)



Hi @genie2600,

A few Q’s.

  • Do the HAP videos stutter during playback in VDMX? If you show FPS in your preview window, are the videos playing at the FPS they were rendered at?

  • Is it only HAP videos? Do other codecs stutter audio as well?

  • What audio / video settings are you using for the HAP codec? (Resolution, frame rate, HAP Q ALPHA, HAP Q, HAP , Audio Bit rate, audio frequency Hz).

  • Are you HAP videos playing from an SSD? Internal or External?




I am following all the rules of your company.
All videos use only hap and sometimes hapQ.
The current problem seems to have something to do with Apple’s t2 chip some time ago.

A few experiments
If you use the Belkin Thunderbolt 3 dock to connect to the audio interface, no problems arise.
No problem with headphone output export
Mac speaker direct no problem
No problem playing in safari or chrome without using dock

vdmx There is a problem even if you play the video at the default value without any settings.

I am currently using Thunderbolt Dock, but I hope this problem can be resolved if possible.



Actually I just noticed this on b0. I have loopback routing Firefox audio and I get a random freeze on the Audio Analysis plugin (see gif recording). Machine: Hackintosh (OSX86), stable used for years.




I’ve tested this on a second machine with the same Loopback set up and the audio is not freezing. Will do some testing on the first machine to see if I can work out what’s happening. Machine: MacBook Pro (15-inch, 2017)




I don’t know if it’s the same problem as me
The most frequently occurring point in my mac is
Many problems occur when sending vdmx to audio interface channel 1/2 in loopback, and then exporting the master channel containing theater audio and vdmx audio from the audio interface to a loop pack and exporting to a capture board or a PC for broadcasting.

same process as above

  1. There is no problem when using the headset port
  2. No problem with Belkin Thunderbolt Dock
  3. There is no problem if you use another browser or player

what i checked

  1. Audio Interface - Same symptoms even after replacing with the same machine (works fine on Windows)
  2. Initialize both macos and vdmx and test at the default values, the same symptoms

This issue was not yesterday or today.
It seems to have been around since Catalina.



Ah ok, I will see if I can test a similar set up to yours later today. Can I check, are you on a real Mac or a Hackintosh (OSX86)?



What i Tested

iMac Pro Catalina
iMac Pro Big Sur
MacBook 2019 Monterey

Audio interface
Behringer xr18
Traktor A10

Loopback 2.2.9



If you use Soundflower on your pre OSX Monterey macs, do you get the same problem?



Soundflower was only used before Mojave, and audio wasn’t the main thing at that time.
If I tested it with a similar blackhole recently, the symptoms were the same.



This is a tested video.
I haven’t used loopback, but I get the same symptoms.
It occurred at 00:24 and 00:39 seconds.
There is no problem with the original video, and the occurrence period is random.

As a result of estimating the frequency of occurrence
in my expectation
When moving the mouse during video playback or clicking something for setting
It seems to happen most of the time when a certain window is opened.



This is a video played with Safari and VDMX under the same conditions.



@genie2600 are there any other audio routing applications you can test? I’m trying to figure out if it is an issue with loopback.

What happens when you play the video with quicktime player?

Is Safari sending at 44.1, at 48Hz? What are the VDMX settings? Is play thru enabled?

Please share screen recording videos on youtube or vimeo if possible. I was unable to download your videos, they estimated 5 minute download and in the last half stalled to 10 hours.



The first video is a video without loopback
The second video is a video comparing safari and vdmx
Even if I change both 44.1 and 48hz, it is the same symptom.



It’s like the last test I can do
The video is long, but take a look



Just a few thoughts here. The audio volume going from VDMX into loopback is very high. From the video it looks like it is almost always peaking above 0dB, which is not ideal. If you lower the volume so that the levels from VDMX through loopback are similar to that of safari (which looks to be half as loud as you have them set for VDMX), does this fix any audio peaking drop outs?

If you play something louder then the system can handle, it peaks, and typically causes distortion, or maybe in this case, it is not sending the full song information through loopback.

Please see if adjusting the audio levels, either in VDMX, or in loopback affect the audio dropout issue.

Thanks for uploading the videos.

1 Like


thank you
But adjusting the volume doesn’t help
Even if I reduce it to 50%, the symptoms are the same

The part I was most suspicious of was the link below

I don’t think Apple has solved this 100% yet.

So I ordered the product below and received it today.

I connected a Behringer to a USB 2.0 port and tested it from 10 am to 6 pm Korean time.

The result is very satisfactory
No problems have appeared so far

I think I’ll have to use it like this for a while

thanks for helping with my problem

1 Like



Wow that’s a bummer, but I’m happy you figured it out. I’m sure this will help someone else down the road. Between this and the yellow dot that never goes away, Apple needs to get their act together.



That one reason for using loopback in your recording and live set up, being able to adjust the various input volumes is really useful for the final Audio Analysis level.



In addition, when performing a clean installation of vdmx, it seems that there are some things that are not installed properly depending on the downloaded file. Check it!

And please improve vdmx execution speed~ (too slow)

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