The issue is that the analog audio Line In to vMix will, with no warning, start stuttering, or cutting in and out on about 1/2 second intervals, through the HDMI external output. Video is fine.

If I were to play a video from vMix while the Line In audio is stuttering, the recorded audio is fine.
The NDI connection carrying the same feed between the same machines does not stutter.

Closing and reopening the audio Line In will fix as will restarting vMix completely.
Closing/reopening the external or reseating the HDMI cable does not fix.
The stuttering audio is received by all software on the recording PC so it's not one in particular.

Anyone have ideas where to troubleshoot? It's hard to duplicate as it starts randomly.
All drivers are up to date.

I know using the 3.5mm Line In on the motherboard is not ideal but I have several vMixs in the field using this method and never had this stutter issue.

I've attached a simple diagram of the setup. Thanks for any direction one might have.

EDIT: I only turned on the NDI to test if it also stutters when the HDMI does. The actual setup is HDMI only.

Hey, thanks for the input.

It's a dedicated Line Level In but it is a 3.5mm yes.

I think the fact that the audio in the NDI output is fine points to something going with the embedding of the analog into the HDMI external output signal.

Audio input must be fine in the circuitry as its OK in NDI and also the meters on the Line In do not show the stuttering, they are OK, but meters on the recording PC are flshing on and off with the signal.

Had a similar problem several years ago, ended up being a motherboard in the process of failing.. Hope that's not the case for you.

- Tom

Hey Tom,

eeegaad, I hope so too. System is only a couple months old and only used in the field 3 times.





Thanks raugert,

I should have mentioned in the OP but I am only using the NDI now as a test to see if it stutters when the HDMI does. Originally when the problem began it was just the single HDMI connecting the machines. Once when it was stuttering (hdmi only, no NDI turned on) I opened up Flash Media Live Encoder and it was receiving the bad audio also.

I have no real knowledge to base it on but my gut is telling me something is losing timing or "glitching" out in the embedding of the analog audio into the BM Intensity card for output. Closing and reopening the Line In input resyncs it. Or something. :/

If I could reproduce it easily I would probably start playing the BM driver shuffle. But so far it's been running all day with no issues.

The plot thickens.

The HDMI output of the BM Intensity Pro 4k is being sent MA audio.
The Line In audio is routed to Bus A output only.
Bus A output is routed directly to the BM card.

Stuttering happened again overnight HOWEVER if I change Line In to send out M instead of Bus A, the BM card sends it cleanly.
M = Clean Audio
A = Stutter
M+A = Both clean and stutter.

My earlier finding that videos played internally where fine and that it was ONLY the line in stuttering is wrong. The reason they played fine is that they were defaulting to M out to the BM card. Which is clean. Once the stutter starts on Line In, if I play anything thru A it stutters out the BM card, but playing it out M is fine.

Woohoo! Thanks Martin!

Since Line In comes from FOH and the Master Out out goes back to FOH we were using that setup as a mix minus, but I'm sure there is another way to skin that cat.