Loss of audio after call to Quartz Create New Clock in Test and Shipping builds

We recently started to make use of the new Quartz subsystem in our game, to support an interactive music system. This is working very well in development builds (editor or packaged), but we are now experiencing a complete loss of audio in our packaged Test and Shipping builds, which appears to relate to Quartz. Additionally, we are unable to exit the game without waiting indefinitely for an audio thread to terminate.

Having played around with the blueprint that our sound designer put together from Dan’s tutorial videos it seems that the audio drop-out occurs when the Create New Clock node runs. Disabling further use of the system makes no difference and it appears this node alone is causing problems. Given the loss of all sound and the hang on exit, I wonder if an audio thread has become deadlocked.

We’re running 4.26 and I’ve looked at a couple of relevant CLs on GitHub. The first, a fix for an audio render thread hang in Quartz, appears to have made it into 4.26. The other, a fix for modification of QuartzTickSubscribers, is in 4.26.1, so I’ve integrated this directly, but it did not have any bearing on this issue.

Has anyone else encountered this issue please? I would be grateful for any suggestions. In the meantime we will have to revert back to our old music system and defer our use of Quartz until we can resolve this.

Many thanks.

Hi Colin,

The issue is 100% fixed in 4.26.1 and we’ve recently shipped Quartz in Fortnite. The fix you need is in CL 14935749.


Awesome, thanks @Minus_Kelvin! That changelist resolved both the drop-out and the hang on exit. I’ve integrated that, along with CL 14952600, as we aren’t in a position to move on to 4.26.1 currently.

Glad to hear it! And apologies. Thanks for reaching out.

The feature came in hot for 4.26.0 and we apparently hadn’t tested dev/release builds. We also just hired an embedded audio engine QA analyst right after 4.26 shipped. Our last one quit before 4.25 released so we’ve been a bit short on audio-domain-specific QA resources.

This is definitely beta, but the good news is that we have shipped Quartz live on Fortnite w/ these changes and it is very stable.

Some upcoming minor feature additions (pure adds) are coming in 4.27 and we’ll probably take it out of beta by then as it’s been quite successful in FN and many licensee projects already.