[OC] Sound Cutouts

After updating my machine (10.15.6) to OC 0.6.0 I experience audio trouble. There are distinctive gaps (audio file below) when playing audio no matter which device I use:

  • External Speaker though
    • Audio Out of Motherboard
    • Case Front of Motherboard
    • Audio Out of Monitor (from Graphics Cards via Display Port) - default way
  • Monitor (from Graphics Cards via Display Port)
  • Headphones through Bluetooth
  • Occurs when sound is captured by the system itself (audio example below)

I am fairly sure that this was not the case back on OC 0.5.7 for where I updated, although I don't listen to audio on my Hack that often. As per my testing with different devices, this doesn't seem to be a hardware, but a software issue. The problem does not occur immediately after boot. It can take more than a day before it kicks in and does not necessarily relate to sleep, although it seems to appear shortly after waking the system from sleep (EDIT: On the other hand, sleep/wake can even fix the already occuring issue for a few minutes.) I am not able to reproduce the problem "on demand" yet, though. The problem is only temporarily fixed by restarting the machine.

Apart from the normal changes during the OC update (sanity checker reported everything ok), I also made some cosmetic changes to my EFI/config:

Audio-relevant components:

Part Model
with Realtek® ALC1220 Codec
CPU AMD Ryzen 5 3600X 3.8GHz 6C
Video Card PowerColor Radeon RX 5700 XT 8GB Red Devil
Memory G.Skill Ripjaws V 2 x 8 GB DDR4-3200C14
Monitor (with Audio Out), over DP AOC 24G2U/BK 24" 1920x1080 144Hz

Audio-relevant active Kexts of my EFI:

Kext Version
AppleALC 1.5.1
Lilu 1.4.6
VirtualSMC 1.1.5
WhateverGreen 1.4.1 1.4.1

The machine is set to be a iMacPro1,1.

Audio settings in macOS's Audio-MIDI-Setup are mainly 2 ch 24-bit Integer 48.0 OR 96.0 kHz for the different devices.

I went though the OC guide's Audio trouble section:

kextstat | grep -E "AppleHDA|AppleALC|Lilu" returns the following to be present:

  • as.vit9696.Lilu (1.4.6)
  • as.vit9696.AppleALC (1.5.1)
  • com.apple.driver.AppleHDAController (283.15)
  • com.apple.driver.AppleHDA (283.15)

HDEF looks fine in IOregistryExplorer, alc-layout-id is 07000000, which is NOT the same as the boot-arg boot-arg alcid=1... Is this correct?

AppleHDA should be stock.

Could this be related to HPET? Or can I change something in the BIOS? I also experience daily freezes that are only solved by rebooting, which have not occurred on OC 0.5.7. Could this and the audio issue be related to bad power management?

Audio Example:

I captured the system's audio through soundflower with QuickTime while triggering the Speaker Configuration sound, a static noise, of Audio-MIDI-Setup and have uploaded it, if you would like to listen to the problem (turn down volume to at least half!):

http://www.mediafire.com/file/y0u3tliob0c6aen/Audio_Gap.mp3/file. I switched between left and right twice, so there are some gaps from switching, but when playing on one side, the static noise should be constant!

(For your convenience, I have uploaded the file to VirusTotal, so it knows the file when you upload it there, as you probably want to.)

Any ideas on what this problem could be related to and where I could start with troubleshooting. Many thanks!

submitted by /u/CrayCJ
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