Crash in SignalProcessing : Assertion failed: GetKeyNumChannels() <= GetNumChannels()

Development Audio
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Hi !
UE5.5.3 and we use meta sounds
we got a team member ( and only one ) that has a crash with our project ( both editor and dev build )

crash is : Assertion failed: GetKeyNumChannels() <= GetNumChannels() [File:D:\build\++UE5\Sync\Engine\Source\Runtime\SignalProcessing\Private\DynamicsProcessor.cpp] [Line: 379]

and in the log we have the folowing :

[2025.02.13-09.05.40:011][548]LogAudioMixer: Warning: FMixerPlatformXAudio2: Changing default audio render device to new device: Role=Console, DeviceName=Casque pour téléphone (2- Arctis 7 Chat), InstanceID=1
[2025.02.13-09.05.40:262][548]LogAudioMixer: Display: StartRunningNullDevice() called, InstanceID=1
[2025.02.13-09.05.40:262][548]LogAudioMixer: Display: FMixerNullCallback: Simulating a h/w device callback at [21ms], ThreadID=30884
[2025.02.13-09.05.40:591][549]LogAudioMixer: Display: StopRunningNullDevice() called, InstanceID=1
[2025.02.13-09.05.40:593][549]LogAudioMixer: Display: Successful Swap new Device is (NumChannels=2, SampleRate=48000, DeviceID={0.0.0.00000000}.{8c098246-d91d-4a4d-9255-888f5ee10573}, Name=Casque pour téléphone (2- Arctis 7 Chat)), Reason=FMixerPlatformXAudio2::OnDefaultRenderDeviceChanged, InstanceID=1, DurationMS=14.66
[2025.02.13-09.05.40:594][549]LogAudioMixer: Display: Output buffers initialized: Frames=1024, Channels=2, Samples=2048, InstanceID=1
[2025.02.13-09.05.40:595][549]LogAudioMixer: Display: Starting AudioMixerPlatformInterface::RunInternal(), InstanceID=1
[2025.02.13-09.05.40:604][550]LogWindows: Error: appError called: Assertion failed: GetKeyNumChannels() <= GetNumChannels() [File:D:\build\++UE5\Sync\Engine\Source\Runtime\SignalProcessing\Private\DynamicsProcessor.cpp] [Line: 379]

somehow it looks like it’s linked to his headset and some "Device Swap " but he did not interact with his headset, it when opening a level, sometime it 100% sometime disconecting the headeset and connecting it back works

after a search it looks like it’s not in the know issues

what can we do to avoid this crash ?
have a good day !

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2

Me and a few others in a project I’m working on get this crash to. Seems related to audio with the city sample but it’s not something I can just delete. It happens when trying to open the project but doesn’t even happen every time.

3

there is a fix in 5.6, https://github.com/EpicGames/UnrealEngine/commit/0aae2fc6714b5ccd39f4683d0b177d932463f686
i’ve ask for it to be backported to 5.5 but no answer so far.

it happend when the number of channel change at a specific timing. ( often it’s switching between 2 and 0 )
from our experience this crash can be triggered by the following:
remote desktop connection
headset with special driver ( no idea why but unpluging those and using good old jack3.5 before starting the game does work )

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