Restore cached iOS audio session on PlatformAudio dispose#350
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Restore cached iOS audio session on PlatformAudio dispose#350MaxHeimbrock wants to merge 1 commit into
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PlatformAudio switches the shared AVAudioSession to PlayAndRecord + VoiceChat on iOS but never restored it on dispose: the restore hook was dead code, and it only set Ambient without reactivating. After a call ended, the session stayed on the VoIP profile and deactivated, degrading normal Unity audio playback (quiet, receiver-biased routing). Snapshot the session's category/mode/options the first time LiveKit configures it (the state Unity set from its iOS Player Settings), and re-apply that snapshot + reactivate when the last PlatformAudio is disposed. Instance lifetime is tracked with an Interlocked counter so restore fires only on the final dispose, matching the native ADM ref-count teardown. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Jul 13, 2026
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one question, lgtm
| /// LiveKit reconfigures the session for VoIP. Subsequent calls are no-ops so the | ||
| /// snapshot always reflects the pristine, pre-LiveKit (Unity-configured) state. | ||
| static void LiveKit_CacheSessionStateIfNeeded() { | ||
| if (s_hasCachedState) { |
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curiously, should we continue caching the latest session rather than simply return here ?
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Sorry this is supposed to be a draft, not ready for review. We have some issues with teardown but this one does not solve it all, I am still investigating.
| // Restore the audio session Unity had before VoIP, but only once the | ||
| // last PlatformAudio is gone (the native ADM is likewise ref-counted). | ||
| if (System.Threading.Interlocked.Decrement(ref _instanceCount) == 0) | ||
| IOSAudioSessionHelper.LiveKit_RestoreDefaultAudioSession(); |
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nit, add a {} for style
| #if UNITY_IOS && !UNITY_EDITOR | ||
| // Tracks live PlatformAudio instances so the iOS audio session is restored | ||
| // only when the last one is disposed (aligned with the native ADM ref-count). | ||
| private static int _instanceCount; |
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nit, initialize it to 0 as default value ?
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Problem
On iOS, constructing
PlatformAudiocallsLiveKit_ConfigureAudioSessionForVoIP(), switching the sharedAVAudioSessiontoPlayAndRecord+VoiceChat. On dispose, nothing restored it:PlatformAudio.Dispose()never called the restore hook —LiveKit_RestoreDefaultAudioSession()was dead code (declared + implemented, zero callers).AVAudioSessionCategoryAmbientand never reactivated.Net effect: after a call ended, the app's session stayed on the VoIP profile and deactivated, so normal Unity audio playback was degraded (quiet, receiver-biased routing).
AudioSettings.Resetdoes not fix this — it only reinitializes Unity's internal (FMOD) engine, not the OS-level session.Change
LiveKitAudioSession.mm: snapshotcategory/mode/categoryOptionsonce, lazily, at the top ofLiveKit_ConfigureAudioSessionForVoIP()— i.e. right before LiveKit first mutates the session, so it captures whatever Unity configured from its iOS Player Settings. RewriteLiveKit_RestoreDefaultAudioSession()to re-apply that snapshot andsetActive:YES(falls back toAmbientonly if nothing was cached).PlatformAudio.cs: track live instances with anInterlockedcounter (iOS-guarded); increment after successful construction, decrement inDispose(), and fire restore only when the count hits 0 — matching the native ADM ref-count teardown.Explicit-
Dispose()only (no finalizer): avoids touchingAVAudioSessionoff the main thread. Kept minimal — the existing automatic-mode /VoiceChatconfig is unchanged.Testing
UNITY_IOSdefined /UNITY_EDITORoff (0 errors) — the guarded code is actually type-checked..mmpassesclang -fsyntax-onlyagainst the iOS SDK under both ARC and MRC (no errors).PlatformAudio, dispose it, then play a UnityAudioSourceand confirm routing/volume return to the pre-call behavior. The newNSLogs report the cached + restored category/mode.Follow-ups (out of scope)
useManualAudio,VideoChat, VPIO gating to keep Unity audio alive during calls) exists as a build artifact underSamples~/Meet/Builds/— not adopted here..mm.metaalso targets visionOS/tvOS, but the C# P/Invoke isUNITY_IOS-only (pre-existing).🤖 Generated with Claude Code