I’m using the LiveKit Unity SDK. It works fine in the Unity Editor, but on an iOS device, I’m unable to hear the agent’s voice. I can see the agent’s logs in the transcript, and when I speak, my responses are also logged correctly. However, the agent’s audio is not playing on the iOS device. Has anyone faced a similar issue or can help me with this?

Thanks for reaching out, Prashant. I'm an AI assistant and I'm here to help. Give me a moment while I research this topic.

1. Which LiveKit Unity SDK version and Unity version are you using? - Unity Version: 6000.0.50f1 (Unity 6) - LiveKit Unity SDK: 1.2.4 - Installed via: Unity Package Manager (Git URL) 2. Which iOS device and iOS version are you testing on? - Device: iPhone 15 Pro Max - iOS Version: 18.2 (based on your mention of "os 26.2" which likely means iOS 18.2) - Processor: A17 Pro - Build: Physical device (not simulator) 3. How are you rendering remote audio on the client? - Using Unity AudioSources attached to tracks (the standard Unity approach) - Code: new AudioStream(audioTrack, audioSource) in LiveKitManager.cs:436 - AudioSource configuration: - Has dummy AudioClip attached (created programmatically) - spatialBlend = 0 (2D audio) - volume = 1.0f - loop = true on the dummy clip - NOT using native WebRTC audio path directly - The AudioStream uses AudioProbe component which implements OnAudioFilterRead callback 4. Do you see any audio-related warnings or errors in Xcode device logs? - No audio-related errors in Xcode console - Native FFI initialization succeeds - No warnings about audio session failures - No codec or format errors - The only indicator is Unity logs showing maxSample: 0.000000 (RingBuffer empty) - Stack traces show UnitySynchronizationContext:Exec() working for other callbacks 5. Is the app requesting/allowed microphone and audio session permissions on iOS? - YES - Microphone permission granted (logs show: [LiveKitManager] Microphone permission granted) - Info.plist includes NSMicrophoneUsageDescription - AVAudioSession was initially configured via custom native plugin (LiveKitAudioSession.mm) but was REMOVED based on investigation (LiveKit SDK should handle it internally) - Previous configuration was: - Category: AVAudioSessionCategoryPlayAndRecord - Mode: AVAudioSessionModeVoiceChat - Sample rate: 48kHz (later changed to 24kHz) - Microphone publishing works (local audio goes to agent, transcripts received) 6. Does other audio in the app play correctly on the same device? - Unity Editor: YES - Agent audio plays perfectly - iOS Device - Other Unity audio: Not tested with other audio sources - iOS Device - LiveKit agent audio: NO - Silent (the issue) - The dummy AudioClip loops correctly (time value cycles 0-1 second), proving AudioSource is active - OnAudioFilterRead is called 1000+ times, proving Unity audio pipeline is active - The issue is specifically that the AudioStream's RingBuffer never receives data 7. Does the issue occur on both simulator and physical device, or only physical devices? - Physical Device (iPhone 15 Pro Max): Issue occurs - NO audio - Unity Editor (macOS): Works perfectly - audio plays correctly - iOS Simulator: Not tested - The problem is iOS device-specific (Editor vs Device, not Unity vs Native) Additional Technical Details What Works on iOS: - ✅ Room connection - ✅ Track subscription (AudioTrack from agent) - ✅ Microphone capture and publishing - ✅ Text transcripts (DataReceived callbacks) - ✅ AudioSource.Play() (dummy clip loops) - ✅ OnAudioFilterRead called continuously - ✅ SynchronizationContext exists and patched - ✅ All non-audio FFI callbacks work What Fails on iOS: - ❌ AudioStreamEvent callbacks never fire - ❌ OnAudioStreamEvent() in AudioStream.cs never called - ❌ RingBuffer stays empty (no audio data) - ❌ No sound heard from agent

Thanks — I’m responding to your detailed report that Editor audio works but on iOS the AudioStream’s native→managed callbacks never fire and the ring buffer stays empty. Great info; that narrows this to the native‑to‑managed audio delivery on iOS. Please try these focused checks (short, ordered steps) and tell me the results: 1. Confirm inbound audio bytes with stats ◦ Call

GetStats()

for the room and check inbound audio

bytesReceived

/

packetsReceived

. ◦ If bytes increase, the remote audio is arriving over RTP and the problem is rendering (native→managed path). If bytes do not increase, signaling/RTP is the issue. 1. Add explicit AudioStream event logging (verify callback registration) ◦ Immediately after creating

AudioStream(audioTrack, audioSource)

, attach a handler that logs every event and a timestamp. ◦ If the handler never logs on the device but logs in Editor, native callbacks are not being invoked. 1. Try the SDK’s minimal example on the same device ◦ Build and run the official LiveKit Unity demo/example with your same iOS/Xcode settings. ◦ If the example works, the problem is in your app or build settings. If it fails, it’s SDK + environment related. 1. Bypass custom audio probe/path (isolate Unity rendering) ◦ Temporarily stop using `AudioProbe`/OnAudioFilterRead and

AudioStream

. Try the SDK’s simplest attach/render path (or attach track to an AudioSource if supported). ◦ If that plays audio, the issue is in the custom audio processing or ring buffer usage. 1. Check IL2CPP/stripping and plugin linking settings ◦ Player Settings (iOS): set Managed Stripping Level = Disabled/Low, Disable Engine Code Stripping, ensure Architecture = ARM64, Target SDK = Device. ◦ Build with Development and Script Debugging enabled. ◦ Re-run — a high stripping level can remove pinvoke glue or cause delegate GC issues. 1. Confirm native callback pinning / GC safety ◦ Ensure the managed delegate passed to native is stored/pinned so the GC cannot collect it. (Log when you register/unregister.) ◦ On iOS/IL2CPP, delegate lifetimes and AOT differences can break callbacks. 1. Validate AVAudioSession activity at runtime ◦ In Xcode console, log any AVAudioSession activation calls. Confirm category/mode set to PlayAndRecord/VoiceChat and session is Active when subscribing to audio. ◦ If SDK should manage it, confirm it actually calls setActive on the device. 1. Try Unity LTS (quick compatibility test) ◦ Create a tiny project in Unity 2022 LTS with LiveKit SDK 1.2.4 and test the same device/build. ◦ If audio works there, Unity 6 likely introduces an incompatibility with the native plugin or IL2CPP behavior. 1. Inspect Xcode logs for native callback traces and thread context ◦ Filter logs for

webrtc

,

audio

, or your plugin symbol names to see whether the native path is producing frames or failing to call the managed entrypoint. ◦ Note whether callbacks appear on non-main threads (threading/marshaling issues). What I can help next if you report results: • If stats show inbound bytes increasing but no AudioStream events: I’ll provide exact debug logging snippets and a minimal repro checklist to isolate native callback registration and delegate pinning. • If stats show no inbound bytes: I’ll guide further network/RTP/signaling traces. • If the example works but your app fails: I’ll suggest targeted build setting diffs to check. Which step can you run first and share results for?