Explore the integration of media technologies within your app. Discuss working with audio, video, camera, and other media functionalities.

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Can't set AVAudio sampleRate and installTap needs bufferSize 4800 at minimum
Two issues: No matter what I set in try audioSession.setPreferredSampleRate(x) the sample rate on both iOS and macOS is always 48000 when the output goes through the speaker, and 24000 when my Airpods connect to an iPhone/iPad. Now, I'm checking the current output loudness to animate a 3D character, using mixerNode.installTap(onBus: 0, bufferSize: y, format: nil) { [weak self] buffer, time in Task { @MainActor in // calculate rms and animate character accordingly but any buffer size under 4800 is just ignored and the buffers I get are 4800 sized. This is ok, when the sampleRate is currently 48000, as 10 samples per second lead to decent visual results. But when AirPods connect, the samplerate is 24000, which means only 5 samples per second, so the character animation looks lame. My AVAudioEngine setup is the following: audioEngine.connect(playerNode, to: pitchShiftEffect, format: format) audioEngine.connect(pitchShiftEffect, to: mixerNode, format: format) audioEngine.connect(mixerNode, to: audioEngine.outputNode, format: nil) Now, I'd be fine if the outputNode runs at whatever if it needs, as long as my tap would get at least 10 samples per second. PS: Specifying my favorite format in the let format = AVAudioFormat(standardFormatWithSampleRate: 48_000, channels: 2)! mixerNode.installTap(onBus: 0, bufferSize: y, format: format) doesn't change anything either
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453
Aug ’25
Apple Music API High Error Rate
I am getting high error rates from the Apple Music API. This has been happening for months now, and it is quite frustrating. It is a mix of 404, 504, and random 500 errors. I hit these endpoints all of the time, so it is not like I am hitting a resource that doesn't exist. Why is this happening? Is this a known issue that is getting worked on?
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95
Jun ’25
How to detect when iOS Camera app starts video recording (with Allow Audio Playback ON)?
Since iOS 18, the system setting “Allow Audio Playback” (enabled by default) allows third-party app audio to continue playing while the user is recording video with the Camera app. This has created a problem for the app I’m developing. ➡️ The problem: My app plays continuous audio in both foreground and background states. If the user starts recording video using the iOS Camera app, the app’s audio — still playing in the background — gets captured in the video — obviously an unintended behavior. Yes, the user could stop the app manually before starting the video recording, but that can’t be guaranteed. As a developer, I need a way to stop the app’s audio before the video recording begins. So far, I haven’t found a reliable way to detect when video recording starts if ‘Allow Audio Playback’ is ON. ➡️ What I’ve tried: — AVAudioSession.interruptionNotification → doesn’t fire — devicesChangedEventStream → not triggered I don’t want to request mic permission (app doesn’t use mic). also, disabling the app from playing audio in the background isn’t an option as it is a crucial part of the user experience ➡️ What I need: A reliable, supported way to detect when the Camera app begins video recording, without requiring mic access — so I can stop audio and avoid unintentional overlap with the user’s recordings. Any official guidance, workarounds, or AVFoundation techniques would be greatly appreciated. Thanks.
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288
Aug ’25
Why a driverkit extension needs a CMIO extension
I developed a driverkit extension based on overriding-the-default-usb-video-class-extension, but the link didn’t give the details of realization. I asked DTS who gave two tips: 1, Do you also have a CMIO extension to load in place of the default overriding-the-default-usb-video-class-extension 2, Your DriverKit extension’s info.plist is also missing the CameraAssistantBundleID. I want to know why a driverkit extension needs a CMIO extension, what’s the data and control flow?
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372
Jun ’25
Telephoto Lens Keeps Switching to Other Lenses on iPhone 16 Pro Max During PPG (Finger on Camera)
Hi, I’m building a PPG-based heart rate feature where the user places their finger over the rear telephoto camera. On iPhone 16 Pro Max, I'm explicitly selecting the telephoto lens like this: videoDevice = AVCaptureDevice.default(.builtInTelephotoCamera, for: .video, position: .back) And trying to lock it: if #available(iOS 15.0, *), device.activePrimaryConstituentDeviceSwitchingBehavior != .unsupported { try? device.lockForConfiguration() device.setPrimaryConstituentDeviceSwitchingBehavior(.locked, restrictedSwitchingBehaviorConditions: []) device.unlockForConfiguration() } I also lock everything else to prevent dynamic changes: try device.lockForConfiguration() device.focusMode = .locked device.exposureMode = .locked device.whiteBalanceMode = .locked device.videoZoomFactor = 1.0 device.automaticallyEnablesLowLightBoostWhenAvailable = false device.automaticallyAdjustsVideoHDREnabled = false device.unlockForConfiguration() Despite this, the camera still switches to another lens, especially under different lighting, even though the user’s finger fully covers the lens. Questions: How can I completely prevent lens switching in this scenario? Would using videoZoomFactor = 3.0 or 5.0 better enforce use of the telephoto lens? Thanks! Gal
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Jul ’25
Can I Fade Out Track Volume Before End Using ApplicationMusicPlayer?
I’m building a music app using Apple Music streaming via ApplicationMusicPlayer. My goal is to decrease the volume of the current song during the last 10 seconds, and when the next track begins, restore the volume to its normal level. I know that ApplicationMusicPlayer doesn’t expose a volume API, and I want to avoid triggering the system volume HUD. ✅ Using Apple Music streaming (not local files) ❓ Is it possible to implement per-track fade-out/fade-in logic with ApplicationMusicPlayer? Appreciate any clarification or official guidance!
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117
Jun ’25
iOS Audio Routing - Bluetooth Output + Built-in Microphone Input
Hello! I'm experiencing an issue with iOS's audio routing system when trying to use Bluetooth headphones for audio output while also recording environmental audio from the built-in microphone. Desired behavior: Play audio through Bluetooth headset (AirPods) Record unprocessed environmental audio from the iPhone's built-in microphone Actual behavior: When explicitly selecting the built-in microphone, iOS reports it's using it (in currentRoute.inputs) However, the actual audio data received is clearly still coming from the AirPods microphone The audio is heavily processed with voice isolation/noise cancellation, removing environmental sounds Environment Details Device: iPhone 12 Pro Max iOS Version: 18.4.1 Hardware: AirPods Audio Framework: AVAudioEngine (also tried AudioQueue) Code Attempted I've tried multiple approaches to force the correct routing: func configureAudioSession() { let session = AVAudioSession.sharedInstance() // Configure to allow Bluetooth output but use built-in mic try? session.setCategory(.playAndRecord, options: [.allowBluetoothA2DP, .defaultToSpeaker]) try? session.setActive(true) // Explicitly select built-in microphone if let inputs = session.availableInputs, let builtInMic = inputs.first(where: { $0.portType == .builtInMic }) { try? session.setPreferredInput(builtInMic) print("Selected input: \(builtInMic.portName)") } // Log the current route let route = session.currentRoute print("Current input: \(route.inputs.first?.portName ?? "None")") // Configure audio engine with native format let inputNode = audioEngine.inputNode let nativeFormat = inputNode.inputFormat(forBus: 0) inputNode.installTap(onBus: 0, bufferSize: 1024, format: nativeFormat) { buffer, time in // Process audio buffer // Despite showing "Built-in Microphone" in route, audio appears to be // coming from AirPods with voice isolation applied - welp! } try? audioEngine.start() } I've also tried various combinations of: Different audio session modes (.default, .measurement, .voiceChat) Different option combinations (with/without .allowBluetooth, .allowBluetoothA2DP) Setting session.setPreferredInput() both before and after activation Diagnostic Observations When AirPods are connected: AVAudioSession.currentRoute.inputs correctly shows "Built-in Microphone" after setPreferredInput() The actual audio data received shows clear signs of AirPods' voice isolation processing Background/environmental sounds are actively filtered out... When recording a test audio played near the phone (not through the app), the recording is nearly silent. Only headset voice goes through. Questions Is there a workaround to force iOS to actually use the built-in microphone while maintaining Bluetooth output? Are there any lower-level configurations that might resolve this issue? Any insights, workarounds, or suggestions would be greatly appreciated. This is blocking a critical feature in my application that requires environmental audio recording while providing audio feedback through headphones 😅
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224
May ’25
How to capture audio from the stream that's playing on the speakers?
Good day, ladies and gents. I have an application that reads audio from the microphone. I'd like it to also be able to read from the Mac's audio output stream. (A bonus would be if it could detect when the Mac is playing music.) I'd eventually be able to figure it out reading docs, but if someone can give a hint, I'd be very grateful, and would owe you the libation of your choice. Here's the code used to set up the AudioUnit: -(NSString*) configureAU { AudioComponent component = NULL; AudioComponentDescription description; OSStatus err = noErr; UInt32 param; AURenderCallbackStruct callback; if( audioUnit ) { AudioComponentInstanceDispose( audioUnit ); audioUnit = NULL; } // was CloseComponent // Open the AudioOutputUnit description.componentType = kAudioUnitType_Output; description.componentSubType = kAudioUnitSubType_HALOutput; description.componentManufacturer = kAudioUnitManufacturer_Apple; description.componentFlags = 0; description.componentFlagsMask = 0; if( component = AudioComponentFindNext( NULL, &description ) ) { err = AudioComponentInstanceNew( component, &audioUnit ); if( err != noErr ) { audioUnit = NULL; return [ NSString stringWithFormat: @"Couldn't open AudioUnit component (ID=%d)", err] ; } } // Configure the AudioOutputUnit: // You must enable the Audio Unit (AUHAL) for input and output for the same device. // When using AudioUnitSetProperty the 4th parameter in the method refers to an AudioUnitElement. // When using an AudioOutputUnit for input the element will be '1' and the output element will be '0'. param = 1; // Enable input on the AUHAL err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &param, sizeof(UInt32) ); chkerr("Couldn't set first EnableIO prop (enable inpjt) (ID=%d)"); param = 0; // Disable output on the AUHAL err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, &param, sizeof(UInt32) ); chkerr("Couldn't set second EnableIO property on the audio unit (disable ootpjt) (ID=%d)"); param = sizeof(AudioDeviceID); // Select the default input device AudioObjectPropertyAddress OutputAddr = { kAudioHardwarePropertyDefaultInputDevice, kAudioObjectPropertyScopeGlobal, kAudioObjectPropertyElementMaster }; err = AudioObjectGetPropertyData( kAudioObjectSystemObject, &OutputAddr, 0, NULL, &param, &inputDeviceID ); chkerr("Couldn't get default input device (ID=%d)"); // Set the current device to the default input unit err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, 0, &inputDeviceID, sizeof(AudioDeviceID) ); chkerr("Failed to hook up input device to our AudioUnit (ID=%d)"); callback.inputProc = AudioInputProc; // Setup render callback, to be called when the AUHAL has input data callback.inputProcRefCon = self; err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, 0, &callback, sizeof(AURenderCallbackStruct) ); chkerr("Could not install render callback on our AudioUnit (ID=%d)"); param = sizeof(AudioStreamBasicDescription); // get hardware device format err = AudioUnitGetProperty( audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 1, &deviceFormat, &param ); chkerr("Could not install render callback on our AudioUnit (ID=%d)"); audioChannels = MAX( deviceFormat.mChannelsPerFrame, 2 ); // Twiddle the format to our liking actualOutputFormat.mChannelsPerFrame = audioChannels; actualOutputFormat.mSampleRate = deviceFormat.mSampleRate; actualOutputFormat.mFormatID = kAudioFormatLinearPCM; actualOutputFormat.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagIsPacked | kAudioFormatFlagIsNonInterleaved; if( actualOutputFormat.mFormatID == kAudioFormatLinearPCM && audioChannels == 1 ) actualOutputFormat.mFormatFlags &= ~kLinearPCMFormatFlagIsNonInterleaved; #if __BIG_ENDIAN__ actualOutputFormat.mFormatFlags |= kAudioFormatFlagIsBigEndian; #endif actualOutputFormat.mBitsPerChannel = sizeof(Float32) * 8; actualOutputFormat.mBytesPerFrame = actualOutputFormat.mBitsPerChannel / 8; actualOutputFormat.mFramesPerPacket = 1; actualOutputFormat.mBytesPerPacket = actualOutputFormat.mBytesPerFrame; // Set the AudioOutputUnit output data format err = AudioUnitSetProperty( audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &actualOutputFormat, sizeof(AudioStreamBasicDescription)); chkerr("Could not change the stream format of the output device (ID=%d)"); param = sizeof(UInt32); // Get the number of frames in the IO buffer(s) err = AudioUnitGetProperty( audioUnit, kAudioDevicePropertyBufferFrameSize, kAudioUnitScope_Global, 0, &audioSamples, &param ); chkerr("Could not determine audio sample size (ID=%d)"); err = AudioUnitInitialize( audioUnit ); // Initialize the AU chkerr("Could not initialize the AudioUnit (ID=%d)"); // Allocate our audio buffers audioBuffer = [self allocateAudioBufferListWithNumChannels: actualOutputFormat.mChannelsPerFrame size: audioSamples * actualOutputFormat.mBytesPerFrame]; if( audioBuffer == NULL ) { [ self cleanUp ]; return [NSString stringWithFormat: @"Could not allocate buffers for recording (ID=%d)", err]; } return nil; } (...again, it would be nice to know if audio output is active and thereby choose the clean output stream over the noisy mic, but that would be a different chunk of code, and my main question may just be a quick edit to this chunk.) Thanks for your attention! ==Dave [p.s. if i get more than one useful answer, can i "Accept" more than one, to spread the credit around?] {pps: of course, the code lines up prettier in a monospaced font!}
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189
Jun ’25
MIDI output form Standalone MIDI Processor Demo App to DAW
I am trying to get MIDI output from the AU Host demo app using the recent MIDI processor example. The processor works correctly in Logic Pro, but I cannot send MIDI from the AUv3 extension in standalone mode using the default host app to another program (e.g., Ableton). The MIDI manager, which is part of the standalone host app, works fine, and I can send MIDI using it directly—Ableton receives it without issues. I have already set the midiOutputNames in the extension, and the midiOutBlock is mapped. However, the MIDI data from the AUv3 extension does not reach Ableton in standalone mode. I suspect the issue is that midiOutBlock might never be called in the plugin, or perhaps an input to the plugin is missing, which prevents it from sending MIDI. I am currently using the default routing. I have modified the MIDI manager such that it works well as described above. Here is a part of my code for SimplePlayEngine.swift and my MIDIManager.swift for reference: @MainActor @Observable public class SimplePlayEngine { private let midiOutBlock: AUMIDIOutputEventBlock = { sampleTime, cable, length, data in return noErr } var scheduleMIDIEventListBlock: AUMIDIEventListBlock? = nil public init() { engine.attach(player) engine.prepare() setupMIDI() } private func setupMIDI() { if !MIDIManager.shared.setupPort(midiProtocol: MIDIProtocolID._2_0, receiveBlock: { [weak self] eventList, _ in if let scheduleMIDIEventListBlock = self?.scheduleMIDIEventListBlock { _ = scheduleMIDIEventListBlock(AUEventSampleTimeImmediate, 0, eventList) } }) { fatalError("Failed to setup Core MIDI") } } func initComponent(type: String, subType: String, manufacturer: String) async -> ViewController? { reset() guard let component = AVAudioUnit.findComponent(type: type, subType: subType, manufacturer: manufacturer) else { fatalError("Failed to find component with type: \(type), subtype: \(subType), manufacturer: \(manufacturer))" ) } do { let audioUnit = try await AVAudioUnit.instantiate( with: component.audioComponentDescription, options: AudioComponentInstantiationOptions.loadOutOfProcess) self.avAudioUnit = audioUnit self.connect(avAudioUnit: audioUnit) return await audioUnit.loadAudioUnitViewController() } catch { return nil } } private func startPlayingInternal() { guard let avAudioUnit = self.avAudioUnit else { return } setSessionActive(true) if avAudioUnit.wantsAudioInput { scheduleEffectLoop() } let hardwareFormat = engine.outputNode.outputFormat(forBus: 0) engine.connect(engine.mainMixerNode, to: engine.outputNode, format: hardwareFormat) do { try engine.start() } catch { isPlaying = false fatalError("Could not start engine. error: \(error).") } if avAudioUnit.wantsAudioInput { player.play() } isPlaying = true } private func resetAudioLoop() { guard let avAudioUnit = self.avAudioUnit else { return } if avAudioUnit.wantsAudioInput { guard let format = file?.processingFormat else { fatalError("No AVAudioFile defined.") } engine.connect(player, to: engine.mainMixerNode, format: format) } } public func connect(avAudioUnit: AVAudioUnit?, completion: @escaping (() -> Void) = {}) { guard let avAudioUnit = self.avAudioUnit else { return } engine.disconnectNodeInput(engine.mainMixerNode) resetAudioLoop() engine.detach(avAudioUnit) func rewiringComplete() { scheduleMIDIEventListBlock = auAudioUnit.scheduleMIDIEventListBlock if isPlaying { player.play() } completion() } let hardwareFormat = engine.outputNode.outputFormat(forBus: 0) engine.connect(engine.mainMixerNode, to: engine.outputNode, format: hardwareFormat) if isPlaying { player.pause() } let auAudioUnit = avAudioUnit.auAudioUnit if !auAudioUnit.midiOutputNames.isEmpty { auAudioUnit.midiOutputEventBlock = midiOutBlock } engine.attach(avAudioUnit) if avAudioUnit.wantsAudioInput { engine.disconnectNodeInput(engine.mainMixerNode) if let format = file?.processingFormat { engine.connect(player, to: avAudioUnit, format: format) engine.connect(avAudioUnit, to: engine.mainMixerNode, format: format) } } else { let stereoFormat = AVAudioFormat(standardFormatWithSampleRate: hardwareFormat.sampleRate, channels: 2) engine.connect(avAudioUnit, to: engine.mainMixerNode, format: stereoFormat) } rewiringComplete() } } and my MIDI Manager @MainActor class MIDIManager: Identifiable, ObservableObject { func setupPort(midiProtocol: MIDIProtocolID, receiveBlock: @escaping @Sendable MIDIReceiveBlock) -> Bool { guard setupClient() else { return false } if MIDIInputPortCreateWithProtocol(client, portName, midiProtocol, &port, receiveBlock) != noErr { return false } for source in self.sources { if MIDIPortConnectSource(port, source, nil) != noErr { print("Failed to connect to source \(source)") return false } } setupVirtualMIDIOutput() return true } private func setupVirtualMIDIOutput() { let virtualStatus = MIDISourceCreate(client, virtualSourceName, &virtualSource) if virtualStatus != noErr { print("❌ Failed to create virtual MIDI source: \(virtualStatus)") } else { print("✅ Created virtual MIDI source: \(virtualSourceName)") } } func sendMIDIData(_ data: [UInt8]) { print("hey") var packetList = MIDIPacketList() withUnsafeMutablePointer(to: &packetList) { ptr in let pkt = MIDIPacketListInit(ptr) _ = MIDIPacketListAdd(ptr, 1024, pkt, 0, data.count, data) if virtualSource != 0 { let status = MIDIReceived(virtualSource, ptr) if status != noErr { print("❌ Failed to send MIDI data: \(status)") } else { print("✅ Sent MIDI data: \(data)") } } } } }
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521
Aug ’25
Some questions about musickit
We are developing an apple music app on phone, the developed web works fine on chrome, but when i load it on webivew on my phone, i can't play the first song, We doubt that the drm init, key exchange, session creation was on the music.play() function, while we trigger the play, the drm or session was not ok for play a real song, so it got an error so we may wanna know: what about the realative process of drm, key, session, etc in the play() function? are there some state detect function to show weather the drm is ok?
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162
Mar ’25
WWDC25 Camera & Photos group lab summary (Part 1 of 3)
(Note: this is part 1 of a 3 part posting. See Part 2 or Part 3) At WWDC25 we launched a new type of Lab event for the developer community - Group Labs. A Group Lab is a panel Q&A designed for a large audience of developers. Group Labs are a unique opportunity for the community to submit questions directly to a panel of Apple engineers and designers. Here are the highlights from the WWDC25 Group Lab for Camera & Photos. WWDC25 Camera & Photos group lab ran for one hour at 6 PM PST on Tuesday June 10th, 2025 Introductory kick-off questions Question 1 Tell us a little about the new AVFoundation Capture APIs we've made available in the new iOS 26 developer preview? Cinematic Capture API (strong/weak focus, tracking focus)(scene monitoring)(simulated aperture)(dog/cat heads/groupIDs) Camera Controls and AirPod Stem Clicks Spatial Audio and Studio Quality AirPod Mics in Camera Lens Smudge Detection Exposure and Focus Rect of Interest Question 2 I built QR code scanning into my app, but on newer iPhones I have to hold the phone very far away from the QR code, otherwise the image is blurry and it doesn't scan. Why is this happening and how can I fix it? Every year, the cameras get better and better as we push the state of the art on iPhone photography and videography. This sometimes results in changes to the characteristics of the lenses. min focus distance newer phones have multiple lenses automatic switching behavior Use virtual device like the builtInDualWide or built in Triple, rather than just the builtInWide Set the videoZoomFactor to 2. You're done. Question 3 Last year, we saw some exciting new APIs introduced in AVFoundation in the health space. With Constant Color photography, developers can take pictures that have constant color regardless of ambient lighting. There are some further advancements this year. Davide, could you tell us about them? constant color photography is mean to remove the "tone mapping" applied to photograph captured with camera app, usually incldsuing artistic intent, and instead try to be a close as possible to the real color of the scene, regardless of the illumination constant color images could be captured in HEIF anf JPEG laste year. this year we are adding Support for the DICOM medical imaging photo format. It is a fomrat used by the health industry to store images related to medical subjects like MRI, skin problems, xray and so on. It's writable and also readable format on all OS26, supported through AVCapturePhotoOutput APIs and through the coregraphics api. for coregrapphics there is a new DICOM entry in the property dictionary which includes all the dicom availbale and defined propertie in a file. finder will also display all those in the info panel (Address why a developer would want to use it) - not for regualr picture taking apps. for those HEIF and JPEG are the preferred delivery format. use dicom if your app produces output that are health related, that you can also share with health providers or your doctors Main session developer questions Question 1 LiDAR vs. Dual Camera depth generation: Which resolution does the LiDAR sensor natively have (iPhone 16 Pro) and when to prefer LiDAR over Dual Camera? Both report formats with output resolutions (we don't advertise sensor resolution) Lidar vs Dual, etc: Lidar: Best for absolute depth, real world scale and computer vision Dual, etc: relative, disparity-based, less power, photo effects Also see: 2022 WWDC session "Discovery advancements in iOS camera capture: Depth, focus and multitasking" Question 2 Can true depth and lidar camera run at 60fps? Lidar can do 30fps (edited) Front true depth can do 60fps. Question 3 What’s the first class way to use PhotoKit to reimplement a high performance photo grid? We’ve been using a LazyVGrid and the photos caching manager, but are never able to hit the holy trinity (60hz, efficient memory footprint, minimal flashes of placeholder/empty cells) use the PHCachingImageManager to get media content delivered before you need to display it specify the size you need for grid sized display set the options PHVideoRequestOptionsDeliveryModeFastFormat, PHImageRequestOptionsDeliveryModeFastFormat and PHImageRequestOptionsResizeModeFast Question 4 For rending live preview of video stream, Is there performance overhead from using async and Swift UI for image updates vs UIViewRepresentable + AVCaptureVideoPreviewLayer.self? AVCaptureVideoPreviewLayer is the most efficient display path Use VDO + AVSampleBufferDisplayLayer if you need to modify the image data Swift UI image is optimized for static image content Question 5 Is there a way to configure the AVFoundation BuiltInLiDarDepthCamera mode to provide a depth map as accurate as ARKit at close range? The AVCaptureDepthDataOutput supports filtering that reduces noise and fills in invalid values. Consider using this for smoother depth maps Question 6 Pyramid-based photo editing in core image (such as adobe camera raw highlights and shadows)? First off you may want to look a the builtin filter called CIHighlightShadowAdjust Also the noise reduction in the CIRawFilter uses a pyramid-based algorithm. You can also write your own pyramid-based algorithms by taking an input image: down sample it by two multiply times using imageByApplyingAffineTransform apply additional CIKernels to each downsampled image as needed. use a custom CIKernel to combine the results. Question 7 Is the best way to integrate an in-app camera for a “non-camera” app UIImagePickerController? Yes, UIImagePickerController provides system-provided UI for capturing photos and movies. Question 8 Hello, my question is on Deferred Photo Processing? Say I have a photo capture app that adds a CIFilter to the capture. How can I take advantage of Deferred Photo Processing? Since I don’t know how to detect when the deferred captured photo is ready CIFilter can be called on the final at that point Photo will have to be re-inserted into the Photo library as adjustment Question 9 For shipping photo style assets in the app that need transparency what is the best format to use? JPEG2000? will moving to this save a lot of space comapred to PNG or other options? If you want lossless compression PNG is good and supports unpremutiplied alpha If you want lossy compression HEIF supports premutiplied or unpremutiplied alpha (Note: this is part 1 of a 3 part posting. See Part 2 or Part 3)
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545
Jul ’25
Capture session interrupted randomly
We are facing a strange issue where a small portion of our large userbase can not start the capture session in our app, as it gets interrupted with the following reason: AVCaptureSessionInterruptionReasonVideoDeviceNotAvailableWithMultipleForegroundApps Our users are all from iPhones, no one is using an iPad. Just to be sure we have set session.isMultitaskingCameraAccessEnabled = true but it does not seem to make any difference. Another weird interruption we are seeing
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123
Jun ’25
Notification interruptions
My app Balletrax is a music player for people to use while they teach ballet. Used to be you could silence notifications during use, but now the customer seems to have to know how to use Focus mode, remember to turn it on and off, and have to check the notifications one does and doesn't want to use. Is there no way to silence all notifications when the app is in use?
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118
Apr ’25
What is the best approach to multi-channel, per-channel volume control.
I've got a setup using AVAudioEngine with several tone generator nodes, each with a chain of processing nodes, the chains then mixed into the main output. Generator ➡️ Effect ➡️... ➡️ .mainMixerNode ➡️ .outputNode). Generator ➡️ Effect ➡️... ⤴️ ... Generator ➡️ Effect ➡️... ⤴️ The user should be able to mute any chain individually. I've found several potential approaches to muting, but not terribly happy with any of them. Adjust the amplitudes directly in my tone generators. Issue: Consumes CPU even when completely muted. 4 generators adds ~15% cpu, even when all chains are muted. Detach/attach chains that are muted/unmuted. Issue: Causes loud clicking/popping sounds whenever muted/unmuted. Fade mixer output volume while detaching/attaching a chain (just cutting the volume immediately to 0 doesn't get rid of the clicking/popping). Issue: Causes all channels to fade during the transition, so not ideal. The rest of these ideas are variations on making volume control+detatch/attach work for individual chains, since approach #3 worked well. Add an AVAudioMixer to the end of each chain (just for volume control). Issue: Only the mixer on the final chain functions -- the others block all output. Not sure what's going on there. Use matrix mixer (for multi-input volume control). Plus detach/attach to reduce CPU if necessary. Not yet attempted, due to perceived complexity and reports of fragility in order of wiring in. A bunch of effort before I even know if it's going to work. Develop my own fader node to put on the end of each channel. Unlike the tone generator (simple AVSourceNode), developing an effect node seems complex and time consuming. Might not even fix CPU use. I'm not completely averse to the learning curve of either 5 or 6, but would rather get some guidance on best approach before diving in. They both seem likely to take more effort than I'd like for the simple behavior I'm trying to achieve.
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363
Jul ’25
how to enumerate build-in media devices?
Hello, I need to enumerate built-in media devices (cameras, microphones, etc.). For this purpose, I am using the CoreAudio and CoreMediaIO frameworks. According to the table 'Daemon-Safe Frameworks' in Apple’s TN2083, CoreAudio is daemon-safe. However, the documentation does not mention CoreMediaIO. Can CoreMediaIO be used in a daemon? If not, are there any documented alternatives to detect built-in cameras in a daemon (e.g., via device classes in IOKit)? Thank you in advance, Pavel
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169
May ’25
iOS 18 Picture-in-Picture dynamically changes UIScreen.main.bounds on iPhone 11 causing keyboard clipping and layout issues
When creating and activating AVPictureInPictureController on iPhone 11 running iOS 18.x, the main screen viewport unexpectedly changes from the native 375×812 logical points to 414×896 points (the size of a different device such as iPhone XR/11 Plus). Additionally, a separate UIWindow with zero CGRect is created. This causes UIKit layout calculations, especially related to the keyboard and safeAreaInsets, to malfunction and results in issues like keyboard clipping and general UI misalignment. The problem appears tied specifically to iOS 18+ behavior and does not manifest on earlier iOS versions or other devices consistently. Steps to Reproduce: Run the app on iPhone 11 with iOS 18.x (including the latest minor updates). Instantiate and start an AVPictureInPictureController during app runtime. Observe that UIScreen.main.bounds changes from 375×812 (native iPhone 11 size) to 414×896. Notice a secondary UIWindow appears with frame CGRectZero. Interact with text inputs that cause the keyboard to appear. The keyboard is clipped or partially obscured, causing UI usability issues. Layout elements dependent on UIScreen.main.bounds or safeAreaInsets behave incorrectly. Expected Behavior: UIScreen.main.bounds should not dynamically change upon PiP controller creation. The coordinate space and viewport should remain accurate to device native dimensions. The keyboard and UI layout should adjust properly with respect to the actual on-screen size and safe areas. Actual Behavior: UIScreen.main.bounds changes to 414×896 upon PiP controller creation on iPhone 11 iOS 18+. A zero-rect secondary UIWindow is created, impacting layout queries. Keyboard clipping and UI layout bugs occur. The app viewport and coordinate space are inconsistent with device hardware.
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268
Jul ’25
Album parquet files don't include song names
The documentation of the Apple Music Feed API states that the Album object would include songs — a list of songs in the album. As per the doc, this would be an array of object Album.RelatedSong, which would include both an id and nameDefault. Unfortunately, the album parquet files only include the song id and not the name of the song itself. Please advise - is the documentation incorrect or are the recently posted parquet files in error?
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May ’25
Image brightness adapts despite exposure lock
Short summary When setting exposureMode to .locked or .custom the brightness of a video stream still changes depending on the composition and contrast of the visible scene. These changes seem to come from contrast enhancements or dynamic range optimizations and totally break any analysis of the image that requires to assess absolute luminance. While exposure lock seems to indeed lock the physical exposure parameters of the camera (shutter speed and ISO), I cannot find any way to control these "soft" modifiers. Details Background I am the developer of the app "phyphox", an educational app that makes the phone's sensors accessible to students as measurement tools in science experiments. Currently I am working on implementing photometric measurements through the camera and one very important aspect of it is luminance measurements. This is particularly relevant since the light sensor of the phone has no publicly accessible API and the camera could to some extend make experiments available to Apple users that are otherwise only possible on Android devices. Implementation The app uses AVFoundation and explicitly picks individual cameras since camera groups do not support custom exposure settings. This means that it handles camera switching during zoom by itself and even implements its own auto exposure routines to optimize for the use in experiments. Therefore it always stays in custom exposure mode. The app uses YUV420 color space and the individual frames are analyzed in Metal using compute shaders. However, the effects discussed here still occur if I remove all code to control the camera and replace it with a simple sequence of setting the exposure mode to custom, setting custom exposure values, setting a fixed white balance and then setting the exposure mode to locked as suggested on stackoverflow. This neither helps on an iPhone 14 Pro nor on an iPhone 8 despite a report on the developer forums that it would resolve the issue for older devices. The app is open source, so the code can be seen in our current development branch (without the changes for the tests here, though) on github. The videos below use the implementation with the suggestion from stackoverflow, but they can be reproduced in the same way with "professional" camera apps that promise manual control over the camera (like the Blackmagic cam to quote a reputable company) as well as the stock camera app after pressing and holding on the preview to enable AE/AF lock. Demonstration These examples were captured on an iPhone 14 Pro. The central part of the image (highlighted by the app using metal shaders after capture) should not change with fixed exposure settings, but significant changes are noticable if there are changes at the edge of the frame when I move a black piece of cardboard in from above: https://share.icloud.com/photos/0b1f_3IB6yAQG-qSH27pm6oDQ The graph above the camera preview is the average luminance (gamma corrected and weighted based on sRGB) across the highlighted central area and as mentioned before it should not change because of something happening at the side of the frame (worst case it should get a bit darker because of the cardboard's shadow). In my opinion, the iPhone changes its mind on the ideal contrast as soon as it has a different exposure histogram because of the dark image part from the cardboard, but that's just me guessing. For completeness here is the same effect in the stock camera app with AE/AF lock enabled: https://share.icloud.com/photos/0cd7QM8ucBZKwPwE9mybnEowg Here you can also see that the iPhone "ramps" the changes. The brightness of the gray area does not change immediately but transitions smoothly, so this is clearly deliberate postprocessing. So... Any suggestion on how to prevent this behavior would be highly appreciated.
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Apr ’25
How to Get Device Orientation in Background (PiP) Mode?
My app is a camera app that supports Picture-in-Picture (PiP) mode. Normally, when the device rotates, I get the device orientation from iOS and use it to rotate the camera feed so that the preview stays correctly aligned. However, when the app enters PiP mode, it is considered to be in the background, and I can no longer receive orientation updates from the system. As a result, I can’t apply rotation corrections to the camera video in PiP mode. Is there any way to retrieve device orientation while the app is in the background (specifically during PiP mode)? Any guidance would be greatly appreciated. Thank you!
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76
May ’25
Can't set AVAudio sampleRate and installTap needs bufferSize 4800 at minimum
Two issues: No matter what I set in try audioSession.setPreferredSampleRate(x) the sample rate on both iOS and macOS is always 48000 when the output goes through the speaker, and 24000 when my Airpods connect to an iPhone/iPad. Now, I'm checking the current output loudness to animate a 3D character, using mixerNode.installTap(onBus: 0, bufferSize: y, format: nil) { [weak self] buffer, time in Task { @MainActor in // calculate rms and animate character accordingly but any buffer size under 4800 is just ignored and the buffers I get are 4800 sized. This is ok, when the sampleRate is currently 48000, as 10 samples per second lead to decent visual results. But when AirPods connect, the samplerate is 24000, which means only 5 samples per second, so the character animation looks lame. My AVAudioEngine setup is the following: audioEngine.connect(playerNode, to: pitchShiftEffect, format: format) audioEngine.connect(pitchShiftEffect, to: mixerNode, format: format) audioEngine.connect(mixerNode, to: audioEngine.outputNode, format: nil) Now, I'd be fine if the outputNode runs at whatever if it needs, as long as my tap would get at least 10 samples per second. PS: Specifying my favorite format in the let format = AVAudioFormat(standardFormatWithSampleRate: 48_000, channels: 2)! mixerNode.installTap(onBus: 0, bufferSize: y, format: format) doesn't change anything either
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453
Activity
Aug ’25
Apple Music API High Error Rate
I am getting high error rates from the Apple Music API. This has been happening for months now, and it is quite frustrating. It is a mix of 404, 504, and random 500 errors. I hit these endpoints all of the time, so it is not like I am hitting a resource that doesn't exist. Why is this happening? Is this a known issue that is getting worked on?
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95
Activity
Jun ’25
How to detect when iOS Camera app starts video recording (with Allow Audio Playback ON)?
Since iOS 18, the system setting “Allow Audio Playback” (enabled by default) allows third-party app audio to continue playing while the user is recording video with the Camera app. This has created a problem for the app I’m developing. ➡️ The problem: My app plays continuous audio in both foreground and background states. If the user starts recording video using the iOS Camera app, the app’s audio — still playing in the background — gets captured in the video — obviously an unintended behavior. Yes, the user could stop the app manually before starting the video recording, but that can’t be guaranteed. As a developer, I need a way to stop the app’s audio before the video recording begins. So far, I haven’t found a reliable way to detect when video recording starts if ‘Allow Audio Playback’ is ON. ➡️ What I’ve tried: — AVAudioSession.interruptionNotification → doesn’t fire — devicesChangedEventStream → not triggered I don’t want to request mic permission (app doesn’t use mic). also, disabling the app from playing audio in the background isn’t an option as it is a crucial part of the user experience ➡️ What I need: A reliable, supported way to detect when the Camera app begins video recording, without requiring mic access — so I can stop audio and avoid unintentional overlap with the user’s recordings. Any official guidance, workarounds, or AVFoundation techniques would be greatly appreciated. Thanks.
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288
Activity
Aug ’25
Why a driverkit extension needs a CMIO extension
I developed a driverkit extension based on overriding-the-default-usb-video-class-extension, but the link didn’t give the details of realization. I asked DTS who gave two tips: 1, Do you also have a CMIO extension to load in place of the default overriding-the-default-usb-video-class-extension 2, Your DriverKit extension’s info.plist is also missing the CameraAssistantBundleID. I want to know why a driverkit extension needs a CMIO extension, what’s the data and control flow?
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372
Activity
Jun ’25
Telephoto Lens Keeps Switching to Other Lenses on iPhone 16 Pro Max During PPG (Finger on Camera)
Hi, I’m building a PPG-based heart rate feature where the user places their finger over the rear telephoto camera. On iPhone 16 Pro Max, I'm explicitly selecting the telephoto lens like this: videoDevice = AVCaptureDevice.default(.builtInTelephotoCamera, for: .video, position: .back) And trying to lock it: if #available(iOS 15.0, *), device.activePrimaryConstituentDeviceSwitchingBehavior != .unsupported { try? device.lockForConfiguration() device.setPrimaryConstituentDeviceSwitchingBehavior(.locked, restrictedSwitchingBehaviorConditions: []) device.unlockForConfiguration() } I also lock everything else to prevent dynamic changes: try device.lockForConfiguration() device.focusMode = .locked device.exposureMode = .locked device.whiteBalanceMode = .locked device.videoZoomFactor = 1.0 device.automaticallyEnablesLowLightBoostWhenAvailable = false device.automaticallyAdjustsVideoHDREnabled = false device.unlockForConfiguration() Despite this, the camera still switches to another lens, especially under different lighting, even though the user’s finger fully covers the lens. Questions: How can I completely prevent lens switching in this scenario? Would using videoZoomFactor = 3.0 or 5.0 better enforce use of the telephoto lens? Thanks! Gal
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201
Activity
Jul ’25
Can I Fade Out Track Volume Before End Using ApplicationMusicPlayer?
I’m building a music app using Apple Music streaming via ApplicationMusicPlayer. My goal is to decrease the volume of the current song during the last 10 seconds, and when the next track begins, restore the volume to its normal level. I know that ApplicationMusicPlayer doesn’t expose a volume API, and I want to avoid triggering the system volume HUD. ✅ Using Apple Music streaming (not local files) ❓ Is it possible to implement per-track fade-out/fade-in logic with ApplicationMusicPlayer? Appreciate any clarification or official guidance!
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117
Activity
Jun ’25
iOS Audio Routing - Bluetooth Output + Built-in Microphone Input
Hello! I'm experiencing an issue with iOS's audio routing system when trying to use Bluetooth headphones for audio output while also recording environmental audio from the built-in microphone. Desired behavior: Play audio through Bluetooth headset (AirPods) Record unprocessed environmental audio from the iPhone's built-in microphone Actual behavior: When explicitly selecting the built-in microphone, iOS reports it's using it (in currentRoute.inputs) However, the actual audio data received is clearly still coming from the AirPods microphone The audio is heavily processed with voice isolation/noise cancellation, removing environmental sounds Environment Details Device: iPhone 12 Pro Max iOS Version: 18.4.1 Hardware: AirPods Audio Framework: AVAudioEngine (also tried AudioQueue) Code Attempted I've tried multiple approaches to force the correct routing: func configureAudioSession() { let session = AVAudioSession.sharedInstance() // Configure to allow Bluetooth output but use built-in mic try? session.setCategory(.playAndRecord, options: [.allowBluetoothA2DP, .defaultToSpeaker]) try? session.setActive(true) // Explicitly select built-in microphone if let inputs = session.availableInputs, let builtInMic = inputs.first(where: { $0.portType == .builtInMic }) { try? session.setPreferredInput(builtInMic) print("Selected input: \(builtInMic.portName)") } // Log the current route let route = session.currentRoute print("Current input: \(route.inputs.first?.portName ?? "None")") // Configure audio engine with native format let inputNode = audioEngine.inputNode let nativeFormat = inputNode.inputFormat(forBus: 0) inputNode.installTap(onBus: 0, bufferSize: 1024, format: nativeFormat) { buffer, time in // Process audio buffer // Despite showing "Built-in Microphone" in route, audio appears to be // coming from AirPods with voice isolation applied - welp! } try? audioEngine.start() } I've also tried various combinations of: Different audio session modes (.default, .measurement, .voiceChat) Different option combinations (with/without .allowBluetooth, .allowBluetoothA2DP) Setting session.setPreferredInput() both before and after activation Diagnostic Observations When AirPods are connected: AVAudioSession.currentRoute.inputs correctly shows "Built-in Microphone" after setPreferredInput() The actual audio data received shows clear signs of AirPods' voice isolation processing Background/environmental sounds are actively filtered out... When recording a test audio played near the phone (not through the app), the recording is nearly silent. Only headset voice goes through. Questions Is there a workaround to force iOS to actually use the built-in microphone while maintaining Bluetooth output? Are there any lower-level configurations that might resolve this issue? Any insights, workarounds, or suggestions would be greatly appreciated. This is blocking a critical feature in my application that requires environmental audio recording while providing audio feedback through headphones 😅
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224
Activity
May ’25
How to capture audio from the stream that's playing on the speakers?
Good day, ladies and gents. I have an application that reads audio from the microphone. I'd like it to also be able to read from the Mac's audio output stream. (A bonus would be if it could detect when the Mac is playing music.) I'd eventually be able to figure it out reading docs, but if someone can give a hint, I'd be very grateful, and would owe you the libation of your choice. Here's the code used to set up the AudioUnit: -(NSString*) configureAU { AudioComponent component = NULL; AudioComponentDescription description; OSStatus err = noErr; UInt32 param; AURenderCallbackStruct callback; if( audioUnit ) { AudioComponentInstanceDispose( audioUnit ); audioUnit = NULL; } // was CloseComponent // Open the AudioOutputUnit description.componentType = kAudioUnitType_Output; description.componentSubType = kAudioUnitSubType_HALOutput; description.componentManufacturer = kAudioUnitManufacturer_Apple; description.componentFlags = 0; description.componentFlagsMask = 0; if( component = AudioComponentFindNext( NULL, &description ) ) { err = AudioComponentInstanceNew( component, &audioUnit ); if( err != noErr ) { audioUnit = NULL; return [ NSString stringWithFormat: @"Couldn't open AudioUnit component (ID=%d)", err] ; } } // Configure the AudioOutputUnit: // You must enable the Audio Unit (AUHAL) for input and output for the same device. // When using AudioUnitSetProperty the 4th parameter in the method refers to an AudioUnitElement. // When using an AudioOutputUnit for input the element will be '1' and the output element will be '0'. param = 1; // Enable input on the AUHAL err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &param, sizeof(UInt32) ); chkerr("Couldn't set first EnableIO prop (enable inpjt) (ID=%d)"); param = 0; // Disable output on the AUHAL err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, &param, sizeof(UInt32) ); chkerr("Couldn't set second EnableIO property on the audio unit (disable ootpjt) (ID=%d)"); param = sizeof(AudioDeviceID); // Select the default input device AudioObjectPropertyAddress OutputAddr = { kAudioHardwarePropertyDefaultInputDevice, kAudioObjectPropertyScopeGlobal, kAudioObjectPropertyElementMaster }; err = AudioObjectGetPropertyData( kAudioObjectSystemObject, &OutputAddr, 0, NULL, &param, &inputDeviceID ); chkerr("Couldn't get default input device (ID=%d)"); // Set the current device to the default input unit err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, 0, &inputDeviceID, sizeof(AudioDeviceID) ); chkerr("Failed to hook up input device to our AudioUnit (ID=%d)"); callback.inputProc = AudioInputProc; // Setup render callback, to be called when the AUHAL has input data callback.inputProcRefCon = self; err = AudioUnitSetProperty( audioUnit, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, 0, &callback, sizeof(AURenderCallbackStruct) ); chkerr("Could not install render callback on our AudioUnit (ID=%d)"); param = sizeof(AudioStreamBasicDescription); // get hardware device format err = AudioUnitGetProperty( audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 1, &deviceFormat, &param ); chkerr("Could not install render callback on our AudioUnit (ID=%d)"); audioChannels = MAX( deviceFormat.mChannelsPerFrame, 2 ); // Twiddle the format to our liking actualOutputFormat.mChannelsPerFrame = audioChannels; actualOutputFormat.mSampleRate = deviceFormat.mSampleRate; actualOutputFormat.mFormatID = kAudioFormatLinearPCM; actualOutputFormat.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagIsPacked | kAudioFormatFlagIsNonInterleaved; if( actualOutputFormat.mFormatID == kAudioFormatLinearPCM && audioChannels == 1 ) actualOutputFormat.mFormatFlags &= ~kLinearPCMFormatFlagIsNonInterleaved; #if __BIG_ENDIAN__ actualOutputFormat.mFormatFlags |= kAudioFormatFlagIsBigEndian; #endif actualOutputFormat.mBitsPerChannel = sizeof(Float32) * 8; actualOutputFormat.mBytesPerFrame = actualOutputFormat.mBitsPerChannel / 8; actualOutputFormat.mFramesPerPacket = 1; actualOutputFormat.mBytesPerPacket = actualOutputFormat.mBytesPerFrame; // Set the AudioOutputUnit output data format err = AudioUnitSetProperty( audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &actualOutputFormat, sizeof(AudioStreamBasicDescription)); chkerr("Could not change the stream format of the output device (ID=%d)"); param = sizeof(UInt32); // Get the number of frames in the IO buffer(s) err = AudioUnitGetProperty( audioUnit, kAudioDevicePropertyBufferFrameSize, kAudioUnitScope_Global, 0, &audioSamples, &param ); chkerr("Could not determine audio sample size (ID=%d)"); err = AudioUnitInitialize( audioUnit ); // Initialize the AU chkerr("Could not initialize the AudioUnit (ID=%d)"); // Allocate our audio buffers audioBuffer = [self allocateAudioBufferListWithNumChannels: actualOutputFormat.mChannelsPerFrame size: audioSamples * actualOutputFormat.mBytesPerFrame]; if( audioBuffer == NULL ) { [ self cleanUp ]; return [NSString stringWithFormat: @"Could not allocate buffers for recording (ID=%d)", err]; } return nil; } (...again, it would be nice to know if audio output is active and thereby choose the clean output stream over the noisy mic, but that would be a different chunk of code, and my main question may just be a quick edit to this chunk.) Thanks for your attention! ==Dave [p.s. if i get more than one useful answer, can i "Accept" more than one, to spread the credit around?] {pps: of course, the code lines up prettier in a monospaced font!}
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189
Activity
Jun ’25
MIDI output form Standalone MIDI Processor Demo App to DAW
I am trying to get MIDI output from the AU Host demo app using the recent MIDI processor example. The processor works correctly in Logic Pro, but I cannot send MIDI from the AUv3 extension in standalone mode using the default host app to another program (e.g., Ableton). The MIDI manager, which is part of the standalone host app, works fine, and I can send MIDI using it directly—Ableton receives it without issues. I have already set the midiOutputNames in the extension, and the midiOutBlock is mapped. However, the MIDI data from the AUv3 extension does not reach Ableton in standalone mode. I suspect the issue is that midiOutBlock might never be called in the plugin, or perhaps an input to the plugin is missing, which prevents it from sending MIDI. I am currently using the default routing. I have modified the MIDI manager such that it works well as described above. Here is a part of my code for SimplePlayEngine.swift and my MIDIManager.swift for reference: @MainActor @Observable public class SimplePlayEngine { private let midiOutBlock: AUMIDIOutputEventBlock = { sampleTime, cable, length, data in return noErr } var scheduleMIDIEventListBlock: AUMIDIEventListBlock? = nil public init() { engine.attach(player) engine.prepare() setupMIDI() } private func setupMIDI() { if !MIDIManager.shared.setupPort(midiProtocol: MIDIProtocolID._2_0, receiveBlock: { [weak self] eventList, _ in if let scheduleMIDIEventListBlock = self?.scheduleMIDIEventListBlock { _ = scheduleMIDIEventListBlock(AUEventSampleTimeImmediate, 0, eventList) } }) { fatalError("Failed to setup Core MIDI") } } func initComponent(type: String, subType: String, manufacturer: String) async -> ViewController? { reset() guard let component = AVAudioUnit.findComponent(type: type, subType: subType, manufacturer: manufacturer) else { fatalError("Failed to find component with type: \(type), subtype: \(subType), manufacturer: \(manufacturer))" ) } do { let audioUnit = try await AVAudioUnit.instantiate( with: component.audioComponentDescription, options: AudioComponentInstantiationOptions.loadOutOfProcess) self.avAudioUnit = audioUnit self.connect(avAudioUnit: audioUnit) return await audioUnit.loadAudioUnitViewController() } catch { return nil } } private func startPlayingInternal() { guard let avAudioUnit = self.avAudioUnit else { return } setSessionActive(true) if avAudioUnit.wantsAudioInput { scheduleEffectLoop() } let hardwareFormat = engine.outputNode.outputFormat(forBus: 0) engine.connect(engine.mainMixerNode, to: engine.outputNode, format: hardwareFormat) do { try engine.start() } catch { isPlaying = false fatalError("Could not start engine. error: \(error).") } if avAudioUnit.wantsAudioInput { player.play() } isPlaying = true } private func resetAudioLoop() { guard let avAudioUnit = self.avAudioUnit else { return } if avAudioUnit.wantsAudioInput { guard let format = file?.processingFormat else { fatalError("No AVAudioFile defined.") } engine.connect(player, to: engine.mainMixerNode, format: format) } } public func connect(avAudioUnit: AVAudioUnit?, completion: @escaping (() -> Void) = {}) { guard let avAudioUnit = self.avAudioUnit else { return } engine.disconnectNodeInput(engine.mainMixerNode) resetAudioLoop() engine.detach(avAudioUnit) func rewiringComplete() { scheduleMIDIEventListBlock = auAudioUnit.scheduleMIDIEventListBlock if isPlaying { player.play() } completion() } let hardwareFormat = engine.outputNode.outputFormat(forBus: 0) engine.connect(engine.mainMixerNode, to: engine.outputNode, format: hardwareFormat) if isPlaying { player.pause() } let auAudioUnit = avAudioUnit.auAudioUnit if !auAudioUnit.midiOutputNames.isEmpty { auAudioUnit.midiOutputEventBlock = midiOutBlock } engine.attach(avAudioUnit) if avAudioUnit.wantsAudioInput { engine.disconnectNodeInput(engine.mainMixerNode) if let format = file?.processingFormat { engine.connect(player, to: avAudioUnit, format: format) engine.connect(avAudioUnit, to: engine.mainMixerNode, format: format) } } else { let stereoFormat = AVAudioFormat(standardFormatWithSampleRate: hardwareFormat.sampleRate, channels: 2) engine.connect(avAudioUnit, to: engine.mainMixerNode, format: stereoFormat) } rewiringComplete() } } and my MIDI Manager @MainActor class MIDIManager: Identifiable, ObservableObject { func setupPort(midiProtocol: MIDIProtocolID, receiveBlock: @escaping @Sendable MIDIReceiveBlock) -> Bool { guard setupClient() else { return false } if MIDIInputPortCreateWithProtocol(client, portName, midiProtocol, &port, receiveBlock) != noErr { return false } for source in self.sources { if MIDIPortConnectSource(port, source, nil) != noErr { print("Failed to connect to source \(source)") return false } } setupVirtualMIDIOutput() return true } private func setupVirtualMIDIOutput() { let virtualStatus = MIDISourceCreate(client, virtualSourceName, &virtualSource) if virtualStatus != noErr { print("❌ Failed to create virtual MIDI source: \(virtualStatus)") } else { print("✅ Created virtual MIDI source: \(virtualSourceName)") } } func sendMIDIData(_ data: [UInt8]) { print("hey") var packetList = MIDIPacketList() withUnsafeMutablePointer(to: &packetList) { ptr in let pkt = MIDIPacketListInit(ptr) _ = MIDIPacketListAdd(ptr, 1024, pkt, 0, data.count, data) if virtualSource != 0 { let status = MIDIReceived(virtualSource, ptr) if status != noErr { print("❌ Failed to send MIDI data: \(status)") } else { print("✅ Sent MIDI data: \(data)") } } } } }
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521
Activity
Aug ’25
Some questions about musickit
We are developing an apple music app on phone, the developed web works fine on chrome, but when i load it on webivew on my phone, i can't play the first song, We doubt that the drm init, key exchange, session creation was on the music.play() function, while we trigger the play, the drm or session was not ok for play a real song, so it got an error so we may wanna know: what about the realative process of drm, key, session, etc in the play() function? are there some state detect function to show weather the drm is ok?
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162
Activity
Mar ’25
WWDC25 Camera & Photos group lab summary (Part 1 of 3)
(Note: this is part 1 of a 3 part posting. See Part 2 or Part 3) At WWDC25 we launched a new type of Lab event for the developer community - Group Labs. A Group Lab is a panel Q&A designed for a large audience of developers. Group Labs are a unique opportunity for the community to submit questions directly to a panel of Apple engineers and designers. Here are the highlights from the WWDC25 Group Lab for Camera & Photos. WWDC25 Camera & Photos group lab ran for one hour at 6 PM PST on Tuesday June 10th, 2025 Introductory kick-off questions Question 1 Tell us a little about the new AVFoundation Capture APIs we've made available in the new iOS 26 developer preview? Cinematic Capture API (strong/weak focus, tracking focus)(scene monitoring)(simulated aperture)(dog/cat heads/groupIDs) Camera Controls and AirPod Stem Clicks Spatial Audio and Studio Quality AirPod Mics in Camera Lens Smudge Detection Exposure and Focus Rect of Interest Question 2 I built QR code scanning into my app, but on newer iPhones I have to hold the phone very far away from the QR code, otherwise the image is blurry and it doesn't scan. Why is this happening and how can I fix it? Every year, the cameras get better and better as we push the state of the art on iPhone photography and videography. This sometimes results in changes to the characteristics of the lenses. min focus distance newer phones have multiple lenses automatic switching behavior Use virtual device like the builtInDualWide or built in Triple, rather than just the builtInWide Set the videoZoomFactor to 2. You're done. Question 3 Last year, we saw some exciting new APIs introduced in AVFoundation in the health space. With Constant Color photography, developers can take pictures that have constant color regardless of ambient lighting. There are some further advancements this year. Davide, could you tell us about them? constant color photography is mean to remove the "tone mapping" applied to photograph captured with camera app, usually incldsuing artistic intent, and instead try to be a close as possible to the real color of the scene, regardless of the illumination constant color images could be captured in HEIF anf JPEG laste year. this year we are adding Support for the DICOM medical imaging photo format. It is a fomrat used by the health industry to store images related to medical subjects like MRI, skin problems, xray and so on. It's writable and also readable format on all OS26, supported through AVCapturePhotoOutput APIs and through the coregraphics api. for coregrapphics there is a new DICOM entry in the property dictionary which includes all the dicom availbale and defined propertie in a file. finder will also display all those in the info panel (Address why a developer would want to use it) - not for regualr picture taking apps. for those HEIF and JPEG are the preferred delivery format. use dicom if your app produces output that are health related, that you can also share with health providers or your doctors Main session developer questions Question 1 LiDAR vs. Dual Camera depth generation: Which resolution does the LiDAR sensor natively have (iPhone 16 Pro) and when to prefer LiDAR over Dual Camera? Both report formats with output resolutions (we don't advertise sensor resolution) Lidar vs Dual, etc: Lidar: Best for absolute depth, real world scale and computer vision Dual, etc: relative, disparity-based, less power, photo effects Also see: 2022 WWDC session "Discovery advancements in iOS camera capture: Depth, focus and multitasking" Question 2 Can true depth and lidar camera run at 60fps? Lidar can do 30fps (edited) Front true depth can do 60fps. Question 3 What’s the first class way to use PhotoKit to reimplement a high performance photo grid? We’ve been using a LazyVGrid and the photos caching manager, but are never able to hit the holy trinity (60hz, efficient memory footprint, minimal flashes of placeholder/empty cells) use the PHCachingImageManager to get media content delivered before you need to display it specify the size you need for grid sized display set the options PHVideoRequestOptionsDeliveryModeFastFormat, PHImageRequestOptionsDeliveryModeFastFormat and PHImageRequestOptionsResizeModeFast Question 4 For rending live preview of video stream, Is there performance overhead from using async and Swift UI for image updates vs UIViewRepresentable + AVCaptureVideoPreviewLayer.self? AVCaptureVideoPreviewLayer is the most efficient display path Use VDO + AVSampleBufferDisplayLayer if you need to modify the image data Swift UI image is optimized for static image content Question 5 Is there a way to configure the AVFoundation BuiltInLiDarDepthCamera mode to provide a depth map as accurate as ARKit at close range? The AVCaptureDepthDataOutput supports filtering that reduces noise and fills in invalid values. Consider using this for smoother depth maps Question 6 Pyramid-based photo editing in core image (such as adobe camera raw highlights and shadows)? First off you may want to look a the builtin filter called CIHighlightShadowAdjust Also the noise reduction in the CIRawFilter uses a pyramid-based algorithm. You can also write your own pyramid-based algorithms by taking an input image: down sample it by two multiply times using imageByApplyingAffineTransform apply additional CIKernels to each downsampled image as needed. use a custom CIKernel to combine the results. Question 7 Is the best way to integrate an in-app camera for a “non-camera” app UIImagePickerController? Yes, UIImagePickerController provides system-provided UI for capturing photos and movies. Question 8 Hello, my question is on Deferred Photo Processing? Say I have a photo capture app that adds a CIFilter to the capture. How can I take advantage of Deferred Photo Processing? Since I don’t know how to detect when the deferred captured photo is ready CIFilter can be called on the final at that point Photo will have to be re-inserted into the Photo library as adjustment Question 9 For shipping photo style assets in the app that need transparency what is the best format to use? JPEG2000? will moving to this save a lot of space comapred to PNG or other options? If you want lossless compression PNG is good and supports unpremutiplied alpha If you want lossy compression HEIF supports premutiplied or unpremutiplied alpha (Note: this is part 1 of a 3 part posting. See Part 2 or Part 3)
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545
Activity
Jul ’25
Capture session interrupted randomly
We are facing a strange issue where a small portion of our large userbase can not start the capture session in our app, as it gets interrupted with the following reason: AVCaptureSessionInterruptionReasonVideoDeviceNotAvailableWithMultipleForegroundApps Our users are all from iPhones, no one is using an iPad. Just to be sure we have set session.isMultitaskingCameraAccessEnabled = true but it does not seem to make any difference. Another weird interruption we are seeing
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Activity
Jun ’25
Notification interruptions
My app Balletrax is a music player for people to use while they teach ballet. Used to be you could silence notifications during use, but now the customer seems to have to know how to use Focus mode, remember to turn it on and off, and have to check the notifications one does and doesn't want to use. Is there no way to silence all notifications when the app is in use?
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118
Activity
Apr ’25
What is the best approach to multi-channel, per-channel volume control.
I've got a setup using AVAudioEngine with several tone generator nodes, each with a chain of processing nodes, the chains then mixed into the main output. Generator ➡️ Effect ➡️... ➡️ .mainMixerNode ➡️ .outputNode). Generator ➡️ Effect ➡️... ⤴️ ... Generator ➡️ Effect ➡️... ⤴️ The user should be able to mute any chain individually. I've found several potential approaches to muting, but not terribly happy with any of them. Adjust the amplitudes directly in my tone generators. Issue: Consumes CPU even when completely muted. 4 generators adds ~15% cpu, even when all chains are muted. Detach/attach chains that are muted/unmuted. Issue: Causes loud clicking/popping sounds whenever muted/unmuted. Fade mixer output volume while detaching/attaching a chain (just cutting the volume immediately to 0 doesn't get rid of the clicking/popping). Issue: Causes all channels to fade during the transition, so not ideal. The rest of these ideas are variations on making volume control+detatch/attach work for individual chains, since approach #3 worked well. Add an AVAudioMixer to the end of each chain (just for volume control). Issue: Only the mixer on the final chain functions -- the others block all output. Not sure what's going on there. Use matrix mixer (for multi-input volume control). Plus detach/attach to reduce CPU if necessary. Not yet attempted, due to perceived complexity and reports of fragility in order of wiring in. A bunch of effort before I even know if it's going to work. Develop my own fader node to put on the end of each channel. Unlike the tone generator (simple AVSourceNode), developing an effect node seems complex and time consuming. Might not even fix CPU use. I'm not completely averse to the learning curve of either 5 or 6, but would rather get some guidance on best approach before diving in. They both seem likely to take more effort than I'd like for the simple behavior I'm trying to achieve.
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363
Activity
Jul ’25
RPBroadcastSampleHandler does not trigger
Add RPSystemBroadcastPickerView to the app, After clicking, no method of SampleHandler is triggered
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2
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912
Activity
Jul ’25
how to enumerate build-in media devices?
Hello, I need to enumerate built-in media devices (cameras, microphones, etc.). For this purpose, I am using the CoreAudio and CoreMediaIO frameworks. According to the table 'Daemon-Safe Frameworks' in Apple’s TN2083, CoreAudio is daemon-safe. However, the documentation does not mention CoreMediaIO. Can CoreMediaIO be used in a daemon? If not, are there any documented alternatives to detect built-in cameras in a daemon (e.g., via device classes in IOKit)? Thank you in advance, Pavel
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169
Activity
May ’25
iOS 18 Picture-in-Picture dynamically changes UIScreen.main.bounds on iPhone 11 causing keyboard clipping and layout issues
When creating and activating AVPictureInPictureController on iPhone 11 running iOS 18.x, the main screen viewport unexpectedly changes from the native 375×812 logical points to 414×896 points (the size of a different device such as iPhone XR/11 Plus). Additionally, a separate UIWindow with zero CGRect is created. This causes UIKit layout calculations, especially related to the keyboard and safeAreaInsets, to malfunction and results in issues like keyboard clipping and general UI misalignment. The problem appears tied specifically to iOS 18+ behavior and does not manifest on earlier iOS versions or other devices consistently. Steps to Reproduce: Run the app on iPhone 11 with iOS 18.x (including the latest minor updates). Instantiate and start an AVPictureInPictureController during app runtime. Observe that UIScreen.main.bounds changes from 375×812 (native iPhone 11 size) to 414×896. Notice a secondary UIWindow appears with frame CGRectZero. Interact with text inputs that cause the keyboard to appear. The keyboard is clipped or partially obscured, causing UI usability issues. Layout elements dependent on UIScreen.main.bounds or safeAreaInsets behave incorrectly. Expected Behavior: UIScreen.main.bounds should not dynamically change upon PiP controller creation. The coordinate space and viewport should remain accurate to device native dimensions. The keyboard and UI layout should adjust properly with respect to the actual on-screen size and safe areas. Actual Behavior: UIScreen.main.bounds changes to 414×896 upon PiP controller creation on iPhone 11 iOS 18+. A zero-rect secondary UIWindow is created, impacting layout queries. Keyboard clipping and UI layout bugs occur. The app viewport and coordinate space are inconsistent with device hardware.
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268
Activity
Jul ’25
Album parquet files don't include song names
The documentation of the Apple Music Feed API states that the Album object would include songs — a list of songs in the album. As per the doc, this would be an array of object Album.RelatedSong, which would include both an id and nameDefault. Unfortunately, the album parquet files only include the song id and not the name of the song itself. Please advise - is the documentation incorrect or are the recently posted parquet files in error?
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87
Activity
May ’25
Image brightness adapts despite exposure lock
Short summary When setting exposureMode to .locked or .custom the brightness of a video stream still changes depending on the composition and contrast of the visible scene. These changes seem to come from contrast enhancements or dynamic range optimizations and totally break any analysis of the image that requires to assess absolute luminance. While exposure lock seems to indeed lock the physical exposure parameters of the camera (shutter speed and ISO), I cannot find any way to control these "soft" modifiers. Details Background I am the developer of the app "phyphox", an educational app that makes the phone's sensors accessible to students as measurement tools in science experiments. Currently I am working on implementing photometric measurements through the camera and one very important aspect of it is luminance measurements. This is particularly relevant since the light sensor of the phone has no publicly accessible API and the camera could to some extend make experiments available to Apple users that are otherwise only possible on Android devices. Implementation The app uses AVFoundation and explicitly picks individual cameras since camera groups do not support custom exposure settings. This means that it handles camera switching during zoom by itself and even implements its own auto exposure routines to optimize for the use in experiments. Therefore it always stays in custom exposure mode. The app uses YUV420 color space and the individual frames are analyzed in Metal using compute shaders. However, the effects discussed here still occur if I remove all code to control the camera and replace it with a simple sequence of setting the exposure mode to custom, setting custom exposure values, setting a fixed white balance and then setting the exposure mode to locked as suggested on stackoverflow. This neither helps on an iPhone 14 Pro nor on an iPhone 8 despite a report on the developer forums that it would resolve the issue for older devices. The app is open source, so the code can be seen in our current development branch (without the changes for the tests here, though) on github. The videos below use the implementation with the suggestion from stackoverflow, but they can be reproduced in the same way with "professional" camera apps that promise manual control over the camera (like the Blackmagic cam to quote a reputable company) as well as the stock camera app after pressing and holding on the preview to enable AE/AF lock. Demonstration These examples were captured on an iPhone 14 Pro. The central part of the image (highlighted by the app using metal shaders after capture) should not change with fixed exposure settings, but significant changes are noticable if there are changes at the edge of the frame when I move a black piece of cardboard in from above: https://share.icloud.com/photos/0b1f_3IB6yAQG-qSH27pm6oDQ The graph above the camera preview is the average luminance (gamma corrected and weighted based on sRGB) across the highlighted central area and as mentioned before it should not change because of something happening at the side of the frame (worst case it should get a bit darker because of the cardboard's shadow). In my opinion, the iPhone changes its mind on the ideal contrast as soon as it has a different exposure histogram because of the dark image part from the cardboard, but that's just me guessing. For completeness here is the same effect in the stock camera app with AE/AF lock enabled: https://share.icloud.com/photos/0cd7QM8ucBZKwPwE9mybnEowg Here you can also see that the iPhone "ramps" the changes. The brightness of the gray area does not change immediately but transitions smoothly, so this is clearly deliberate postprocessing. So... Any suggestion on how to prevent this behavior would be highly appreciated.
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176
Activity
Apr ’25
How to Get Device Orientation in Background (PiP) Mode?
My app is a camera app that supports Picture-in-Picture (PiP) mode. Normally, when the device rotates, I get the device orientation from iOS and use it to rotate the camera feed so that the preview stays correctly aligned. However, when the app enters PiP mode, it is considered to be in the background, and I can no longer receive orientation updates from the system. As a result, I can’t apply rotation corrections to the camera video in PiP mode. Is there any way to retrieve device orientation while the app is in the background (specifically during PiP mode)? Any guidance would be greatly appreciated. Thank you!
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76
Activity
May ’25