I am developing an Xcode/Swift/SwiftUI app for real-time music visualization. I allow the user to push a button to toggle between microphone-input and file-play input (but never both at the same time). My app runs fine on my Mac and on my iPad, but on my iPhone, the speaker audio is only at half-volume (and appears to be only coming from the back speakers) - even when I am in file-play mode. I have traced the problem to one offending line in my code - namely the declaration
let mic = engine.inputNode // where engine = AVAudioEngine()
When I comment-out this line, the iPhone speaker level (for file-play mode) is fine. But when I un-comment it, the iPhone speaker level is barely audible. Even when I wrap this line inside a conditional if(micEnabled){} construct, the sound level is fine at first; but as soon as I select the microphone and then toggle back to file-play, the volume again decreases.
I suspect that iOS detects when a microphone is declared and automatically reduces the speaker volume to avoid audio feedback. This would make sense because nobody wants music playing when they are speaking on a telephone call. But it would also make sense to provide developers a way to override this feature if they want to handle it themselves. In my case, for the microphone-input case, I purposely assign the audio stream a zero-volume after it is tapped and before going to the speaker.
My source code is available here. All of the audio code is inside the MuVis / Shared / AudioManager.swift class.
Can anyone help me to get the file-play mode to work with full volume on my iPhone - while also allowing the user the option to select microphone-input mode?
Many thanks to Rob Napier for pointing me in the right direction for solving my problem.
As a macOS-only developer, I had ignored AVAudioSession (since it caused compiler errors on macOS). When I converted my MuVis app from macOS-only to multiplatform, I simply started a new Xcode project with the appropriate multiplatform settings, and then pasted my existing code into the shared folder. After cleaning up a few errors (mostly calls to NSObject), it magically worked on all Apple platforms - except for the iPhone audio problem described in my question. After a little research and a lot of trial-and-error, I found that my audio-volume problem is solved by inserting the following code into my setupAudio() function:
#if os(iOS)
// For iOS devices, set the audioSession category, mode, and options:
let session = AVAudioSession.sharedInstance() // Get the singleton instance of an AVAudioSession.
do {
if(filePlayEnabled) {
// This is required by iOS to prevent output audio from going only to the iPhone's rear speaker.
try session.setCategory(AVAudioSession.Category.playAndRecord, mode: AVAudioSession.Mode.default, options: [.defaultToSpeaker])
}
else {
try session.setCategory(AVAudioSession.Category.playAndRecord, mode: AVAudioSession.Mode.default, options: [])
}
} catch { print("Failed to set audioSession category.") }
#endif
Again, thank you Rob.
Related
I have an avassetwriter capture session to record a video and 2 avplayerqueues to playback the immediately recorded video and the other, to playback past saved videos.
My problem is the audio input does not use my bluetooth earphones, and performs playback and record via the iphone device inputs/outputs.
I did not implement any override to default to the speaker, understand I need to handle a route change via notification observer in the case of toggling between bluetooth and device, and also tried setting the AVAudioSession.sharedInstance() .playbackAndRecording category to .allowBluetooth to no avail.
Any guidance would be appreciated as I have not come across an existing answer online..
let audioSession = AVAudioSession.sharedInstance()
//Executed right before playing avqueueplayer media
do {
try audioSession.setCategory(.playback)
try audioSession.setActive(true)
} catch {
fatalError("Error Setting Up Audio Session")
}
//Executed right after avqueueplayer finishes media
do {
try audioSession.setCategory(.recording, options: [.allowBluetooth])
try audioSession.setActive(true)
} catch {
fatalError("Error Setting Up Audio Session")
}
Did you read carefully the documentation for .allowBluetooth and .allowBluetoothA2DP? These do not mean what you likely think they mean, since passing both is rarely what developers mean. Do not guess what AVFoundation will do based on the names of things; you must read the documentation. The names of things are not obvious, and are actively misleading in several places.
If you want to record from Bluetooth headphones, you cannot support A2DP. A2DP is a unidirectional protocol (playback only). You will need to use HFP, which is what .allowBluetooth means. Remove .allowBluetoothA2DP. Note that this is significantly reduce your audio quality.
If you have distinct periods of recording vs playback, then you want to change your category when you change modes. Do not just set .playAndRecord because you will record at some point and playback at another. If you switch to a playback-only situation, switch to .playback. It is legal to change categories while the session is active (again, see the docs; there are many subtle rules).
You haven't listed what your Bluetooth earphones are, so it's not clear whether they support both A2DP and HFP. That has significant impact on how routing occurs. See the docs for .allowBluetoothA2DP on this.
I am having an intermittent (aargh!) problem playing Text-to-Speech in the background, triggered from Apple Watch. I have properly set up the background mode, the AVSession category, and the WatchKitExtensionRequest handler. (See below.) I had this working before, and can't figure out what changed. (Could it be iOS 9 has issues? "Before" means, among other things, iOS 8.)
The problem is this: when the app gets the request from the Watch and the app is either in the background or the phone is sleeping (locked), the speech sometimes plays right away, and other times doesn't play until the app is brought to the foreground. The OS seems to be sometimes queuing the audio, and sometimes not. I can't find any common thread between success and failure cases. I can verify with logging that the call to speakUtterance() is being made in all situations. But its behavior varies, apparently randomly. The only clue is that it might be the case that the longer the app is in the background, the less likely it is to speak right away.
This is making me pull my hair out. Suggestions welcome.
In info.plist:
Required background modes: App plays audio or streams audio/video using AirPlay
In AppDelegate.application:didFinishLaunching:withOptions():
do {
try AVAudioSession.sharedInstance().setCategory(
AVAudioSessionCategoryPlayback,
withOptions:.DuckOthers
)
try AVAudioSession.sharedInstance().setActive(true)
} catch let error as NSError {
// etc...
}
In AppDelegate.application:handleWatchKitExtensionRequest...():
var bgTaskId:UIBackgroundTaskIdentifier = 0
bgTaskId = application.beginBackgroundTaskWithName(
"Prose WKE handler",
expirationHandler: {
application.endBackgroundTask(bgTaskId)
}
)
//... Post notification to call Text-to-Speech
application.endBackgroundTask(bgTaskId)
Here's a workaround: play a second snippet of sound (I used a half-second of silence), using AVAudioPlayer, right after the call to speakUtterance(), This seems to "jog the pipeline".
For my APP, one of the important function is to mute the iPhone, but I can't find any available iOS API that I can use to mute the phone(or change the ringer volume level to minimum). Is their a specific API for developer to mute (or change the ringer volume of) the phone, if their is not, is there a indirect way to do this?
I believe you can only mute other application sounds. You need to configure the AVAudioSession category :
AVAudioSession Class Reference : http://goo.gl/rh7CX7 .
Look for which fit the most for your application. You only need to set it once in your code (make sure it's called).
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategorySoloAmbient, error: nil) // AVAudioSessionCategorySoloAmbient is default AVAudioSession.sharedInstance().setActive(true, error: nil)
No.
Applications developed using the official SDK cannot change (and in most cases cannot even access) system-wide settings.
It is possible, but only using private API's. I only went as far as muting the ringer, but you should be able to control the master level as well.
See How to disable iOS System Sounds
I placed 2 VLCMediaPlayer in the IPad ViewController.
Then I want to mute one of the players.
I executed the following code from VLCAudio class:
[VLCMediaPlayer.audio setMute:YES];
But the voice of the player was still on.
Then I added another piece of code:
[VLCMediaPlayer.audio setVolume:0];
Nothing had been changed.
Is it because both setMute and setVolue functions don’t work under the ISO VLCKit?
If so, how to mute VLCMediaPlayer by coding?
Set the current audio track to -1. Performance-wise, this is more efficient, too, since the audio information isn't even decoded.
Volume control (incl. mute) isn't supported with current versions of MobileVLCKit on iOS, but on the Mac only.
If you want to mute from the beginning, I found a way to do it.
Before you send play msg to the player instance, you should init it with options, such as
self.player = [[VLCMediaPlayer alloc] initWithOptions:#[#"--gain=0"]];
where "--gain=0" which means audio gain set to 0. This is not the documentation method, may not work on every version of mobile vlc framework. But it works for me.
If you want to mute while playing, you can try
self.player.currentAudioTrackIndex = -1;
This also works for me!
I'm setting up an AVAudioSession when the app launches and setting the delegate to the appDelegate. Everything seems to be working (playback, etc) except that beginInterruption on the delegate is not being called when the phone receives a call. When the call ends endInterruption is being called though.
The only thought I have is that the audio player code I'm using used to be based on AVAudioPlayer, but is now using AVPlayer. The callbacks for the AVAudioPlayer delegate for handling interrupts are still in there, but it seems odd that they would conflict in any way.
Looking at the header, in iOS6, it looks like AVAudioSessionDelegate is now deprecated.
Use AVAudioSessionInterruptionNotification instead in iOS6.
Update: That didn't work. I think there's a bug in the framework.
Yes, in my experience, beginInterruption, nor the newly documented AVAudioSessionInterruptionNotification work properly. What I had to do was track the status of the player using a local flag, then handle the endInterruption:withFlags: method in order to track recovery from interruptions.
With iOS 6, the resuming from an interruption will at least keep your AudioPlayer in the right place, so there was no need for me to store the last known play time of my AVAudioPlayer, I simply had to hit play.
Here's the solution that I came up with. It seems like iOS 6 kills your audio with a Media Reset if an AVPlayer stays resident too long. What ends up happening, is the AVPlayer plays, but no sound comes out. The rate on the AVPlayer is 1, but there's absolutely no sound. To add pain to the situation, there's no error on either the AVAudioSession setActive, nor the AVPlayer itself that indicates that there's a problem.
Add to the fact that you can't depend on appWillResignActive, because your app may already be in the background if you're depending on remote control gestures at all.
The final solution I implemented was to add a periodic observer on the AVPlayer, and record the last known time. When I receive the event that I've been given back control, I create a new AVPlayer, load it with the AVPlayerItem, and seekToTime to the proper time.
It's quite an annoying workaround, but at least it works, and avoids the periodic crashes that were happening.
I can confirm that using the C api, the interruption method is also not called when the interruption begins; only when it ends
(AudioSessionInitialize (nil, nil, interruptionListenerCallback, (__bridge void *)(self));
I've also filed a bug report with apple for the issue.
Edit: This is fixed in iOS 6.1 (but not iOS 6.0.1)
Just call:
[[AVAudioSession sharedInstance] setDelegate: self];
I just checked on my iPhone 5 (running iOS 6.0) by setting a breakpoint in the AudioSessionInterruptionListener callback function that was declared in AudioSessionInitialize(), and this interrupt callback does, in fact, get called when the app has an active audio session and audio unit and is interrupted with an incoming phone call (Xcode shows the app stopped at the breakpoint at the beginning of the interruption, which I then continue from).
I have the app then stop its audio unit and de-activate its audio session. Then, on the end interruption callback, the app re-activates the audio session and restarts the audio unit without problems (the app is recording audio properly afterwards).
I built a brand new audio streaming (AVPlayer) application atop iOS 6.0.x and found the same problem.
Delegates are now deprecated and we have to use notifications, that's great, however here's my findings:
During an incoming phone call I get only AVAudioSessionInterruptionTypeEnded in my handler, along with AVAudioSessionInterruptionOptionShouldResume. Audio session gets suspended automatically (audio fades) and I just need to resume playback of AVPlayer.
However when attempting to launch a game, such as CSR Racing, I oddly get the dreaded AVAudioSessionInterruptionTypeBegan but no sign when my application can resume playback, not even killing the game.
Now, this may depend on other factors, such as my audio category (in my case AVAudioSessionCategoryPlayback) and the mixing settings of both applications (kAudioSessionProperty_OverrideCategoryMixWithOthers), I'm not sure, but definitely I see something out of place.
Hopefully others reported that on 6.1beta this is fixed and I yet have to upgrade, so we'll see.