I have an application that uses location services in the background. Works fine.
But what I want to do, at a certain point, is to check some audio levels while the application is in the background. For some reason it doesn't seem to work. When running in foreground, the function works fine, but when in the back ground, the audio recorder average and peak input is always -120..
This is what I use to do the trick (that doesn't seem to work apparently..)
....
[recorder record];
if (levelTimer == nil) {
bgTask = 0;
app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask];
}];
levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.02 target: self selector: #selector(levelTimerCallback:) userInfo: nil repeats: YES];
}
...
And yes, the levelTimerCallback is called every 0.02 seconds, even when in the background, so I assume that the beginBackgroundTaskWithExpirationHandler works fine.
Any thoughts or some hints?
Currently, the only supported way to record in the background on an iOS device is to include audio for the UIBackgroundModes key in the app's plist, enable an appropriate Audio Session for recording, and start recording (or playing) audio before the app goes into the background.
If the app uses the Audio Queues or the RemoteIO Audio Unit API for recording, the buffer callbacks can just throw away all the audio buffers until the time of interest, and then compute the energy represented by the PCM samples for the amount of time required when needed.
I dont think iPhone will allow recording in the background. Only few services are allowed when the app goes into background. Logically if your app stays into background for a long time it would then consume a lot of battery as well as buffer to store audio, unless you have time and memory managed these resources. This would also pose issues for your app when you submit it to the App Store.
Although you can refer to this link for knowing what can be run in the background.
I hope this might help u clear things in a way.
iPhone : Running services in the background
Good Luck!!!
There is an app I know of that has background recording. Beatmaker 2. You need to turn run in the background on in the settings of device under beatmaker 2. In beatmaker create an audio track and start recording. Them use the home button on device to exit app but its still recording. You can get creative with different interfaces as well. I do this to feed the iPhone 4 line out into an audio track in beatmaker 2. You can record the audio of anything playing in the foreground. (YouTube videos apps music from your iTunes library. You can edit the waves also after recorded.
Related
I have developed an iPhone app which gets the microphone recorder inputs every second using NSTimer, calculate the amplitude of sound, and take appropriate action if required. I have noticed that when my iPhone gets locked, my application stops running(it doesn't fire the timer callback function). When I unlock iPhone, it start automatically. Could anyone please tell me how can I allow application responding when iPhone gets locked? Is there any other way around such that iPhone shouldn't get locked when my application is running? What should be Apple's recomendation on this?
I found this article but not sure it is correct way to do.
Thanks.
You cannot prevent timer from being stopped when application goes into idle state. Only one possible way is to disable idleTimer of the application.
application.idleTimerDisabled = TRUE;
//or
//Disable screen dimming if no user input occur on device.
[[UIApplication sharedApplication] setIdleTimerDisabled:YES];
I am trying to figure out a way to record audio in the background of an iOS application and have it streamed to the server.
I have pretty much got this working for when the app is in the foreground. I use AVAudioRecorder to record input for X seconds. Once I get the callback that this has finished, I record for another X seconds. Each recording session gets stored to a different file and I send these files asynchronously to the server.
However, this doesn't seem to work while my app goes into background mode.
When going into the background, the current record session continues recording until the X seconds are up, however my app gets suspended, before I can start another recording session.
Any ideas?
Here's the code for my callback:
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)aRecorder successfully:(BOOL)flag {
NSLog(#"hello");
[self initRecorder];
[recorder recordForDuration:5];
}
You can't restart recording in the background.
So use the Audio Queue or Audio Unit RemoteIO APIs instead, which will give you smaller "chunks" (callback buffer blocks) of audio without stopping the audio recording.
Concatenate small audio callback chunks into larger file chunks if needed for your network protocol.
Background audio playing is supported with multitasking but it's not very clear that background audio recording is. However, I have not tried it. The Audio Unit API might let you continue to record audio while the application is in the background. However, this is kind of a trick and I Imagine it might get pulled out at some point.
I'm making an alarm clock app with multitasking support. However, I'm stuck with some limitations of the sdk.
I need to play selected alarm sound whenever the alarm time comes with some properties set by the user.
These properties:
- Alarm sound can be a music from the user's iPod library, and also some sound files in application bundle.
- Alarm sound can be set to play as progressive.
Moreover, alarm sound must be played in background in a loop until the user cancels or wakes the app.
First logical thing that came to my mind was to use local notifications, but with local notifications you can play sound files that are only in app bundle(not iPod music) and that are at most 30 seconds long. Also you are not get notified when the user cancels the notification alert, iOS just stops playing your sound.
Now I'm thinking of using background audio playing option and play silence until the alarm time, and then play the alarm sound while also showing a local notification without sound. But again how will I know if user cancelled the local notification alert and stop playing audio. However according to Apple's documentation iPod music playing(and use of shared resources) is still not allowed for an app that is playing background audio.
I also can't understand how some other apps are doing some of these features. For example, Night Stand HD can play iPod music while in the background, and an app named "Progressive Alarm Clock" can play progressive sound while in the background.
Any ideas and suggestions on these issues? Any of your help will be greatly appreciated
I would say what you want to do is not possible with the current restrictions of iOS. That said you can probably fake a progressive alarm by doing what the developer of Progressive Alarm Clock do to play the progressive alarm. By scheduling many local notifications, one after each other. He has divided the alarm sounds into chunks of say 10 s each with progressive volume levels. This is a very crude example to show how the progressive alarm can be faked.
UILocalNotification *notif1 = [[UILocalNotification alloc] init];
notif1.fireDate = [NSDate dateWithTimeIntervalSinceNow:15];
notif1.soundName = UILocalNotificationDefaultSoundName;
notif1.alertBody = #"Alarm";
[[UIApplication sharedApplication] scheduleLocalNotification:notif1];
[notif1 release];
UILocalNotification *notif2 = [[UILocalNotification alloc] init];
notif2.fireDate = [NSDate dateWithTimeIntervalSinceNow:20];
notif2.soundName = UILocalNotificationDefaultSoundName;
[[UIApplication sharedApplication] scheduleLocalNotification:notif2];
[notif2 release];
This will first display a notification and play the default sound after 15 seconds. After 5 seconds more the sound will be played again. By having a bunch of sound files where the volume is increasing the progressive sound can be faked just by scheduling more local notifications. This will of course only work if you have an alarm sound that can be easily divided into chunks, just like the bells in Progressive Alarm Clock. Unfortunately you can't cancel the alarm by tapping cancel in the notification. You have to start the application to do that.
Whatever the Progressive Alarm Clock developer is doing, it's not what Robert Höglund is describing, AFAIK, since the alarm will sound even if the phone is in silent, and UILocalNotification doesn't seem to have any way to allow for this. In addition, if you kill the app manually while an alarm is pending, the app will notify you that it needs to relaunch. This seems to suggest that it must be somehow running in the background.
first of all, I know there is only support for voip, audio and location apps to run in background and that they will run just while the audio is been played or while using location services, etc.
What I want to know is if there is a way to keep my app running on background fully operational, doesn't matter the impact on battery's life.
That way the user of my app can select from settings to keep alive the app whenever he wants and just for the amount of time he wish. e.g if he is waiting for something that requires the app to be running, after receiving the messages he can turn off the keep alive functionality.
I don't know if this is possible but I had read some post that say so but unfortunately they didn't say how to =(
UPDATE: In this tutorial, I found that Acrobits has two apps on the Apple Store that "can force the application to stay alive and awake in the background". So there is a way to do this?
From ioS 7 onwards, there are newer ways for apps to run in background. Apple now recognizes that apps have to constantly download and process data constantly.
Here is the new list of all the apps which can run in background.
Apps that play audible content to the user while in the background, such as a music player app
Apps that record audio content while in the background.
Apps that keep users informed of their location at all times, such as a navigation app
Apps that support Voice over Internet Protocol (VoIP)
Apps that need to download and process new content regularly
Apps that receive regular updates from external accessories
You can declare app's supported background tasks in Info.plist using X Code 5+. For eg. adding UIBackgroundModes key to your app’s Info.plist file and adding a value of 'fetch' to the array allows your app to regularly download and processes small amounts of content from the network. You can do the same in the 'capabilities' tab of Application properties in XCode 5 (attaching a snapshot)
You can find more about this in Apple documentation
You can perform tasks for a limited time after your application is directed to go to the background, but only for the duration provided. Running for longer than this will cause your application to be terminated. See the "Completing a Long-Running Task in the Background" section of the iOS Application Programming Guide for how to go about this.
Others have piggybacked on playing audio in the background as a means of staying alive as a background process, but Apple will only accept such an application if the audio playback is a legitimate function. Item 2.16 on Apple's published review guidelines states:
Multitasking apps may only use
background services for their intended
purposes: VoIP, audio playback,
location, task completion, local
notifications, etc
If any background task runs more than 10 minutes,then the task will be suspended and code block specified with beginBackgroundTaskWithExpirationHandler is called to clean up the task. background remaining time can be checked with [[UIApplication sharedApplication] backgroundTimeRemaining].
Initially when the App is in foreground backgroundTimeRemaining is set to bigger value. When the app goes to background, you can see backgroundTimeRemaining value decreases from 599.XXX ( 1o minutes). once the backgroundTimeRemaining becomes ZERO, the background task will be suspended.
//1)Creating iOS Background Task
__block UIBackgroundTaskIdentifier background_task;
background_task = [application beginBackgroundTaskWithExpirationHandler:^ {
//This code block is execute when the application’s
//remaining background time reaches ZERO.
}];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//### background task starts
//#### background task ends
});
//2)Making background task Asynchronous
if([[UIDevice currentDevice] respondsToSelector:#selector(isMultitaskingSupported)])
{
NSLog(#"Multitasking Supported");
__block UIBackgroundTaskIdentifier background_task;
background_task = [application beginBackgroundTaskWithExpirationHandler:^ {
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
}];
**//Putting All together**
//To make the code block asynchronous
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//### background task starts
NSLog(#"Running in the background\n");
while(TRUE)
{
NSLog(#"Background time Remaining: %f",[[UIApplication sharedApplication] backgroundTimeRemaining]);
[NSThread sleepForTimeInterval:1]; //wait for 1 sec
}
//#### background task ends
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
});
}
else
{
NSLog(#"Multitasking Not Supported");
}
For running on stock iOS devices, make your app an audio player/recorder or a VOIP app, a legitimate one for submitting to the App store, or a fake one if only for your own use.
Even this won't make an app "fully operational" whatever that is, but restricted to limited APIs.
Depends what it does. If your app takes up too much memory, or makes calls to functions/classes it shouldn't, SpringBoard may terminate it. However, it will most likely be rejected by Apple, as it does not follow their 7 background uses.
May be the link will Help bcz u might have to implement the code in Appdelegate in app run in background method ..
Also consult the developer.apple.com site for application class
Here is link for runing app in background
My app uses NSTimer and it appears that NSTimer doesn't fire when the iPhone goes into the stand-by mode (either by pressing the hardware button or by the idle timer).
When I activate the iPhone again, my app is still in the foreground. What happens to third party apps when the iPhone is the stand-by mode?
Although it's not evident here, I believe the original poster did find an answer to his question by starting a thread (available here) in the iPhone Developer Forums (which I eventually had to find myself because the information wasn't shared here).
In case someone else has the same question and finds the page in the future, here's a helpful response that was posted by someone on the Apple forum called "eskimo1" (which I have edited slightly such that it is easier to read without having the context provided by the entire original thread):
Regarding iPhone app status terminology, "active" does not mean "awake", it means "attached to the GUI". Think of it being analogous to "frontmost" in Mac OS X. When you lock the device your app deactivates but the device may or may not go to sleep
iPhone OS rarely sleeps if the device is connected to main power (i.e., via USB). It can sleep if running on battery, however.
A short time after the screen is locked (20 seconds according to Oliver Drobnik), the device sleeps. This is like closing the lid on your laptop; all activity on the main CPU halts.
This does not happen if the device is playing audio in the right audio session. See DTS Q&A QA1626 "Audio Session - Ensuring audio playback continues when screen is locked" for details.
Note that the idleTimerDisabled property (which can be turned on to prevent the screen from turning off while the app is running) is about locking the screen after user inactivity. It's not directly related to system sleep (it's indirectly related in that the system may sleep shortly after it's locked).
See Application Interruptions in the iPhone OS Programming Guide, especially the applicationWillResignActive and applicationDidBecomeActive events. (The whole guide is certainly worth reading.) When You ignore the events, the timer seems to go on for a while and then stops. Sounds logical, the application could easily drain the battery if kept running. And what exactly happens to the application? I guess it simply does not get any CPU time – it freezes and only thaws when You turn the machine back “on.”
My first advice is do not disable the idle timer, that is just a hack. If you want to keep a timer alive during UI events run the timer on the current run loop using NSCommonModes:
// create timer and add it to the current run loop using common modes
self.timer = [NSTimer timerWithTimeInterval:.1 target:self selector:#selector(handleTimer) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
I used the information on this post for a small sample that I was building. This is the code that I used when I initiated the playback to prevent the audio from stopping:
AudioSession.Category = AudioSessionCategory.MediaPlayback;
And when the application is done with the playback to reset to the original value:
AudioSession.Category = AudioSessionCategory.SoloAmbientSound;
The full sample is here:
http://github.com/migueldeicaza/monotouch-samples/tree/master/StreamingAudio/
I was faced with this issue recently in an app I am working on that uses several timers and plays some audio prompts and made two relatively simple changes:
In the AppDelegate I implemented the following methods and there mere presence allows the app to continue when the screen is locked
// this receives the notification when the device is locked
- (void)applicationWillResignActive:(UIApplication *)application
{
}
// this receives the notification that the application is about to become active again
- (void)applicationWillBecomeActive:(NSNotification *)aNotification
{
}
references: UIApplicationDelegate Protocol Reference & NSApplication Class Reference in the API doc (accessible via Xcode, just search for applicationWillBecomeActive).
Made the main viewcontroller class an AVAudioPlayerDelegate and used this code from Apple's "AddMusic" sample to make the audio alerts the app played mix nicely into the iPod audio etc...
I just dropped this code into a method that is called during viewDidLoad. If this interests you, you fall into the "who should read this doc" category for this: Audio Session Programming Guide
// Registers this class as the delegate of the audio session.
[[AVAudioSession sharedInstance] setDelegate: self];
// The AmbientSound category allows application audio to mix with Media Player
// audio. The category also indicates that application audio should stop playing
// if the Ring/Siilent switch is set to "silent" or the screen locks.
[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryAmbient error: nil];
// Activates the audio session.
NSError *activationError = nil;
[[AVAudioSession sharedInstance] setActive: YES error: &activationError];
I believe your application should run normally when suspended. (think Pandora Radio)
Check to see if your timer is being deallocated due to your view being hidden or some other event occurring.