AVAudioRecorder：无法记录其他记录应用程序

Question

I know this is a difficult question, because I sometimes see it, sometimes not. I use AVAudioRecorder to record audio in my application. It can run fine. But sometimes when I navigate to other apps and use microphone function of those apps, and back to my app, my record functionality can not record, all the record files have length is 0s.

After I debug, I found out that: [recorder prepareToRecord] return TRUE (this method to create record file - for example .caf file) [recorder record] always return FALSE (this is the problem)

I don't know why [recorder record] return FALSE. Do anyone see this problem before and can tell me how to fix this?

Thank you very much.

Answer 1

当您的应用程序变为活动状态时，您需要激活AVAudioSession

Answer 2

Once you loose recording, you must RESTART the audio recording again and you HAVE to be in the foreground to do this. You can capture audio interruption events for interrupted and interrupted ended. BUT there is currently bugs in this and you many not get the ended events.

 AVCaptureSession            *captureSession;
 .......
 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(audioInterruptionEnded) name:AVCaptureSessionInterruptionEndedNotification object:captureSession];
 [captureSession addObserver: self forKeyPath:@"running" options:0x3 context:nil];
 [captureSession addObserver: self forKeyPath:@"interrupted" options:0x3 context:nil];

There are two ways to capture audio. Using the higher level AVCapture Session, or the Lower level AudioQueue, but both are restricted by the first paragraph.

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context 
{
    if ([keyPath isEqualToString:@"interrupted"]) 
    { 
          // try restart here if in foreground
          // post local notification if in background to bring to foreground and then restart
    }
}