在录制音频片段时设置时间限制？

Question

I looked for search terms along the lines of the post title, but alas..

I am building an iPhone app using AVFoundation.

Is there a correct procedure to limit the amount of audio that will be recorded? I would like a maximum of 10 seconds.

Thanks for any help/advice/tips/pointers..

Answer 1

AVAudioRecorder has the following method:

- (BOOL)recordForDuration:(NSTimeInterval)duration

I think that will do the trick!

http://developer.apple.com/library/ios/#documentation/AVFoundation/Reference/AVAudioRecorder_ClassReference/Reference/Reference.html#//apple_ref/doc/uid/TP40008238

Answer 2

I don't normally work with AVFoundation so I don't know the exact method/class names (I filled in my own), but a workaround to this would be having a recurring NSTimer beginning when the recording originally starts. Something like this:

@interface blahblah
...
int rec_time;
NSTimer *timer;
Recorder *recorder;
...
@end

@implementation blahblah
...
-(void)beginRecording {
    [recorder startRecording];
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0
    target:self
    selector:@selector(recordingTime)
    userInfo:nil
    repeats:YES];
}

-(int)recordingTime {
    if (rec_time >= 10) {
        [recorder endRecording];
        [timer invalidate];
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"You recorded for too long!"...;
        return;
    }

    rec_time = rec_time + 1;

}
...
@end

Answer 3

This is an example from the iOS Programming Cookbook, i found it very useful and straigtforward. After starting to record, you call the stop function with delay of 10 seconds, when it stops recording it will automatically call the delegate method audioRecorderDidFinishRecording:successfully .

@implementation ViewController{

   AVAudioRecorder *recorder;
   AVAudioPlayer *player;
}   

- (IBAction)recordPauseTapped:(id)sender {
// Stop the audio player before recording
   if (player.playing) {
     [player stop];
   }

   if (!recorder.recording) {
      AVAudioSession *session = [AVAudioSession sharedInstance];
      [session setActive:YES error:nil];

      // Start recording
      [recorder record];

     [recordPauseButton setBackgroundImage:recordingImage forState:UIControlStateNormal];
     [self performSelector:@selector(stopRecording)
               withObject:self afterDelay:10.0f];

     } else {
       [recorder stop];

       AVAudioSession *audioSession = [AVAudioSession sharedInstance];
       [audioSession setActive:NO error:nil];
     }
} 

- (void)stopRecording {
  [recorder stop];

  AVAudioSession *audioSession = [AVAudioSession sharedInstance];
  [audioSession setActive:NO error:nil];
}

 - (void) audioRecorderDidFinishRecording:(AVAudioRecorder *)avrecorder    successfully:(BOOL)flag{
    NSLog(@"after 10 sec");
}