iOS - Overwrite the particular audio recording In specific time - iphone

Question

Hi I need to develop an app that can record, play, stop and overwrite audio. I have done the Recording by using AvAudioRecorder:
NSDictionary *audioSettings = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithFloat: 44100],AVSampleRateKey,
[NSNumber numberWithInt: kAudioFormatLinearPCM],AVFormatIDKey,
[NSNumber numberWithInt: 2],AVNumberOfChannelsKey,
[NSNumber numberWithInt: AVAudioQualityLow], AVEncoderAudioQualityKey,
nil];
self.audioRecorder = [[AVAudioRecorder alloc]
initWithURL:audioFileURL
settings:audioSettings
error:nil];
[sliderTimer invalidate];
[self.audioRecorder record];
sliderTimer = [NSTimer scheduledTimerWithTimeInterval:0.2
target:self
selector:#selector(updateSlider)
userInfo:nil repeats:YES];
...and playback is done using AVplayer.
But I dont know how to overwrite the recording. This the outline of my overwrite implementation:
Stop Recording
Move the slider position to the particular point
Then, start recording.
This is the functionality to overwrite the previous recordings.
So, As per the steps I have written
[self.audioRecorder stop];
[[self audioSlider] setValue:self.audioSlider.value animated:YES];
[self.audioRecorder recordAtTime:self.audioSlider.value forDuration:self.audioSlider.maximumValue];
...but its not working. Instead, they totally re-record the file. Could any body help me for this critical situation.

Answer 1

Create audioSession object,its upto you whether you want to activate or deactivate your app’s audio session.(AVAudioSession)
audioSession = [AVAudioSession sharedInstance];
[audioSession setCategory :AVAudioSessionCategoryPlayAndRecord error:&err];
if(err) {
NSLog(#"audioSession: %# %d %#", [err domain], [err code], [[err userInfo] description]);
return;
}
[audioSession setActive:YES error:&err];
Start recording proces,
-startRecording
{
[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatAppleIMA4] forKey:AVFormatIDKey];
// We can use 44100, 32000, 24000, 16000 or 12000 depending on sound quality
[recordSetting setValue:[NSNumber numberWithFloat:32000.0] forKey:AVSampleRateKey];
// We can use 2(if using additional h/w) or 1 (iPhone only has one microphone)
[recordSetting setValue:[NSNumber numberWithInt: 1] forKey:AVNumberOfChannelsKey];
mediaPath = [[NSString stringWithFormat:#"%#/myVoice.mp3", DOCUMENTS_FOLDER] retain];//where you want to save your recorded audio.
NSURL *url = [NSURL fileURLWithPath:mediaPath];
err = nil;
NSData *audioData = [NSData dataWithContentsOfFile:[url path] options: 0 error:&err];
recorder = [[ AVAudioRecorder alloc] initWithURL:url settings:recordSetting error:&err];
[recorder setDelegate:self];
[recorder prepareToRecord];
recorder.meteringEnabled = YES;
BOOL audioHWAvailable = audioSession.inputAvailable;
if (! audioHWAvailable) {
UIAlertView *cantRecordAlert = [[UIAlertView alloc] initWithTitle: #"Warning"
message: #"Audio input hardware not available"
delegate: nil cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[cantRecordAlert show];
[cantRecordAlert release];
return;
}
[recorder record];
}
Pause recording:
-pauseRecording
{
[recorder pause];
//[recorder updateMeters];
}
Again resume the process..audiosession will do it for you...
-resumerecording
{
[recorder record];
//[recorder updateMeters];
}
EDIT: [recorder updateMeters]; should be called periodically which refreshes the average and peak power values for all channels of an audio recorder.
You can use timer for that.
For example:
NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:#selector(updateAudioDisplay) userInfo:NULL repeats:YES];
-(void)updateAudioDisplay
{
if (!recorder.isRecording)
{
[recorder updateMeters];
}
else
{
if (recorder == nil) {
//recording is not yet started
}
else
{
//paused
}
}
}
You can download the sample code from here.