avaudiorecorder 在开始录制之前显示延迟 3 秒 [重复]

Question

可能重复：
Delay in Recording using avaudiorecorder

我正在使用 ios5 在 Xcode4 上运行应用程序，但遇到一个问题，从按下录制按钮到实际开始录制有 3 秒的延迟。我已经搜索了所有地方，但没有找到任何适合我的解决方案。

这里是代码

    -(void) recordBtnClick:(UIButton *)sender

  {    

      if (!recordBtn && !playBtn)
        {   
           NSLog(@"recording pressed");

           [recordButton setBackgroundImage:[UIImage imageNamed:@"stop.png"]               forState:UIControlStateNormal];

           recordBtn=YES;

         //startRecording;

       // Init audio with record capability
       AVAudioSession *audioSession = [AVAudioSession sharedInstance];
         [audioSession setCategory:AVAudioSessionCategoryRecord error:nil];

        NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc]  initWithCapacity:10];

     if(recordEncoding == ENC_PCM)
       {
        [recordSettings setObject:[NSNumber numberWithInt: kAudioFormatLinearPCM] forKey: AVFormatIDKey];
        [recordSettings setObject:[NSNumber numberWithFloat:16000.0] forKey: AVSampleRateKey];
        [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey];
        [recordSettings setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];
        [recordSettings setObject:[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey];
        [recordSettings setObject:[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey];   
    }
    else
    {
        NSNumber *formatObject;

        switch (recordEncoding) {
            case (ENC_AAC): 
                formatObject = [NSNumber numberWithInt: kAudioFormatMPEG4AAC];
                break;
            case (ENC_ALAC):
                formatObject = [NSNumber numberWithInt: kAudioFormatAppleLossless];
                break;
            case (ENC_IMA4):
                formatObject = [NSNumber numberWithInt: kAudioFormatAppleIMA4];
                break;
            case (ENC_ILBC):
                formatObject = [NSNumber numberWithInt: kAudioFormatiLBC];
                break;
            case (ENC_ULAW):
                formatObject = [NSNumber numberWithInt: kAudioFormatULaw];
                break;
            default:
                formatObject = [NSNumber numberWithInt: kAudioFormatAppleIMA4];
        }

        [recordSettings setObject:formatObject forKey: AVFormatIDKey];
        [recordSettings setObject:[NSNumber numberWithFloat:44100.0] forKey: AVSampleRateKey];
        [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey];
        [recordSettings setObject:[NSNumber numberWithInt:12800] forKey:AVEncoderBitRateKey];
        [recordSettings setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];
        [recordSettings setObject:[NSNumber numberWithInt: AVAudioQualityHigh] forKey: AVEncoderAudioQualityKey];
    }
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *recDir = [paths objectAtIndex:0];
    NSURL *url = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@/audio%d.wav",recDir,nextCount]];

    NSError *error = nil;
    audioRecorder = [[ AVAudioRecorder alloc] initWithURL:url settings:recordSettings error:&error];
    audioRecorder.delegate=self;
    if(!audioRecorder){
        NSLog(@"recorder: %@ %d %@", [error domain], [error code], [[error userInfo] description]);
        UIAlertView *alert =
        [[UIAlertView alloc] initWithTitle: @"Warning"
                                   message: [error localizedDescription]
                                  delegate: nil
                         cancelButtonTitle:@"OK"
                         otherButtonTitles:nil];
        [alert show];
        [alert release];
        return;
    }

    //prepare to record
    [audioRecorder prepareToRecord];
   //audioRecorder.meteringEnabled = YES;

    BOOL audioHWAvailable = audioSession.inputIsAvailable;
    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;
    }
    [audioRecorder recordForDuration:(NSTimeInterval) 25];


    NSLog(@"recording");
    // ---------------- record code finished ----------------//
  }else{
    [recordButton setBackgroundImage:[UIImage imageNamed:@"record.png"] forState:UIControlStateNormal];
    recordBtn=NO;
    [audioRecorder stop];
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryPlayback error:nil];


  }

 }

Answer 1

在显示应用的录制按钮之前，请做好录制准备和所需的所有初始化。