最近准备做一个关于录音和播放的项目！查了一些资料，很简单的做了一个，下面我就分享一下iPhone的录音和播放的使用心得。
iPhone的录音和播放使用到了media层的内容，media层处于cocoa层之下，用到的很大一部分都是c语言的结构。
1、引入框架。
#import <AVFoundation/AVFoundation.h>
2、创建录音项。
- (void) prepareToRecord

{

AVAudioSession *audioSession = [AVAudioSession sharedInstance];

NSError *err = nil;

[audioSession setCategory :AVAudioSessionCategoryPlayAndRecord error:&err];

if(err){

NSLog(@"audioSession: %@ %d %@", [err domain], [err code], [[err userInfo] description]);

return;

}

[audioSession setActive:YES error:&err];

err = nil;

if(err){

NSLog(@"audioSession: %@ %d %@", [err domain], [err code], [[err userInfo] description]);

return;

}

recordSetting = [[NSMutableDictionary alloc] init];

[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey:AVFormatIDKey];

[recordSetting setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey];

[recordSetting setValue:[NSNumber numberWithInt: 2] forKey:AVNumberOfChannelsKey];

[recordSetting setValue :[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];

[recordSetting setValue :[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey];

[recordSetting setValue :[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey];

// Create a new dated file

NSDate *now = [NSDate dateWithTimeIntervalSinceNow:0];

NSString *caldate = [now description];

recorderFilePath = [[NSString stringWithFormat:@"%@/%@.caf", DOCUMENTS_FOLDER, caldate] retain];

NSURL *url = [NSURL fileURLWithPath:recorderFilePath];

err = nil;

recorder = [[ AVAudioRecorder alloc] initWithURL:url settings:recordSetting error:&err];

if(!recorder){

NSLog(@"recorder: %@ %d %@", [err domain], [err code], [[err userInfo] description]);

UIAlertView *alert =

[[UIAlertView alloc] initWithTitle: @"Warning"

message: [err localizedDescription]

delegate: nil

cancelButtonTitle:@"OK"

otherButtonTitles:nil];

[alert show];

[alert release];

return;

}

//prepare to record

[recorder setDelegate:self];

[recorder prepareToRecord];

recorder.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;

}

}

以上这个方法就是创建了录音项，其中包括录音的路径和一些音频属性，但只是准备录音还没有录，如果要录的话还要加入以下的方法：
-(void)startrecorder

{

[recorder record];

}

这样就在我们创建的路径下开始了录音。完成录音很简单：

- (void) stopRecording{

[recorder stop];

}

这里顺便提一下录音的代理方法：

- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *) aRecorder successfully:(BOOL)flag

{

NSLog(@"recorder successfully");

UIAlertView *recorderSuccessful = [[UIAlertView alloc] initWithTitle:@"" message:@"录音成功"delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

[recorderSuccessful show];

[recorderSuccessful release];

}

- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)arecorder error:(NSError *)error

{

btnRecorder.enabled = NO;

UIAlertView *recorderFailed = [[UIAlertView alloc] initWithTitle:@"" message:@"发生错误"delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

[recorderFailed show];

[recorderFailed release];

}

以上两个代理方法分别指定了录音的成功或失败。

录音中有一个的录音对象有一个averagePowerForChannel和peakPowerForChannel的属性分别为声音的最高振幅和平均振幅，有了他们就可以做一个动态的振幅的录音效果。

- (void) updateAudioDisplay {

if (isStart == NO) {

currentTimeLabel.text = @"--:--";

} else {

double currentTime = recorder.currentTime;

currentTimeLabel.text = [NSString stringWithFormat: @"d:d",

(int) currentTime/60,

(int) currentTime%60];

//START:code.RecordViewController.setlevelmeters

[recorder updateMeters];

[leftLevelMeter setPower: [recorder averagePowerForChannel:0]

peak: [recorder peakPowerForChannel: 0]];

if (! rightLevelMeter.hidden) {

[rightLevelMeter setPower: [recorder averagePowerForChannel:1]

peak: [recorder peakPowerForChannel: 1]];

}

//END:code.RecordViewController.setlevelmeters

}

}

以上就是录音相关的内容。

下面说一下播放的方法：

void SystemSoundsDemoCompletionProc (

SystemSoundID  soundID,

void           *clientData)

{

AudioServicesDisposeSystemSoundID (soundID);

((AudioRecorderPlayerAppDelegate*)clientData).statusLabel.text = @"Stopped";

};

-(void)playAudio

{

//START:code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound

// create a system sound id for the selected row

SystemSoundID soundID;

OSStatus err = kAudioServicesNoError;

// special case: vibrate//震动

//soundID = kSystemSoundID_Vibrate; //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.vibratesystemsound"/>

// find corresponding CAF file

//NSString *cafName = [NSString stringWithFormat: @"%@",recorderFilePath]; //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.rowtonumberstring"/>

NSURL *url = [NSURL fileURLWithPath:recorderFilePath];

//NSString *cafPath =

//[[NSBundle mainBundle] pathForResource:cafName ofType:@"caf"]; //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.findcafinbundle"/>

//NSURL *cafURL = [NSURL fileURLWithPath:url]; //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.fileurlwithpath"/>

err = AudioServicesCreateSystemSoundID((CFURLRef) url, &soundID); //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.createsystemsound"/>

//END:code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound

//START:code.SystemSoundsDemo.SystemSoundsDemoViewController.registercompletionprocandplaysound

if (err == kAudioServicesNoError) {

// set up callback for sound completion

err = AudioServicesAddSystemSoundCompletion //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.addcompletionproc"/>

(soundID,// sound to monitor

NULL,// run loop (NULL==main)

NULL,// run loop mode (NULL==default)

SystemSoundsDemoCompletionProc, // callback function //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.completionprocroutine"/>

self // data to provide on callback

); //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.addcompletionprocend"/>

statusLabel.text = @"Playing"; //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.setlabel"/>

AudioServicesPlaySystemSound (soundID); //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.playsound"/>

}

if (err != kAudioServicesNoError) { //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.errorblockstart"/>

CFErrorRef error = CFErrorCreate(NULL, kCFErrorDomainOSStatus, err, NULL); //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.createcferror"/>

NSString *errorDesc = (NSString*) CFErrorCopyDescription (error); //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.copycferrordescription"/>

UIAlertView *cantPlayAlert =

[[UIAlertView alloc] initWithTitle:@"Cannot Play:"

message: errorDesc

delegate:nil

cancelButtonTitle:@"OK"

otherButtonTitles:nil];

[cantPlayAlert show];

[cantPlayAlert release];

[errorDesc release]; //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.releaseerrordescription"/>

CFRelease (error); //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.releaseerror"/>

} //<label id="code.SystemSoundsDemo.SystemSoundsDemoViewController.createsystemsound.errorblockend"/>

//END:code.SystemSoundsDemo.SystemSoundsDemoViewController.registercompletionprocandplaysound

}

通过以上的方法就应该能够实现播放，播放的时候也是可以加入振幅过程的，大家可以试试！这样一个iPhone录音机就做好了！哈哈