项目名：SpeakHere
功能：录制并播放用户录制的音频

框架：AVFoundation.framework

实现步骤：
以下例子用到了AVAudioRecorder和AVAudioPlay来录制和播放音频，并且预先设置了一系列音频参数及保存路径。AVAudioRecorder和AVAudioPlay提供了相比openAL更为便捷的录音和播放方式，便于实现一些简单的录音和播放功能。
1. 设置音频参数及保存路径

 1    NSNumber *sampleRate, *formatId, *numberOfChannels, *audioQuality;
 2         
 3 // recording file path
 4    filePath = [NSHomeDirectory() stringByAppendingPathComponent: @"Documents/recording.caf"];
 5         
 6 // set up record settings
 7    sampleRate = [NSNumber numberWithFloat: 44100.0];
 8    formatId = [NSNumber numberWithInt: kAudioFormatAppleLossless];
 9    numberOfChannels = [NSNumber numberWithInt: 1];
10    audioQuality = [NSNumber numberWithInt: AVAudioQualityMax];
11 // save settings in NSDictionary
12    NSDictionary *recordSettings = [[NSDictionary alloc] initWithObjectsAndKeys: sampleRate, AVSampleRateKey, formatId, AVFor            matIDKey, numberOfChannels, AVNumberOfChannelsKey, audioQuality, AVEncoderAudioQualityKey, nil];

 



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2. 开始和停止录音

// init recorder
recorder = [[AVAudioRecorder alloc] initWithURL: [NSURL fileURLWithPath:filePath] settings: recordSettings error: nil]; 
[recorder record];
[recorder stop];



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3. 开始和停止播放

1 player = [[AVAudioPlayer alloc] initWithContentsOfURL: [NSURL fileURLWithPath:filePath] error: nil];
2 [player play];
3 [player stop];



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