录音(PCM格式)、播放、lame转码成MP3

引入下面两个库。lame是个第三方库。

#import <AVFoundation/AVFoundation.h>

#import "lame.framework/Headers/lame.h"

#pragma mark - 音频转码

/**
 *  音频转码，由 PCM 转码为 MP3
 */
- ( void )convertToMP3
{
    NSString * mp3FileName = @"sendRecord.mp3" ;
    NSString * documentPath = [ NSSearchPathForDirectoriesInDomains ( NSDocumentDirectory , NSUserDomainMask , YES ) lastObject ];
    NSString *mp3FilePath = [documentPath stringByAppendingPathComponent :mp3FileName];
    NSString * audioFilePath = [ NSString stringWithFormat : @"%@/audio.caf" , documentPath];
   
    NSLog ( @"audioPath:%@" , audioFilePath);
   
    @try {
        int read, write;
       
        FILE *pcm = fopen ([audioFilePath cStringUsingEncoding : 1 ], "rb" );  //source 被转换的音频文件位置
        fseek (pcm, 4 * 1024 , SEEK_CUR );                                   //skip file header
        FILE *mp3 = fopen ([mp3FilePath cStringUsingEncoding : 1 ], "wb" );  //output 输出生成的 Mp3 文件位置
       
        const int PCM_SIZE = 8192 ;
        const int MP3_SIZE = 8192 ;
        short int pcm_buffer[PCM_SIZE* 2 ];
        unsigned char mp3_buffer[MP3_SIZE];
       
        lame_t lame = lame_init ();
        lame_set_in_samplerate (lame, 11025.0 );
        lame_set_VBR (lame, vbr_default );
        lame_init_params (lame);
       
        do {
            read = fread (pcm_buffer, 2 * sizeof ( short int ), PCM_SIZE, pcm);
            if (read == 0 )
                write = lame_encode_flush (lame, mp3_buffer, MP3_SIZE);
            else
                write = lame_encode_buffer_interleaved (lame, pcm_buffer, read, mp3_buffer, MP3_SIZE);
           
            fwrite (mp3_buffer, write, 1 , mp3);
           
        } while (read != 0 );
       
        lame_close (lame);
        fclose (mp3);
        fclose (pcm);
    }
    @catch (NSException *exception) {
        NSLog ( @"%@" ,[exception description ]);
    }
    @finally
    {
        NSLog ( @"MP3 生成成功 :%@" , mp3FilePath);
    }
}

#pragma mark - 取得录音文件保存路径
/**
 *  取得录音原始文件保存路径
 *
 *  @return 录音原始文件路径
 */
- ( NSURL *)getSavePath{
    NSString *urlStr=[ NSSearchPathForDirectoriesInDomains ( NSDocumentDirectory , NSUserDomainMask , YES ) lastObject ];
    urlStr=[urlStr stringByAppendingPathComponent : @"audio.caf" ];
    NSURL *url=[ NSURL fileURLWithPath :urlStr];
    return url;
}

- ( NSString *)getSavePathToString{
    NSString *urlStr=[ NSSearchPathForDirectoriesInDomains ( NSDocumentDirectory , NSUserDomainMask , YES ) lastObject ];
    urlStr=[urlStr stringByAppendingPathComponent : @"audio.caf" ];
    return urlStr;
}

/**
 *  取得 MP3 文件保存路径
 *
 *  @return MP3 文件路径
 */
- ( NSURL *)getMP3Path
{
    // 播放 MP3
    NSString * mp3FileName = @"sendRecord.mp3" ;
    NSString * documentPath = [ NSSearchPathForDirectoriesInDomains ( NSDocumentDirectory , NSUserDomainMask , YES ) lastObject ];
    NSString *mp3FilePath = [documentPath stringByAppendingPathComponent :mp3FileName];
    return [ NSURL fileURLWithPath :mp3FilePath];
}

- ( NSString *)getMP3PathToString
{
    // 播放 MP3
    NSString * mp3FileName = @"sendRecord.mp3" ;
    NSString * documentPath = [ NSSearchPathForDirectoriesInDomains ( NSDocumentDirectory , NSUserDomainMask , YES ) lastObject ];
    NSString *mp3FilePath = [documentPath stringByAppendingPathComponent :mp3FileName];
    return mp3FilePath;
}

#pragma mark - 取得录音文件设置
/**
 *  取得录音文件设置
 *
 *  @return 录音设置
 */
-( NSDictionary *)getAudioSetting{
    NSMutableDictionary *dicM=[ NSMutableDictionary dictionary ];
    // 设置录音格式
    [dicM setObject : @( kAudioFormatLinearPCM ) forKey : AVFormatIDKey ];
    // 设置录音采样率， 8000 是电话采样率，对于一般录音已经够了
    [dicM setObject : @(11025.0) forKey : AVSampleRateKey ];
    // 设置通道 , 这里采用单声道
    [dicM setObject : @(2) forKey : AVNumberOfChannelsKey ];
    // 每个采样点位数 , 分为 8 、 16 、 24 、 32
    [dicM setObject : @(16) forKey : AVLinearPCMBitDepthKey ];
    // 是否使用浮点数采样
    //    [dicM setObject:@(YES) forKey:AVLinearPCMIsFloatKey];
    // 音频编码质量
    [dicM setObject : @( AVAudioQualityLow ) forKey : AVEncoderAudioQualityKey ];
    //.... 其他设置等
    return dicM;
}

#pragma mark - 懒加载
- ( AVAudioRecorder *)audioRecorder{
    if ( _audioRecorder == nil ) {
        // 录音相关
        AVAudioSession *audioSession=[ AVAudioSession sharedInstance ];
        // 设置为播放和录音状态，以便可以在录制完之后播放录音
        [audioSession setCategory : AVAudioSessionCategoryPlayAndRecord error : nil ];
        [audioSession setActive : YES error : nil ];
       
        // 创建录音文件保存路径
        NSURL * url = [ self getSavePath ];
        // 创建录音格式设置
        NSDictionary * setting = [ self getAudioSetting ];
        // 创建录音机
        NSError * error = nil ;
        _audioRecorder = [[ AVAudioRecorder alloc ] initWithURL :url settings :setting error :&error];
       
        _audioRecorder . delegate = self ;
        if (error) {
            NSLog ( @" 创建录音机对象时发生错误，错误信息： %@" , error. localizedDescription );
            return nil ;
        }
    }
    return _audioRecorder ;
}

/**
 *  创建播放器
 *
 *  @return 播放器
 */
- ( AVAudioPlayer *)audioPlayer{
    if ( _audioPlayer == nil ) {
        // 录音相关
        AVAudioSession *audioSession=[ AVAudioSession sharedInstance ];
        // 设置为播放和录音状态，以便可以在录制完之后播放录音
        [audioSession setCategory : AVAudioSessionCategoryPlayback error : nil ];
        [audioSession setActive : YES error : nil ];
        NSURL * url = [ self getSavePath ];
       
        NSError * error = nil ;
        _audioPlayer = [[ AVAudioPlayer alloc ] initWithContentsOfURL :url error :&error];
        _audioPlayer . volume = 1.0 ;
        _audioPlayer . numberOfLoops = 0 ;
        _audioPlayer . delegate = self ;
        [ _audioPlayer prepareToPlay ];
        if (error) {
            NSLog ( @" 创建播放器过程中发生错误，错误信息： %@" , error. localizedDescription );
            return nil ;
        }
    }
    return _audioPlayer ;

}