• (BOOL)switchPCMToMp3Path:(NSString *)mp3FilePath {
  NSString *filePath = self.filePath;

  NSFileManager *manager = [NSFileManager defaultManager];
  long long l = [[manager attributesOfItemAtPath:filePath error:nil] fileSize];
  if (!filePath ||l==0) {
  return NO;
  }

  @try {
  int read, write;

    FILE *pcm = fopen([filePath cStringUsingEncoding:1], "rb");//被转换的文件
    fseek(pcm, 4*1024, SEEK_CUR);
    FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], "wb");//转换后文件的存放位置
    
    int channel = kDefaultChannel;
    const int PCM_SIZE = 8192;
    const int MP3_SIZE = 8192;
    short int pcm_buffer[PCM_SIZE*channel];
    unsigned char mp3_buffer[MP3_SIZE];
    
    lame_t lame = lame_init();
    lame_set_num_channels(lame,channel);
    lame_set_in_samplerate(lame, kDefaultSampleRate);//录音16000
    //关键这一句！！！！！！！！！！！！
    lame_set_VBR_mean_bitrate_kbps(lame, 24);
  

// lame_set_VBR(lame, vbr_default);//压缩级别参数：
lame_set_brate(lame,32);/* 比特率 */

    lame_set_mode(lame,MONO);
    
    lame_set_quality(lame,2);/* 2=high  5 = medium  7=low */
    
    lame_init_params(lame);
    
    do {
        read = (int)fread(pcm_buffer, channel*sizeof(short int), PCM_SIZE, pcm);
        if (read == 0)
            write = lame_encode_flush(lame, mp3_buffer, MP3_SIZE);
        else {
            if (channel == 2) {
                write = lame_encode_buffer_interleaved(lame, pcm_buffer, read, mp3_buffer, MP3_SIZE);
            }else {//单声道走这
                write = lame_encode_buffer(lame, pcm_buffer, NULL, read, mp3_buffer, MP3_SIZE);
            }
            
        }
        
        fwrite(mp3_buffer, write, 1, mp3);
        
    } while (read != 0);
    lame_mp3_tags_fid(lame, mp3);
    lame_close(lame);
    fclose(mp3);
    fclose(pcm);
}
@catch (NSException *exception) {
    NSLog(@"转码异常：%@",[exception description]);
}
@finally {
    
}

return YES;

}