iOS的音频文件的格式转换示例

// 为pcm文件写入wav头
  (NSData*) writeWavHead:(NSData *)audioData {
 long sampleRate = [[self GetAudioRecorderSettingDict][AVSampleRateKey] longValue];
 long numOfChannelsKey = [[self GetAudioRecorderSettingDict][AVNumberOfChannelsKey] longValue];
 Byte waveHead[44];
 waveHead[0] = 'R';
 waveHead[1] = 'I';
 waveHead[2] = 'F';
 waveHead[3] = 'F';
 
 long totalDatalength = [audioData length]   44;
 waveHead[4] = (Byte)(totalDatalength & 0xff);
 waveHead[5] = (Byte)((totalDatalength >> 8) & 0xff);
 waveHead[6] = (Byte)((totalDatalength >> 16) & 0xff);
 waveHead[7] = (Byte)((totalDatalength >> 24) & 0xff);
 
 waveHead[8] = 'W';
 waveHead[9] = 'A';
 waveHead[10] = 'V';
 waveHead[11] = 'E';
 
 waveHead[12] = 'f';
 waveHead[13] = 'm';
 waveHead[14] = 't';
 waveHead[15] = ' ';
 
 waveHead[16] = 16; //size of 'fmt '
 waveHead[17] = 0;
 waveHead[18] = 0;
 waveHead[19] = 0;
 
 waveHead[20] = 1; //format
 waveHead[21] = 0;
 
 waveHead[22] = numOfChannelsKey; //chanel
 waveHead[23] = 0;
 
 waveHead[24] = (Byte)(sampleRate & 0xff);
 waveHead[25] = (Byte)((sampleRate >> 8) & 0xff);
 waveHead[26] = (Byte)((sampleRate >> 16) & 0xff);
 waveHead[27] = (Byte)((sampleRate >> 24) & 0xff);
 
 long byteRate = sampleRate * 2 * (16 >> 3);;
 waveHead[28] = (Byte)(byteRate & 0xff);
 waveHead[29] = (Byte)((byteRate >> 8) & 0xff);
 waveHead[30] = (Byte)((byteRate >> 16) & 0xff);
 waveHead[31] = (Byte)((byteRate >> 24) & 0xff);
 
 waveHead[32] = 2*(16 >> 3);
 waveHead[33] = 0;
 
 waveHead[34] = 16;
 waveHead[35] = 0;
 
 waveHead[36] = 'd';
 waveHead[37] = 'a';
 waveHead[38] = 't';
 waveHead[39] = 'a';
 
 long totalAudiolength = [audioData length];
 
 waveHead[40] = (Byte)(totalAudiolength & 0xff);
 waveHead[41] = (Byte)((totalAudiolength >> 8) & 0xff);
 waveHead[42] = (Byte)((totalAudiolength >> 16) & 0xff);
 waveHead[43] = (Byte)((totalAudiolength >> 24) & 0xff);
 
 NSMutableData *pcmData = [[NSMutableData alloc]initWithBytes:&waveHead length:sizeof(waveHead)];
 [pcmData appendData:audioData];
 
 
 return pcmData;
 // [pcmData writeToFile:kVoiceWav atomically:true];
 
}

//录音格式的设置
  (NSDictionary*)GetAudioRecorderSettingDict{
 NSDictionary *recordSetting = [[NSDictionary alloc] initWithObjectsAndKeys:
         [NSNumber numberWithFloat: 8000],AVSampleRateKey, //采样率
         [NSNumber numberWithInt: kAudioFormatLinearPCM],AVFormatIDKey,
         [NSNumber numberWithInt:16],AVLinearPCMBitDepthKey,//采样位数 默认 16
         [NSNumber numberWithInt: 2], AVNumberOfChannelsKey,//通道的数目
         nil];
 return recordSetting;
}

/**
 * 转换wav到amr
 *
 * @param wavPath wav文件路径
 * @param isDelete 转换成功后是否删除源文件
 *
 * @return NO 失败 YES成功
 */
  (BOOL) wav2Amr:(NSString *)wavPath isDeleteSourchFile:(BOOL)isDelete;
 
/**
 * 转换amr到wav
 *
 * @param amrPath amr文件路径
 * @param isDelete 转换成功后是否删除源文件
 *
 * @return NO 失败 YES成功
 */
  (BOOL) amr2Wav:(NSString *)amrPath isDeleteSourchFile:(BOOL)isDelete;
 
/**
 * 转换pcm到mp3
 *
 * @param pcmPath pcm文件路径
 * @param isDelete 转换成功后是否删除源文件
 *
 * @return NO 失败 YES成功
 */
  (BOOL) pcm2Mp3: (NSString *)pcmPath isDeleteSourchFile:(BOOL)isDelete;
/**
 * 转换pcm到wav
 *
 * @param pcmPath pcm文件路径
 * @param isDelete 转换成功后是否删除源文件
 *
 * @return NO 失败 YES成功
 */
  (BOOL) pcm2Wav: (NSString *)pcmPath isDeleteSourchFile:(BOOL)isDelete;
 
/**
 * 转换pcm到amr
 *
 * @param pcmPath pcm文件路径
 * @param isDelete 转换成功后是否删除源文件
 *
 * @return NO 失败 YES成功
 */
  (BOOL) pcm2Amr:(NSString *)pcmPath isDeleteSourchFile:(BOOL)isDelete;
 
/**
 * 为pcm文件写入wav头 
 */
  (NSData*) writeWavHead:(NSData *)audioData;
void conventToMp3(NSString *pcmFile,NSString *mp3File);
 
/**
 录音格式设置,转换的时候需要获取.(如:采样率、采样位数、通道的数目)
 建议使用此设置，如有修改，则转换amr时也要对应修改参数，比较麻烦
 
 @returns 录音设置
 */
  (NSDictionary*)GetAudioRecorderSettingDict;