PCM是采样的原始音频数据, 是无压缩的原始数据, 给pcm添加wav的文件头, 就是wav文件, 所以wav也是一种无损的音频格式. 比pcm多44字节大小的头文件.
oc中给pcm添加wav头文件代码如下:
- (void)addWavHeaderForPcmData:(NSString *)filePath wavPath:(NSString *)wavFilePath {
FILE *fout;
short NumChannels = 1; //录音通道数
short BitsPerSample = 16; //线性采样位数
int SamplingRate = 16000; //录音采样率(Hz)
int numOfSamples = (int)[[NSData dataWithContentsOfFile:filePath] length];
int ByteRate = NumChannels*BitsPerSample*SamplingRate/8;
short BlockAlign = NumChannels*BitsPerSample/8;
int DataSize = NumChannels*numOfSamples*BitsPerSample/8;
int chunkSize = 16;
int totalSize = 46 + DataSize;
short audioFormat = 1;
if((fout = fopen([wavFilePath cStringUsingEncoding:1], "w")) == NULL) {
NSLog(@"Error opening out file ");
}
fwrite("RIFF", sizeof(char), 4,fout);
fwrite(&totalSize, sizeof(int), 1, fout);
fwrite("WAVE", sizeof(char), 4, fout);
fwrite("fmt ", sizeof(char), 4, fout);
fwrite(&chunkSize, sizeof(int),1,fout);
fwrite(&audioFormat, sizeof(short), 1, fout);
fwrite(&NumChannels, sizeof(short),1,fout);
fwrite(&SamplingRate, sizeof(int), 1, fout);
fwrite(&ByteRate, sizeof(int), 1, fout);
fwrite(&BlockAlign, sizeof(short), 1, fout);
fwrite(&BitsPerSample, sizeof(short), 1, fout);
fwrite("data", sizeof(char), 4, fout);
fwrite(&DataSize, sizeof(int), 1, fout);
fclose(fout);
NSMutableData *pamdata = [NSMutableData dataWithContentsOfFile:filePath];
NSFileHandle *handle;
handle = [NSFileHandle fileHandleForUpdatingAtPath:wavFilePath];
[handle seekToEndOfFile];
[handle writeData:pamdata];
[handle closeFile];
}
