C++解析wav文件方法介紹

更新時(shí)間：2022年09月05日 09:24:43 作者：略游

最近將項(xiàng)目改為跨平臺(tái)，于是音頻模塊從微軟的XAudio2改用OpenAL庫(kù)。之前使用MSDN的代碼，所以現(xiàn)在改為了C++標(biāo)準(zhǔn)的寫(xiě)法，適用性更廣

一、前言

一開(kāi)始本來(lái)在網(wǎng)上找代碼，不過(guò)改了好幾個(gè)都不是很好用。因?yàn)楹芏鄔av文件的fmt塊后面并不是data塊，經(jīng)常還帶有其他塊，正確的方法應(yīng)該是按MSDN的方法，找到data塊再讀取。

二、接口

最后接口如下：

class AudioReader
{
public:
	struct PCM
	{
		int _numChannel;//通道數(shù) 1,2 AL_FORMAT_MONO8,AL_FORMAT_STEREO8
		int _bitPerSample;//采樣數(shù) 8,16 
		byte* _data;
		size_t _size;
		size_t _freq;//采樣率
		void Delete() { delete[] _data; }
	}; 
	static bool ReadWAV(string_view path_name, PCM& pcm);
};

三、具體步驟

打開(kāi)文件，這里就是普通的文件流，按二進(jìn)制、只讀打開(kāi)文件即可：

ifstream ifs;
if (!g_file->GetFile(path_name, ifs))
{
	debug_err(format("打開(kāi)文件失?。簕}", path_name));
	return false;
}

查找riff塊：

uint32_t dwChunkSize;
uint32_t dwChunkPosition;
//查找riff塊
FindChunk(ifs, fourccRIFF, dwChunkSize, dwChunkPosition);
uint32_t filetype;
ReadChunkData(ifs, &filetype, sizeof(uint32_t), dwChunkPosition);
if (filetype != fourccWAVE)
{
	debug_err(format("匹配標(biāo)記失?。╢ourccWAVE）：{}", path_name));
	return false;
}

其中fourccRIFF和fourccWAVE是我們定義的標(biāo)記，也就是處理了下大小端，如下：

#ifdef DND_ENDIAN_BIG
#define fourccRIFF 'RIFF'
#define fourccDATA 'data'
#define fourccFMT 'fmt '
#define fourccWAVE 'WAVE'
#define fourccXWMA 'XWMA'
#define fourccDPDS 'dpds'
#endif
#ifdef DND_ENDIAN_LITTLE
#define fourccRIFF 'FFIR'
#define fourccDATA 'atad'
#define fourccFMT ' tmf'
#define fourccWAVE 'EVAW'
#define fourccXWMA 'AMWX'
#define fourccDPDS 'sdpd'
#endif

而FindChunk和ReadChunkData兩個(gè)函數(shù)，分別是查找一個(gè)塊，和讀取一個(gè)塊。代碼實(shí)現(xiàn)有點(diǎn)長(zhǎng)，可以參考后面我給出的完整源碼。

接著，查找并讀取fmt塊，這個(gè)塊描述了wav文件的音頻屬性，結(jié)構(gòu)如下（部分字段會(huì)用到）：

//16字節(jié)
struct WAVEFormat 
{
	int16_t audioFormat;
	int16_t numChannels;
	int32_t sampleRate;
	int32_t byteRate;
	int16_t blockAlign;
	int16_t bitsPerSample;
};

//查找fmt塊
if (!FindChunk(ifs, fourccFMT, dwChunkSize, dwChunkPosition))
{
	debug_err(format("查找塊失?。╢ourccFMT）：{}", path_name));
	return false;
}
//讀wave信息
WAVEFormat wave_format;
if (!ReadChunkData(ifs, &wave_format, dwChunkSize, dwChunkPosition))
{
	debug_err(format("讀取塊失敗（wave_format）：{}", path_name));
	return false;
};

接下來(lái)查找data塊，根據(jù)返回的大小分配內(nèi)存：

//查找音頻數(shù)據(jù)
if (!FindChunk(ifs, fourccDATA, dwChunkSize, dwChunkPosition))
{
	debug_err(format("查找塊失?。╢ourccDATA）：{}", path_name));
	return false;
};
pcm._data = new byte[dwChunkSize];

然后讀取data塊，將數(shù)據(jù)讀取到我們分配的內(nèi)存pcm._data。然后記錄下一些重要的字段。由于OpenaAL不能直接播放32位（只8、16）的數(shù)據(jù)，這里簡(jiǎn)單返回失敗。

if (!ReadChunkData(ifs, pcm._data, dwChunkSize, dwChunkPosition))
{
	debug_err(format("讀取塊失敗（pcm數(shù)據(jù)）：{}", path_name));
	pcm.Delete();
	return false;
};
pcm._size = dwChunkSize;
pcm._numChannel = wave_format.numChannels;
pcm._bitPerSample = wave_format.bitsPerSample;
pcm._freq = wave_format.sampleRate;
if (pcm._bitPerSample == 32)
{
	debug_err(format("不支持32位：{}", path_name));
	pcm.Delete();
	return false;
}
return true;

四、完整源碼

可以此處獲取最新的源碼（我將來(lái)會(huì)添加ogg格式的解析），也可以用下面的：傳送門(mén)

//.h
class AudioReader
{
public:
	struct PCM
	{
		int _numChannel;//通道數(shù) 1,2 AL_FORMAT_MONO8,AL_FORMAT_STEREO8
		int _bitPerSample;//采樣數(shù) 8,16 
		byte* _data;
		size_t _size;
		size_t _freq;//采樣率
		void Delete() { delete[] _data; }
	}; 
	static bool ReadWAV(string_view path_name, PCM& pcm);
};
//16字節(jié)
struct WAVEFormat 
{
	int16_t audioFormat;
	int16_t numChannels;
	int32_t sampleRate;
	int32_t byteRate;
	int16_t blockAlign;
	int16_t bitsPerSample;
};
//.cpp
#ifdef DND_ENDIAN_BIG
#define fourccRIFF 'RIFF'
#define fourccDATA 'data'
#define fourccFMT 'fmt '
#define fourccWAVE 'WAVE'
#define fourccXWMA 'XWMA'
#define fourccDPDS 'dpds'
#endif
#ifdef DND_ENDIAN_LITTLE
#define fourccRIFF 'FFIR'
#define fourccDATA 'atad'
#define fourccFMT ' tmf'
#define fourccWAVE 'EVAW'
#define fourccXWMA 'AMWX'
#define fourccDPDS 'sdpd'
#endif
bool FindChunk(ifstream& ifs, uint32_t fourcc, uint32_t& size, uint32_t& pos)
{
	bool ret = true;
	ifs.seekg(0);
	if (ifs.fail())
		return false;
	uint32_t dwChunkType;
	uint32_t dwChunkDataSize;
	uint32_t dwRIFFDataSize = 0;
	uint32_t dwFileType;
	uint32_t bytesRead = 0;
	uint32_t dwOffset = 0;
	while (ret)
	{
		ifs.read((char*)&dwChunkType, sizeof(uint32_t));
		ifs.read((char*)&dwChunkDataSize, sizeof(uint32_t));
		switch (dwChunkType)
		{
		case fourccRIFF:
			dwRIFFDataSize = dwChunkDataSize;
			dwChunkDataSize = 4;
			ifs.read((char*)&dwFileType, sizeof(uint32_t));
			break;
		default:
			ifs.seekg(dwChunkDataSize, std::ios::cur);
			if (ifs.fail())
				return false;
			break;
		}
		dwOffset += sizeof(uint32_t) * 2;
		if (dwChunkType == fourcc)
		{
			size = dwChunkDataSize;
			pos = dwOffset;
			return true;
		}
		dwOffset += dwChunkDataSize;
		if (bytesRead >= dwRIFFDataSize)
			return false;
	}
	return true;
}
bool ReadChunkData(ifstream& ifs, void* buffer, uint32_t size, uint32_t pos)
{
	ifs.seekg(pos);
	if (ifs.fail())
		return false;
	ifs.read((char*)buffer, size);
	return true;
}
bool AudioReader::ReadWAV(string_view path_name, PCM& pcm)
{
	ifstream ifs;
	if (!g_file->GetFile(path_name, ifs))
	{
		debug_err(format("打開(kāi)文件失敗：{}", path_name));
		return false;
	}
	uint32_t dwChunkSize;
	uint32_t dwChunkPosition;
	//查找riff塊
	FindChunk(ifs, fourccRIFF, dwChunkSize, dwChunkPosition);
	uint32_t filetype;
	ReadChunkData(ifs, &filetype, sizeof(uint32_t), dwChunkPosition);
	if (filetype != fourccWAVE)
	{
		debug_err(format("匹配標(biāo)記失?。╢ourccWAVE）：{}", path_name));
		return false;
	}
	//查找fmt塊
	if (!FindChunk(ifs, fourccFMT, dwChunkSize, dwChunkPosition))
	{
		debug_err(format("查找塊失?。╢ourccFMT）：{}", path_name));
		return false;
	}
	//讀wave信息
	WAVEFormat wave_format;
	if (!ReadChunkData(ifs, &wave_format, dwChunkSize, dwChunkPosition))
	{
		debug_err(format("讀取塊失敗（wave_format）：{}", path_name));
		return false;
	};
	//查找音頻數(shù)據(jù)
	if (!FindChunk(ifs, fourccDATA, dwChunkSize, dwChunkPosition))
	{
		debug_err(format("查找塊失?。╢ourccDATA）：{}", path_name));
		return false;
	};
	pcm._data = new byte[dwChunkSize];
	if (!ReadChunkData(ifs, pcm._data, dwChunkSize, dwChunkPosition))
	{
		debug_err(format("讀取塊失?。╬cm數(shù)據(jù)）：{}", path_name));
		pcm.Delete();
		return false;
	};
	pcm._size = dwChunkSize;
	pcm._numChannel = wave_format.numChannels;
	pcm._bitPerSample = wave_format.bitsPerSample;
	pcm._freq = wave_format.sampleRate;
	if (pcm._bitPerSample == 32)
	{
		debug_err(format("不支持32位：{}", path_name));
		pcm.Delete();
		return false;
	}
	return true;
}

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