实现一个PHP WAV接合方案

WAV PCM文件的最大优点在于，你无需进行任何绑定操作，就能将来自两个文件的二进制音频数据连接起来。你只需把其中一个文件的二进制数据粘合到另一个文件的末尾，再调整一下Subchunk2Size值，即可实现两个文件的接合。唯一的缺点是这两个文件的格式必须相同；在本例中，不涉及问题。

当解析音频文件时，先将二进制音频数据读入一个缓冲数组中，然后再将另一个文件的数据读到这个数组的末端。重复这一过程直到所有的文件都被读取完毕。创建一个FILESTRUCT结构，填入格式信息，调整Subchunk2Size值，将Data成员设为缓冲数组，将FILESTRUCT写为需要的输出格式。对于基于PHP的Web发布系统，其输出为标准输出。以下为示范代码：

function StitchFiles(&$fsFile, &$sFiles) { $fsFiles = array(); //FILESTRUCT $lFileSize = 0; $lOffset = 0; $bData = array(); //byte for ($i = 0; $i < count($sFiles); $i++) { $fsFiles[$i] = new FILESTRUCT(); SetFile($fsFiles[$i], $sFiles[$i]); $lSize = CalcLittleEndianValue($fsFiles[$i]->Subchunk2Size); $lFileSize = $lFileSize + $lSize; $bData = array_merge($bData, $fsFiles[$i]->Data); $lOffset = $lOffset + $lSize; } $fsFile->ChunkID = $GLOBALS["ChunkID_"]; $fsFile->ChunkSize = GetLittleEndianByteArray(36 + $lFileSize); $fsFile->Format = $GLOBALS["FileFormat_"]; $fsFile->Subchunk1ID = $GLOBALS["Subchunk1ID_"]; $fsFile->Subchunk1Size = array(0x10, 0x0, 0x0, 0x0); $fsFile->AudioFormat = $GLOBALS["AudioFormat_"]; $fsFile->NumChannels = $GLOBALS["Stereo_"]; $fsFile->SampleRate = $GLOBALS["SampleRate_"]; $fsFile->ByteRate = GetLittleEndianByteArray( CalcLittleEndianValue($GLOBALS["SampleRate_"]) * CalcLittleEndianValue($GLOBALS["Stereo_"]) * (CalcLittleEndianValue($GLOBALS["BitsPerSample_"]) / 8)); $fsFile->BlockAlign = array_splice(GetLittleEndianByteArray(CalcLittleEndianValue($GLOBALS["Stereo_"] ) * (CalcLittleEndianValue($GLOBALS["BitsPerSample_"]) / 8)), 0, 2); $fsFile->BitsPerSample = $GLOBALS["BitsPerSample_"]; $fsFile->Subchunk2ID = $GLOBALS["Subchunk2ID_"]; $fsFile->Subchunk2Size = GetLittleEndianByteArray($lFileSize); $fsFile->Data = $bData; }

本调用的第一个参数是对FILESTRUCT对象的引用。第二个参数是对一列文件名字符串的引用。在每次for循环中，我都将列表中的一个文件名载入一个FILESTRUCT中，然后再将每一个FILESTRUCT的Data属性提取出来，并合并到一个现有的缓冲区中。完成以上操作后，我通过一个事先声明的全局变量对FILESTRUCT参数对象的属性进行设定，然后改变Subchunk2Size属性，并将Data属性设为新的缓冲区。

你可能注意到，我使用了一些功能函数来填充FILESTRUCT结构、计算来自little endian字节数组的数值、创建little endian字节数组和拆分字符串为二进制数组。以下为这些函数：

function SetFile(&$fsFile_, $sFileName) { $lSize = 1; if (file_exists($sFileName)) { $fil = fopen($sFileName, "rb"); $contents = fread($fil, count($fsFile_->ChunkID)); $fsFile_->ChunkID = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->ChunkSize)); $fsFile_->ChunkSize = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->Format)); $fsFile_->Format = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->Subchunk1ID)); $fsFile_->Subchunk1ID = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->Subchunk1Size)); $fsFile_->Subchunk1Size = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->AudioFormat)); $fsFile_->AudioFormat = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->NumChannels)); $fsFile_->NumChannels = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->SampleRate)); $fsFile_->SampleRate = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->ByteRate)); $fsFile_->ByteRate = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->BlockAlign)); $fsFile_->BlockAlign = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->BitsPerSample)); $fsFile_->BitsPerSample = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->Subchunk2ID)); $fsFile_->Subchunk2ID = bin_split($contents, 1); $contents = fread($fil, count($fsFile_->Subchunk2Size)); $fsFile_->Subchunk2Size = bin_split($contents, 1); $lSize = CalcLittleEndianValue($fsFile_->Subchunk2Size); $contents = fread($fil, $lSize); $fsFile_->Data = bin_split($contents, 1); fclose($fil); } } function CalcLittleEndianValue(&$bValue) { $lSize_ = 0; for ($iByte = 0; $iByte < count($bValue); $iByte++) { $lSize_ += ($bValue[$iByte] * pow(16, ($iByte * 2))); } return $lSize_; } function GetLittleEndianByteArray($lValue) { $running = 0; $b = array(0, 0, 0, 0); $running = $lValue / pow(16,6); $b[3] = floor($running); $running -= $b[3]; $running *= 256; $b[2] = floor($running); $running -= $b[2]; $running *= 256; $b[1] = floor($running); $running -= $b[1]; $running *= 256; $b[0] = round($running); return $b; } function bin_split($text, $c) { $arr = array(); $len = strlen($text); $a = 0; while($a < $len) { if ($a + $c > $len) { $c = $len - $a; } $arr[$a] = ord(substr($text, $a, $c)); $a += $c; } return $arr; }

为了实现这个类的功能，你可以创建一个CStitcher实例并调用StitchFiles()方法，以传递合适的参数：

$ChunkID_ = array(0x52, 0x49, 0x46, 0x46); //"RIFF" big endian
$FileFormat_ = array(0x57, 0x41, 0x56, 0x45); //"WAVE" big endian
$Subchunk1ID_ = array(0x66, 0x6D, 0x74, 0x20); //"fmt" big endian
$AudioFormat_ = array(0x1, 0x0); //PCM = 1 little endian
$Stereo_ = array(0x2, 0x0); //Stereo = 2 little endian
$Mono_ = array(0x1, 0x0); //Mono = 1 little endian
$SampleRate_ = array(0x44, 0xAC, 0x0, 0x0); //44100 little endian
$BitsPerSample_ = array(0x10, 0x0); //16 little endian
$Subchunk2ID_ = array(0x64, 0x61, 0x74, 0x61); //"data" big endian
$files = array("C:InetpubwwwrootTestPHP.wav",
"C:InetpubwwwrootTestPHP.wav");
$Stitcher = new CStitcher();
$file = new FILESTRUCT();
$Stitcher->StitchFiles($file, $files);

可用以下代码将二进制数据写到HTTP输出中：

header('Content-type: audio/x-wav', true); header('Content-Disposition: attachment;filename=stitch.wav'); foreach($file->ChunkID as $val) { print chr($val); } foreach($file->ChunkSize as $val) { print chr($val); } foreach($file->Format as $val) { print chr($val); } foreach($file->Subchunk1ID as $val) { print chr($val); } foreach($file->Subchunk1Size as $val) { print chr($val); } foreach($file->AudioFormat as $val) { print chr($val); } foreach($file->NumChannels as $val) { print chr($val); } foreach($file->SampleRate as $val) { print chr($val); } foreach($file->ByteRate as $val) { print chr($val); } foreach($file->BlockAlign as $val) { print chr($val); } foreach($file->BitsPerSample as $val) { print chr($val); } foreach($file->Subchunk2ID as $val) { print chr($val); } foreach($file->Subchunk2Size as $val) { print chr($val); } foreach($file->Data as $val) { print chr($val); }

以下是一段HTML代码，用于测试结果：

<html>
<head>
<script language="JavaScript">
function play_soundbyte() {
bgsound1.src = "wavstitch.php";
}
</script>
</head>
<bgsound id="bgsound1" loop="1">
<body>

<a href="javascript:play_soundbyte();">Click here to play soundbyte.</a>

</body>
</html>

如果你有兴趣学习更多关于WAV PCM f格式的知识，请访问我获得这类信息的网站。