php - 在 PHP 中生成 wav 音调

Question

我想在 php 中生成一个正弦波。但是构建我的 wav 我需要以字节为单位给出值。我不知道该怎么做:

这是我的代码:

$freqOfTone = 440;
$sampleRate = 44100;
$samplesCount = 80000;

$amplitude = 0.25 * 32768;
$w = 2 * pi() * $freqOfTone / $sampleRate;

//$dataArray = new


$text = "RIFF"
."80036"
."WAVE"
."fmt "
."16"
."1"
."1"
."44100"
."44100"
."1"
."8"
."data"
."80000";

for ($n = 0; $n < $samplesCount; $n++)
{
    $text .= (int)($amplitude *  sin($n * $w)); 
}


$myfile = fopen("sine.wav", "w") or die("Unable to open file!");

fwrite($myfile, $text);

fclose($myfile);

Answer 1

问题是您的算法将数字写为文本。而 .wav文件对数据二进制进行编码。

例如，您可以使用 pack 对数据进行分组。

$freqOfTone = 440;
$sampleRate = 44100;
$samplesCount = 80000;

$amplitude = 0.25 * 32768;
$w = 2 * pi() * $freqOfTone / $sampleRate;

$samples = array();
for ($n = 0; $n < $samplesCount; $n++) {
    $samples[] = (int)($amplitude *  sin($n * $w));
}

$srate = 44100; //sample rate
$bps = 16; //bits per sample
$Bps = $bps/8; //bytes per sample /// I EDITED

$str = call_user_func_array("pack",
    array_merge(array("VVVVVvvVVvvVVv*"),
        array(//header
            0x46464952, //RIFF
            160038,      //File size
            0x45564157, //WAVE
            0x20746d66, //"fmt " (chunk)
            16, //chunk size
            1, //compression
            1, //nchannels
            $srate, //sample rate
            $Bps*$srate, //bytes/second
            $Bps, //block align
            $bps, //bits/sample
            0x61746164, //"data"
            160000 //chunk size
        ),
        $samples //data
    )
);
$myfile = fopen("sine.wav", "wb") or die("Unable to open file!");
fwrite($myfile, $str);
fclose($myfile);

这会产生这个 file .

请注意，您不能只是重复使用上面的 header 。有些方面是硬编码的不同(如文件的大小、 channel 数、比特率等)。但是，如果阅读 documentation , 可以轻松地相应地修改 header 。