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In audio programming, generating a standard WAV file header is a fundamental yet crucial step. WAV files are audio files based on the RIFF (Resource Interchange File Format) format, which is clear and easy to read. This article will manually construct a valid WAV file header using PHP's pack() function, helping developers gain a deeper understanding of the structure of the WAV format.
A standard WAV file header can generally be divided into the following sections:
RIFF Chunk: Marks the file as a RIFF file.
WAVE Marker: Indicates that the file type is WAVE.
fmt Subchunk: Contains audio format information (sampling rate, number of channels, bit depth, etc.).
data Subchunk: Contains the actual audio data.
The structure is as follows:
| ChunkID | ChunkSize | Format |
|--------|-----------|--------|
| 'RIFF' | 36 + SubChunk2Size | 'WAVE' |
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<p>| Subchunk2ID | Subchunk2Size | Data |<br>
PHP's pack() function can pack data into a binary string, making it suitable for constructing the WAV file header. Below is a simple example of generating a 16-bit, mono, 44.1kHz WAV file header, assuming the audio data size is $dataSize bytes:
<?php
<p>function createWavHeader($dataSize, $sampleRate = 44100, $bitsPerSample = 16, $channels = 1)<br>
{<br>
$byteRate = $sampleRate * $channels * $bitsPerSample / 8;<br>
$blockAlign = $channels * $bitsPerSample / 8;<br>
$header = '';</p>
$header .= pack('A4', 'RIFF'); // ChunkID
$header .= pack('V', 36 + $dataSize); // ChunkSize
$header .= pack('A4', 'WAVE'); // Format
// fmt Subchunk
$header .= pack('A4', 'fmt '); // Subchunk1ID
$header .= pack('V', 16); // Subchunk1Size
$header .= pack('v', 1); // AudioFormat (1 = PCM)
$header .= pack('v', $channels); // NumChannels
$header .= pack('V', $sampleRate); // SampleRate
$header .= pack('V', $byteRate); // ByteRate
$header .= pack('v', $blockAlign); // BlockAlign
$header .= pack('v', $bitsPerSample); // BitsPerSample
// data Subchunk
$header .= pack('A4', 'data'); // Subchunk2ID
$header .= pack('V', $dataSize); // Subchunk2Size
return $header;
}
// Example: Write an empty WAV file
$dataSize = 44100 * 2 * 1; // 1 second of mono 16-bit audio data
$header = createWavHeader($dataSize);
file_put_contents('output.wav', $header . str_repeat("\x00", $dataSize));
echo "WAV file created. You can download the test file from m66.net.";
$sampleRate: The sample rate, common values include 44100, 48000, etc.
$bitsPerSample: The bit depth of each sample, typically 8 or 16.
$channels: The number of channels, 1 for mono, 2 for stereo.
$dataSize: The actual byte size of the audio data, calculated as: duration * sample rate * number of channels * bit depth / 8.
Using pack() to construct the WAV file header is ideal for the following scenarios:
Server-side dynamic generation of audio streams.
Export of custom audio recording formats.
Development of data compression and audio packaging analysis tools.
