What does a WAV header look like?
Inspect the hex with xxd, a WAV header is 42 bytes and is then followed by
the sample data.
xxd example.wav | head -10
00000000: 5249 4646 2400 0080 5741 5645 666d 7420 RIFF$...WAVEfmt
00000010: 1000 0000 0100 0100 d007 0000 a00f 0000 ................
00000020: 0100 1000 6461 7461 0000 0080 0000 4582 ....data......E.
00000030: e2d0 126c 9e57 c4b4 308c d41f be7f 0a10 ...l.W..0.......
00000040: 4586 57c2 9f62 9f62 57c2 4586 0a10 be7f E.W..b.bW.E.....
00000050: d41f 308c c4b4 9e57 126c e2d0 4582 0000 ..0....W.l..E...
00000060: bb7d 1e2f ee93 62a8 3c4b d073 2ce0 4280 .}./..b.<K.s,.B.
00000070: f6ef bb79 a93d 619d 619d a93d bb79 f6ef ...y.=a.a..=.y..
00000080: 4280 2ce0 d073 3c4b 62a8 ee93 1e2f bb7d B.,..s<Kb..../.}
00000090: 0000 4582 e2d0 126c 9e57 c4b4 308c d41f ..E....l.W..0...
Bash
#!/bin/bash
[[ $# == 1 ]] && count=$1 || count=750
# Fetch some samples
nibbles=8
readarray samples < <(xxd -cols $nibbles -plain -s 42 -len $(( nibbles * count )))
# Loop through samples
i=0
for s in ${samples[*]}; do
# Extract left channel only
s=${s:0:4}
# Shift so all values are positive
echo -e $i\\t$(( 16#$s + 16#ffff ))
(( ++i ))
done | graph -T png
JavaScript
<input type="file" id="pcm" /><br>
<p id="status"></p>
<script>
"use strict";
onload = function() {
// Create a canvas element
const canvas = document.createElement("canvas");
const body = document.getElementsByTagName("body")[0];
// Add it to the DOM
body.appendChild(canvas);
const context = canvas.getContext("2d");
// Set canvas size
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Create file open handler
document.getElementById("pcm").onchange = function(e) {
const file = e.target.files[0];
const reader = new FileReader(file);
const status = document.getElementById("status");
status.innerText = "File size " + file.size + "\n\n";
// Read WAV header
var start = 0;
const headerSize = 44;
var end = start + headerSize;
reader.readAsArrayBuffer(file.slice(start, end));
start += headerSize + 2;
reader.onload = function(e) {
// Read a block of samples
reader.onload = function(e) {
// const samples = new Uint8Array(e.target.result);
const samples = new Int16Array(e.target.result);
for (var i = 0; i < samples.length; i += 1) {
// const s = ~samples[i] + 1;
const s = ~(samples[i] - 1) / 0x7fff;
// const s = samples[i];
// var s = (samples[i + 1] << 8 | samples[i]) / 128;
// var s = (samples[i] << 8 | samples[i+1]) / 128;
// s = ~(s - 1);
context.fillRect(i/1000, canvas.height * s + canvas.height / 2, .1, .1);
}
}
const block = 2 * 1200 * 1000;
// const block = 2 * 10;
end = start + block;
reader.readAsArrayBuffer(file.slice(start, end));
start += block;
}
}
}
</script>