Reimar/video-compressor
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Use one-pass encoding with more accurate bitrate

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This commit is contained in:
Reimar 2026-01-06 09:20:24 +01:00
parent c0a1b0fca3
commit 4feab31ef0
Signed by: Reimar
GPG Key ID: 93549FA07F0AE268
3 changed files with 16 additions and 24 deletions
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31
public/assets/scripts/main.js
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@ -21,31 +21,31 @@ async function compress() {
console.log("[ffmpeg]", event.type, event.message);
});
let pass = 1;
updateProgress(0, pass);
updateProgress(0);
ffmpeg.on("progress", event => {
updateProgress(event.progress, pass);
updateProgress(event.progress);
});
await ffmpeg.load({ coreURL: "/assets/scripts/core/package/dist/umd/ffmpeg-core.js" });
await ffmpeg.writeFile(file.name, await readFromBlob(file));
// Use Two-Pass to create a video file with desired file size
// https://trac.ffmpeg.org/wiki/Encode/H.264#twopass
// Calculate target bitrate to create a video file with desired file size (https://trac.ffmpeg.org/wiki/Encode/H.264#twopass)
let bitrate = targetFilesize / videoLength;
bitrate -= 128; // Subtract audio bitrate
bitrate -= (bitrate / 100) * 5; // Subtract 5% to compensate for overhead
bitrate = Math.floor(bitrate);
const bitrate = Math.floor(targetFilesize / videoLength) - 128; // Subtract audio bitrate
if (bitrate <= 0) {
showSection("file-picker");
alert("Selected file size is too low for this video");
return;
}
console.debug("Target bitrate:", bitrate, "Video length:", videoLength);
const options = ["-i", file.name, "-preset", "ultrafast", "-c:v", "libx264", "-b:v", bitrate + "k"];
await ffmpeg.exec([...options, "-pass", "1", "-vsync", "cfr", "-f", "null", "/dev/null"]);
pass = 2;
await ffmpeg.exec([...options, "-pass", "2", "-c:a", "copy", "-b:a", "128k", "compressed.mp4"]);
await ffmpeg.exec(["-i", file.name, "-preset", "ultrafast", "-c:v", "libx264", "-b:v", bitrate + "k", "-c:a", "copy", "-b:a", "128k", "compressed.mp4"]);
const video = await ffmpeg.readFile("compressed.mp4");
@ -60,10 +60,9 @@ function cancel() {
showSection("file-picker");
}
function updateProgress(progress, pass) {
function updateProgress(progress) {
const percent = (progress * 100).toFixed(1) + "%";
document.getElementById("progress-step-value").innerText = pass;
document.getElementById("progress-percentage").innerText = percent;
document.getElementById("progress-indicator").style.clipPath = `rect(0 ${percent} 100% 0)`;
}

8
public/assets/style/main.css
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@ -180,7 +180,7 @@ label {
height: 2rem;
max-width: 500px;
border-radius: 2rem;
margin: auto;
margin: 3rem auto auto;
background-color: #E0E0E0;
position: relative;
}
@ -198,9 +198,3 @@ label {
font-weight: bold;
font-size: 1.2rem;
}
#progress-step {
font-weight: bold;
margin-top: 3rem;
margin-bottom: 0.5rem;
}

1
public/index.html
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@ -39,7 +39,6 @@
<h3 id="loading-title">Please wait...</h3>
<p id="loading-description">Your video is being compressed. This may take a while.</p>
<p id="progress-step">Step <span id="progress-step-value">1</span>/2</p>
<div id="progress-container">
<div id="progress-indicator"></div>
</div>