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mp4wasm.html
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<html>
<script src="mp4box.all.js"></script>
<script src="mp4wasm.js"></script>
<script>
async function reencode(file) {
const startNow = performance.now();
let decoder;
let encoder;
let mp4wasm;
let mp4wasmOutputFile;
let mp4wasmMux;
let track = null;
let decodedFrameIndex = 0;
let encodedFrameIndex = 0;
let nextKeyFrameTimestamp = 0;
let sampleDurations = [];
const mp4boxInputFile = MP4Box.createFile();
mp4boxInputFile.onError = error => console.error(error);
mp4boxInputFile.onReady = async (info) => {
track = info.videoTracks[0];
mp4wasm = await new MP4Wasm();
mp4wasmOutputFile = createVirtualFile();
const trak = mp4boxInputFile.getTrackById(track.id);
const duration = (trak.samples_duration / trak.mdia.mdhd.timescale) * 1000;
const fps = Math.round((track.nb_samples / duration) * 1000);
mp4wasmMux = mp4wasm.create_muxer(
{
width: track.track_width,
height: track.track_height,
fps,
fragmentation: true,
sequential: false,
hevc: false,
},
function mux_write(data_ptr, size, offset) {
mp4wasmOutputFile.seek(offset);
const data = mp4wasm.HEAPU8.subarray(data_ptr, data_ptr + size);
return mp4wasmOutputFile.write(data) !== data.byteLength;
}
);
decoder = new VideoDecoder({
async output(inputFrame) {
const bitmap = await createImageBitmap(inputFrame);
const outputFrame = new VideoFrame(bitmap, {
timestamp: inputFrame.timestamp,
});
const keyFrameEveryHowManySeconds = 2;
let keyFrame = false;
if (inputFrame.timestamp >= nextKeyFrameTimestamp) {
keyFrame = true;
nextKeyFrameTimestamp = inputFrame.timestamp + keyFrameEveryHowManySeconds * 1e6;
}
encoder.encode(outputFrame, { keyFrame });
inputFrame.close();
outputFrame.close();
decodedFrameIndex++;
displayProgress();
},
error(error) {
console.error(error);
}
});
let description;
for (const entry of trak.mdia.minf.stbl.stsd.entries) {
if (entry.avcC || entry.hvcC) {
const stream = new DataStream(undefined, 0, DataStream.BIG_ENDIAN);
if (entry.avcC) {
entry.avcC.write(stream);
} else {
entry.hvcC.write(stream);
}
description = new Uint8Array(stream.buffer, 8); // Remove the box header.
break;
}
}
decoder.configure({
codec: track.codec,
codedHeight: track.track_width,
codedWidth: track.track_width,
hardwareAcceleration: 'prefer-hardware',
description,
});
encoder = new VideoEncoder({
output(chunk) {
let uint8 = new Uint8Array(chunk.byteLength);
chunk.copyTo(uint8);
const p = mp4wasm._malloc(uint8.byteLength);
mp4wasm.HEAPU8.set(uint8, p);
mp4wasm.mux_nal(mp4wasmMux, p, uint8.byteLength);
mp4wasm._free(p);
encodedFrameIndex++;
displayProgress();
},
error(error) {
console.error(error);
}
});
encoder.configure({
codec: 'avc1.4d0034',
width: track.track_width,
height: track.track_height,
avc: {
format: 'annexb',
},
hardwareAcceleration: 'prefer-hardware',
bitrate: 20_000_000,
});
mp4boxInputFile.setExtractionOptions(track.id, null, {nbSamples: Infinity});
mp4boxInputFile.start();
};
function displayProgress() {
progress.innerText =
"Decoding frame " + decodedFrameIndex + " (" + Math.round(100 * decodedFrameIndex / track.nb_samples) + "%)\n" +
"Encoding frame " + encodedFrameIndex + " (" + Math.round(100 * encodedFrameIndex / track.nb_samples) + "%)\n";
}
mp4boxInputFile.onSamples = async (track_id, ref, samples) => {
for (const sample of samples) {
decoder.decode(new EncodedVideoChunk({
type: sample.is_sync ? "key" : "delta",
timestamp: sample.cts * 1_000_000 / sample.timescale,
duration: sample.duration * 1_000_000 / sample.timescale,
data: sample.data
}));
}
await decoder.flush();
await encoder.flush();
encoder.close();
decoder.close();
mp4wasm.finalize_muxer(mp4wasmMux);
const data = mp4wasmOutputFile.contents();
let url = URL.createObjectURL(new Blob([data], { type: "video/mp4" }));
let anchor = document.createElement("a");
anchor.href = url;
anchor.download = "mp4wasm.mp4";
anchor.click();
const seconds = (performance.now() - startNow) / 1000;
progress.innerText =
"Re-encoded " + encodedFrameIndex + " frames in " + (Math.round(seconds * 100) / 100) + "s at " +
Math.round(encodedFrameIndex / seconds) + " fps";
};
var reader = new FileReader();
reader.onload = function() {
this.result.fileStart = 0;
mp4boxInputFile.appendBuffer(this.result);
mp4boxInputFile.flush();
};
reader.readAsArrayBuffer(file);
}
function createVirtualFile(initialCapacity = 1024 * 1024) {
let cursor = 0;
let usedBytes = 0;
let contents = new Uint8Array(initialCapacity);
return {
contents: function () {
return contents.slice(0, usedBytes);
},
seek: function (offset) {
// offset in bytes
cursor = offset;
},
write: function (data) {
const size = data.byteLength;
expand(cursor + size);
contents.set(data, cursor);
cursor += size;
usedBytes = Math.max(usedBytes, cursor);
return size;
},
};
function expand(newCapacity) {
var prevCapacity = contents.length;
if (prevCapacity >= newCapacity) {
return; // No need to expand, the storage was already large enough.
}
newCapacity = Math.max(newCapacity, (prevCapacity * 2.0) >>> 0);
const oldContents = contents;
contents = new Uint8Array(newCapacity); // Allocate new storage.
if (usedBytes > 0) {
contents.set(oldContents.subarray(0, usedBytes), 0);
}
}
}
</script>
<p>
Select a video to re-encode:
<input type="file" onchange="reencode(event.target.files[0])"></input>
<div id="progress"></div>
</p>