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index.js
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const MP4Box = require('mp4box');
const { readByBlocksWorker, readByBlocks } = require('./code/readBlock');
const InlineWorker = require('./code/inline-worker');
//Will convert the final uint8Array to buffer
//https://stackoverflow.com/a/12101012/3362074
function toBuffer(ab) {
var buf = Buffer.alloc(ab.byteLength);
var view = new Uint8Array(ab);
for (var i = 0; i < buf.length; ++i) {
buf[i] = view[i];
}
return buf;
}
//And back
function toArrayBuffer(buf) {
var ab = new ArrayBuffer(buf.length);
var view = new Uint8Array(ab);
for (var i = 0; i < buf.length; ++i) {
view[i] = buf[i];
}
return ab;
}
function GPMFExtract (
file,
{ browserMode, progress, useWorker = true, cancellationToken } = {}
) {
if (!file) {
throw new TypeError('File not provided');
}
var trackId;
var nb_samples;
/** @type {{ terminate(): void }} */
var fileReaderByBlocks;
return new Promise(function (resolve, reject) {
var mp4boxFile = MP4Box.createFile();
var uintArr;
//Will store timing data to help analyse the extracted data
var timing = {};
mp4boxFile.onError = reject;
//When the data is ready, look for the right track
mp4boxFile.onReady = function (videoData) {
var foundVideo = false;
for (var i = 0; i < videoData.tracks.length; i++) {
//Find the metadata track. Collect Id and number of samples
if (videoData.tracks[i].codec == 'gpmd') {
trackId = videoData.tracks[i].id;
nb_samples = videoData.tracks[i].nb_samples;
timing.start = videoData.tracks[i].created;
// Try to correct GoPro's badly encoded time zone
timing.start.setMinutes(
timing.start.getMinutes() + timing.start.getTimezoneOffset()
);
} else if (
!foundVideo &&
(videoData.tracks[i].type === 'video' ||
videoData.tracks[i].name === 'VideoHandler' ||
videoData.tracks[i].track_height > 0)
) {
// Only confirm video track if found by type, in case more than one meet the other conditions
if (videoData.tracks[i].type === 'video') foundVideo = true;
var vid = videoData.tracks[i];
timing.videoDuration = vid.movie_duration / vid.movie_timescale;
//Deduce framerate from video track
timing.frameDuration = timing.videoDuration / vid.nb_samples;
}
}
if (trackId != null) {
//Request the track
mp4boxFile.setExtractionOptions(trackId, null, {
nbSamples: nb_samples
});
//When samples arrive
mp4boxFile.onSamples = function (id, user, samples) {
// No need to close a closed stream
var totalSamples = samples.reduce(function (acc, cur) {
return acc + cur.size;
}, 0);
//Save the time and duration of each sample
timing.samples = [];
//Store them in Uint8Array
uintArr = new Uint8Array(totalSamples);
var runningCount = 0;
samples.forEach(function (sample) {
timing.samples.push({ cts: sample.cts, duration: sample.duration });
// The loop prevents Firefox from crashing
for (var i = 0; i < sample.size; i++) {
uintArr.set(sample.data, runningCount);
}
runningCount += sample.size;
});
//Convert to Buffer if in Node
var rawData = browserMode ? uintArr : toBuffer(uintArr);
//And return it
resolve({ rawData, timing });
};
mp4boxFile.start();
} else {
fileReaderByBlocks.terminate('Track not found');
// Terminating the worker causes an error to be thrown
}
};
//Use chunk system in browser
if (browserMode) {
//Define functions the child process will call
function onParsedBuffer (unit8array, offset) {
const buffer = unit8array.buffer;
if (buffer.byteLength === 0) {
fileReaderByBlocks.terminate('File not compatible');
}
buffer.fileStart = offset;
if (cancellationToken?.cancelled) {
fileReaderByBlocks.terminate('Canceled by user');
} else {
mp4boxFile.appendBuffer(buffer);
}
};
// var flush = mp4boxFile.flush;
//Try to use a web worker to avoid blocking the browser
if (useWorker && typeof window !== 'undefined' && window.Worker) {
fileReaderByBlocks = new InlineWorker(readByBlocksWorker, {});
fileReaderByBlocks.onmessage = function (e) {
//Run functions when the web worker requests them
if (e.data[0] === 'progress' && progress) progress(e.data[1]);
else if (e.data[0] === 'onParsedBuffer') {
onParsedBuffer(e.data[1], e.data[2]);
} else if (e.data[0] === 'flush') {
mp4boxFile.flush();
} else if (e.data[0] === 'onError') {
reject(e.data[1]);
}
};
//If the worker crashes, run the old function
fileReaderByBlocks.onerror = function (e) {
if (e == 'Track not found') {
//The file has finished reading and did not find any track, no need to retry
reject(e);
return;
}
mp4boxFile = MP4Box.createFile();
fileReaderByBlocks = readByBlocks(file, {
chunkSize: 1024 * 1024 * 2,
progress,
onParsedBuffer,
flush: () => mp4boxFile.flush(),
onError: reject,
});
};
//Start worker
fileReaderByBlocks.postMessage(['readBlock', file]);
//If workers not supported, use old strategy
} else {
fileReaderByBlocks = readByBlocks(file, {
chunkSize: 1024 * 1024 * 2,
progress,
onParsedBuffer,
flush: () => mp4boxFile.flush(),
onError: reject,
});
}
} else {
//Nodejs
if (typeof file === 'function') {
file(mp4boxFile);
} else if (typeof Buffer == 'function' && file instanceof Buffer) {
var arrayBuffer = toArrayBuffer(file);
if (arrayBuffer.byteLength === 0) reject('File not compatible');
arrayBuffer.fileStart = 0;
//Assign data to mp4box
mp4boxFile.appendBuffer(arrayBuffer);
} else {
reject('File not compatible');
}
}
});
};
module.exports = GPMFExtract;
exports = module.exports;
exports.GPMFExtract = GPMFExtract;