Looping fix for Depthy.me

Inject patched version of Whammy to make videos generated by depthy.me loop in Firefox.
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// ==UserScript==
// @name         Looping fix for Depthy.me
// @namespace    https://greasyfork.org/en/users/9042-diacritical
// @version      0.1
// @description  Inject patched version of Whammy to make videos generated by depthy.me loop in Firefox.
// @match        *://depthy.me/*
// @grant        none
// ==/UserScript==
 
/*
Copyright (C) 2013 Kevin Kwok
 
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
 
/*
	var vid = new Whammy.Video();
	vid.add(canvas or data url)
	vid.compile()
*/
 
window.Whammy = (function(){
	// in this case, frames has a very specific meaning, which will be
	// detailed once i finish writing the code
 
	function toWebM(frames, outputAsArray){
		var info = checkFrames(frames);
 
		//max duration by cluster in milliseconds
		var CLUSTER_MAX_DURATION = 30000;
 
		var EBML = [
			{
				"id": 0x1a45dfa3, // EBML
				"data": [
					{
						"data": 1,
						"id": 0x4286 // EBMLVersion
					},
					{
						"data": 1,
						"id": 0x42f7 // EBMLReadVersion
					},
					{
						"data": 4,
						"id": 0x42f2 // EBMLMaxIDLength
					},
					{
						"data": 8,
						"id": 0x42f3 // EBMLMaxSizeLength
					},
					{
						"data": "webm",
						"id": 0x4282 // DocType
					},
					{
						"data": 2,
						"id": 0x4287 // DocTypeVersion
					},
					{
						"data": 2,
						"id": 0x4285 // DocTypeReadVersion
					}
				]
			},
			{
				"id": 0x18538067, // Segment
				"data": [
					{
						"id": 0x1549a966, // Info
						"data": [
							{
								"data": 1e6, //do things in millisecs (num of nanosecs for duration scale)
								"id": 0x2ad7b1 // TimecodeScale
							},
							{
								"data": "whammy",
								"id": 0x4d80 // MuxingApp
							},
							{
								"data": "whammy",
								"id": 0x5741 // WritingApp
							},
							{
								"data": doubleToString(info.duration),
								"id": 0x4489 // Duration
							}
						]
					},
					{
						"id": 0x1654ae6b, // Tracks
						"data": [
							{
								"id": 0xae, // TrackEntry
								"data": [
									{
										"data": 1,
										"id": 0xd7 // TrackNumber
									},
									{
										"data": 1,
										"id": 0x73c5 // TrackUID
									},
									{
										"data": 0,
										"id": 0x9c // FlagLacing
									},
									{
										"data": "und",
										"id": 0x22b59c // Language
									},
									{
										"data": "V_VP8",
										"id": 0x86 // CodecID
									},
									{
										"data": "VP8",
										"id": 0x258688 // CodecName
									},
									{
										"data": 1,
										"id": 0x83 // TrackType
									},
									{
										"id": 0xe0,  // Video
										"data": [
											{
												"data": info.width,
												"id": 0xb0 // PixelWidth
											},
											{
												"data": info.height,
												"id": 0xba // PixelHeight
											}
										]
									}
								]
							}
						]
					},
					{
						"id": 0x1c53bb6b, // Cues
						"data": [
							//cue insertion point
						]
					}
 
					//cluster insertion point
				]
			}
		 ];
 
 
		var segment = EBML[1];
		var cues = segment.data[2];
 
		//Generate clusters (max duration)
		var frameNumber = 0;
		var clusterTimecode = 0;
		while(frameNumber < frames.length){
 
			var cuePoint = {
					"id": 0xbb, // CuePoint
					"data": [
						{
							"data": Math.round(clusterTimecode),
							"id": 0xb3 // CueTime
						},
						{
							"id": 0xb7, // CueTrackPositions
							"data": [
								{
									"data": 1,
									"id": 0xf7 // CueTrack
								},
								{
									"data": 0, // to be filled in when we know it
									"size": 8,
									"id": 0xf1 // CueClusterPosition
								}
							]
						}
					]
				};
 
			cues.data.push(cuePoint);
 
			var clusterFrames = [];
			var clusterDuration = 0;
			do {
				clusterFrames.push(frames[frameNumber]);
				clusterDuration += frames[frameNumber].duration;
				frameNumber++;
			}while(frameNumber < frames.length && clusterDuration < CLUSTER_MAX_DURATION);
 
			var clusterCounter = 0;
			var cluster = {
					"id": 0x1f43b675, // Cluster
					"data": [
						{
							"data": Math.round(clusterTimecode),
							"id": 0xe7 // Timecode
						}
					].concat(clusterFrames.map(function(webp){
						var block = makeSimpleBlock({
							discardable: 0,
							frame: webp.data.slice(4),
							invisible: 0,
							keyframe: 1,
							lacing: 0,
							trackNum: 1,
							timecode: Math.round(clusterCounter)
						});
						clusterCounter += webp.duration;
						return {
							data: block,
							id: 0xa3
						};
					}))
				}
 
			//Add cluster to segment
			segment.data.push(cluster);
			clusterTimecode += clusterDuration;
		}
 
		//First pass to compute cluster positions
		var position = 0;
		for(var i = 0; i < segment.data.length; i++){
			if (i >= 3) {
				cues.data[i-3].data[1].data[1].data = position;
			}
			var data = generateEBML([segment.data[i]], outputAsArray);
			position += data.size || data.byteLength || data.length;
			if (i != 2) { // not cues
				//Save results to avoid having to encode everything twice
				segment.data[i] = data;
			}
		}
 
		return generateEBML(EBML, outputAsArray)
	}
 
	// sums the lengths of all the frames and gets the duration, woo
 
	function checkFrames(frames){
		var width = frames[0].width,
			height = frames[0].height,
			duration = frames[0].duration;
		for(var i = 1; i < frames.length; i++){
			if(frames[i].width != width) throw "Frame " + (i + 1) + " has a different width";
			if(frames[i].height != height) throw "Frame " + (i + 1) + " has a different height";
			if(frames[i].duration < 0 || frames[i].duration > 0x7fff) throw "Frame " + (i + 1) + " has a weird duration (must be between 0 and 32767)";
			duration += frames[i].duration;
		}
		return {
			duration: duration,
			width: width,
			height: height
		};
	}
 
 
	function numToBuffer(num){
		var parts = [];
		while(num > 0){
			parts.push(num & 0xff)
			num = num >> 8
		}
		return new Uint8Array(parts.reverse());
	}
 
	function numToFixedBuffer(num, size){
		var parts = new Uint8Array(size);
		for(var i = size - 1; i >= 0; i--){
			parts[i] = num & 0xff;
			num = num >> 8;
		}
		return parts;
	}
 
	function strToBuffer(str){
		// return new Blob([str]);
 
		var arr = new Uint8Array(str.length);
		for(var i = 0; i < str.length; i++){
			arr[i] = str.charCodeAt(i)
		}
		return arr;
		// this is slower
		// return new Uint8Array(str.split('').map(function(e){
		// 	return e.charCodeAt(0)
		// }))
	}
 
 
	//sorry this is ugly, and sort of hard to understand exactly why this was done
	// at all really, but the reason is that there's some code below that i dont really
	// feel like understanding, and this is easier than using my brain.
 
	function bitsToBuffer(bits){
		var data = [];
		var pad = (bits.length % 8) ? (new Array(1 + 8 - (bits.length % 8))).join('0') : '';
		bits = pad + bits;
		for(var i = 0; i < bits.length; i+= 8){
			data.push(parseInt(bits.substr(i,8),2))
		}
		return new Uint8Array(data);
	}
 
	function generateEBML(json, outputAsArray){
		var ebml = [];
		for(var i = 0; i < json.length; i++){
			if (!('id' in json[i])){
				//already encoded blob or byteArray
				ebml.push(json[i]);
				continue;
			}
 
			var data = json[i].data;
			if(typeof data == 'object') data = generateEBML(data, outputAsArray);
			if(typeof data == 'number') data = ('size' in json[i]) ? numToFixedBuffer(data, json[i].size) : bitsToBuffer(data.toString(2));
			if(typeof data == 'string') data = strToBuffer(data);
 
			if(data.length){
				var z = z;
			}
 
			var len = data.size || data.byteLength || data.length;
			var zeroes = Math.ceil(Math.ceil(Math.log(len)/Math.log(2))/8);
			var size_str = len.toString(2);
			var padded = (new Array((zeroes * 7 + 7 + 1) - size_str.length)).join('0') + size_str;
			var size = (new Array(zeroes)).join('0') + '1' + padded;
 
			//i actually dont quite understand what went on up there, so I'm not really
			//going to fix this, i'm probably just going to write some hacky thing which
			//converts that string into a buffer-esque thing
 
			ebml.push(numToBuffer(json[i].id));
			ebml.push(bitsToBuffer(size));
			ebml.push(data)
 
 
		}
 
		//output as blob or byteArray
		if(outputAsArray){
			//convert ebml to an array
			var buffer = toFlatArray(ebml)
			return new Uint8Array(buffer);
		}else{
			return new Blob(ebml, {type: "video/webm"});
		}
	}
 
	function toFlatArray(arr, outBuffer){
		if(outBuffer == null){
			outBuffer = [];
		}
		for(var i = 0; i < arr.length; i++){
			if(typeof arr[i] == 'object'){
				//an array
				toFlatArray(arr[i], outBuffer)
			}else{
				//a simple element
				outBuffer.push(arr[i]);
			}
		}
		return outBuffer;
	}
 
	//OKAY, so the following two functions are the string-based old stuff, the reason they're
	//still sort of in here, is that they're actually faster than the new blob stuff because
	//getAsFile isn't widely implemented, or at least, it doesn't work in chrome, which is the
	// only browser which supports get as webp
 
	//Converting between a string of 0010101001's and binary back and forth is probably inefficient
	//TODO: get rid of this function
	function toBinStr_old(bits){
		var data = '';
		var pad = (bits.length % 8) ? (new Array(1 + 8 - (bits.length % 8))).join('0') : '';
		bits = pad + bits;
		for(var i = 0; i < bits.length; i+= 8){
			data += String.fromCharCode(parseInt(bits.substr(i,8),2))
		}
		return data;
	}
 
	function generateEBML_old(json){
		var ebml = '';
		for(var i = 0; i < json.length; i++){
			var data = json[i].data;
			if(typeof data == 'object') data = generateEBML_old(data);
			if(typeof data == 'number') data = toBinStr_old(data.toString(2));
 
			var len = data.length;
			var zeroes = Math.ceil(Math.ceil(Math.log(len)/Math.log(2))/8);
			var size_str = len.toString(2);
			var padded = (new Array((zeroes * 7 + 7 + 1) - size_str.length)).join('0') + size_str;
			var size = (new Array(zeroes)).join('0') + '1' + padded;
 
			ebml += toBinStr_old(json[i].id.toString(2)) + toBinStr_old(size) + data;
 
		}
		return ebml;
	}
 
	//woot, a function that's actually written for this project!
	//this parses some json markup and makes it into that binary magic
	//which can then get shoved into the matroska comtainer (peaceably)
 
	function makeSimpleBlock(data){
		var flags = 0;
		if (data.keyframe) flags |= 128;
		if (data.invisible) flags |= 8;
		if (data.lacing) flags |= (data.lacing << 1);
		if (data.discardable) flags |= 1;
		if (data.trackNum > 127) {
			throw "TrackNumber > 127 not supported";
		}
		var out = [data.trackNum | 0x80, data.timecode >> 8, data.timecode & 0xff, flags].map(function(e){
			return String.fromCharCode(e)
		}).join('') + data.frame;
 
		return out;
	}
 
	// here's something else taken verbatim from weppy, awesome rite?
 
	function parseWebP(riff){
		var VP8 = riff.RIFF[0].WEBP[0];
 
		var frame_start = VP8.indexOf('\x9d\x01\x2a'); //A VP8 keyframe starts with the 0x9d012a header
		for(var i = 0, c = []; i < 4; i++) c[i] = VP8.charCodeAt(frame_start + 3 + i);
 
		var width, horizontal_scale, height, vertical_scale, tmp;
 
		//the code below is literally copied verbatim from the bitstream spec
		tmp = (c[1] << 8) | c[0];
		width = tmp & 0x3FFF;
		horizontal_scale = tmp >> 14;
		tmp = (c[3] << 8) | c[2];
		height = tmp & 0x3FFF;
		vertical_scale = tmp >> 14;
		return {
			width: width,
			height: height,
			data: VP8,
			riff: riff
		}
	}
 
	// i think i'm going off on a riff by pretending this is some known
	// idiom which i'm making a casual and brilliant pun about, but since
	// i can't find anything on google which conforms to this idiomatic
	// usage, I'm assuming this is just a consequence of some psychotic
	// break which makes me make up puns. well, enough riff-raff (aha a
	// rescue of sorts), this function was ripped wholesale from weppy
 
	function parseRIFF(string){
		var offset = 0;
		var chunks = {};
 
		while (offset < string.length) {
			var id = string.substr(offset, 4);
			var len = parseInt(string.substr(offset + 4, 4).split('').map(function(i){
				var unpadded = i.charCodeAt(0).toString(2);
				return (new Array(8 - unpadded.length + 1)).join('0') + unpadded
			}).join(''),2);
			var data = string.substr(offset + 4 + 4, len);
			offset += 4 + 4 + len;
			chunks[id] = chunks[id] || [];
 
			if (id == 'RIFF' || id == 'LIST') {
				chunks[id].push(parseRIFF(data));
			} else {
				chunks[id].push(data);
			}
		}
		return chunks;
	}
 
	// here's a little utility function that acts as a utility for other functions
	// basically, the only purpose is for encoding "Duration", which is encoded as
	// a double (considerably more difficult to encode than an integer)
	function doubleToString(num){
		return [].slice.call(
			new Uint8Array(
				(
					new Float64Array([num]) //create a float64 array
				).buffer) //extract the array buffer
			, 0) // convert the Uint8Array into a regular array
			.map(function(e){ //since it's a regular array, we can now use map
				return String.fromCharCode(e) // encode all the bytes individually
			})
			.reverse() //correct the byte endianness (assume it's little endian for now)
			.join('') // join the bytes in holy matrimony as a string
	}
 
	function WhammyVideo(speed, quality){ // a more abstract-ish API
		this.frames = [];
		this.duration = 1000 / speed;
		this.quality = quality || 0.8;
	}
 
	WhammyVideo.prototype.add = function(frame, duration){
		if(typeof duration != 'undefined' && this.duration) throw "you can't pass a duration if the fps is set";
		if(typeof duration == 'undefined' && !this.duration) throw "if you don't have the fps set, you ned to have durations here.";
		if(frame.canvas){ //CanvasRenderingContext2D
			frame = frame.canvas;
		}
		if(frame.toDataURL){
			frame = frame.toDataURL('image/webp', this.quality)
		}else if(typeof frame != "string"){
			throw "frame must be a a HTMLCanvasElement, a CanvasRenderingContext2D or a DataURI formatted string"
		}
		if (!(/^data:image\/webp;base64,/ig).test(frame)) {
			throw "Input must be formatted properly as a base64 encoded DataURI of type image/webp";
		}
		this.frames.push({
			image: frame,
			duration: duration || this.duration
		})
	}
 
	WhammyVideo.prototype.compile = function(outputAsArray){
		return new toWebM(this.frames.map(function(frame){
			var webp = parseWebP(parseRIFF(atob(frame.image.slice(23))));
			webp.duration = frame.duration;
			return webp;
		}), outputAsArray)
	}
 
	return {
		Video: WhammyVideo,
		fromImageArray: function(images, fps, outputAsArray){
			return toWebM(images.map(function(image){
				var webp = parseWebP(parseRIFF(atob(image.slice(23))))
				webp.duration = 1000 / fps;
				return webp;
			}), outputAsArray)
		},
		toWebM: toWebM
		// expose methods of madness
	}
})()