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whammy.js
/*
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);
chunks[id] = chunks[id] || [];
if (id == 'RIFF' || id == 'LIST') {
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].push(parseRIFF(data));
} else if (id == 'WEBP') {
// Use (offset + 8) to skip past "VP8 "/"VP8L"/"VP8X" field after "WEBP"
chunks[id].push(string.substr(offset + 8));
offset = string.length;
} else {
// Unknown chunk type; push entire payload
chunks[id].push(string.substr(offset + 4));
offset = string.length;
}
}
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 need to have durations here.";
if(frame.canvas){ //CanvasRenderingContext2D
frame = frame.canvas;
}
if(frame.toDataURL){
// frame = frame.toDataURL('image/webp', this.quality);
// quickly store image data so we don't block cpu. encode in compile method.
frame = frame.getContext('2d').getImageData(0, 0, frame.width, frame.height);
}else if(typeof frame != "string"){
throw "frame must be a a HTMLCanvasElement, a CanvasRenderingContext2D or a DataURI formatted string"
}
if (typeof frame === "string" && !(/^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
});
};
// deferred webp encoding. Draws image data to canvas, then encodes as dataUrl
WhammyVideo.prototype.encodeFrames = function(callback){
if(this.frames[0].image instanceof ImageData){
var frames = this.frames;
var tmpCanvas = document.createElement('canvas');
var tmpContext = tmpCanvas.getContext('2d');
tmpCanvas.width = this.frames[0].image.width;
tmpCanvas.height = this.frames[0].image.height;
var encodeFrame = function(index){
console.log('encodeFrame', index);
var frame = frames[index];
tmpContext.putImageData(frame.image, 0, 0);
frame.image = tmpCanvas.toDataURL('image/webp', this.quality);
if(index < frames.length-1){
setTimeout(function(){ encodeFrame(index + 1); }, 1);
}else{
callback();
}
}.bind(this);
encodeFrame(0);
}else{
callback();
}
};
WhammyVideo.prototype.compile = function(outputAsArray, callback){
this.encodeFrames(function(){
var webm = new toWebM(this.frames.map(function(frame){
var webp = parseWebP(parseRIFF(atob(frame.image.slice(23))));
webp.duration = frame.duration;
return webp;
}), outputAsArray);
callback(webm);
}.bind(this));
};
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
}
})()
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