mirror of https://github.com/electron/electron
501 lines
14 KiB
JavaScript
501 lines
14 KiB
JavaScript
/*
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https://github.com/antimatter15/whammy
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The MIT License (MIT)
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Copyright (c) 2015 Kevin Kwok
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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function atob (str) {
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return Buffer.from(str, 'base64').toString('binary');
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}
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// in this case, frames has a very specific meaning, which will be
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// detailed once i finish writing the code
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function ToWebM (frames) {
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const info = checkFrames(frames);
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// max duration by cluster in milliseconds
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const CLUSTER_MAX_DURATION = 30000;
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const EBML = [
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{
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id: 0x1a45dfa3, // EBML
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data: [
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{
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data: 1,
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id: 0x4286 // EBMLVersion
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},
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{
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data: 1,
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id: 0x42f7 // EBMLReadVersion
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},
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{
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data: 4,
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id: 0x42f2 // EBMLMaxIDLength
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},
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{
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data: 8,
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id: 0x42f3 // EBMLMaxSizeLength
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},
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{
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data: 'webm',
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id: 0x4282 // DocType
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},
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{
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data: 2,
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id: 0x4287 // DocTypeVersion
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},
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{
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data: 2,
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id: 0x4285 // DocTypeReadVersion
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}
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]
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},
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{
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id: 0x18538067, // Segment
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data: [
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{
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id: 0x1549a966, // Info
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data: [
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{
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data: 1e6, // do things in millisecs (num of nanosecs for duration scale)
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id: 0x2ad7b1 // TimecodeScale
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},
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{
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data: 'whammy',
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id: 0x4d80 // MuxingApp
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},
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{
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data: 'whammy',
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id: 0x5741 // WritingApp
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},
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{
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data: doubleToString(info.duration),
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id: 0x4489 // Duration
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}
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]
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},
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{
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id: 0x1654ae6b, // Tracks
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data: [
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{
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id: 0xae, // TrackEntry
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data: [
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{
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data: 1,
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id: 0xd7 // TrackNumber
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},
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{
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data: 1,
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id: 0x73c5 // TrackUID
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},
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{
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data: 0,
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id: 0x9c // FlagLacing
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},
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{
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data: 'und',
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id: 0x22b59c // Language
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},
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{
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data: 'V_VP8',
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id: 0x86 // CodecID
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},
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{
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data: 'VP8',
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id: 0x258688 // CodecName
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},
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{
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data: 1,
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id: 0x83 // TrackType
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},
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{
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id: 0xe0, // Video
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data: [
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{
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data: info.width,
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id: 0xb0 // PixelWidth
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},
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{
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data: info.height,
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id: 0xba // PixelHeight
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}
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]
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}
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]
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}
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]
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},
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{
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id: 0x1c53bb6b, // Cues
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data: [
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// cue insertion point
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]
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}
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// cluster insertion point
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]
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}
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];
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const segment = EBML[1];
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const cues = segment.data[2];
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// Generate clusters (max duration)
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let frameNumber = 0;
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let clusterTimecode = 0;
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while (frameNumber < frames.length) {
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const cuePoint = {
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id: 0xbb, // CuePoint
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data: [
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{
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data: Math.round(clusterTimecode),
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id: 0xb3 // CueTime
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},
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{
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id: 0xb7, // CueTrackPositions
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data: [
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{
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data: 1,
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id: 0xf7 // CueTrack
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},
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{
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data: 0, // to be filled in when we know it
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size: 8,
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id: 0xf1 // CueClusterPosition
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}
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]
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}
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]
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};
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cues.data.push(cuePoint);
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const clusterFrames = [];
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let clusterDuration = 0;
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do {
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clusterFrames.push(frames[frameNumber]);
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clusterDuration += frames[frameNumber].duration;
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frameNumber++;
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} while (frameNumber < frames.length && clusterDuration < CLUSTER_MAX_DURATION);
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let clusterCounter = 0;
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const cluster = {
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id: 0x1f43b675, // Cluster
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data: [
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{
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data: Math.round(clusterTimecode),
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id: 0xe7 // Timecode
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}
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].concat(clusterFrames.map(function (webp) {
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const block = makeSimpleBlock({
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discardable: 0,
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frame: webp.data.slice(4),
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invisible: 0,
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keyframe: 1,
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lacing: 0,
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trackNum: 1,
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timecode: Math.round(clusterCounter)
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});
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clusterCounter += webp.duration;
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return {
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data: block,
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id: 0xa3
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};
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}))
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};
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// Add cluster to segment
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segment.data.push(cluster);
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clusterTimecode += clusterDuration;
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}
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// First pass to compute cluster positions
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let position = 0;
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for (let i = 0; i < segment.data.length; i++) {
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if (i >= 3) {
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cues.data[i - 3].data[1].data[1].data = position;
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}
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const data = generateEBML([segment.data[i]]);
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position += data.size || data.byteLength || data.length;
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if (i !== 2) { // not cues
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// Save results to avoid having to encode everything twice
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segment.data[i] = data;
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}
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}
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return generateEBML(EBML);
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}
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// sums the lengths of all the frames and gets the duration, woo
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function checkFrames (frames) {
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const width = frames[0].width;
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const height = frames[0].height;
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let duration = frames[0].duration;
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for (let i = 1; i < frames.length; i++) {
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if (frames[i].width !== width) throw new Error('Frame ' + (i + 1) + ' has a different width');
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if (frames[i].height !== height) throw new Error('Frame ' + (i + 1) + ' has a different height');
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if (frames[i].duration < 0 || frames[i].duration > 0x7fff) throw new Error('Frame ' + (i + 1) + ' has a weird duration (must be between 0 and 32767)');
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duration += frames[i].duration;
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}
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return {
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duration: duration,
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width: width,
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height: height
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};
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}
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function numToBuffer (num) {
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const parts = [];
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while (num > 0) {
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parts.push(num & 0xff);
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num = num >> 8;
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}
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return new Uint8Array(parts.reverse());
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}
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function numToFixedBuffer (num, size) {
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const parts = new Uint8Array(size);
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for (let i = size - 1; i >= 0; i--) {
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parts[i] = num & 0xff;
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num = num >> 8;
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}
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return parts;
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}
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function strToBuffer (str) {
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// return new Blob([str]);
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const arr = new Uint8Array(str.length);
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for (let i = 0; i < str.length; i++) {
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arr[i] = str.charCodeAt(i);
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}
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return arr;
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// this is slower
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// return new Uint8Array(str.split('').map(function(e){
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// return e.charCodeAt(0)
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// }))
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}
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// sorry this is ugly, and sort of hard to understand exactly why this was done
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// at all really, but the reason is that there's some code below that i dont really
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// feel like understanding, and this is easier than using my brain.
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function bitsToBuffer (bits) {
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const data = [];
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const pad = (bits.length % 8) ? (new Array(1 + 8 - (bits.length % 8))).join('0') : '';
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bits = pad + bits;
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for (let i = 0; i < bits.length; i += 8) {
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data.push(parseInt(bits.substr(i, 8), 2));
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}
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return new Uint8Array(data);
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}
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function generateEBML (json) {
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const ebml = [];
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for (const item of json) {
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if (!('id' in item)) {
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// already encoded blob or byteArray
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ebml.push(item);
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continue;
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}
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let data = item.data;
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if (typeof data === 'object') data = generateEBML(data);
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if (typeof data === 'number') data = ('size' in item) ? numToFixedBuffer(data, item.size) : bitsToBuffer(data.toString(2));
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if (typeof data === 'string') data = strToBuffer(data);
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const len = data.size || data.byteLength || data.length;
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const zeroes = Math.ceil(Math.ceil(Math.log(len) / Math.log(2)) / 8);
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const sizeStr = len.toString(2);
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const padded = (new Array((zeroes * 7 + 7 + 1) - sizeStr.length)).join('0') + sizeStr;
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const size = (new Array(zeroes)).join('0') + '1' + padded;
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// i actually dont quite understand what went on up there, so I'm not really
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// going to fix this, i'm probably just going to write some hacky thing which
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// converts that string into a buffer-esque thing
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ebml.push(numToBuffer(item.id));
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ebml.push(bitsToBuffer(size));
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ebml.push(data);
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}
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// convert ebml to an array
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const buffer = toFlatArray(ebml);
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return new Uint8Array(buffer);
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}
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function toFlatArray (arr, outBuffer) {
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if (outBuffer == null) {
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outBuffer = [];
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}
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for (const item of arr) {
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if (typeof item === 'object') {
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// an array
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toFlatArray(item, outBuffer);
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} else {
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// a simple element
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outBuffer.push(item);
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}
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}
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return outBuffer;
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}
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function makeSimpleBlock (data) {
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let flags = 0;
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if (data.keyframe) flags |= 128;
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if (data.invisible) flags |= 8;
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if (data.lacing) flags |= (data.lacing << 1);
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if (data.discardable) flags |= 1;
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if (data.trackNum > 127) {
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throw new Error('TrackNumber > 127 not supported');
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}
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const out = [data.trackNum | 0x80, data.timecode >> 8, data.timecode & 0xff, flags].map(function (e) {
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return String.fromCharCode(e);
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}).join('') + data.frame;
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return out;
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}
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// here's something else taken verbatim from weppy, awesome rite?
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function parseWebP (riff) {
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const VP8 = riff.RIFF[0].WEBP[0];
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const frameStart = VP8.indexOf('\x9d\x01\x2a'); // A VP8 keyframe starts with the 0x9d012a header
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const c = [];
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for (let i = 0; i < 4; i++) c[i] = VP8.charCodeAt(frameStart + 3 + i);
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// the code below is literally copied verbatim from the bitstream spec
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let tmp = (c[1] << 8) | c[0];
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const width = tmp & 0x3FFF;
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const horizontalScale = tmp >> 14;
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tmp = (c[3] << 8) | c[2];
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const height = tmp & 0x3FFF;
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const verticalScale = tmp >> 14;
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return {
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width,
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height,
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horizontalScale,
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verticalScale,
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data: VP8,
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riff: riff
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};
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}
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// i think i'm going off on a riff by pretending this is some known
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// idiom which i'm making a casual and brilliant pun about, but since
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// i can't find anything on google which conforms to this idiomatic
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// usage, I'm assuming this is just a consequence of some psychotic
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// break which makes me make up puns. well, enough riff-raff (aha a
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// rescue of sorts), this function was ripped wholesale from weppy
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function parseRIFF (string) {
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let offset = 0;
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const chunks = {};
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while (offset < string.length) {
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const id = string.substr(offset, 4);
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chunks[id] = chunks[id] || [];
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if (id === 'RIFF' || id === 'LIST') {
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const len = parseInt(string.substr(offset + 4, 4).split('').map(function (i) {
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const unpadded = i.charCodeAt(0).toString(2);
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return (new Array(8 - unpadded.length + 1)).join('0') + unpadded;
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}).join(''), 2);
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const data = string.substr(offset + 4 + 4, len);
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offset += 4 + 4 + len;
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chunks[id].push(parseRIFF(data));
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} else if (id === 'WEBP') {
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// Use (offset + 8) to skip past "VP8 "/"VP8L"/"VP8X" field after "WEBP"
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chunks[id].push(string.substr(offset + 8));
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offset = string.length;
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} else {
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// Unknown chunk type; push entire payload
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chunks[id].push(string.substr(offset + 4));
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offset = string.length;
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}
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}
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return chunks;
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}
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// here's a little utility function that acts as a utility for other functions
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// basically, the only purpose is for encoding "Duration", which is encoded as
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// a double (considerably more difficult to encode than an integer)
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function doubleToString (num) {
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return Array.prototype.slice.call(
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new Uint8Array(
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(
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new Float64Array([num]) // create a float64 array
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).buffer) // extract the array buffer
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, 0) // convert the Uint8Array into a regular array
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.map(function (e) { // since it's a regular array, we can now use map
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return String.fromCharCode(e); // encode all the bytes individually
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})
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.reverse() // correct the byte endianness (assume it's little endian for now)
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.join(''); // join the bytes in holy matrimony as a string
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}
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function WhammyVideo (speed, quality = 0.8) { // a more abstract-ish API
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this.frames = [];
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this.duration = 1000 / speed;
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this.quality = quality;
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}
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/**
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*
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* @param {string} frame
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* @param {number} [duration]
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*/
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WhammyVideo.prototype.add = function (frame, duration) {
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if (typeof duration !== 'undefined' && this.duration) throw new Error("you can't pass a duration if the fps is set");
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if (typeof duration === 'undefined' && !this.duration) throw new Error("if you don't have the fps set, you need to have durations here.");
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if (frame.canvas) { // CanvasRenderingContext2D
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frame = frame.canvas;
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}
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if (frame.toDataURL) {
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// frame = frame.toDataURL('image/webp', this.quality);
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// quickly store image data so we don't block cpu. encode in compile method.
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frame = frame.getContext('2d').getImageData(0, 0, frame.width, frame.height);
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} else if (typeof frame !== 'string') {
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throw new TypeError('frame must be a a HTMLCanvasElement, a CanvasRenderingContext2D or a DataURI formatted string');
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}
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if (typeof frame === 'string' && !(/^data:image\/webp;base64,/ig).test(frame)) {
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throw new Error('Input must be formatted properly as a base64 encoded DataURI of type image/webp');
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}
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this.frames.push({
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image: frame,
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duration: duration || this.duration
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});
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};
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WhammyVideo.prototype.compile = function (callback) {
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const webm = new ToWebM(this.frames.map(function (frame) {
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const webp = parseWebP(parseRIFF(atob(frame.image.slice(23))));
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webp.duration = frame.duration;
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return webp;
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}));
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callback(webm);
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};
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export const WebmGenerator = WhammyVideo;
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