feat: batch video upscaling with folder upload, directory save, and result comparison (#1051)

* feat: support batch video upscaling with folder upload and directory save

- Add multi-file selection and entire folder upload (webkitdirectory)
- Support drag & drop of both files and folders via FileSystemEntry API
- Add save directory picker using File System Access API (showDirectoryPicker)
- Process videos sequentially with per-file progress and status tracking
- Add right-side result list with click-to-compare functionality
- Add per-video duration and total batch duration display
- Add retry button for failed items with error detail display
- Remove auto-play on comparison viewer load
- Fix worker error handling: handle "error" command to reject stale promises
- Fix event listener accumulation in video comparison (AbortController)
- Fix XSS risk by escaping HTML in all innerHTML injections
- Fix URL revocation timing in download to prevent large file truncation
- Extract writeToSaveDirectory and truncateName helpers to reduce duplication
- Add Usage Guide panel explaining single/multiple/folder upload options

Files changed:
  docs/upscaler/index.html  (+1110/-181)
  docs/upscaler/upscaler.js (+110)

* fix: prevent auto-play and resource consumption during upscaling

- Set preload="metadata" on preview and comparison video elements
- Explicitly pause preview video after setting src in showVideoPreview
- Remove preview video seek sync from batch processing progress callbacks
  (was causing continuous decode during upscaling, wasting GPU resources)
- Remove preview video seek sync from retry progress callback
- All videos now require manual play; no background resource usage

* fix: improve upscaled video quality with higher bitrate and codec support

- Raise base bitrate from 2.5 Mbps (25e5) to 8 Mbps (8e6) for standard and
  firefox processors, preventing quality loss when source videos have high
  bitrates (e.g. 720p @ 16.7 Mbps was producing 1440p @ 10 Mbps, smaller
  than the original file)
- Double the bitrate for mediabunny processor (X.n1 * 2) to account for the
  4x pixel increase from 2x upscaling
- Add H.264 Level 5.1 (avc1.640033) and Level 5.2 (avc1.640034) codecs to
  the fallback lists, since Level 4.0 (avc1.640028, ~24.6 Mbps) cannot
  support the higher bitrates for 1440p+ outputs
- Add latencyMode: "quality" to VideoEncoder configs for both standard and
  firefox processors, prioritizing encoding quality over latency (suitable
  for offline processing)

* feat: add video data comparison panel for original vs upscaled metrics

- Add a comparison data table below the file info bar showing 6 metrics:
  Resolution, File Size, Duration, Est. Bitrate, Pixels, Process Time
- Display per-metric change percentage with color-coded indicators:
  green (↑) for improvements, red (↓) for regressions, gray for neutral
- Estimated bitrate calculated from file size × 8 / video duration
- Table renders after both original and upscaled video metadata loads
- Auto-hide panel on reset

* fix: make video data comparison panel full-width and responsive

- Move comparison data table from inside the left column to the full-width
  area below the left/right layout, so it is no longer constrained by the
  comparison viewer column width
- Remove table-fixed colgroup and overflow-x-auto that caused horizontal
  scrolling on smaller screens
- Table now uses w-full auto-layout, displaying all 4 columns (Metric,
  Original, Upscaled, Change) without requiring horizontal scrolling

---------

Co-authored-by: rionzhao <rionzhao@tencent.com>

compiled/artplayer-plugin-multiple-subtitles.legacy.js

@@ -0,0 +1,7 @@
+/*!
+ * artplayer-plugin-multiple-subtitles.js v1.2.0
+ * Github: https://github.com/zhw2590582/ArtPlayer
+ * (c) 2017-2026 Harvey Zhao
+ * Released under the MIT License.
+ */
+!function(e,t){"object"===typeof exports&&"undefined"!==typeof module?module.exports=t():"function"==typeof define&&define.amd?(t.artplayerPluginMultipleSubtitles=t(),define(function(){return t.artplayerPluginMultipleSubtitles})):(e="undefined"!==typeof globalThis?globalThis:e||self).artplayerPluginMultipleSubtitles=t()}(this,function(){"use strict";var e=Object.defineProperty,t=Object.defineProperties,n=Object.getOwnPropertyDescriptors,i=Object.getOwnPropertySymbols,a=Object.prototype.hasOwnProperty,s=Object.prototype.propertyIsEnumerable,r=(t,n,i)=>n in t?e(t,n,{enumerable:!0,configurable:!0,writable:!0,value:i}):t[n]=i,o=(e,t)=>{for(var n in t||(t={}))a.call(t,n)&&r(e,n,t[n]);if(i)for(var n of i(t))s.call(t,n)&&r(e,n,t[n]);return e},l=(e,t,n)=>new Promise((i,a)=>{var s=e=>{try{o(n.next(e))}catch(t){a(t)}},r=e=>{try{o(n.throw(e))}catch(t){a(t)}},o=e=>e.done?i(e.value):Promise.resolve(e.value).then(s,r);o((n=n.apply(e,t)).next())}),f={direction:"horizontal",snapToLines:!0,linePosition:"auto",lineAlign:"start",textPosition:"auto",positionAlign:"auto",size:100,alignment:"center"},c=function(e){e||(e={"&amp":"&","&lt":"<","&gt":">","&lrm":"\u200e","&rlm":"\u200f","&nbsp":"\xa0"}),this.entities=e,this.parse=function(t,n){t=t.replace(/\0/g,"\ufffd");var i=Date.now(),a=0,s=t.split(/\r\n|\r|\n/),r=!1,o=[],l=[],c=[];function p(e,t){c.push({message:e,line:a+1,col:t})}var m=s[a],g=m.length,h="WEBVTT",v=0,b=6;for("\ufeff"===m[0]&&(v=1,b+=1),(g<b||m.indexOf(h)!==0+v||g>b&&" "!==m[b]&&"\t"!==m[b])&&p('No valid signature. (File needs to start with "WEBVTT".)'),a++;""!=s[a]&&void 0!=s[a];){if(p("No blank line after the signature."),-1!=s[a].indexOf("--\x3e")){r=!0;break}a++}for(;void 0!=s[a];){for(var x;!r&&""==s[a];)a++;if(!r&&void 0==s[a])break;x=Object.assign({},f,{id:"",startTime:0,endTime:0,pauseOnExit:!1,direction:"horizontal",snapToLines:!0,linePosition:"auto",lineAlign:"start",textPosition:"auto",positionAlign:"auto",size:100,alignment:"center",text:"",tree:null});var T=!0;if(-1==s[a].indexOf("--\x3e")){if(x.id=s[a],/^NOTE($|[ \t])/.test(x.id)){for(a++;""!=s[a]&&void 0!=s[a];)-1!=s[a].indexOf("--\x3e")&&p("Cannot have timestamp in a comment."),a++;continue}if(/^STYLE($|[ \t])/.test(x.id)){var y=[],w=!1;for(a++;""!=s[a]&&void 0!=s[a];)-1!=s[a].indexOf("--\x3e")&&(p("Cannot have timestamp in a style block."),w=!0),y.push(s[a]),a++;if(l.length){p("Style blocks cannot appear after the first cue.");continue}w||o.push(y.join("\n"));continue}if(""==s[++a]||void 0==s[a]){p("Cue identifier cannot be standalone.");continue}if(-1==s[a].indexOf("--\x3e")){T=!1,p("Cue identifier needs to be followed by timestamp.");continue}}r=!1;var O=new u(s[a],p),P=0;if(l.length>0&&(P=l[l.length-1].startTime),!T||O.parse(x,P)){for(a++;""!=s[a]&&void 0!=s[a];){if(-1!=s[a].indexOf("--\x3e")){p("Blank line missing before cue."),r=!0;break}""!=x.text&&(x.text+="\n"),x.text+=s[a],a++}var I=new d(x.text,p,n,e);x.tree=I.parse(x.startTime,x.endTime),l.push(x)}else for(x=null,a++;""!=s[a]&&void 0!=s[a];){if(-1!=s[a].indexOf("--\x3e")){r=!0;break}a++}}return l.sort(function(e,t){return e.startTime<t.startTime?-1:e.startTime>t.startTime?1:e.endTime>t.endTime?-1:e.endTime<t.endTime?1:0}),{cues:l,errors:c,time:Date.now()-i,styles:o}}},u=function(e,t){var n=/[\u0020\t\f]/,i=/[^\u0020\t\f]/,a=(e=e,0),s=function(e){t(e,a+1)};function r(t){for(;void 0!=e[a]&&t.test(e[a]);)a++}function o(t){for(var n="";void 0!=e[a]&&t.test(e[a]);)n+=e[a],a++;return n}function l(){var t,n,i,r,l="minutes";if(void 0!=e[a])if(/\d/.test(e[a]))if(((t=o(/\d/)).length>2||parseInt(t,10)>59)&&(l="hours"),":"==e[a])if(a++,2==(n=o(/\d/)).length){if("hours"==l||":"==e[a]){if(":"!=e[a])return void s("No seconds found or minutes is greater than 59.");if(a++,2!=(i=o(/\d/)).length)return void s("Must be exactly two digits.")}else{if(2!=t.length)return void s("Must be exactly two digits.");i=n,n=t,t="0"}if("."==e[a])if(a++,3==(r=o(/\d/)).length)if(parseInt(n,10)>59)s("You cannot have more than 59 minutes.");else{if(!(parseInt(i,10)>59))return 60*parseInt(t,10)*60+60*parseInt(n,10)+parseInt(i,10)+parseInt(r,10)/1e3;s("You cannot have more than 59 seconds.")}else s("Milliseconds must be given in three digits.");else s('No decimal separator (".") found.')}else s("Must be exactly two digits.");else s("No time unit separator found.");else s("Timestamp must start with a character in the range 0-9.");else s("No timestamp found.")}this.parse=function(t,o){if(r(n),t.startTime=l(),void 0!=t.startTime)if(t.startTime<o&&s("Start timestamp is not greater than or equal to start timestamp of previous cue."),i.test(e[a])&&s("Timestamp not separated from '--\x3e' by whitespace."),r(n),"-"==e[a])if(a++,"-"==e[a])if(a++,">"==e[a]){if(a++,i.test(e[a])&&s("'--\x3e' not separated from timestamp by whitespace."),r(n),t.endTime=l(),void 0!=t.endTime)return t.endTime<=t.startTime&&s("End timestamp is not greater than start timestamp."),i.test(e[a]),r(n),function(e,t){for(var i=e.split(n),a=[],r=0;r<i.length;r++)ifLine truncated