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>

assets/example/index.js

@@ -0,0 +1,190 @@
+var art = new Artplayer({
+  container: '.artplayer-app',
+  url: '/assets/sample/video.mp4',
+  poster: '/assets/sample/poster.jpg',
+  volume: 0.5,
+  isLive: false,
+  muted: false,
+  autoplay: false,
+  pip: true,
+  autoSize: true,
+  autoMini: true,
+  screenshot: true,
+  setting: true,
+  loop: true,
+  flip: true,
+  playbackRate: true,
+  aspectRatio: true,
+  fullscreen: true,
+  fullscreenWeb: true,
+  subtitleOffset: true,
+  miniProgressBar: true,
+  mutex: true,
+  backdrop: true,
+  playsInline: true,
+  autoPlayback: true,
+  airplay: true,
+  theme: '#23ade5',
+  lang: navigator.language.toLowerCase(),
+  moreVideoAttr: {
+    crossOrigin: 'anonymous',
+  },
+  settings: [
+    {
+      width: 200,
+      html: 'Subtitle',
+      tooltip: 'Bilingual',
+      icon: '<img width="22" height="22" src="/assets/img/subtitle.svg">',
+      selector: [
+        {
+          html: 'Display',
+          tooltip: 'Show',
+          switch: true,
+          onSwitch(item) {
+            item.tooltip = item.switch ? 'Hide' : 'Show'
+            art.subtitle.show = !item.switch
+            return !item.switch
+          },
+        },
+        {
+          default: true,
+          html: 'Bilingual',
+          url: '/assets/sample/subtitle.srt',
+        },
+        {
+          html: 'Chinese',
+          url: '/assets/sample/subtitle.cn.srt',
+        },
+        {
+          html: 'Japanese',
+          url: '/assets/sample/subtitle.jp.srt',
+        },
+      ],
+      onSelect(item) {
+        art.subtitle.switch(item.url, {
+          name: item.html,
+        })
+        return item.html
+      },
+    },
+    {
+      html: 'Switcher',
+      icon: '<img width="22" height="22" src="/assets/img/state.svg">',
+      tooltip: 'OFF',
+      switch: false,
+      onSwitch(item) {
+        item.tooltip = item.switch ? 'OFF' : 'ON'
+        console.info('You clicked on the custom switch', item.switch)
+        return !item.switch
+      },
+    },
+    {
+      html: 'Slider',
+      icon: '<img width="22" height="22" src="/assets/img/state.svg">',
+      tooltip: '5x',
+      range: [5, 1, 10, 0.1],
+      onRange(item) {
+        return `${item.range[0]}x`
+      },
+    },
+    {
+      html: 'Button',
+      icon: '<img width="22" height="22" src="/assets/img/state.svg">',
+      tooltip: 'tooltip',
+      onClick() {
+        return 'Button clicked'
+      },
+    },
+  ],
+  contextmenu: [
+    {
+      html: 'Custom menu',
+      click(contextmenu) {
+        console.info('You clicked on the custom menu')
+        contextmenu.show = false
+      },
+    },
+  ],
+  layers: [
+    {
+      html: '<img width="100" src="/assets/sample/layer.png">',
+      click() {
+        window.open('https://aimu.app')
+        console.info('You clicked on the custom layer')
+      },
+      style: {
+        position: 'absolute',
+        top: '20px',
+        right: '20px',
+        opacity: '.9',
+      },
+    },
+  ],
+  quality: [
+    {
+      default: true,
+      html: 'SD 480P',
+      url: '/assets/sample/video.mp4?q=480',
+    },
+    {
+      html: 'HD 720P',
+      url: '/assets/sample/video.mp4?q=720',
+    },
+  ],
+  thumbnails: {
+    url: '/assets/sample/thumbnails.png',
+    number: 60,
+    column: 10,
+    scale: 0.85,
+  },
+  subtitle: {
+    url: '/assets/sample/subtitle.srt',
+    type: 'srt',
+    style: {
+      color: '#fe9200',
+      fontSize: '20px',
+    },
+    encoding: 'utf-8',
+  },
+  highlight: [
+    {
+      time: 15,
+      text: 'One more chance',
+    },
+    {
+      time: 30,
+      text: '谁でもいいはずなのに',
+    },
+    {
+      time: 45,
+      text: '夏の想い出がまわる',
+    },
+    {
+      time: 60,
+      text: 'こんなとこにあるはずもないのに',
+    },
+    {
+      time: 75,
+      text: '终わり',
+    },
+  ],
+  controls: [
+    {
+      position: 'right',
+      html: 'Control',
+      index: 1,
+      tooltip: 'Control Tooltip',
+      style: {
+        marginRight: '20px',
+      },
+      click() {
+        console.info('You clicked on the custom control')
+      },
+    },
+  ],
+  icons: {
+    loading: '<img src="/assets/img/ploading.gif">',
+    state: '<img width="150" height="150" src="/assets/img/state.svg">',
+    indicator: '<img width="16" height="16" src="/assets/img/indicator.svg">',
+  },
+})