perf: preload short episodes earlier with current playback priority

README.md

@@ -187,3 +187,11 @@ python3 scripts/sync_source.py --check
 站源是 Go 原生 provider（`native/core/provider_*.go`），不是运行期加载的 Python 源。新增站源需接入：`provider_huangguo.go`（常量 / 白名单 / `canonicalProviderSource` / `GetHuangguoChapters`）、`provider_media.go`（baseURL / host 反查 / 播放分派）、`app_categories.go`、`app_cover_metadata.go`、`app_runtime.go`（Config 字段 + 目录 / 搜索 / 详情分派 + 空页放行），并在 `lib/models.dart` 登记 `SourceSite`。
 
 注意：Go RE2 正则**不支持 lookahead**。解析多线路播放列表时不能用 `(?=...)` 做分段，否则非捕获组会消耗下一段开头；应改用显式字符串截断（从容器标记之后查找下一段标记）。
+
+## 短剧下一集预加载优化
+
+原策略需要当前集播放到一半或剩余 45 秒以内，并保持 5 秒缓冲；电视的向前读取上限也是约 5 秒，预加载可能迟迟不能触发。时长不超过 2 分钟的短剧现在播放约 2 秒、有至少 3 秒缓冲即可开始准备下一集；不足 8 秒的极短视频按约四分之一时长触发。长视频保留播放后段触发，临近结尾按实际剩余时长检查缓冲。
+
+预加载启动防抖缩短为 200 毫秒；当前缓冲低于 1.5 秒时取消未完成的预取，缓冲恢复到 3 秒后重试，已准备的结果保留。仍然只准备下一集，原生开头数据预取保持最多 4 MiB / 6 秒限制。自动连播和手动下一集均复用匹配的会话；过期、集数、画质或在线模式不匹配的结果不会交给播放器，无效结果会释放。播放日记新增准备耗时、预取字节数和复用记录，不包含新增媒体地址或凭证。
+
+基于上游源码的 7 项预加载策略/生命周期测试和 2 项合成 TV 切集测试通过：80 秒短剧在第 2 秒、3 秒缓冲时触发，自动和手动切集均使用预取会话、没有第二次地址解析。播放器 open 耗时日志只记录打开流程，不代表首帧显示耗时。真机切集等待时长尚未验证，不保证无缝播放。

lib/app_layout.dart

@@ -6,7 +6,7 @@ import 'package:flutter/services.dart';
 
 export 'app_build.dart';
 
-const appVersion = '0.2.64';
+const appVersion = '0.2.65';
 
 ThemeData televisionTheme(ThemeData theme) {
   final colors = theme.colorScheme;

lib/main.dart

@@ -24,7 +24,7 @@ import 'diary_service.dart';
 
 Future<void> main(List<String> arguments) async {
   WidgetsFlutterBinding.ensureInitialized();
-  DiaryService.add('[App] 应用启动，版本: 0.2.64+71, 平台: ${Platform.operatingSystem}');
+  DiaryService.add('[App] 应用启动，版本: $appVersion, 平台: ${Platform.operatingSystem}');
   if (Platform.isAndroid) {
     await SystemChrome.setEnabledSystemUIMode(SystemUiMode.edgeToEdge);
     SystemChrome.setSystemUIOverlayStyle(AppTheme.systemBars(Brightness.dark));

lib/playback_preloader.dart

@@ -3,8 +3,34 @@ import 'dart:async';
 import 'package:flutter/foundation.dart';
 
 import 'core_bridge.dart';
+import 'diary_service.dart';
 import 'models.dart';
 
+enum PlaybackPreloadAction { wait, prepare, pause }
+
+PlaybackPreloadAction playbackPreloadAction({
+  required Duration duration,
+  required Duration position,
+  required Duration buffer,
+}) {
+  final length = duration.inMilliseconds;
+  final elapsed = position.inMilliseconds;
+  final remaining = length - elapsed;
+  if (length <= 0 || remaining <= 0) return PlaybackPreloadAction.pause;
+  final headroom = buffer.inMilliseconds - elapsed;
+  final pauseThreshold = remaining < 1500 ? remaining : 1500;
+  if (headroom < pauseThreshold) return PlaybackPreloadAction.pause;
+  final start = length < 8000 ? (length ~/ 4).clamp(500, 2000) : 2000;
+  if (elapsed < start ||
+      (length > 120000 && elapsed < length ~/ 2 && remaining > 45000)) {
+    return PlaybackPreloadAction.wait;
+  }
+  final requiredBuffer = remaining < 3000 ? remaining : 3000;
+  return headroom >= requiredBuffer
+      ? PlaybackPreloadAction.prepare
+      : PlaybackPreloadAction.wait;
+}
+
 class PlaybackPreloader extends ChangeNotifier {
   PlaybackPreloader(this.repository, {DateTime Function()? now})
     : _now = now ?? DateTime.now;
@@ -31,7 +57,7 @@ class PlaybackPreloader extends ChangeNotifier {
           : '下一集播放地址已准备';
     }
     if (loading || _delay != null) return '正在准备下一集';
-    return error.isNotEmpty ? '下一集预加载暂不可用，切集时会重新获取' : '播放后段提前准备下一集';
+    return error.isNotEmpty ? '下一集预加载暂不可用，切集时会重新获取' : '播放稳定后提前准备下一集';
   }
 
   String _key(Drama drama, Episode episode, int quality, bool online) =>
@@ -61,10 +87,11 @@ class PlaybackPreloader extends ChangeNotifier {
       return;
     }
     final ticket = _generation;
-    _delay = Timer(const Duration(milliseconds: 600), () async {
+    _delay = Timer(const Duration(milliseconds: 200), () async {
       _delay = null;
       loading = true;
       notifyListeners();
+      final elapsed = Stopwatch()..start();
       try {
         final plan = await repository.preload(
           drama,
@@ -76,7 +103,10 @@ class PlaybackPreloader extends ChangeNotifier {
           if (plan != null) await repository.release(plan.session);
           return;
         }
-        if (plan == null || plan.url.isEmpty) throw AppFailure('未取得预加载结果');
+        if (plan == null || plan.url.isEmpty) {
+          if (plan != null) _release(plan);
+          throw AppFailure('未取得预加载结果');
+        }
         var expires = _now().add(const Duration(minutes: 2));
         if (plan.expiresAt > 0) {
           final authorizationExpiry = DateTime.fromMillisecondsSinceEpoch(
@@ -93,6 +123,9 @@ class PlaybackPreloader extends ChangeNotifier {
         _ready = plan;
         _expires = expires;
         error = '';
+        DiaryService.add(
+          '[Preload] ready episode=${episode.number} bytes=${plan.prefetchedBytes} elapsedMs=${elapsed.elapsedMilliseconds}',
+        );
       } catch (failure) {
         if (_closed || ticket != _generation) return;
         error = failure.toString();
@@ -118,7 +151,12 @@ class PlaybackPreloader extends ChangeNotifier {
             _now().isBefore(_expires)
         ? _ready
         : null;
-    if (result != null) _ready = null;
+    if (result != null) {
+      _ready = null;
+      DiaryService.add(
+        '[Preload] reuse episode=${episode.number} bytes=${result.prefetchedBytes}',
+      );
+    }
     clear();
     return result;
   }

lib/player_screen.dart

@@ -673,14 +673,16 @@ class _PlayerScreenState extends State<PlayerScreen>
       _preloader.pause();
       return;
     }
-    final duration = state.duration.inMilliseconds;
-    final position = state.position.inMilliseconds;
-    if (duration <= 0 ||
-        position < 2000 ||
-        (position < duration ~/ 2 && duration - position > 45000) ||
-        state.buffer.inMilliseconds - position < 5000) {
+    final action = playbackPreloadAction(
+      duration: state.duration,
+      position: state.position,
+      buffer: state.buffer,
+    );
+    if (action == PlaybackPreloadAction.pause) {
+      _preloader.pause();
       return;
     }
+    if (action != PlaybackPreloadAction.prepare) return;
     _preloader.prepare(
       widget.detail.drama,
       widget.detail.episodes[_index + 1],
@@ -906,6 +908,7 @@ class _PlayerScreenState extends State<PlayerScreen>
       return;
     }
     _interactions.cancel();
+    final opening = Stopwatch()..start();
     if (widget.handoff != null &&
         handoffPlan == null &&
         recoveryAction == null) {
@@ -1014,8 +1017,14 @@ class _PlayerScreenState extends State<PlayerScreen>
               await platform.setProperty('vd-lavc-skiploopfilter', 'all');
               await platform.setProperty('vd-lavc-skipidct', 'all');
               await platform.setProperty('vd-lavc-threads', '2');
-              await platform.setProperty('demuxer-max-bytes', '${4 * 1024 * 1024}');
-              await platform.setProperty('demuxer-max-back-bytes', '${1 * 1024 * 1024}');
+              await platform.setProperty(
+                'demuxer-max-bytes',
+                '${4 * 1024 * 1024}',
+              );
+              await platform.setProperty(
+                'demuxer-max-back-bytes',
+                '${1 * 1024 * 1024}',
+              );
               await platform.setProperty('demuxer-readahead-secs', '5');
             } else {
               await platform.setProperty('hwdec', 'auto-safe');
@@ -1045,7 +1054,9 @@ class _PlayerScreenState extends State<PlayerScreen>
         _plan = plan;
         installed = true;
         _acceptErrors = true;
-        DiaryService.add('[Play] 调用 _player.open: url=${plan.url}, headers=${plan.headers.keys.toList()}');
+        DiaryService.add(
+          '[Play] 调用 _player.open: url=${plan.url}, headers=${plan.headers.keys.toList()}',
+        );
         await _player.open(
           Media(
             plan.url,
@@ -1060,6 +1071,9 @@ class _PlayerScreenState extends State<PlayerScreen>
           return;
         }
         _openedIndex = index;
+        DiaryService.add(
+          '[Play] opened episode=${widget.detail.episodes[index].number} preloaded=${warmed != null} elapsedMs=${opening.elapsedMilliseconds}',
+        );
         _enhancement.mediaReady();
         _attachLanPlayback();
         _health.reset();
@@ -1768,7 +1782,8 @@ class _PlayerScreenState extends State<PlayerScreen>
                       crossAxisAlignment: WrapCrossAlignment.center,
                       children: [
                         FilledButton.tonalIcon(
-                          onPressed: () => DiaryService.showDiaryDialog(context),
+                          onPressed: () =>
+                              DiaryService.showDiaryDialog(context),
                           icon: const Icon(Icons.receipt_long_rounded),
                           label: const Text('查看播放日记'),
                         ),
@@ -1779,8 +1794,8 @@ class _PlayerScreenState extends State<PlayerScreen>
                             label: const Text('改为在线播放'),
                           )
                         else if (!_localFailure &&
-                              !widget.localOnly &&
-                              widget.repository.supportsSourceManagement)
+                            !widget.localOnly &&
+                            widget.repository.supportsSourceManagement)
                           SourceDiagnosticsButton(
                             repository: widget.repository,
                             store: widget.store,

pubspec.yaml

@@ -1,7 +1,7 @@
 name: duanju_app
 description: 独立运行的多端短剧应用
 publish_to: none
-version: 0.2.64+71
+version: 0.2.65+72
 
 environment:
   sdk: '>=3.12.0 <4.0.0'