FFmpeg software H.264 decoder: opt-in via pubspec flag

- Gate buildFfmpegJni + jniLibs packaging on `ux: enable_ffmpeg` in the
  consuming app's pubspec (default off) -- no LGPL / H.264-patent
  exposure unless explicitly enabled
- appInfoBuilder generates kUxEnableFfmpeg from the same flag so apps
  register the FFmpeg LGPL notice eagerly, pubspec-only (no dart-define)
- Add registerFfmpegLicense() + bundled LGPL-2.1 text asset
- FFmpeg compliance docs (LICENSES-3RDPARTY.md, android/ffmpeg/README.md)
- Network video streaming: XVideoPlayerController.network

lib/builder.dart

@@ -22,6 +22,8 @@ class _AppInfoBuilder implements Builder {
     final buildNumber =
         plus < 0 ? 0 : int.tryParse(combined.substring(plus + 1)) ?? 0;
 
+    final enableFfmpeg = _readUxFlag(raw, 'enable_ffmpeg');
+
     await buildStep.writeAsString(
       AssetId(pkg, 'lib/app_info.g.dart'),
       '''
@@ -29,7 +31,35 @@ class _AppInfoBuilder implements Builder {
 import 'package:ux/ux.dart';
 
 const kAppInfo = AppInfo(version: '$version', buildNumber: $buildNumber);
+
+/// Mirrors the app's `ux: enable_ffmpeg` pubspec setting as a compile-time
+/// constant. Gate FFmpeg-dependent code (e.g. registerFfmpegLicense()) on
+/// this — pubspec stays the single source of truth.
+const kUxEnableFfmpeg = $enableFfmpeg;
 ''',
     );
   }
+
+  /// Reads a boolean under the top-level `ux:` mapping, e.g. `ux: { $key: ... }`.
+  /// Scans manually (no YAML dep) and ignores the indented `ux:` dependency
+  /// entry by only entering the block on a non-indented `ux:` line.
+  static bool _readUxFlag(String pubspec, String key) {
+    var inUxBlock = false;
+    var enabled = false;
+    for (final rawLine in pubspec.split('\n')) {
+      final hash = rawLine.indexOf('#');
+      final line = hash >= 0 ? rawLine.substring(0, hash) : rawLine;
+      if (line.trim().isEmpty) continue;
+      final indented = line.startsWith(' ') || line.startsWith('\t');
+      if (!indented) {
+        inUxBlock = line.trimRight() == 'ux:' || line.startsWith('ux:');
+      } else if (inUxBlock) {
+        final t = line.trim();
+        if (t.startsWith('$key:')) {
+          enabled = t.substring(key.length + 1).trim().toLowerCase() == 'true';
+        }
+      }
+    }
+    return enabled;
+  }
 }

lib/src/video/ffmpeg_license.dart

@@ -0,0 +1,64 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart' show rootBundle;
+
+/// Whether the FFmpeg notice has already been added to [LicenseRegistry].
+/// Registration adds a stream provider, so guard against duplicates.
+bool _registered = false;
+
+/// Registers the FFmpeg LGPL-2.1 attribution with [LicenseRegistry].
+///
+/// Call this at startup gated on the generated `kUxEnableFfmpeg` constant
+/// (from `app_info.g.dart`, which the ux build_runner builder derives from the
+/// app's `ux: enable_ffmpeg` pubspec flag) — e.g.
+/// `if (kUxEnableFfmpeg) registerFfmpegLicense();`. That keeps pubspec the
+/// single source of truth, registers eagerly (the notice shows without playing
+/// a video), and needs no `--dart-define`. Idempotent — registers at most once.
+void registerFfmpegLicense() {
+  if (_registered) return;
+  _registered = true;
+  LicenseRegistry.addLicense(_ffmpegLicenseEntries);
+}
+
+/// Attribution shown above the LGPL text. Keep in sync with
+/// `android/ffmpeg/build_ffmpeg.sh` (`FFMPEG_TAG`) and
+/// `android/ffmpeg/README.md`.
+const String _attribution = '''
+This application includes FFmpeg, used unmodified as a software video
+decoder on Android via the "ux" package (libffmpegJNI.so, loaded at runtime).
+
+FFmpeg is copyright (c) the FFmpeg developers and is licensed under the
+GNU Lesser General Public License, version 2.1 (LGPL-2.1). The binary is
+dynamically loaded by the app; the LGPL boundary is preserved and no
+copyleft is imposed on the application.
+
+Version: FFmpeg release/6.0, built from upstream source with the H.264
+decoder enabled only (decode-only, no encoders). It is configured WITHOUT
+--enable-gpl and WITHOUT --enable-nonfree, so the binary is LGPL-only.
+
+The corresponding FFmpeg source and the build/link scripts (which document
+the exact configure flags) are available on request for at least three
+years; the application's own source code is not included in that offer.
+The shared library can be rebuilt and replaced from those sources, as
+required by section 6 of the LGPL. Contact: alex@swipelab.co
+
+The full text of the LGPL v2.1 follows.''';
+
+Stream<LicenseEntry> _ffmpegLicenseEntries() async* {
+  String lgpl;
+  try {
+    lgpl = await rootBundle
+        .loadString('packages/ux/assets/licenses/ffmpeg_LGPL-2.1.txt');
+  } catch (error, stack) {
+    // A missing asset must never break license collection; the attribution
+    // paragraph below still names FFmpeg and its license.
+    FlutterError.reportError(
+      FlutterErrorDetails(exception: error, stack: stack),
+    );
+    lgpl = '';
+  }
+
+  yield LicenseEntryWithLineBreaks(
+    const <String>['FFmpeg (libavcodec, libavutil, libswresample)'],
+    lgpl.isEmpty ? _attribution : '$_attribution\n\n$lgpl',
+  );
+}

lib/src/video/x_video_player.dart

@@ -130,17 +130,26 @@ class XVideoPlayerValue {
 
 /// Owns one native video-player session. The surface mirrors the
 /// subset of `package:video_player`'s `VideoPlayerController` the app
-/// currently uses — only the `.file(...)` constructor, the standard
-/// playback controls, and the `value` getters compose / gallery /
-/// outgoing-media read.
+/// currently uses — the `.file(...)` / `.network(...)` constructors, the
+/// standard playback controls, and the `value` getters compose /
+/// gallery / outgoing-media read.
 ///
 /// Lifecycle: construct → [initialize] → use → [dispose]. After
 /// [dispose] every other method throws [XVideoPlayerException("disposed")].
 class XVideoPlayerController extends ChangeNotifier
     implements ValueListenable<XVideoPlayerValue> {
-  XVideoPlayerController.file(io.File file) : _file = file;
+  /// Play a local file.
+  XVideoPlayerController.file(io.File file) : _uri = 'file://${file.path}';
 
-  final io.File _file;
+  /// Stream from a network URL. The native side hands the URI straight
+  /// to Media3 (Android, `MediaItem.fromUri`) / `AVURLAsset` (Apple),
+  /// both of which stream http(s) natively — no extra setup.
+  XVideoPlayerController.network(Uri uri) : _uri = uri.toString();
+
+  /// Fully-qualified source URI handed to the native side at
+  /// [initialize]. `file://...` for [XVideoPlayerController.file], the
+  /// raw URL for [XVideoPlayerController.network].
+  final String _uri;
 
   XVideoPlayerValue _value = XVideoPlayerValue.uninitialized;
 
@@ -185,7 +194,7 @@ class XVideoPlayerController extends ChangeNotifier
   Future<void> _initInternal() async {
     try {
       final result = await XVideoPlayerBackend.instance.create(
-        uri: 'file://${_file.path}',
+        uri: _uri,
       );
       _handle = result.handle;
       _textureId = result.textureId;

lib/src/video/x_video_player_backend.dart

@@ -16,8 +16,9 @@ abstract class XVideoPlayerBackend {
   /// Swap to inject a fake before any UI code mounts a controller.
   static XVideoPlayerBackend instance = MethodChannelXVideoPlayerBackend();
 
-  /// Allocate a native player instance bound to [uri] (currently always
-  /// `file://...`). Returns the handle and, on Apple platforms, the
+  /// Allocate a native player instance bound to [uri] (`file://...` for
+  /// local playback, or an http(s) URL for network streaming). Returns
+  /// the handle and, on Apple platforms, the
   /// Flutter texture id; Android returns `textureId: null` because the
   /// render path is a platform view that takes the handle as creation
   /// params.

lib/ux.dart

@@ -14,6 +14,7 @@ export 'src/camera/camera.dart';
 export 'src/camera/camera_backend.dart' show XCameraBackend, XCameraCreateResult, XCameraEvent, XCameraDeviceOrientationChanged, XCameraSessionError, XCameraSessionInterrupted, XCameraSessionResumed, XCameraDiagnostic, XCameraPreviewSizeChanged;
 export 'src/camera/camera_channel.dart' show MethodChannelXCameraBackend;
 export 'src/camera/camera_preview.dart';
+export 'src/video/ffmpeg_license.dart' show registerFfmpegLicense;
 export 'src/video/x_video_player.dart';
 export 'src/video/x_video_player_backend.dart' show XVideoPlayerBackend, XVideoPlayerCreateResult, XVideoPlayerMetadata, XVideoPlayerEvent, XVideoPlayerStateChanged, XVideoPlayerSizeChanged, XVideoPlayerCompleted, XVideoPlayerError;
 export 'src/video/x_video_player_channel.dart' show MethodChannelXVideoPlayerBackend;