video: prevent frame capture when video is not ready

lib/widgets/viewer/overlay/bottom/video.dart

@@ -245,6 +245,18 @@ class _ButtonRow extends StatelessWidget {
         );
         break;
       case VideoAction.captureFrame:
+        child = ValueListenableBuilder<bool>(
+          valueListenable: controller?.renderingVideoNotifier ?? ValueNotifier(false),
+          builder: (context, canDo, child) {
+            return IconButton(
+              icon: child!,
+              onPressed: canDo ? onPressed : null,
+              tooltip: action.getText(context),
+            );
+          },
+          child: Icon(action.getIcon()),
+        );
+        break;
       case VideoAction.replay10:
       case VideoAction.selectStreams:
       case VideoAction.setSpeed:
@@ -265,6 +277,7 @@ class _ButtonRow extends StatelessWidget {
   }
 
   PopupMenuEntry<VideoAction> _buildPopupMenuItem(BuildContext context, VideoAction action) {
+    var enabled = true;
     Widget? child;
     switch (action) {
       case VideoAction.togglePlay:
@@ -274,6 +287,9 @@ class _ButtonRow extends StatelessWidget {
         );
         break;
       case VideoAction.captureFrame:
+        enabled = controller?.renderingVideoNotifier.value ?? false;
+        child = MenuRow(text: action.getText(context), icon: action.getIcon());
+        break;
       case VideoAction.replay10:
       case VideoAction.selectStreams:
       case VideoAction.setSpeed:
@@ -282,6 +298,7 @@ class _ButtonRow extends StatelessWidget {
     }
     return PopupMenuItem(
       value: action,
+      enabled: enabled,
       child: child,
     );
   }

lib/widgets/viewer/video/controller.dart

@@ -27,6 +27,8 @@ abstract class AvesVideoController {
 
   Stream<VideoStatus> get statusStream;
 
+  ValueNotifier<bool> get renderingVideoNotifier;
+
   bool get isReady;
 
   bool get isPlaying => status == VideoStatus.playing;

lib/widgets/viewer/video/fijkplayer.dart

@@ -38,6 +38,9 @@ class IjkPlayerAvesVideoController extends AvesVideoController {
   @override
   final double maxSpeed = 2;
 
+  @override
+  final ValueNotifier<bool> renderingVideoNotifier = ValueNotifier(false);
+
   @override
   final ValueNotifier<double> sarNotifier = ValueNotifier(1);
 
@@ -52,6 +55,10 @@ class IjkPlayerAvesVideoController extends AvesVideoController {
       _staticInitialized = true;
     }
     _instance = FijkPlayer();
+    _valueStream.firstWhere((value) => value.videoRenderStart).then(
+          (value) => renderingVideoNotifier.value = true,
+          onError: (error) {},
+        );
     _startListening();
   }
 
@@ -340,9 +347,13 @@ class IjkPlayerAvesVideoController extends AvesVideoController {
     return Map.fromEntries(_streams.map((stream) => MapEntry(stream, selectedIndices.contains(stream.index))));
   }
 
-  // TODO TLAD [video] bug: crash when video stream is not supported
   @override
-  Future<Uint8List> captureFrame() => _instance.takeSnapShot();
+  Future<Uint8List> captureFrame() {
+    if (!_instance.value.videoRenderStart) {
+      return Future.error('cannot capture frame when video is not rendered');
+    }
+    return _instance.takeSnapShot();
+  }
 
   @override
   Widget buildPlayerWidget(BuildContext context) {