Library not usable inside a Flutter dart isolate

[One-djey]

Description
I can't use the flutter library inside an isolate.
Any operation using FFmpegKit, FFprobeKit or FFmpegKitConfig fails.

Expected behavior
ffmpeg_kit_flutter should be usable outside the main thread: inside any isolate.

Current behavior
While trying to FFmpegKit.executeWithArgumentsAsync([...]) an unhandled exception is thrown:
E/flutter (25355): Null check operator used on a null value

To Reproduce
Implement this great tutorial about Isolates in dart
Then try any FFmpeg execution with FFmpegKit.executeWithArgumentsAsync inside the myIsolate function of the tutorial.

Screenshots
NA

Logs

E/flutter (25355): [ERROR:flutter/runtime/dart_isolate.cc(1137)] Unhandled exception:
E/flutter (25355): Null check operator used on a null value
E/flutter (25355): #0      EventChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:512:86)
E/flutter (25355): #1      EventChannel.receiveBroadcastStream.<anonymous closure> (package:flutter/src/services/platform_channel.dart:532:7)
E/flutter (25355): #2      EventChannel.receiveBroadcastStream.<anonymous closure> (package:flutter/src/services/platform_channel.dart:531:64)
E/flutter (25355): #3      _runGuarded (dart:async/stream_controller.dart:773:24)
E/flutter (25355): #4      _BroadcastStreamController._subscribe (dart:async/broadcast_stream_controller.dart:207:7)
E/flutter (25355): #5      _ControllerStream._createSubscription (dart:async/stream_controller.dart:786:19)
E/flutter (25355): #6      _StreamImpl.listen (dart:async/stream_impl.dart:473:9)
E/flutter (25355): #7      FFmpegKitInitializer._initialize (package:ffmpeg_kit_flutter/src/ffmpeg_kit_flutter_initializer.dart:256:44)
E/flutter (25355): #8      FFmpegKitInitializer.initialize (package:ffmpeg_kit_flutter/src/ffmpeg_kit_flutter_initializer.dart:50:23)
E/flutter (25355): #9      FFmpegKitConfig.init (package:ffmpeg_kit_flutter/ffmpeg_kit_config.dart:48:32)
E/flutter (25355): #10     AbstractSession.createFFmpegSession (package:ffmpeg_kit_flutter/abstract_session.dart:70:29)
E/flutter (25355): #11     FFmpegSession.create (package:ffmpeg_kit_flutter/ffmpeg_session.dart:40:43)
E/flutter (25355): #12     FFmpegKit.executeWithArgumentsAsync (package:ffmpeg_kit_flutter/ffmpeg_kit.dart:51:41)
E/flutter (25355): #13     myIsolate.<anonymous closure> (package:my_app/main.dart:157:45)
E/flutter (25355): <asynchronous suspension>

Environment

• Platform: Flutter on Android
• Architecture: arm64-v8a (Pixel 4A 5G)
• Version ffmpeg_kit_flutter 4.5.0
• Android Studio version 4.1.3
• Android NDK version 23.1.7779620

Other
A StackOverflow question has been asked for this same error on another domain. It might help for the resolution.

[tanersener]

As far as I remember, this is a limitation coming from flutter, not something we ignored. Other plugins that use platform channels also suffer from it. See flutter issue #13937.

[One-djey]

As recommended by one of the comments in the Flutter's issue @tanersener mentioned, I will try to use isolate_handler and come back to you, if it's working.

[One-djey]

After having tuned many things in my code and migrated to isolate_handler, I have another issue, but which seems closely related to the previous one:

I/flutter (20344): Loading ffmpeg-kit-flutter.
I/flutter (20344): [Isolate] ERROR: MissingPluginException(No implementation found for method getLogLevel on channel flutter.arthenica.com/ffmpeg_kit)
I/flutter (20344): #0      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:156:7)
I/flutter (20344): #1      FFmpegKitInitializer._initialize (package:ffmpeg_kit_flutter_audio/src/ffmpeg_kit_flutter_initializer.dart:258:22)
I/flutter (20344): #2      FFmpegKitInitializer.initialize (package:ffmpeg_kit_flutter_audio/src/ffmpeg_kit_flutter_initializer.dart:50:7)
I/flutter (20344): #3      FFmpegKitConfig.init (package:ffmpeg_kit_flutter_audio/ffmpeg_kit_config.dart:48:5)
I/flutter (20344): #4      AbstractSession.createFFmpegSession (package:ffmpeg_kit_flutter_audio/abstract_session.dart:70:7)
I/flutter (20344): #5      FFmpegSession.create (package:ffmpeg_kit_flutter_audio/ffmpeg_session.dart:40:21)
I/flutter (20344): #6      FFmpegKit.executeWithArgumentsAsync (package:ffmpeg_kit_flutter_audio/ffmpeg_kit.dart:51:21)
I/flutter (20344): <asynchronous suspension>


======== Exception caught by services library ======================================================
The following MissingPluginException was thrown while activating platform stream on channel flutter.arthenica.com/ffmpeg_kit_event:
MissingPluginException(No implementation found for method listen on channel flutter.arthenica.com/ffmpeg_kit_event)

When the exception was thrown, this was the stack: 
#0      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:156:7)
#1      EventChannel.receiveBroadcastStream.<anonymous closure> (package:flutter/src/services/platform_channel.dart:545:9)
====================================================================================================

I'm not sure @tanersener can fix it.
I am disappointed by this beautiful speech:

[isolate_handler] use a mechanism called platform channel to communicate between the Dart and the native sides, a message passing mechanism using the MethodChannel type. This mechanism depends on elements of the underlying UI engine to function. Standard isolates don't have that underlying engine because it's not something they normally need but this means that any call to a plugin (eg. to something as simple as path_provider) will fail.

Even with that, the ffmpeg_kit_flutter doesn't work inside an isolate.

[One-djey]

@tanersener do you have any workaround?

[tanersener]

No, I don't know how to overcome this.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[mpcreza]

Hi @tanersener , i get same error when use with flutter_background_service. this plugin work with other plugins if no requires UI, i don't understand why ffmpeg needs UI.

Error:

ERROR: MissingPluginException(No implementation found for method getLogLevel on channel flutter.arthenica.com/ffmpeg_kit)

ERROR:flutter/lib/ui/ui_dart_state.cc

I also tested with old flutter_ffmpeg plugin and it worked.

[tanersener]

@mpcreza ffmpeg-kit is not the renamed version of flutter_ffmpeg. There are big changes under the hood. The main difference is ffmpeg-kit is a federated plugin, flutter_ffmpeg is not. In ffmpeg-kit we also followed the best practices from official flutter plugins. So, they are quite different.

I don't know what is the issue with flutter_background_service, those two lines doesn't tell me much. I suggest creating a separate issue and filling out issue template fields if you need assistance about that.

[mpcreza]

@tanersener you're right.
If I create a new issue, it will be very similar to this issue, because the problem I have with the flutter_background_service is related to isolate. now should I create a new issues or explain more here?

[tanersener]

@mpcreza If your stack trace is identical to the one given in the first post then you have the same problem. You can add the details here. But we don't have a solution or workaround for isolates yet.