Voice chat over a mumble server in flutter

Question

i am trying to implement a voice chat on a mumble server using flutter and dumble package, i have tried many many things and end up with this code that of course does not work ;) this is why i am here to get assistance and advices on how to setup everything correctly .

for the sender user i am using mic_stream package to record voice .

based on some code from the dumble demo :

_client = await MumbleClient.connect(
       options: connectionoptions,
       onBadCertificate: (X509Certificate certificate) {
         //Accept every certificate
         return true;
       });

       
   audioOutput = _client.audio.sendAudio(codec: AudioCodec.opus);
   // _client.self.add(new SelfCallback(client.self.session));
   var lib = await opus_flutter.load();
   initOpus(lib);
   encoder = StreamOpusEncoder.bytes(
       frameTime: frameTime,
       floatInput: false,
       sampleRate: inputSampleRate,
       channels: channels,
       application: Application.voip);


Future<bool> StartRecording() async {
   mic_stream.MicStream.shouldRequestPermission(true);

   Stream<List<int>> microphoneStream = (await mic_stream.MicStream.microphone(
           audioSource: mic_stream.AudioSource.DEFAULT,
           sampleRate: 48000,
           channelConfig: mic_stream.ChannelConfig.CHANNEL_IN_MONO,
           audioFormat: AUDIO_FORMAT))!
       .cast<List<int>>();

   microphoneStream
       .asyncMap((List<int> bytes) async {
         return bytes;
       })
       .transform(encoder)
       .map((Uint8List audioBytes) => AudioFrame.outgoing(frame: audioBytes))
       .pipe(audioOutput);
   setState(() {
     _isRecording = true;
   });

   listener = microphoneStream!.listen(
     (data) {
       //this block is executed when data event is recieved by listener
       print(data);
     },
    );
   return true;
 }

with that i can see the data flow in the console

the reciever user :

_client.audio.add(StreamAudioListener());

class StreamAudioListener with AudioListener {
 final AudioPlayer _audioPlayer = AudioPlayer();
 

  @override
  Future<void> onAudioReceived(Stream<AudioFrame> voiceData, AudioCodec codec,
      User? speaker, TalkMode talkMode) async {
 

    if (codec == AudioCodec.opus) {
     
      StreamOpusDecoder decoder = StreamOpusDecoder.bytes(
          floatOutput: false, sampleRate: outputSampleRate, channels: channels);
      var audiostream = voiceData
          .map<Uint8List>((AudioFrame frame) =>
              frame.frame) //we are only interested in the bytes
          .cast<Uint8List?>()
          .transform(decoder)
          .cast<Uint8List>();

      audiostream.listen(
        (data) async {
          // print(data);
          try {
            await _audioPlayer.setAudioSource(
              CustomStreamAudioSource(data),
            );
            // await _audioPlayer.play();
          } catch (e) {
            print("exception"); // print error details
            print(e); // print error details
            print(data); // print error details
          }
        },
        onError: (err) {
          //this block is executed when error event is recieved by listener
          print('Error: ${err}');
        },
        cancelOnError:
            false, //this decides if subscription is cancelled on error or not
        onDone: () {
          //this block is executed when done event is recieved by listener
          print('StreamDone!');
        },
      );  
     
    } else {
      print('But we don\'t know how do decode $codec');
    }
  }
}

please note that on the audiostream.listen i am using just_audio package to play the audio bytes from the stream .

the problem is that i can't hear any sound and periodically get an onerror callback however i can see the stream bytes flow on the listen event so the data is recieved from the sender peer.

i can see both users connected on the mumble client application but no sound is transfered between them .

any help , idea, suggestion is welcome .

thanks .

ps : i know about webrtc ;)