First try

AudioMixer has same issue transitioning from silence to encoded
audio and back, it seems.  This makes that go away, but I don't
like it.  Better to support a flush function in the encoder but
for now lets do this and be sure it is the entire issue.

assignment-client/src/audio/AudioMixer.cpp

@@ -819,6 +819,9 @@ void AudioMixer::broadcastMixes() {
                     std::unique_ptr<NLPacket> mixPacket;
 
                     if (mixHasAudio) {
+                        // may need to flush, this checks
+                        nodeData->flushEncoder();
+                        
                         int mixPacketBytes = sizeof(quint16) + AudioConstants::MAX_CODEC_NAME_LENGTH_ON_WIRE 
                                                              + AudioConstants::NETWORK_FRAME_BYTES_STEREO;
                         mixPacket = NLPacket::create(PacketType::MixedAudio, mixPacketBytes);
@@ -852,6 +855,9 @@ void AudioMixer::broadcastMixes() {
                         // pack number of silent audio samples
                         quint16 numSilentSamples = AudioConstants::NETWORK_FRAME_SAMPLES_STEREO;
                         mixPacket->writePrimitive(numSilentSamples);
+
+                        // we will need to flush encoder since we are sending silent packets outside it
+                        nodeData->shouldFlushEncoder();
                     }
 
                     // Send audio environment

assignment-client/src/audio/AudioMixerClientData.cpp

@@ -366,6 +366,16 @@ void AudioMixerClientData::sendSelectAudioFormat(SharedNodePointer node, const Q
     nodeList->sendPacket(std::move(replyPacket), *node);
 }
 
+void AudioMixerClientData::flushEncoder() {
+    static QByteArray zeros(AudioConstants::NETWORK_FRAME_BYTES_STEREO, 0);
+    static QByteArray encodedZeros;
+    if (_shouldFlushEncoder) {
+        _shouldFlushEncoder = false;
+        if (_encoder) {
+            _encoder->encode(zeros, encodedZeros);
+        }
+    }
+}
 
 void AudioMixerClientData::setupCodec(CodecPluginPointer codec, const QString& codecName) {
     cleanupCodec(); // cleanup any previously allocated coders first

assignment-client/src/audio/AudioMixerClientData.h

@@ -77,6 +77,8 @@ public:
             encodedBuffer = decodedBuffer;
         }
     }
+    void flushEncoder();
+    void shouldFlushEncoder() { _shouldFlushEncoder = true; }
 
     QString getCodecName() { return _selectedCodecName; }
 
@@ -105,6 +107,8 @@ private:
     QString _selectedCodecName;
     Encoder* _encoder{ nullptr }; // for outbound mixed stream
     Decoder* _decoder{ nullptr }; // for mic stream
+
+    bool _shouldFlushEncoder { false };
 };
 
 #endif // hifi_AudioMixerClientData_h