From 175d1be7ca9fceb90addd992368c728ce0cdf294 Mon Sep 17 00:00:00 2001
From: Ken Cooke <ken@highfidelity.io>
Date: Tue, 23 May 2017 12:32:41 -0700
Subject: [PATCH] Implement state-machine to detect gate opening/closing. Fixes
 bugs with mute.

---
 libraries/audio-client/src/AudioClient.cpp | 27 +++++++++++++---------
 libraries/audio-client/src/AudioClient.h   |  1 +
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/libraries/audio-client/src/AudioClient.cpp b/libraries/audio-client/src/AudioClient.cpp
index a7d5be22ef..573e0a455f 100644
--- a/libraries/audio-client/src/AudioClient.cpp
+++ b/libraries/audio-client/src/AudioClient.cpp
@@ -1057,19 +1057,24 @@ void AudioClient::handleAudioInput(QByteArray& audioBuffer) {
         }
 
         emit inputReceived(audioBuffer);
-
-        if (_noiseGate.openedInLastBlock()) {
-            emit noiseGateOpened();
-        } else if (_noiseGate.closedInLastBlock()) {
-            emit noiseGateClosed();
-        }
     }
 
-    // the codec needs a flush frame before sending silent packets, so
-    // do not send one if the gate closed in this block (eventually this can be crossfaded).
-    auto packetType = _shouldEchoToServer ?
-        PacketType::MicrophoneAudioWithEcho : PacketType::MicrophoneAudioNoEcho;
-    if (_lastInputLoudness == 0.0f && !_noiseGate.closedInLastBlock()) {
+    // state machine to detect gate opening and closing
+    bool audioGateOpen = (_lastInputLoudness != 0.0f);
+    bool openedInLastBlock = !_audioGateOpen && audioGateOpen;  // the gate just opened
+    bool closedInLastBlock = _audioGateOpen && !audioGateOpen;  // the gate just closed
+    _audioGateOpen = audioGateOpen;
+
+    if (openedInLastBlock) {
+        emit noiseGateOpened();
+    } else if (closedInLastBlock) {
+        emit noiseGateClosed();
+    }
+
+    // the codec must be flushed to silence before sending silent packets,
+    // so delay the transition to silent packets by one packet after becoming silent.
+    auto packetType = _shouldEchoToServer ? PacketType::MicrophoneAudioWithEcho : PacketType::MicrophoneAudioNoEcho;
+    if (!audioGateOpen && !closedInLastBlock) {
         packetType = PacketType::SilentAudioFrame;
         _silentOutbound.increment();
     } else {
diff --git a/libraries/audio-client/src/AudioClient.h b/libraries/audio-client/src/AudioClient.h
index 563c01d98a..c82f406f86 100644
--- a/libraries/audio-client/src/AudioClient.h
+++ b/libraries/audio-client/src/AudioClient.h
@@ -363,6 +363,7 @@ private:
 
     AudioNoiseGate _noiseGate;
     AudioGate* _audioGate { nullptr };
+    bool _audioGateOpen { false };
 
     AudioPositionGetter _positionGetter;
     AudioOrientationGetter _orientationGetter;