From fa29a27695d1b99208ae7b7add37814bc3951b51 Mon Sep 17 00:00:00 2001
From: Jonathan Naylor <naylorjs@yahoo.com>
Date: Sat, 9 May 2020 12:53:50 +0100
Subject: [PATCH 1/3] Ensure all output audio is flushed before leaving FM
 state.

---
 FM.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/FM.cpp b/FM.cpp
index 7695e81..94bd693 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -245,7 +245,7 @@ void CFM::stateMachine(bool validSignal)
   }
 
   if (m_state == FS_LISTENING && m_modemState == STATE_FM) {
-    if (!m_callsign.isRunning() && !m_rfAck.isRunning()) {
+    if (!m_callsign.isRunning() && !m_rfAck.isRunning() && m_outputRB.getData() == 0U) {
       DEBUG1("Change to STATE_IDLE");
       m_modemState = STATE_IDLE;
       m_callsignTimer.stop();

From 3bb7cde3223f448e74201b400a552043f14dfff5 Mon Sep 17 00:00:00 2001
From: Jonathan Naylor <naylorjs@yahoo.com>
Date: Sat, 9 May 2020 13:01:02 +0100
Subject: [PATCH 2/3] Add input audio delay to match the CTCSS decoder results.

---
 FM.cpp | 14 ++++++++++++++
 FM.h   |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/FM.cpp b/FM.cpp
index 94bd693..66bd5af 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -46,8 +46,10 @@ m_cosInvert(false),
 m_rfAudioBoost(1U),
 m_downsampler(128U),//Size might need adjustement
 m_rxLevel(1),
+m_inputRB(4800U),   // 200ms of audio
 m_outputRB(2400U)   // 100ms of audio
 {
+  insertDelay(100U);
 }
 
 void CFM::samples(bool cos, const q15_t* samples, uint8_t length)
@@ -68,6 +70,10 @@ void CFM::samples(bool cos, const q15_t* samples, uint8_t length)
 
     uint8_t ctcssState = m_ctcssRX.process(currentSample);
 
+    // Delay the audio by 100ms to better match the CTCSS detector output
+    m_inputRB.put(currentSample);
+    m_inputRB.get(currentSample);
+
     if (CTCSS_NOT_READY(ctcssState) && m_modemState != STATE_FM) {
       //Not enough samples to determine if you have CTCSS, just carry on
       continue;
@@ -462,6 +468,14 @@ void CFM::beginRelaying()
   m_ackMinTimer.start();
 }
 
+void CFM::insertDelay(uint16_t ms)
+{
+  uint32_t nSamples = ms * 24U;
+
+  for (uint32_t i = 0U; i < nSamples; i++)
+    m_inputRB.put(0);
+}
+
 void CFM::insertSilence(uint16_t ms)
 {
   uint32_t nSamples = ms * 24U;
diff --git a/FM.h b/FM.h
index 4901d6a..29887a8 100644
--- a/FM.h
+++ b/FM.h
@@ -84,6 +84,7 @@ private:
   q15_t                m_rfAudioBoost;
   CFMDownsampler       m_downsampler;
   q15_t                m_rxLevel;
+  CFMRB                m_inputRB;
   CFMRB                m_outputRB;
 
   void stateMachine(bool validSignal);
@@ -99,6 +100,8 @@ private:
 
   void sendCallsign();
   void beginRelaying();
+
+  void insertDelay(uint16_t ms);
   void insertSilence(uint16_t ms);
 };
 

From c04e207821ddd67882a7b887357ef1290fd2918b Mon Sep 17 00:00:00 2001
From: Jonathan Naylor <naylorjs@yahoo.com>
Date: Sat, 9 May 2020 13:10:02 +0100
Subject: [PATCH 3/3] Insert the missing silence.

---
 FM.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/FM.cpp b/FM.cpp
index 55fd0f0..8bf2448 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -342,6 +342,8 @@ void CFM::listeningState(bool validRFSignal, bool validExtSignal)
         sendCallsign();
     }
 
+    insertSilence(50U);
+
     beginRelaying();
 
     m_callsignTimer.start();