From 70d1a4f6f90a638a8be95b7ad5a7880a0e075df6 Mon Sep 17 00:00:00 2001
From: Jan Holthuis <jan.holthuis@ruhr-uni-bochum.de>
Date: Sun, 14 Mar 2021 15:35:20 +0100
Subject: [PATCH] MidiBeatClockReceiver: Use the average interval over the last
 24 ticks

---
 .../midi/midibeatclockreceiver.cpp            | 22 ++++++++++++++-----
 src/controllers/midi/midibeatclockreceiver.h  |  3 +++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/controllers/midi/midibeatclockreceiver.cpp b/src/controllers/midi/midibeatclockreceiver.cpp
index 59360e14ac59..b5cfd93f41b0 100644
--- a/src/controllers/midi/midibeatclockreceiver.cpp
+++ b/src/controllers/midi/midibeatclockreceiver.cpp
@@ -2,10 +2,6 @@
 
 #include "controllers/midi/midimessage.h"
 
-namespace {
-constexpr int kPulsesPerQuarterNote = 24;
-}
-
 namespace mixxx {
 
 MidiBeatClockReceiver::MidiBeatClockReceiver()
@@ -37,8 +33,22 @@ void MidiBeatClockReceiver::receive(unsigned char status, Duration timestamp) {
         break;
     case MidiOpCode::MIDI_TIMING_CLK:
         if (m_lastTimestamp != Duration::empty() && timestamp != Duration::empty()) {
-            Duration interval = timestamp - m_lastTimestamp;
-            m_bpm = Bpm(1000000000.0 / interval.toDoubleNanos() / kPulsesPerQuarterNote * 60.0);
+            m_intervalRingBuffer[m_clockTickIndex] = timestamp - m_lastTimestamp;
+
+            int numValues = 0;
+            Duration sumIntervals;
+            for (int i = 0; i < kPulsesPerQuarterNote; i++) {
+                if (m_intervalRingBuffer[i] != Duration::empty()) {
+                    sumIntervals += m_intervalRingBuffer[i];
+                    numValues++;
+                }
+            }
+            DEBUG_ASSERT(numValues >= 1);
+
+            m_bpm = Bpm(1000000000.0 /
+                    (sumIntervals.toDoubleNanos() / numValues) /
+                    kPulsesPerQuarterNote * 60.0);
+            qWarning() << m_bpm;
         }
         m_clockTickIndex = (m_clockTickIndex + 1) % kPulsesPerQuarterNote;
         m_lastTimestamp = timestamp;
diff --git a/src/controllers/midi/midibeatclockreceiver.h b/src/controllers/midi/midibeatclockreceiver.h
index aa7fb3a055de..7a5cee68c102 100644
--- a/src/controllers/midi/midibeatclockreceiver.h
+++ b/src/controllers/midi/midibeatclockreceiver.h
@@ -5,6 +5,8 @@ namespace mixxx {
 
 class MidiBeatClockReceiver {
   public:
+    static constexpr int kPulsesPerQuarterNote = 24;
+
     MidiBeatClockReceiver();
     static bool canReceiveMidiStatus(unsigned char status);
     void receive(unsigned char status, Duration timestamp);
@@ -24,6 +26,7 @@ class MidiBeatClockReceiver {
     bool m_isPlaying;
     Duration m_lastTimestamp;
     int m_clockTickIndex;
+    Duration m_intervalRingBuffer[kPulsesPerQuarterNote];
 };
 
 } // namespace mixxx