BPM detect

1 files changed, 37 insertions, 0 deletions

diff --git a/BPMDetect.cpp b/BPMDetect.cpp
new file mode 100644
index 0000000..756747d
--- /dev/null
+++ b/BPMDetect.cpp
@@ -0,0 +1,37 @@
+#include "BPMDetect.h"
+
+#include "log.h"
+
+BPMDetect::BPMDetect(int divider):
+  m_divider{divider},
+  m_count{}
+{
+}
+
+// Strategy: evaluate last 3 valid beats
+// always skip m_divider-1 beats
+void BPMDetect::receive_event()
+{
+  // guard by divider
+  ++m_count;
+  if (m_count < m_divider) {
+    return;
+  } else {
+    m_count = 0;
+  }
+
+  // calculate bpm
+  time_point now = clock_type::now();
+
+  m_timestamps.push_back(now);
+
+  while (m_timestamps.size() > 3) {
+    m_timestamps.pop_front();
+  }
+
+  if (m_timestamps.size() == 3) {
+    int bpm = 60 * 2 / std::chrono::duration<double>(m_timestamps.back() - m_timestamps.front()).count();
+
+    signal_bpm(bpm);
+  }
+}