From 1e652d7d3434a612118a276de6ff7dcec16bd97b Mon Sep 17 00:00:00 2001
From: Jordan Woyak <jordan.woyak@gmail.com>
Date: Tue, 11 Feb 2020 17:30:16 -0600
Subject: InputCommon: Add calibration functionality to IMUGyroscope.

---
 .../ControllerEmu/ControlGroup/IMUGyroscope.cpp    | 101 ++++++++++++++++++++-
 1 file changed, 100 insertions(+), 1 deletion(-)

(limited to 'Source/Core/InputCommon/ControllerEmu/ControlGroup/IMUGyroscope.cpp')

diff --git a/Source/Core/InputCommon/ControllerEmu/ControlGroup/IMUGyroscope.cpp b/Source/Core/InputCommon/ControllerEmu/ControlGroup/IMUGyroscope.cpp
index 6109f20b8c..8837c67f13 100644
--- a/Source/Core/InputCommon/ControllerEmu/ControlGroup/IMUGyroscope.cpp
+++ b/Source/Core/InputCommon/ControllerEmu/ControlGroup/IMUGyroscope.cpp
@@ -15,6 +15,15 @@
 
 namespace ControllerEmu
 {
+// Maximum period for calculating an average stable value.
+// Just to prevent failures due to timer overflow.
+static constexpr auto MAXIMUM_CALIBRATION_DURATION = std::chrono::hours(1);
+
+// If calibration updates do not happen at this rate, restart calibration period.
+// This prevents calibration across periods of no regular updates. (e.g. between game sessions)
+// This is made slightly lower than the UI update frequency of 30.
+static constexpr auto WORST_ACCEPTABLE_CALIBRATION_UPDATE_FREQUENCY = 25;
+
 IMUGyroscope::IMUGyroscope(std::string name, std::string ui_name)
     : ControlGroup(std::move(name), std::move(ui_name), GroupType::IMUGyroscope)
 {
@@ -31,7 +40,79 @@ IMUGyroscope::IMUGyroscope(std::string name, std::string ui_name)
               _trans("°/s"),
               // i18n: Refers to the dead-zone setting of gyroscope input.
               _trans("Angular velocity to ignore.")},
-             1, 0, 180);
+             2, 0, 180);
+
+  AddSetting(&m_calibration_period_setting,
+             {_trans("Calibration Period"),
+              // i18n: "s" is the symbol for seconds.
+              _trans("s"),
+              // i18n: Refers to the "Calibration" setting of gyroscope input.
+              _trans("Time period of stable input to trigger calibration. (zero to disable)")},
+             3, 0, 30);
+}
+
+void IMUGyroscope::RestartCalibration() const
+{
+  m_calibration_period_start = Clock::now();
+  m_running_calibration.Clear();
+}
+
+void IMUGyroscope::UpdateCalibration(const StateData& state) const
+{
+  const auto now = Clock::now();
+  const auto calibration_period = m_calibration_period_setting.GetValue();
+
+  // If calibration time is zero. User is choosing to not calibrate.
+  if (!calibration_period)
+  {
+    // Set calibration to zero.
+    m_calibration = {};
+    RestartCalibration();
+    return;
+  }
+
+  // If there is no running calibration a new gyro was just mapped or calibration was just enabled,
+  // apply the current state as calibration, it's often better than zeros.
+  if (!m_running_calibration.Count())
+  {
+    m_calibration = state;
+  }
+  else
+  {
+    const auto calibration_freq =
+        m_running_calibration.Count() /
+        std::chrono::duration_cast<std::chrono::duration<double>>(now - m_calibration_period_start)
+            .count();
+
+    const auto potential_calibration = m_running_calibration.Mean();
+    const auto current_difference = state - potential_calibration;
+    const auto deadzone = GetDeadzone();
+
+    // Check for required calibration update frequency
+    // and if current data is within deadzone distance of mean stable value.
+    if (calibration_freq < WORST_ACCEPTABLE_CALIBRATION_UPDATE_FREQUENCY ||
+        std::any_of(current_difference.data.begin(), current_difference.data.end(),
+                    [&](auto c) { return std::abs(c) > deadzone; }))
+    {
+      RestartCalibration();
+    }
+  }
+
+  // Update running mean stable value.
+  m_running_calibration.Push(state);
+
+  // Apply calibration after configured time.
+  const auto calibration_duration = now - m_calibration_period_start;
+  if (calibration_duration >= std::chrono::duration<double>(calibration_period))
+  {
+    m_calibration = m_running_calibration.Mean();
+
+    if (calibration_duration >= MAXIMUM_CALIBRATION_DURATION)
+    {
+      RestartCalibration();
+      m_running_calibration.Push(m_calibration);
+    }
+  }
 }
 
 auto IMUGyroscope::GetRawState() const -> StateData
@@ -44,10 +125,21 @@ auto IMUGyroscope::GetRawState() const -> StateData
 std::optional<IMUGyroscope::StateData> IMUGyroscope::GetState() const
 {
   if (controls[0]->control_ref->BoundCount() == 0)
+  {
+    // Set calibration to zero.
+    m_calibration = {};
+    RestartCalibration();
     return std::nullopt;
+  }
 
   auto state = GetRawState();
 
+  // If the input gate is disabled, miscalibration to zero values would occur.
+  if (ControlReference::GetInputGate())
+    UpdateCalibration(state);
+
+  state -= m_calibration;
+
   // Apply "deadzone".
   for (auto& c : state.data)
     c *= std::abs(c) > GetDeadzone();
@@ -60,4 +152,11 @@ ControlState IMUGyroscope::GetDeadzone() const
   return m_deadzone_setting.GetValue() / 360 * MathUtil::TAU;
 }
 
+bool IMUGyroscope::IsCalibrating() const
+{
+  const auto calibration_period = m_calibration_period_setting.GetValue();
+  return calibration_period && (Clock::now() - m_calibration_period_start) >=
+                                   std::chrono::duration<double>(calibration_period);
+}
+
 }  // namespace ControllerEmu
-- 
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