feat: the trigger can ignore a noise band and reject HF before comparing

src/condition.hpp

@@ -33,11 +33,17 @@ struct EventCondition {
   double width_s = 1.0e-3;           ///< PulseWidth only.
   double width2_s = 2.0e-3;          ///< PulseWidth, Within/Outside only.
   double timeout_s = 1.0e-3;         ///< Dropout only.
+  /// Half-width of the amplitude band around `level` a sample must leave before
+  /// a crossing counts. 0 is the bare comparator. In signal units.
+  double noise_band = 0.0;
+  /// Corner of a one-pole low pass applied to the sample before any comparison.
+  /// 0 is off. In Hz.
+  double hf_fc = 0.0;
 
   bool operator==(const EventCondition& o) const noexcept {
     return type == o.type && level == o.level && level2 == o.level2 && edge == o.edge &&
            cmp == o.cmp && width_s == o.width_s && width2_s == o.width2_s &&
-           timeout_s == o.timeout_s;
+           timeout_s == o.timeout_s && noise_band == o.noise_band && hf_fc == o.hf_fc;
   }
   bool operator!=(const EventCondition& o) const noexcept { return !(*this == o); }
 };
@@ -60,7 +66,10 @@ class EventDetector {
   /// Re-applying the same condition is a no-op, deliberately: the producer calls this on
   /// every packet, and resetting there would restart the machine before any pulse could
   /// close. A genuinely different condition resets, because its state means nothing.
-  void configure(const EventCondition& c) noexcept;
+  ///
+  /// `dt` is the stored sample interval (`Partition::slot_dt()`), needed for the
+  /// HF reject's pole. A no-op unless the condition or the interval changed.
+  void configure(const EventCondition& c, double dt) noexcept;
   void reset() noexcept;
 
   /// One sample, in stream order. Returns the event's own stream time, or `kNoEvent`.
@@ -80,6 +89,10 @@ class EventDetector {
   bool crossed_down(double v) const noexcept {
     return prev_ > cond_.level && v <= cond_.level;
   }
+  /// The HF reject, applied to every sample before any comparison.
+  double filter(double v) noexcept;
+  /// `up`/`down` for the edge condition, through the band if there is one.
+  void decide(double v, bool& up, bool& down) noexcept;
   double feed_edge(double value, double t) noexcept;
   double feed_pulse(double value, double t) noexcept;
   double feed_window(double value, double t) noexcept;
@@ -98,6 +111,15 @@ class EventDetector {
   bool inside_ = false;        ///< Window: which side of the band the previous sample was.
   double last_cross_s_ = 0.0;  ///< Dropout: when the signal was last seen crossing.
   bool dropped_ = false;       ///< Dropout: the timeout has already been reported.
+  /// One-pole prefilter. `pole_a_ == 1` passes the input through, so "off"
+  /// costs no branch. `pole_y_` is the filtered value.
+  double dt_ = 0.0;
+  double pole_a_ = 1.0;
+  double pole_y_ = 0.0;
+  bool pole_have_ = false;
+  /// Which side of the band the signal was last *decided* to be on: +1 above,
+  /// -1 below, 0 undecided. A sample inside the band decides nothing.
+  int side_ = 0;
 };
 
 }  // namespace udpscope