From e574aeb592b2026c742d46e9951ef70b8bf9d214 Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Mon, 27 Jul 2020 21:01:07 +0200
Subject: [PATCH] Filter shortcut by relative formula

---
 src/sfizz/Config.h      | 4 ++++
 src/sfizz/Smoothers.cpp | 8 +++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/sfizz/Config.h b/src/sfizz/Config.h
index 60c2f0a2..03f7f378 100644
--- a/src/sfizz/Config.h
+++ b/src/sfizz/Config.h
@@ -103,6 +103,10 @@ namespace config {
        Background file loading
      */
     static constexpr int backgroundLoaderPthreadPriority = 50; // expressed in %
+    /**
+       @brief Ratio to target under which smoothing is considered as completed
+     */
+    static constexpr float smoothingShortcutThreshold = 5e-3;
 } // namespace config
 
 } // namespace sfz
diff --git a/src/sfizz/Smoothers.cpp b/src/sfizz/Smoothers.cpp
index 59fcc5b9..fda61be0 100644
--- a/src/sfizz/Smoothers.cpp
+++ b/src/sfizz/Smoothers.cpp
@@ -31,7 +31,13 @@ void Smoother::process(absl::Span<const float> input, absl::Span<float> output,
     if (input.size() == 0)
         return;
 
-    if (canShortcut && std::abs(input.front() - current()) < config::virtuallyZero) {
+    if (canShortcut) {
+        float in = input.front();
+        float rel = std::abs(in - current()) / (std::abs(in) + config::virtuallyZero);
+        canShortcut = rel < config::smoothingShortcutThreshold;
+    }
+
+    if (canShortcut) {
         if (input.data() != output.data())
             copy<float>(input, output);