Merge pull request #458 from jpcima/flex-eg-transition

FlexEG zero-delay transition

src/sfizz/FlexEnvelope.cpp

@@ -144,6 +144,9 @@ void FlexEnvelope::Impl::process(absl::Span<float> out)
         const bool isReleased = isReleased_;
         while ((!stageSustained_ && currentTime_ >= stageTime_) ||
                (stageSustained_ && isReleased)) {
+            // If stage is of zero duration, immediate transition to level
+            if (!stageSustained_ && stageTime_ == 0)
+                currentLevel_ = stageTargetLevel_;
             if (!advanceToNextStage()) {
                 out.remove_prefix(frameIndex);
                 fill(out, 0.0f);

tests/FlexEGT.cpp

@@ -9,6 +9,7 @@
 #include "sfizz/FlexEnvelope.h"
 #include "catch2/catch.hpp"
 #include "TestHelpers.h"
+#include <array>
 using namespace Catch::literals;
 using namespace sfz::literals;
 
@@ -261,3 +262,29 @@ TEST_CASE("[FlexEG] Detailed numerical envelope test (with shapes)")
     envelope.process(absl::MakeSpan(output));
     REQUIRE( approxEqual<float>(output, expected, 0.01f) );
 }
+
+TEST_CASE("[FlexEG] Zero delay transitions")
+{
+    sfz::Synth synth;
+
+    synth.loadSfzString(fs::current_path(), R"(
+        <region> sample=*sine
+        eg1_time1=0  eg1_level1=1
+        eg1_time2=1  eg1_level2=0
+        eg1_time3=1  eg1_level3=.5 eg1_sustain=3
+        eg1_time4=1  eg1_level4=1
+    )");
+    sfz::FlexEnvelope envelope;
+    REQUIRE(synth.getNumRegions() == 1);
+    REQUIRE(synth.getRegionView(0)->flexEGs.size() == 1);
+    envelope.configure(&synth.getRegionView(0)->flexEGs[0]);
+    envelope.setSampleRate(10);
+    envelope.start(1);
+
+    std::array<float, 2> output;
+    envelope.process(absl::MakeSpan(output));
+    REQUIRE(output[0] == 0.0f);
+    REQUIRE(output[1] == Approx(0.9f).margin(0.01f));
+    // Note(jpc): 0.9 is because EG pre-increments the time counter, slope is
+    //            1 frame off into the future
+}