Avoid unneccessary playMonoSamplesWithGain with empty spans

daschuer · Nov 8, 2024 · b1a5637 · b1a5637
1 parent 4850f4e
commit b1a5637
Showing 1 changed file with 29 additions and 47 deletions.
diff --git a/src/effects/backends/builtin/metronomeeffect.cpp b/src/effects/backends/builtin/metronomeeffect.cpp
@@ -26,41 +26,11 @@ std::size_t playMonoSamplesWithGain(std::span<const CSAMPLE> monoSource,
     return framesPlayed;
 }
 
-template<class T>
-std::span<T> subspan_clamped(std::span<T> in, typename std::span<T>::size_type offset) {
-    // TODO (Swiftb0y): should we instead create a wrapper type that implements
-    // UB-free "clamped" operations?
-    return in.subspan(std::min(offset, in.size()));
-}
-
 constexpr std::size_t framesPerBeat(
         mixxx::audio::SampleRate framesPerSecond, double beatsPerMinute) {
     double framesPerMinute = framesPerSecond * 60;
     return static_cast<std::size_t>(framesPerMinute / beatsPerMinute);
 }
-// returns where in the output buffer to start playing the next click.
-// If there the span is empty, no click should be played yet.
-std::span<CSAMPLE> syncedClickOutput(double beatFractionBufferEnd,
-        std::optional<GroupFeatureBeatLength> beatLengthAndScratch,
-        std::span<CSAMPLE> output) {
-    if (!beatLengthAndScratch.has_value() || beatLengthAndScratch->scratch_rate == 0.0) {
-        return {};
-    }
-    double beatLength = beatLengthAndScratch->frames / beatLengthAndScratch->scratch_rate;
-
-    const bool needsPreviousBeat = beatLength < 0;
-    double beatToBufferEndFrames = std::abs(beatLength) *
-            (needsPreviousBeat ? (1 - beatFractionBufferEnd)
-                               : beatFractionBufferEnd);
-    std::size_t beatToBufferEndSamples =
-            static_cast<std::size_t>(beatToBufferEndFrames) *
-            mixxx::kEngineChannelOutputCount;
-
-    if (beatToBufferEndSamples <= output.size()) {
-        return output.last(beatToBufferEndSamples);
-    }
-    return {};
-}
 
 } // namespace
 
@@ -160,25 +130,37 @@ void MetronomeEffect::processChannel(
 
     const CSAMPLE_GAIN gain = db2ratio(static_cast<float>(m_pGainParameter->value()));
 
-    playMonoSamplesWithGain(subspan_clamped(click, gs->framesSinceLastClick), output, gain);
+    if (gs->framesSinceLastClick < click.size()) {
+        playMonoSamplesWithGain(click.subspan(gs->framesSinceLastClick), output, gain);
+    }
     gs->framesSinceLastClick += engineParameters.framesPerBuffer();
 
-    std::span<CSAMPLE> outputBufferOffset = [&] {
-        if (shouldSync && hasBeatInfo) {
-            return syncedClickOutput(*groupFeatures.beat_fraction_buffer_end,
-                    groupFeatures.beat_length,
-                    output);
-        } else {
-            // EngineParameters::sampleRate in reality returns the framerate.
-            mixxx::audio::SampleRate framesPerSecond = engineParameters.sampleRate();
-            std::size_t offset = gs->framesSinceLastClick %
-                    framesPerBeat(framesPerSecond,
-                            m_pBpmParameter->value());
-            return subspan_clamped(output, offset * mixxx::kEngineChannelOutputCount);
+    if (shouldSync && hasBeatInfo) {
+        double beatFractionBufferEnd = *groupFeatures.beat_fraction_buffer_end;
+        GroupFeatureBeatLength beatLengthAndScratch = *groupFeatures.beat_length;
+        if (beatLengthAndScratch.scratch_rate == 0.0) {
+            return;
         }
-    }();
-
-    if (!outputBufferOffset.empty()) {
-        gs->framesSinceLastClick = playMonoSamplesWithGain(click, outputBufferOffset, gain);
+        double beatLength = beatLengthAndScratch.frames / beatLengthAndScratch.scratch_rate;
+        const bool needsPreviousBeat = beatLength < 0;
+        double beatToBufferEndFrames = std::abs(beatLength) *
+                (needsPreviousBeat ? (1 - beatFractionBufferEnd)
+                                   : beatFractionBufferEnd);
+        std::size_t beatToBufferEndSamples =
+                static_cast<std::size_t>(beatToBufferEndFrames) *
+                mixxx::kEngineChannelOutputCount;
+
+        if (beatToBufferEndSamples <= output.size()) {
+            gs->framesSinceLastClick = playMonoSamplesWithGain(click, output.last(beatToBufferEndSamples), gain);
+        }            
+    } else {
+        // EngineParameters::sampleRate in reality returns the framerate.
+        mixxx::audio::SampleRate framesPerSecond = engineParameters.sampleRate();
+        std::size_t offset = (gs->framesSinceLastClick %
+                framesPerBeat(framesPerSecond, m_pBpmParameter->value())) *
+                mixxx::kEngineChannelOutputCount; 
+        if (offset < output.size()) {
+             gs->framesSinceLastClick = playMonoSamplesWithGain(click, output.subspan(offset), gain);
+        }   
     }
 }