Widen the deck row block to 1028 so the filter tie-line is exact, and accumulate the meter's block peaks instead of sampling one in 47

src/shell/instrument/processor_state.cpp

@@ -183,11 +183,16 @@ void ReaSamplerProcessor::setLimiterEnabled(bool on) {
     setInstrumentParams(params);
 }
 
-MasterBusMeter ReaSamplerProcessor::masterBusMeter() const {
+MasterBusMeter ReaSamplerProcessor::masterBusMeter() {
     MasterBusMeter m;
-    m.peakL = meterPeakL_.load(std::memory_order_relaxed);
-    m.peakR = meterPeakR_.load(std::memory_order_relaxed);
-    m.minGain = meterMinGain_.load(std::memory_order_relaxed);
+    // Exchange, not load: the accumulators hold the window since this was last called, and
+    // clearing them here is what starts the next window. The audio thread's own fold is a
+    // load-max-store, so a store landing between this exchange and that store can retain one
+    // window's peak for one extra frame — it can never LOSE one, which is the property that
+    // matters for a peak meter.
+    m.peakL = meterPeakL_.exchange(0.f, std::memory_order_relaxed);
+    m.peakR = meterPeakR_.exchange(0.f, std::memory_order_relaxed);
+    m.minGain = meterMinGain_.exchange(1.f, std::memory_order_relaxed);
     m.clip = meterClip_.load(std::memory_order_relaxed);
     return m;
 }