From 5443bf3f979bf4c6a2e5d17c2e03db4c7c525d28 Mon Sep 17 00:00:00 2001
From: Jan Svabenik <jan@svabi.ch>
Date: Tue, 17 Mar 2026 19:44:50 +0100
Subject: [PATCH] Flush IQ buffer on FFT reconfig

---
 cmd/sdrd/main.go            |  4 ++++
 internal/mock/source.go     |  2 ++
 internal/sdr/source.go      |  4 ++++
 internal/sdrplay/sdrplay.go | 10 ++++++++++
 4 files changed, 20 insertions(+)

diff --git a/cmd/sdrd/main.go b/cmd/sdrd/main.go
index 64a9580..e8b4a18 100644
--- a/cmd/sdrd/main.go
+++ b/cmd/sdrd/main.go
@@ -436,6 +436,10 @@ func runDSP(ctx context.Context, src sdr.Source, cfg config.Config, det *detecto
 			dcEnabled = upd.dcBlock
 			iqEnabled = upd.iqBalance
 			if cfg.FFTSize != prevFFT || cfg.UseGPUFFT != prevUseGPU {
+				if flushable, ok := src.(sdr.Flushable); ok {
+					flushable.Flush()
+				}
+				gotSamples = false
 				if gpuEngine != nil {
 					gpuEngine.Close()
 					gpuEngine = nil
diff --git a/internal/mock/source.go b/internal/mock/source.go
index 7481025..377559e 100644
--- a/internal/mock/source.go
+++ b/internal/mock/source.go
@@ -61,3 +61,5 @@ func (s *Source) ReadIQ(n int) ([]complex64, error) {
 func (s *Source) Stats() sdr.SourceStats {
 	return sdr.SourceStats{}
 }
+
+func (s *Source) Flush() {}
diff --git a/internal/sdr/source.go b/internal/sdr/source.go
index 7f77969..9ed74d8 100644
--- a/internal/sdr/source.go
+++ b/internal/sdr/source.go
@@ -22,4 +22,8 @@ type StatsProvider interface {
 	Stats() SourceStats
 }
 
+type Flushable interface {
+	Flush()
+}
+
 var ErrNotImplemented = errors.New("sdrplay support not built; build with -tags sdrplay or use --mock")
diff --git a/internal/sdrplay/sdrplay.go b/internal/sdrplay/sdrplay.go
index c4029a7..72d37a8 100644
--- a/internal/sdrplay/sdrplay.go
+++ b/internal/sdrplay/sdrplay.go
@@ -287,6 +287,16 @@ func (s *Source) Stats() sdr.SourceStats {
 	return sdr.SourceStats{BufferSamples: s.size, Dropped: s.dropped, Resets: s.resets}
 }
 
+func (s *Source) Flush() {
+	s.mu.Lock()
+	s.head = 0
+	s.size = 0
+	s.mu.Unlock()
+	if s.cond != nil {
+		s.cond.Broadcast()
+	}
+}
+
 func min(a, b int) int {
 	if a < b {
 		return a