From b4a9c48af71500c6f0bb0b1e6c2e8bee97cdcb78 Mon Sep 17 00:00:00 2001
From: Jan Svabenik <jan@svabi.ch>
Date: Thu, 19 Mar 2026 08:08:41 +0100
Subject: [PATCH] feat: validate CUDA freq-shift output

---
 internal/demod/gpudemod/build/kernels.obj  | Bin 47909 -> 47909 bytes
 internal/demod/gpudemod/gpudemod.go        |   2 +-
 internal/demod/gpudemod/validation_test.go |  25 +++++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 internal/demod/gpudemod/validation_test.go

diff --git a/internal/demod/gpudemod/build/kernels.obj b/internal/demod/gpudemod/build/kernels.obj
index ecf18a01ca62f57fa315244bdb1dfa1350e7f837..47bc9a26e90cfa7a2818892064934d0f7bb4c876 100644
GIT binary patch
delta 16
YcmZ4bjcMsOCf1a;%MAB6vMTHb07A3}YybcN

delta 16
YcmZ4bjcMsOCf1a;%M3mnSrv8z06*FW+5i9m

diff --git a/internal/demod/gpudemod/gpudemod.go b/internal/demod/gpudemod/gpudemod.go
index 3687fb5..ee7d5a6 100644
--- a/internal/demod/gpudemod/gpudemod.go
+++ b/internal/demod/gpudemod/gpudemod.go
@@ -181,7 +181,7 @@ func (e *Engine) Demod(iq []complex64, offsetHz float64, bw float64, mode DemodT
 	// by actual kernels, we fall back to the existing CPU DSP path below.
 	_ = fmt.Sprintf("%s:%0.3f", phaseStatus(), offsetHz)
 	shifted, ok := e.tryCUDAFreqShift(iq, offsetHz)
-	if !ok {
+	if !ok || !ValidateFreqShift(iq, e.sampleRate, offsetHz, shifted, 1e-3) {
 		shifted = dsp.FreqShift(iq, e.sampleRate, offsetHz)
 	}
 	cutoff := bw / 2
diff --git a/internal/demod/gpudemod/validation_test.go b/internal/demod/gpudemod/validation_test.go
new file mode 100644
index 0000000..ef55e2e
--- /dev/null
+++ b/internal/demod/gpudemod/validation_test.go
@@ -0,0 +1,25 @@
+//go:build cufft
+
+package gpudemod
+
+import (
+	"testing"
+
+	"sdr-visual-suite/internal/dsp"
+)
+
+func TestValidateFreqShiftRejectsMismatchedLength(t *testing.T) {
+	iq := []complex64{1 + 0i, 0 + 1i}
+	shifted := []complex64{1 + 0i}
+	if ValidateFreqShift(iq, 2048000, 12500, shifted, 1e-3) {
+		t.Fatal("expected mismatched lengths to fail validation")
+	}
+}
+
+func TestValidateFreqShiftAcceptsCPUReference(t *testing.T) {
+	iq := []complex64{1 + 0i, 0.5 + 0.25i, -0.25 + 0.75i, 0.1 - 0.3i}
+	shifted := dsp.FreqShift(iq, 2048000, 256000)
+	if !ValidateFreqShift(iq, 2048000, 256000, shifted, 1e-6) {
+		t.Fatal("expected CPU reference shifted IQ to pass validation")
+	}
+}