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third_party/sendspin-go/internal/server/flac_encoder_test.go

@@ -0,0 +1,123 @@
+// ABOUTME: Tests for the FLAC encoder
+// ABOUTME: Verifies round-trip encode produces valid FLAC frames with compression
+package server
+
+import (
+	"testing"
+)
+
+func TestFLACEncoder_RoundTrip(t *testing.T) {
+	const (
+		sampleRate = 48000
+		channels   = 2
+		bitDepth   = 24
+		blockSize  = 960 // 20ms at 48kHz
+	)
+
+	enc, err := NewFLACEncoder(sampleRate, channels, bitDepth, blockSize)
+	if err != nil {
+		t.Fatalf("NewFLACEncoder: %v", err)
+	}
+	defer enc.Close()
+
+	header := enc.CodecHeader()
+	if len(header) < 42 {
+		t.Fatalf("codec header too short: %d bytes (min 42)", len(header))
+	}
+	if string(header[:4]) != "fLaC" {
+		t.Errorf("codec header missing fLaC marker, got %q", header[:4])
+	}
+
+	// Create a simple test signal
+	samples := make([]int32, blockSize*channels)
+	for i := range samples {
+		samples[i] = int32((i % 256) << 16)
+	}
+
+	flacBytes, err := enc.Encode(samples)
+	if err != nil {
+		t.Fatalf("Encode: %v", err)
+	}
+	if len(flacBytes) == 0 {
+		t.Fatal("Encode returned empty bytes")
+	}
+
+	pcmSize := len(samples) * 3 // 24-bit = 3 bytes per sample
+	t.Logf("Encoded %d samples → %d FLAC bytes (%.1f%% of PCM %d bytes)",
+		len(samples), len(flacBytes), float64(len(flacBytes))/float64(pcmSize)*100, pcmSize)
+}
+
+func TestFLACEncoder_MultipleBlocks(t *testing.T) {
+	enc, err := NewFLACEncoder(48000, 2, 24, 960)
+	if err != nil {
+		t.Fatalf("NewFLACEncoder: %v", err)
+	}
+	defer enc.Close()
+
+	samples := make([]int32, 960*2)
+	for i := 0; i < 10; i++ {
+		data, err := enc.Encode(samples)
+		if err != nil {
+			t.Fatalf("Encode block %d: %v", i, err)
+		}
+		if len(data) == 0 {
+			t.Fatalf("Encode block %d returned empty", i)
+		}
+	}
+}
+
+func TestFLACEncoder_16Bit(t *testing.T) {
+	enc, err := NewFLACEncoder(44100, 2, 16, 882)
+	if err != nil {
+		t.Fatalf("NewFLACEncoder: %v", err)
+	}
+	defer enc.Close()
+
+	header := enc.CodecHeader()
+	if string(header[:4]) != "fLaC" {
+		t.Errorf("missing fLaC marker")
+	}
+
+	samples := make([]int32, 882*2)
+	data, err := enc.Encode(samples)
+	if err != nil {
+		t.Fatalf("Encode: %v", err)
+	}
+	if len(data) == 0 {
+		t.Fatal("empty encode")
+	}
+}
+
+func TestFLACEncoder_Compression(t *testing.T) {
+	// Silence should compress extremely well with prediction analysis enabled
+	enc, err := NewFLACEncoder(48000, 2, 24, 960)
+	if err != nil {
+		t.Fatalf("NewFLACEncoder: %v", err)
+	}
+	defer enc.Close()
+
+	silence := make([]int32, 960*2) // all zeros
+	data, err := enc.Encode(silence)
+	if err != nil {
+		t.Fatalf("Encode: %v", err)
+	}
+
+	pcmSize := 960 * 2 * 3 // 24-bit stereo
+	ratio := float64(len(data)) / float64(pcmSize) * 100
+	t.Logf("Silence: %d PCM bytes → %d FLAC bytes (%.1f%%)", pcmSize, len(data), ratio)
+
+	// Silence should compress to well under 10% of PCM size
+	if ratio > 20 {
+		t.Errorf("silence compression ratio %.1f%% is too high — prediction analysis may not be working", ratio)
+	}
+}
+
+func TestFLACEncoder_Close(t *testing.T) {
+	enc, err := NewFLACEncoder(48000, 2, 24, 960)
+	if err != nil {
+		t.Fatalf("NewFLACEncoder: %v", err)
+	}
+	if err := enc.Close(); err != nil {
+		t.Errorf("Close: %v", err)
+	}
+}