Add steady-state decode benchmark

decode_steady_bench_test.go

@@ -0,0 +1,56 @@
+// SPDX-FileCopyrightText: 2026 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+package opus
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"testing"
+
+	"github.com/pion/opus/pkg/oggreader"
+)
+
+// BenchmarkDecodeSteady measures the steady-state, per-frame decode cost. Unlike
+// BenchmarkDecode -- which is skipped unless -oggfile is given, and which rebuilds the
+// decoder and re-parses the stream on every iteration -- this benchmark runs by default
+// on the embedded tiny.ogg: it parses the packets once, reuses a single decoder and
+// output buffer, warms up the decoder's scratch buffers, and then loops over the same
+// packets. That isolates the recurring per-frame work from one-time setup.
+func BenchmarkDecodeSteady(b *testing.B) {
+	var pkts [][]byte
+	ogg, _, err := oggreader.NewWith(bytes.NewReader(tinyogg))
+	if err != nil {
+		b.Fatal(err)
+	}
+	for {
+		segments, _, err := ogg.ParseNextPage()
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		if err != nil {
+			b.Fatal(err)
+		}
+		if len(segments) > 0 && bytes.HasPrefix(segments[0], []byte("OpusTags")) {
+			continue
+		}
+		pkts = append(pkts, segments...)
+	}
+
+	decoder := NewDecoder()
+	var out [1920]byte
+	// Warm up the decoder's scratch buffers so the timed loop measures steady state.
+	for i := range pkts {
+		_, _, _ = decoder.Decode(pkts[i], out[:]) //nolint:errcheck // warm-up only
+	}
+
+	b.ResetTimer()
+	for range b.N {
+		for i := range pkts {
+			if _, _, err := decoder.Decode(pkts[i], out[:]); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+}