From 7f288e541da1a9d2167e853e135bbdef80313545 Mon Sep 17 00:00:00 2001
From: Stein Ivar Berghei <stein-ivar@berghei.no>
Date: Mon, 28 Nov 2022 00:42:51 +0100
Subject: [PATCH] Add opus streamer used in new ambiance

---
 opus/decode.go      | 87 +++++++++++++++++++++++++++++++++++++++++++++
 opus/decode_test.go | 79 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 166 insertions(+)
 create mode 100644 opus/decode.go
 create mode 100644 opus/decode_test.go

diff --git a/opus/decode.go b/opus/decode.go
new file mode 100644
index 0000000..d2a82e2
--- /dev/null
+++ b/opus/decode.go
@@ -0,0 +1,87 @@
+package opus
+
+import (
+	"io"
+	"log"
+	"sync"
+
+	"github.com/faiface/beep"
+	"github.com/pkg/errors"
+	opusd "gopkg.in/hraban/opus.v2"
+)
+
+type decoder struct {
+	sync.Mutex
+
+	rc  io.ReadSeekCloser
+	r   *opusd.Stream
+	err error
+}
+
+func New(f io.ReadSeekCloser) (beep.StreamSeeker, error) {
+	d := new(decoder)
+	st, err := opusd.NewStream(f)
+	if err != nil {
+		return d, err
+	}
+
+	d.rc = f
+	d.r = st
+
+	return d, nil
+}
+
+func (s *decoder) Err() error { return s.err }
+
+func (d *decoder) Stream(samples [][2]float64) (n int, ok bool) {
+	if d.err != nil {
+		return 0, false
+	}
+	var tmp [2]float32
+	for i := range samples {
+		dn, err := d.r.ReadFloat32(tmp[:])
+
+		if dn == 1 {
+			samples[i][0], samples[i][1] = float64(tmp[0]), float64(tmp[1])
+			n++
+			ok = true
+		}
+		if err == io.EOF {
+			ok = false
+			break
+		}
+		if err != nil {
+			ok = false
+			d.err = errors.Wrap(err, "ogg/opus")
+			break
+		}
+	}
+
+	return n, ok
+}
+
+func (d *decoder) Len() int {
+	return 0
+}
+
+func (d *decoder) Position() int {
+	return 0
+}
+
+func (d *decoder) Seek(p int) error {
+	_, err := d.rc.Seek(int64(p), io.SeekStart)
+	if err != nil {
+		log.Println(err)
+		return errors.Wrap(err, "ogg/opus")
+	}
+
+	st, err := opusd.NewStream(d.rc)
+	if err != nil {
+		log.Println(err)
+		return errors.Wrap(err, "ogg/opus")
+	}
+
+	d.r = st
+
+	return nil
+}
diff --git a/opus/decode_test.go b/opus/decode_test.go
new file mode 100644
index 0000000..14d7079
--- /dev/null
+++ b/opus/decode_test.go
@@ -0,0 +1,79 @@
+package opus
+
+import (
+	"context"
+	"log"
+	"os"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/faiface/beep"
+)
+
+var (
+	mu        sync.Mutex
+	mixer     beep.Mixer
+	frameSize int = 960
+	samples       = make([][2]float64, frameSize)
+	buf       []byte
+	maxBytes  int = (frameSize * 2) * 2
+	done      chan struct{}
+)
+
+func update() {
+	mu.Lock()
+	mixer.Stream(samples)
+	mu.Unlock()
+
+	for i := range samples {
+		for c := range samples[i] {
+			val := samples[i][c]
+			if val < -1 {
+				val = -1
+			}
+			if val > +1 {
+				val = +1
+			}
+			valInt16 := int16(val * (1<<15 - 1))
+			low := byte(valInt16)
+			high := byte(valInt16 >> 8)
+			buf[i*4+c*2+0] = low
+			buf[i*4+c*2+1] = high
+		}
+	}
+
+	//log.Printf("%+v", buf)
+}
+
+func TestMain(t *testing.T) {
+	buf = make([]byte, maxBytes)
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute*9)
+	defer cancel()
+
+	file, err := os.Open("test.opus")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	d, err := New(file)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	loop := beep.Loop(-1, d)
+
+	mu.Lock()
+	mixer.Add(loop)
+	mu.Unlock()
+
+	for {
+		select {
+		default:
+			update()
+		case <-ctx.Done():
+			return
+		}
+	}
+}