feat(go/audio): implement basic audio output with oto

splitting implementation into a separate package to potentially allow for other sorts of output, too.

go.mod

@@ -1,3 +1,5 @@
 module github.com/vsariola/sointu
 
 go 1.15
+
+require github.com/hajimehoshi/oto v0.6.6

go4k/audio/convertbuffer.go

@@ -0,0 +1,22 @@
+package audio
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"math"
+)
+
+// FloatBufferTo16BitLE is a naive helper method to convert []float32 buffers to
+// 16-bit little-endian integer buffers.
+// TODO: optimize/refactor this, current is far from the best solution
+func FloatBufferTo16BitLE(buff []float32) ([]byte, error) {
+	var buf bytes.Buffer
+	for i, v := range buff {
+		uv := int16(v * math.MaxInt16)
+		if err := binary.Write(&buf, binary.LittleEndian, uv); err != nil {
+			return nil, fmt.Errorf("error converting buffer (@ %v, value %v) to bytes: %w", i, v, err)
+		}
+	}
+	return buf.Bytes(), nil
+}

go4k/audio/convertbuffer_test.go

@@ -0,0 +1,48 @@
+package audio
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestFloatBufferToBytes(t *testing.T) {
+	floats := []float32{0, 0.000489128, 0, 0.0019555532, 0, 0.0043964, 0, 0.007806882, 0, 0.012180306, 0, 0.017508084, 0, 0.023779746, 0, 0.030982954, 0, 0.039103523, 0, 0.04812544, 0, 0.05803088, 0, 0.068800256, 0, 0.08041221, 0, 0.09284368, 0, 0.10606992, 0, 0.120064534, 0, 0.13479951, 0, 0.1502453, 0, 0.16637078, 0, 0.18314338, 0, 0.20052913, 0, 0.21849263, 0, 0.23699719, 0, 0.2560048, 0, 0.27547634, 0, 0.29537144, 0, 0.31564865, 0, 0.33626547, 0, 0.35717854, 0, 0.37834346, 0, 0.39971504, 0, 0.4212474, 0, 0.4428938, 0, 0.46460703, 0, 0.48633927, 0, 0.50804216, 0, 0.52966696, 0, 0.5511646, 0, 0.57248586, 0, 0.5935812, 0, 0.6144009, 0, 0.63489544, 0, 0.6550152, 0, 0.67471063, 0, 0.6939326, 0, 0.712632, 0, 0.7307603, 0, 0.7482692, 0, 0.7651111, 0, 0.7812389}
+	bytes := []byte{0x0, 0x0, 0x10, 0x0, 0x0, 0x0, 0x40, 0x0, 0x0, 0x0, 0x90, 0x0, 0x0, 0x0, 0xff, 0x0, 0x0, 0x0, 0x8f, 0x1, 0x0, 0x0, 0x3d, 0x2, 0x0, 0x0, 0xb, 0x3, 0x0, 0x0, 0xf7, 0x3, 0x0, 0x0, 0x1, 0x5, 0x0, 0x0, 0x28, 0x6, 0x0, 0x0, 0x6d, 0x7, 0x0, 0x0, 0xce, 0x8, 0x0, 0x0, 0x4a, 0xa, 0x0, 0x0, 0xe2, 0xb, 0x0, 0x0, 0x93, 0xd, 0x0, 0x0, 0x5e, 0xf, 0x0, 0x0, 0x40, 0x11, 0x0, 0x0, 0x3b, 0x13, 0x0, 0x0, 0x4b, 0x15, 0x0, 0x0, 0x71, 0x17, 0x0, 0x0, 0xaa, 0x19, 0x0, 0x0, 0xf7, 0x1b, 0x0, 0x0, 0x55, 0x1e, 0x0, 0x0, 0xc4, 0x20, 0x0, 0x0, 0x42, 0x23, 0x0, 0x0, 0xce, 0x25, 0x0, 0x0, 0x66, 0x28, 0x0, 0x0, 0xa, 0x2b, 0x0, 0x0, 0xb7, 0x2d, 0x0, 0x0, 0x6d, 0x30, 0x0, 0x0, 0x29, 0x33, 0x0, 0x0, 0xeb, 0x35, 0x0, 0x0, 0xb0, 0x38, 0x0, 0x0, 0x77, 0x3b, 0x0, 0x0, 0x3f, 0x3e, 0x0, 0x0, 0x7, 0x41, 0x0, 0x0, 0xcb, 0x43, 0x0, 0x0, 0x8c, 0x46, 0x0, 0x0, 0x46, 0x49, 0x0, 0x0, 0xf9, 0x4b, 0x0, 0x0, 0xa4, 0x4e, 0x0, 0x0, 0x43, 0x51, 0x0, 0x0, 0xd6, 0x53, 0x0, 0x0, 0x5c, 0x56, 0x0, 0x0, 0xd2, 0x58, 0x0, 0x0, 0x36, 0x5b, 0x0, 0x0, 0x88, 0x5d, 0x0, 0x0, 0xc6, 0x5f, 0x0, 0x0, 0xee, 0x61, 0x0, 0x0, 0xfe, 0x63}
+	converted, err := FloatBufferTo16BitLE(floats)
+	if err != nil {
+		t.Fatalf("FloatBufferTo16BitLE threw an error")
+	}
+	for i, v := range converted {
+		if bytes[i] != v {
+			t.Fail()
+			t.Errorf("Unexpected conversion output byte %x (expected %x) at position %v", v, bytes[i], i)
+		}
+	}
+	if !reflect.DeepEqual(converted, bytes) {
+		t.Fatalf("Unexpected conversion output from FloatBufferTo16BitLE")
+	}
+}
+
+func TestFloatBufferToBytesLimits(t *testing.T) {
+	floats := []float32{0, 1, -1, 0.999, -0.999}
+	bytes := []byte{
+		0x0, 0x0,
+		0xFF, 0x7F, // float 1 = 0x7FFF = 0111111111111111
+		0x01, 0x80, // float -1 = 0x8001 = 1000000000000001
+		0xDE, 0x7F, // float 0.999 = 0x7FDE = 0111111111011110
+		0x22, 0x80, // float -0.999 = 0x8022 = 1000000000100010
+	}
+	converted, err := FloatBufferTo16BitLE(floats)
+	if err != nil {
+		t.Fatalf("FloatBufferTo16BitLE threw an error")
+	}
+	for i, v := range converted {
+		if bytes[i] != v {
+			t.Fail()
+			t.Errorf("Unexpected conversion output byte %x (expected %x) at position %v", v, bytes[i], i)
+		}
+	}
+	if !reflect.DeepEqual(converted, bytes) {
+		t.Fatalf("Unexpected conversion output from FloatBufferTo16BitLE")
+	}
+}

go4k/audio/oto/otoplayer.go

@@ -0,0 +1,54 @@
+package oto
+
+import (
+	"fmt"
+	"github.com/hajimehoshi/oto"
+	"github.com/vsariola/sointu/go4k/audio"
+)
+
+// OtoPlayer wraps github.com/hajimehoshi/oto to play sointu-style float32[] audio
+type OtoPlayer struct {
+	context *oto.Context
+	player  *oto.Player
+}
+
+// Play implements the audio.Player interface for OtoPlayer
+func (o *OtoPlayer) Play(floatBuffer []float32) (err error) {
+	if byteBuffer, err := audio.FloatBufferTo16BitLE(floatBuffer); err != nil {
+		return fmt.Errorf("error writing to player: %w", err)
+	} else if _, err := o.player.Write(byteBuffer); err != nil {
+		return fmt.Errorf("error writing to player: %w", err)
+	} else {
+		fmt.Printf("%#v\n", floatBuffer[0:100])
+		fmt.Printf("%#v\n", byteBuffer[0:200])
+	}
+
+	return nil
+}
+
+// Close disposes of resources
+func (o *OtoPlayer) Close() error {
+	if err := o.player.Close(); err != nil {
+		return fmt.Errorf("error closing player: %w", err)
+	}
+	if err := o.context.Close(); err != nil {
+		return fmt.Errorf("error closing oto context: %w", err)
+	}
+	return nil
+}
+
+const otoBufferSize = 8192
+
+// NewPlayer creates and initializes a new OtoPlayer
+func NewPlayer() (*OtoPlayer, error) {
+	context, err := oto.NewContext(44100, 2, 2, otoBufferSize)
+	if err != nil {
+		return nil, fmt.Errorf("cannot create oto context: %w", err)
+	}
+	player := context.NewPlayer()
+
+	return &OtoPlayer{
+		context: context,
+		player:  player,
+	}, nil
+}

go4k/audio/player.go

@@ -0,0 +1,6 @@
+package audio
+
+type Player interface {
+	Play(buffer []float32) (err error)
+	Close()
+}