Add examples/audio and OggStream struct

examples/_resources/audio/license.md

@@ -0,0 +1,11 @@
+# License
+
+## ragtime.ogg
+
+```
+Title:  Frog Legs Rag (1906, piano roll)
+Artist: James Scott
+Album:  Frog Legs: Ragtime Era Favorites
+
+Attribution-NonCommercial-ShareAlike: http://creativecommons.org/licenses/by-nc-sa/3.0/
+```

examples/audio/main.go

@@ -0,0 +1,58 @@
+// Copyright 2016 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"github.com/hajimehoshi/ebiten/exp/audio"
+)
+
+const (
+	screenWidth  = 320
+	screenHeight = 240
+)
+
+var audioContext *audio.Context
+
+func update(screen *ebiten.Image) error {
+	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
+	return nil
+}
+
+func main() {
+	// Use a FLAC file so far: I couldn't find any good OGG/Vorbis decoder in pure Go.
+	f, err := ebitenutil.OpenFile("_resources/audio/ragtime.ogg")
+	if err != nil {
+		log.Fatal(err)
+	}
+	// TODO: sampleRate should be obtained from the ogg file.
+	audioContext = audio.NewContext(22050)
+	s, err := audioContext.NewOggStream(f)
+	if err != nil {
+		log.Fatal(err)
+	}
+	p, err := audioContext.NewPlayer(s)
+	if err != nil {
+		log.Fatal(err)
+	}
+	p.Play()
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "PCM (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}

exp/audio/ogg.go

@@ -0,0 +1,62 @@
+// Copyright 2016 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !js
+
+package audio
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+
+	"github.com/hajimehoshi/go-vorbis"
+)
+
+type OggStream struct {
+	buf *bytes.Reader
+}
+
+func (c *Context) NewOggStream(src io.Reader) (*OggStream, error) {
+	decoded, channels, sampleRate, err := vorbis.Decode(src)
+	if err != nil {
+		return nil, err
+	}
+	if channels != 2 {
+		return nil, errors.New("audio: number of channels must be 2")
+	}
+	if sampleRate != c.sampleRate {
+		return nil, fmt.Errorf("audio: sample rate must be %d but %d", c.sampleRate, sampleRate)
+	}
+	// TODO: Read all data once so that Seek can be implemented easily.
+	// We should look for a wiser way.
+	b, err := ioutil.ReadAll(decoded)
+	if err != nil {
+		return nil, err
+	}
+	s := &OggStream{
+		buf: bytes.NewReader(b),
+	}
+	return s, nil
+}
+
+func (s *OggStream) Read(p []byte) (int, error) {
+	return s.buf.Read(p)
+}
+
+func (s *OggStream) Seek(offset int64, whence int) (int64, error) {
+	return s.buf.Seek(offset, whence)
+}

exp/audio/ogg_js.go

@@ -0,0 +1,69 @@
+// Copyright 2016 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build js
+
+package audio
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+
+	"github.com/gopherjs/gopherjs/js"
+)
+
+type OggStream struct {
+	buf *bytes.Reader
+}
+
+// TODO: This just uses decodeAudioData can treat audio files other than Ogg/Vorbis.
+// TODO: This doesn't work on iOS which doesn't have Ogg/Vorbis decoder.
+
+func (c *Context) NewOggStream(src io.Reader) (*OggStream, error) {
+	b, err := ioutil.ReadAll(src)
+	if err != nil {
+		return nil, err
+	}
+	s := &OggStream{}
+	ch := make(chan struct{})
+
+	// TODO: 1 is a correct second argument?
+	oc := js.Global.Get("OfflineAudioContext").New(2, 1, c.sampleRate)
+	oc.Call("decodeAudioData", js.NewArrayBuffer(b), func(buf *js.Obbmaiject) {
+		defer close(ch)
+		il := buf.Call("getChannelData", 0).Interface().([]float32)
+		ir := buf.Call("getChannelData", 1).Interface().([]float32)
+		b := make([]byte, len(il)*4)
+		for i := 0; i < len(il); i++ {
+			l := int16(il[i] * (1 << 15))
+			r := int16(ir[i] * (1 << 15))
+			b[4*i] = uint8(l)
+			b[4*i+1] = uint8(l >> 8)
+			b[4*i+2] = uint8(r)
+			b[4*i+3] = uint8(r >> 8)
+		}
+		s.buf = bytes.NewReader(b)
+	})
+	<-ch
+	return s, nil
+}
+
+func (s *OggStream) Read(p []byte) (int, error) {
+	return s.buf.Read(p)
+}
+
+func (s *OggStream) Seek(offset int64, whence int) (int64, error) {
+	return s.buf.Seek(offset, whence)
+}