ebiten/internal/audio/audio_js.go

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// Copyright 2015 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
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import (
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"io/ioutil"
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"github.com/gopherjs/gopherjs/js"
)
var context *js.Object
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type audioProcessor struct {
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src ReadSeekCloser
sampleRate int
position float64
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}
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func toLR(data []byte) ([]int16, []int16) {
l := make([]int16, len(data)/4)
r := make([]int16, len(data)/4)
for i := 0; i < len(data)/4; i++ {
l[i] = int16(data[4*i]) | int16(data[4*i+1])<<8
r[i] = int16(data[4*i+2]) | int16(data[4*i+3])<<8
}
return l, r
}
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func (a *audioProcessor) play() error {
// TODO: Reading all data at once is temporary implemntation. Treat this as stream.
buf, err := ioutil.ReadAll(a.src)
if err != nil {
return err
}
if len(buf) == 0 {
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return nil
}
const channelNum = 2
const bytesPerSample = channelNum * 16 / 8
b := context.Call("createBuffer", channelNum, len(buf)/bytesPerSample, a.sampleRate)
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l := b.Call("getChannelData", 0)
r := b.Call("getChannelData", 1)
il, ir := toLR(buf)
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const max = 1 << 15
for i := 0; i < len(il); i++ {
l.SetIndex(i, float64(il[i])/max)
r.SetIndex(i, float64(ir[i])/max)
}
s := context.Call("createBufferSource")
s.Set("buffer", b)
s.Call("connect", context.Get("destination"))
s.Call("start", a.position)
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a.position += b.Get("duration").Float()
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return nil
}
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func play(src ReadSeekCloser, sampleRate int) error {
a := &audioProcessor{
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src: src,
sampleRate: sampleRate,
position: context.Get("currentTime").Float(),
}
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return a.play()
}
func initialize() {
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// Do nothing in node.js.
if js.Global.Get("require") != js.Undefined {
return
}
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class := js.Global.Get("AudioContext")
if class == js.Undefined {
class = js.Global.Get("webkitAudioContext")
}
if class == js.Undefined {
return
}
context = class.New()
audioEnabled = true
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}