ebiten/exp/audio/audio.go
2016-04-04 02:16:26 +09:00

275 lines
5.9 KiB
Go

// 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.
package audio
import (
"fmt"
"io"
"runtime"
"sync"
"time"
"github.com/hajimehoshi/ebiten"
)
type mixedPlayersStream struct {
context *Context
writtenBytes int
}
func min(a, b int) int {
if a < b {
return a
}
return b
}
const (
channelNum = 2
bytesPerSample = 2
bitsPerSample = bytesPerSample * 8
// TODO: This assumes that channelNum is a power of 2.
mask = ^(channelNum*bytesPerSample - 1)
)
func (s *mixedPlayersStream) Read(b []byte) (int, error) {
s.context.Lock()
defer s.context.Unlock()
bytesPerFrame := s.context.sampleRate * bytesPerSample * channelNum / ebiten.FPS
x := s.context.frames*bytesPerFrame + len(b)
if x <= s.writtenBytes {
return 0, nil
}
if len(s.context.players) == 0 {
l := min(len(b), x-s.writtenBytes)
l &= mask
copy(b, make([]byte, l))
s.writtenBytes += l
return l, nil
}
closed := []*Player{}
l := len(b)
for p := range s.context.players {
_, err := p.readToBuffer(l)
if err == io.EOF {
closed = append(closed, p)
} else if err != nil {
return 0, err
}
l = min(p.bufferLength(), l)
}
l &= mask
b16s := [][]int16{}
for p := range s.context.players {
b16s = append(b16s, p.bufferToInt16(l))
}
for i := 0; i < l/2; i++ {
x := 0
for _, b16 := range b16s {
x += int(b16[i])
}
if x > (1<<15)-1 {
x = (1 << 15) - 1
}
if x < -(1 << 15) {
x = -(1 << 15)
}
b[2*i] = byte(x)
b[2*i+1] = byte(x >> 8)
}
for p := range s.context.players {
p.proceed(l)
}
for _, p := range closed {
delete(s.context.players, p)
}
s.writtenBytes += l
return l, nil
}
// TODO: Enable to specify the format like Mono8?
type Context struct {
sampleRate int
stream *mixedPlayersStream
players map[*Player]struct{}
frames int
sync.Mutex
}
func NewContext(sampleRate int) (*Context, error) {
// TODO: Panic if one context exists.
c := &Context{
sampleRate: sampleRate,
players: map[*Player]struct{}{},
}
c.stream = &mixedPlayersStream{
context: c,
}
if err := startPlaying(c.stream, c.sampleRate); err != nil {
return nil, fmt.Errorf("audio: NewContext error: %v", err)
}
return c, nil
}
// Update proceeds the inner (logical) time of the context by 1/60 second.
// This is expected to be called in the game's updating function (sync mode)
// or an independent goroutine with timers (unsync mode).
// In sync mode, the game logical time syncs the audio logical time and
// you will find audio stops when the game stops e.g. when the window is deactivated.
// In unsync mode, the audio never stops even when the game stops.
func (c *Context) Update() {
c.Lock()
defer c.Unlock()
c.frames++
}
// SampleRate returns the sample rate.
func (c *Context) SampleRate() int {
c.Lock()
defer c.Unlock()
return c.sampleRate
}
type ReadSeekCloser interface {
io.ReadSeeker
io.Closer
}
type Player struct {
context *Context
src ReadSeekCloser
buf []byte
pos int64
volume float64
}
// NewPlayer creates a new player with the given data to the given channel.
// The given data is queued to the end of the buffer.
// This may not be played immediately when data already exists in the buffer.
//
// src's format must be linear PCM (16bits, 2 channel stereo, little endian)
// without a header (e.g. RIFF header).
func (c *Context) NewPlayer(src ReadSeekCloser) (*Player, error) {
c.Lock()
defer c.Unlock()
p := &Player{
context: c,
src: src,
buf: []byte{},
volume: 1,
}
// Get the current position of the source.
pos, err := p.src.Seek(0, 1)
if err != nil {
return nil, err
}
p.pos = pos
runtime.SetFinalizer(p, (*Player).Close)
return p, nil
}
func (p *Player) Close() error {
runtime.SetFinalizer(p, nil)
return p.src.Close()
}
func (p *Player) readToBuffer(length int) (int, error) {
bb := make([]byte, length)
n, err := p.src.Read(bb)
if 0 < n {
p.buf = append(p.buf, bb[:n]...)
}
return n, err
}
func (p *Player) bufferToInt16(lengthInBytes int) []int16 {
r := make([]int16, lengthInBytes/2)
for i := 0; i < lengthInBytes/2; i++ {
r[i] = int16(p.buf[2*i]) | (int16(p.buf[2*i+1]) << 8)
r[i] = int16(float64(r[i]) * p.volume)
}
return r
}
func (p *Player) proceed(length int) {
p.buf = p.buf[length:]
p.pos += int64(length)
}
func (p *Player) bufferLength() int {
return len(p.buf)
}
func (p *Player) Play() error {
p.context.Lock()
defer p.context.Unlock()
p.context.players[p] = struct{}{}
return nil
}
func (p *Player) IsPlaying() bool {
_, ok := p.context.players[p]
return ok
}
func (p *Player) Rewind() error {
return p.Seek(0)
}
func (p *Player) Seek(offset time.Duration) error {
p.buf = []byte{}
o := int64(offset) * bytesPerSample * channelNum * int64(p.context.sampleRate) / int64(time.Second)
o &= mask
pos, err := p.src.Seek(o, 0)
if err != nil {
return err
}
p.pos = pos
return nil
}
func (p *Player) Pause() error {
p.context.Lock()
defer p.context.Unlock()
delete(p.context.players, p)
return nil
}
func (p *Player) Current() time.Duration {
return time.Duration(p.pos/bytesPerSample/channelNum) * time.Second / time.Duration(p.context.sampleRate)
}
func (p *Player) Volume() float64 {
return p.volume
}
// SetVolume sets the volume.
// volume must be in between 0 and 1. This function panics otherwise.
func (p *Player) SetVolume(volume float64) {
// The condition must be true when volume is NaN.
if !(0 <= volume && volume <= 1) {
panic("audio: volume must be in between 0 and 1")
}
p.volume = volume
}
// TODO: Panning