561 lines
10 KiB
Go
561 lines
10 KiB
Go
// Copyright 2021 The Oto Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package mux offers APIs for a low-level multiplexer of audio players.
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// Usually you don't have to use this.
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package mux
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import (
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"errors"
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"fmt"
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"io"
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"math"
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"runtime"
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"sync"
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"time"
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)
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// Format must sync with oto's Format.
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type Format int
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const (
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FormatFloat32LE Format = iota
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FormatUnsignedInt8
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FormatSignedInt16LE
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)
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func (f Format) ByteLength() int {
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switch f {
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case FormatFloat32LE:
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return 4
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case FormatUnsignedInt8:
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return 1
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case FormatSignedInt16LE:
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return 2
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}
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panic(fmt.Sprintf("mux: unexpected format: %d", f))
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}
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// Mux is a low-level multiplexer of audio players.
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type Mux struct {
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sampleRate int
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channelCount int
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format Format
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players map[*playerImpl]struct{}
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buf []float32
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cond *sync.Cond
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}
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// New creates a new Mux.
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func New(sampleRate int, channelCount int, format Format) *Mux {
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m := &Mux{
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sampleRate: sampleRate,
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channelCount: channelCount,
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format: format,
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cond: sync.NewCond(&sync.Mutex{}),
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}
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go m.loop()
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return m
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}
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func (m *Mux) shouldWait() bool {
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for p := range m.players {
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if p.canReadSourceToBuffer() {
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return false
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}
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}
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return true
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}
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func (m *Mux) wait() {
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m.cond.L.Lock()
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defer m.cond.L.Unlock()
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for m.shouldWait() {
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m.cond.Wait()
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}
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}
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func (m *Mux) loop() {
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var players []*playerImpl
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for {
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m.wait()
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m.cond.L.Lock()
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for i := range players {
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players[i] = nil
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}
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players = players[:0]
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for p := range m.players {
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players = append(players, p)
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}
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m.cond.L.Unlock()
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allZero := true
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for _, p := range players {
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n := p.readSourceToBuffer()
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if n != 0 {
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allZero = false
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}
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}
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// Sleeping is necessary especially on browsers.
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// Sometimes a player continues to read 0 bytes from the source and this loop can be a busy loop in such case.
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if allZero {
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time.Sleep(time.Millisecond)
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}
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}
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}
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func (m *Mux) addPlayer(player *playerImpl) {
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m.cond.L.Lock()
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defer m.cond.L.Unlock()
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if m.players == nil {
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m.players = map[*playerImpl]struct{}{}
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}
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m.players[player] = struct{}{}
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m.cond.Signal()
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}
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func (m *Mux) removePlayer(player *playerImpl) {
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m.cond.L.Lock()
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defer m.cond.L.Unlock()
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delete(m.players, player)
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m.cond.Signal()
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}
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// ReadFloat32s fills buf with the multiplexed data of the players as float32 values.
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func (m *Mux) ReadFloat32s(buf []float32) {
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m.cond.L.Lock()
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players := make([]*playerImpl, 0, len(m.players))
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for p := range m.players {
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players = append(players, p)
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}
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m.cond.L.Unlock()
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for i := range buf {
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buf[i] = 0
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}
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for _, p := range players {
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p.readBufferAndAdd(buf)
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}
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m.cond.Signal()
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}
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type Player struct {
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p *playerImpl
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}
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type playerState int
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const (
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playerPaused playerState = iota
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playerPlay
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playerClosed
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)
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type playerImpl struct {
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mux *Mux
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src io.Reader
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prevVolume float64
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volume float64
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err error
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state playerState
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tmpbuf []byte
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buf []byte
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eof bool
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bufferSize int
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m sync.Mutex
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}
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func (m *Mux) NewPlayer(src io.Reader) *Player {
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pl := &Player{
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p: &playerImpl{
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mux: m,
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src: src,
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prevVolume: 1,
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volume: 1,
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bufferSize: m.defaultBufferSize(),
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},
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}
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runtime.SetFinalizer(pl, (*Player).Close)
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return pl
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}
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func (p *Player) Err() error {
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return p.p.Err()
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}
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func (p *playerImpl) Err() error {
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p.m.Lock()
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defer p.m.Unlock()
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return p.err
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}
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func (p *Player) Play() {
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p.p.Play()
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}
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func (p *playerImpl) Play() {
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// Goroutines don't work effiently on Windows. Avoid using them (hajimehoshi/ebiten#1768).
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if runtime.GOOS == "windows" {
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p.m.Lock()
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defer p.m.Unlock()
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p.playImpl()
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} else {
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ch := make(chan struct{})
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go func() {
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p.m.Lock()
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defer p.m.Unlock()
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close(ch)
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p.playImpl()
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}()
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<-ch
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}
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}
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func (p *Player) SetBufferSize(bufferSize int) {
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p.p.setBufferSize(bufferSize)
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}
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func (p *playerImpl) setBufferSize(bufferSize int) {
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p.m.Lock()
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defer p.m.Unlock()
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orig := p.bufferSize
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p.bufferSize = bufferSize
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if bufferSize == 0 {
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p.bufferSize = p.mux.defaultBufferSize()
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}
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if orig != p.bufferSize {
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p.tmpbuf = nil
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}
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}
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func (p *playerImpl) ensureTmpBuf() []byte {
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if p.tmpbuf == nil {
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p.tmpbuf = make([]byte, p.bufferSize)
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}
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return p.tmpbuf
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}
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// read reads the source to buf.
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// read unlocks the mutex temporarily and locks when reading finishes.
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// This avoids locking during an external function call Read (#188).
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//
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// When read is called, the mutex m must be locked.
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func (p *playerImpl) read(buf []byte) (int, error) {
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p.m.Unlock()
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defer p.m.Lock()
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return p.src.Read(buf)
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}
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// addToPlayers adds p to the players set.
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//
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// When addToPlayers is called, the mutex m must be locked.
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func (p *playerImpl) addToPlayers() {
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p.m.Unlock()
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defer p.m.Lock()
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p.mux.addPlayer(p)
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}
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// removeFromPlayers removes p from the players set.
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//
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// When removeFromPlayers is called, the mutex m must be locked.
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func (p *playerImpl) removeFromPlayers() {
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p.m.Unlock()
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defer p.m.Lock()
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p.mux.removePlayer(p)
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}
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func (p *playerImpl) playImpl() {
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if p.err != nil {
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return
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}
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if p.state != playerPaused {
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return
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}
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p.state = playerPlay
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if !p.eof {
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buf := p.ensureTmpBuf()
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for len(p.buf) < p.bufferSize {
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n, err := p.read(buf)
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if err != nil && err != io.EOF {
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p.setErrorImpl(err)
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return
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}
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p.buf = append(p.buf, buf[:n]...)
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if err == io.EOF {
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p.eof = true
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break
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}
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}
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}
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if p.eof && len(p.buf) == 0 {
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p.state = playerPaused
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}
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p.addToPlayers()
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}
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func (p *Player) Pause() {
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p.p.Pause()
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}
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func (p *playerImpl) Pause() {
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p.m.Lock()
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defer p.m.Unlock()
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if p.state != playerPlay {
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return
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}
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p.state = playerPaused
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}
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func (p *Player) Seek(offset int64, whence int) (int64, error) {
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return p.p.Seek(offset, whence)
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}
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func (p *playerImpl) Seek(offset int64, whence int) (int64, error) {
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p.m.Lock()
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defer p.m.Unlock()
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// If a player is playing, keep playing even after this seeking.
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if p.state == playerPlay {
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defer p.playImpl()
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}
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// Reset the internal buffer.
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p.resetImpl()
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// Check if the source implements io.Seeker.
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s, ok := p.src.(io.Seeker)
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if !ok {
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return 0, errors.New("mux: the source must implement io.Seeker")
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}
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return s.Seek(offset, whence)
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}
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func (p *Player) Reset() {
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p.p.Reset()
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}
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func (p *playerImpl) Reset() {
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p.m.Lock()
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defer p.m.Unlock()
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p.resetImpl()
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}
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func (p *playerImpl) resetImpl() {
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if p.state == playerClosed {
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return
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}
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p.state = playerPaused
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p.buf = p.buf[:0]
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p.eof = false
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}
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func (p *Player) IsPlaying() bool {
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return p.p.IsPlaying()
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}
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func (p *playerImpl) IsPlaying() bool {
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p.m.Lock()
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defer p.m.Unlock()
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return p.state == playerPlay
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}
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func (p *Player) Volume() float64 {
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return p.p.Volume()
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}
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func (p *playerImpl) Volume() float64 {
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p.m.Lock()
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defer p.m.Unlock()
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return p.volume
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}
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func (p *Player) SetVolume(volume float64) {
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p.p.SetVolume(volume)
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}
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func (p *playerImpl) SetVolume(volume float64) {
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p.m.Lock()
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defer p.m.Unlock()
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p.volume = volume
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if p.state != playerPlay {
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p.prevVolume = volume
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}
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}
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func (p *Player) BufferedSize() int {
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return p.p.BufferedSize()
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}
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func (p *playerImpl) BufferedSize() int {
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p.m.Lock()
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defer p.m.Unlock()
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return len(p.buf)
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}
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func (p *Player) Close() error {
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runtime.SetFinalizer(p, nil)
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return p.p.Close()
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}
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func (p *playerImpl) Close() error {
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p.m.Lock()
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defer p.m.Unlock()
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return p.closeImpl()
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}
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func (p *playerImpl) closeImpl() error {
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p.removeFromPlayers()
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if p.state == playerClosed {
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return p.err
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}
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p.state = playerClosed
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p.buf = nil
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return p.err
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}
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func (p *playerImpl) readBufferAndAdd(buf []float32) int {
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p.m.Lock()
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defer p.m.Unlock()
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if p.state != playerPlay {
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return 0
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}
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format := p.mux.format
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bitDepthInBytes := format.ByteLength()
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n := len(p.buf) / bitDepthInBytes
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if n > len(buf) {
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n = len(buf)
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}
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prevVolume := float32(p.prevVolume)
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volume := float32(p.volume)
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channelCount := p.mux.channelCount
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rateDenom := float32(n / channelCount)
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src := p.buf[:n*bitDepthInBytes]
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for i := 0; i < n; i++ {
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var v float32
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switch format {
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case FormatFloat32LE:
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v = math.Float32frombits(uint32(src[4*i]) | uint32(src[4*i+1])<<8 | uint32(src[4*i+2])<<16 | uint32(src[4*i+3])<<24)
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case FormatUnsignedInt8:
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v8 := src[i]
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v = float32(v8-(1<<7)) / (1 << 7)
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case FormatSignedInt16LE:
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v16 := int16(src[2*i]) | (int16(src[2*i+1]) << 8)
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v = float32(v16) / (1 << 15)
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default:
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panic(fmt.Sprintf("mux: unexpected format: %d", format))
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}
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if volume == prevVolume {
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buf[i] += v * volume
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} else {
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rate := float32(i/channelCount) / rateDenom
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if rate > 1 {
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rate = 1
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}
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buf[i] += v * (volume*rate + prevVolume*(1-rate))
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}
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}
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p.prevVolume = p.volume
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copy(p.buf, p.buf[n*bitDepthInBytes:])
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p.buf = p.buf[:len(p.buf)-n*bitDepthInBytes]
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if p.eof && len(p.buf) == 0 {
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p.state = playerPaused
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}
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return n
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}
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func (p *playerImpl) canReadSourceToBuffer() bool {
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p.m.Lock()
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defer p.m.Unlock()
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if p.eof {
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return false
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}
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return len(p.buf) < p.bufferSize
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}
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func (p *playerImpl) readSourceToBuffer() int {
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p.m.Lock()
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defer p.m.Unlock()
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if p.err != nil {
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return 0
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}
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if p.state == playerClosed {
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return 0
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}
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if len(p.buf) >= p.bufferSize {
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return 0
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}
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buf := p.ensureTmpBuf()
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n, err := p.read(buf)
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if err != nil && err != io.EOF {
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p.setErrorImpl(err)
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return 0
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}
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p.buf = append(p.buf, buf[:n]...)
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if err == io.EOF {
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p.eof = true
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if len(p.buf) == 0 {
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p.state = playerPaused
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}
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}
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return n
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}
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func (p *playerImpl) setErrorImpl(err error) {
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p.err = err
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p.closeImpl()
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}
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// TODO: The term 'buffer' is confusing. Name each buffer with good terms.
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// defaultBufferSize returns the default size of the buffer for the audio source.
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// This buffer is used when unreading on pausing the player.
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func (m *Mux) defaultBufferSize() int {
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bytesPerSample := m.channelCount * m.format.ByteLength()
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s := m.sampleRate * bytesPerSample / 2 // 0.5[s]
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// Align s in multiples of bytes per sample, or a buffer could have extra bytes.
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return s / bytesPerSample * bytesPerSample
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}
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