examples: add an example to play a video

Closes #110
Updates #1768
Updates ebitengine/oto#235

examples/video/license.md

@@ -0,0 +1,9 @@
+# License
+
+## `shibuya.mpg`, `shibuya_noaudio.mpg`
+
+https://commons.wikimedia.org/wiki/File:Shibuya_Crossing,_Tokyo,_Japan_(video).webm
+
+"Shibuya Crossing, Tokyo, Japan (video).webm" by Basile Morin
+
+The Creative Commons Attribution-Share Alike 4.0 International license

examples/video/main.go

@@ -0,0 +1,87 @@
+// Copyright 2024 The Ebitengine Authors
+//
+// 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 (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"io"
+	"log"
+	"os"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/audio"
+)
+
+//go:embed shibuya.mpg
+var shibuya_mpg []byte
+
+type Game struct {
+	player *mpegPlayer
+}
+
+func (g *Game) Update() error {
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	g.player.Draw(screen)
+}
+
+func (g *Game) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeight int) {
+	return outsideWidth, outsideHeight
+}
+
+func main() {
+	// Initialize audio context.
+	_ = audio.NewContext(48000)
+
+	// If you want to play your own video, the video must be an MPEG-1 video with 48000 audio sample rate.
+	// You can convert the video to MPEG-1 with the below command:
+	//
+	//     ffmpeg -i YOUR_VIDEO -c:v mpeg1video -q:v 8 -c:a mp2 -format mpeg -ar 48000 output.mpg
+	//
+	// You can adjust quality by changing -q:v value. A lower value indicates better quality.
+	var in io.ReadSeeker
+	if len(os.Args) > 1 {
+		f, err := os.Open(os.Args[1])
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer func() {
+			_ = f.Close()
+		}()
+		in = f
+	} else {
+		in = bytes.NewReader(shibuya_mpg)
+		fmt.Println("Play the default video. You can specify a video file as an argument.")
+	}
+
+	player, err := newMPEGPlayer(in)
+	if err != nil {
+		log.Fatal(err)
+	}
+	g := &Game{
+		player: player,
+	}
+	player.Play()
+
+	ebiten.SetWindowTitle("Video (Ebiten Demo)")
+	ebiten.SetWindowResizingMode(ebiten.WindowResizingModeEnabled)
+	if err := ebiten.RunGame(g); err != nil {
+		log.Fatal(err)
+	}
+}

examples/video/mpegplayer.go

@@ -0,0 +1,220 @@
+// Copyright 2024 The Ebitengine Authors
+//
+// 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"
+	"io"
+	"sync"
+	"time"
+
+	"github.com/gen2brain/mpeg"
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/audio"
+)
+
+type mpegPlayer struct {
+	mpg *mpeg.MPEG
+
+	currentFrame *ebiten.Image
+	audioPlayer  *audio.Player
+
+	// These members are used when the video doesn't have an audio stream.
+	refTime time.Time
+
+	m sync.Mutex
+}
+
+func newMPEGPlayer(src io.Reader) (*mpegPlayer, error) {
+	mpg, err := mpeg.New(src)
+	if err != nil {
+		return nil, err
+	}
+	if mpg.NumVideoStreams() == 0 {
+		return nil, fmt.Errorf("video: no video streams")
+	}
+	if !mpg.HasHeaders() {
+		return nil, fmt.Errorf("video: missing headers")
+	}
+
+	p := &mpegPlayer{
+		mpg:          mpg,
+		currentFrame: ebiten.NewImage(mpg.Width(), mpg.Height()),
+	}
+
+	// If the video doesn't have an audio stream, initialization is done.
+	if mpg.NumAudioStreams() == 0 {
+		return p, nil
+	}
+
+	// If the video has an audio stream, initialize an audio player.
+	ctx := audio.CurrentContext()
+	if ctx == nil {
+		return nil, fmt.Errorf("video: audio.Context is not initialized")
+	}
+	if mpg.Channels() != 2 {
+		return nil, fmt.Errorf("video: mpeg audio stream must be 2 but was %d", mpg.Channels())
+	}
+	if ctx.SampleRate() != mpg.Samplerate() {
+		return nil, fmt.Errorf("video: mpeg audio stream sample rate %d doesn't match with audio context sample rate %d", mpg.Samplerate(), ctx.SampleRate())
+	}
+
+	mpg.SetAudioFormat(mpeg.AudioS16)
+
+	audioPlayer, err := ctx.NewPlayer(&mpegAudio{
+		audio: mpg.Audio(),
+		m:     &p.m,
+	})
+	if err != nil {
+		return nil, err
+	}
+	p.audioPlayer = audioPlayer
+
+	return p, nil
+}
+
+// updateFrame upadtes the current video frame.
+func (p *mpegPlayer) updateFrame() {
+	p.m.Lock()
+	defer p.m.Unlock()
+
+	var pos float64
+	if p.audioPlayer != nil {
+		pos = p.audioPlayer.Position().Seconds()
+	} else {
+		if p.refTime != (time.Time{}) {
+			pos = time.Since(p.refTime).Seconds()
+		}
+	}
+
+	video := p.mpg.Video()
+	if video.HasEnded() {
+		p.currentFrame.Clear()
+		return
+	}
+
+	d := 1 / p.mpg.Framerate()
+	var mpegFrame *mpeg.Frame
+	for video.Time()+d <= pos && !video.HasEnded() {
+		mpegFrame = video.Decode()
+	}
+
+	if mpegFrame == nil {
+		return
+	}
+	p.currentFrame.WritePixels(mpegFrame.RGBA().Pix)
+}
+
+// Draw draws the current frame onto the given screen.
+func (p *mpegPlayer) Draw(screen *ebiten.Image) {
+	p.updateFrame()
+	frame := p.currentFrame
+	sw, sh := screen.Bounds().Dx(), screen.Bounds().Dy()
+	fw, fh := frame.Bounds().Dx(), frame.Bounds().Dy()
+
+	op := ebiten.DrawImageOptions{}
+	wf, hf := float64(sw)/float64(fw), float64(sh)/float64(fh)
+	s := wf
+	if hf < wf {
+		s = hf
+	}
+	op.GeoM.Scale(s, s)
+
+	offsetX, offsetY := float64(screen.Bounds().Min.X), float64(screen.Bounds().Min.Y)
+	op.GeoM.Translate(offsetX+(float64(sw)-float64(fw)*s)/2, offsetY+(float64(sh)-float64(fh)*s)/2)
+	op.Filter = ebiten.FilterLinear
+
+	screen.DrawImage(frame, &op)
+}
+
+// Play starts playing the video.
+func (p *mpegPlayer) Play() {
+	p.m.Lock()
+	defer p.m.Unlock()
+
+	if p.mpg.HasEnded() {
+		return
+	}
+
+	if p.audioPlayer != nil {
+		if p.audioPlayer.IsPlaying() {
+			return
+		}
+		// Play refers (*mpegAudio).Read function, where the same mutex is used.
+		// In order to avoid dead lock, use a different goroutine to start playing.
+		// This issue happens especially on Windows where goroutines at Play are avoided in Oto (#1768).
+		// TODO: Remove this hack in the future (ebitengine/oto#235).
+		go p.audioPlayer.Play()
+		return
+	}
+
+	if p.refTime != (time.Time{}) {
+		return
+	}
+	p.refTime = time.Now()
+}
+
+type mpegAudio struct {
+	audio *mpeg.Audio
+
+	// leftovers is the remaining audio samples of the previous Read call.
+	leftovers []byte
+
+	// m is the mutex shared with the mpegPlayer.
+	// As *mpeg.MPEG is not concurrent safe, this mutex is necessary.
+	m *sync.Mutex
+}
+
+func (a *mpegAudio) Read(buf []byte) (int, error) {
+	a.m.Lock()
+	defer a.m.Unlock()
+
+	var readBytes int
+	if len(a.leftovers) > 0 {
+		n := copy(buf, a.leftovers)
+		readBytes += n
+		buf = buf[n:]
+
+		copy(a.leftovers, a.leftovers[n:])
+		a.leftovers = a.leftovers[:len(a.leftovers)-n]
+	}
+
+	for len(buf) > 0 && !a.audio.HasEnded() {
+		mpegSamples := a.audio.Decode()
+		if mpegSamples == nil {
+			break
+		}
+
+		bs := make([]byte, len(mpegSamples.S16)*2)
+		for i, s := range mpegSamples.S16 {
+			bs[i*2] = byte(s)
+			bs[i*2+1] = byte(s >> 8)
+		}
+
+		n := copy(buf, bs)
+		readBytes += n
+		buf = buf[n:]
+
+		if n < len(bs) {
+			a.leftovers = append(a.leftovers, bs[n:]...)
+			break
+		}
+	}
+
+	if a.audio.HasEnded() {
+		return readBytes, io.EOF
+	}
+	return readBytes, nil
+}

go.mod

@@ -22,6 +22,7 @@ require (
 )
 
 require (
+	github.com/gen2brain/mpeg v0.2.2 // indirect
 	github.com/jfreymuth/vorbis v1.0.2 // indirect
 	golang.org/x/mod v0.16.0 // indirect
 )

go.sum

@@ -6,6 +6,8 @@ github.com/ebitengine/oto/v3 v3.3.0-alpha.1 h1:J2nBmQwPLKc4+yLObytq1jKNydI96l6Ej
 github.com/ebitengine/oto/v3 v3.3.0-alpha.1/go.mod h1:T2/VV0UWG97GEEf4kORMU2nCneYT/YmwSTxPutSVaUg=
 github.com/ebitengine/purego v0.8.0-alpha.1 h1:52AgJTNaQRi7YtOtdJl4hkxNWhAGMxuDuDjOVIp5Ojk=
 github.com/ebitengine/purego v0.8.0-alpha.1/go.mod h1:y8L+ZRLphbdPW2xs41fur/KaW57yTzrFsqsclHyHrTM=
+github.com/gen2brain/mpeg v0.2.2 h1:9VhRzbbTShC54H6LGl3r+K+zZHSfL7lauyYhlj090nw=
+github.com/gen2brain/mpeg v0.2.2/go.mod h1:i/ebyRRv/IoHixuZ9bElZnXbmfoUVPGQpdsJ4sVuX38=
 github.com/go-text/typesetting v0.1.1-0.20240402181327-ced1d6822703 h1:AqtMl9yw7r319Ah4W2afQm3Ql+PEsQKHds18tGvKhog=
 github.com/go-text/typesetting v0.1.1-0.20240402181327-ced1d6822703/go.mod h1:2+owI/sxa73XA581LAzVuEBZ3WEEV2pXeDswCH/3i1I=
 github.com/go-text/typesetting-utils v0.0.0-20240317173224-1986cbe96c66 h1:GUrm65PQPlhFSKjLPGOZNPNxLCybjzjYBzjfoBGaDUY=