2024-04-11 08:28:23 +02:00
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// Copyright 2024 The Ebitengine 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 main
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import (
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"fmt"
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"io"
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"sync"
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"time"
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"github.com/gen2brain/mpeg"
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"github.com/hajimehoshi/ebiten/v2"
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"github.com/hajimehoshi/ebiten/v2/audio"
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)
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type mpegPlayer struct {
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mpg *mpeg.MPEG
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currentFrame *ebiten.Image
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audioPlayer *audio.Player
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// These members are used when the video doesn't have an audio stream.
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refTime time.Time
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m sync.Mutex
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}
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func newMPEGPlayer(src io.Reader) (*mpegPlayer, error) {
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mpg, err := mpeg.New(src)
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if err != nil {
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return nil, err
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}
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if mpg.NumVideoStreams() == 0 {
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return nil, fmt.Errorf("video: no video streams")
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}
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if !mpg.HasHeaders() {
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return nil, fmt.Errorf("video: missing headers")
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}
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p := &mpegPlayer{
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mpg: mpg,
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currentFrame: ebiten.NewImage(mpg.Width(), mpg.Height()),
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}
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// If the video doesn't have an audio stream, initialization is done.
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if mpg.NumAudioStreams() == 0 {
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return p, nil
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}
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// If the video has an audio stream, initialize an audio player.
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ctx := audio.CurrentContext()
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if ctx == nil {
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return nil, fmt.Errorf("video: audio.Context is not initialized")
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}
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if mpg.Channels() != 2 {
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return nil, fmt.Errorf("video: mpeg audio stream must be 2 but was %d", mpg.Channels())
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}
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if ctx.SampleRate() != mpg.Samplerate() {
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return nil, fmt.Errorf("video: mpeg audio stream sample rate %d doesn't match with audio context sample rate %d", mpg.Samplerate(), ctx.SampleRate())
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}
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mpg.SetAudioFormat(mpeg.AudioS16)
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audioPlayer, err := ctx.NewPlayer(&mpegAudio{
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audio: mpg.Audio(),
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m: &p.m,
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})
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if err != nil {
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return nil, err
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}
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p.audioPlayer = audioPlayer
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return p, nil
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}
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2024-04-11 15:43:48 +02:00
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// updateFrame upadtes the current video frame.
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func (p *mpegPlayer) updateFrame() {
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2024-04-11 08:28:23 +02:00
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p.m.Lock()
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defer p.m.Unlock()
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var pos float64
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if p.audioPlayer != nil {
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pos = p.audioPlayer.Position().Seconds()
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} else {
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if p.refTime != (time.Time{}) {
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pos = time.Since(p.refTime).Seconds()
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}
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}
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video := p.mpg.Video()
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if video.HasEnded() {
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p.currentFrame.Clear()
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return
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}
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d := 1 / p.mpg.Framerate()
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var mpegFrame *mpeg.Frame
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for video.Time()+d <= pos && !video.HasEnded() {
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mpegFrame = video.Decode()
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}
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if mpegFrame == nil {
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return
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}
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p.currentFrame.WritePixels(mpegFrame.RGBA().Pix)
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}
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// Draw draws the current frame onto the given screen.
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func (p *mpegPlayer) Draw(screen *ebiten.Image) {
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p.updateFrame()
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2024-04-11 08:28:23 +02:00
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frame := p.currentFrame
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sw, sh := screen.Bounds().Dx(), screen.Bounds().Dy()
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fw, fh := frame.Bounds().Dx(), frame.Bounds().Dy()
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op := ebiten.DrawImageOptions{}
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wf, hf := float64(sw)/float64(fw), float64(sh)/float64(fh)
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s := wf
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if hf < wf {
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s = hf
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}
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op.GeoM.Scale(s, s)
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offsetX, offsetY := float64(screen.Bounds().Min.X), float64(screen.Bounds().Min.Y)
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op.GeoM.Translate(offsetX+(float64(sw)-float64(fw)*s)/2, offsetY+(float64(sh)-float64(fh)*s)/2)
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op.Filter = ebiten.FilterLinear
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screen.DrawImage(frame, &op)
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}
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// Play starts playing the video.
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func (p *mpegPlayer) Play() {
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p.m.Lock()
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defer p.m.Unlock()
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if p.mpg.HasEnded() {
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return
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}
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if p.audioPlayer != nil {
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if p.audioPlayer.IsPlaying() {
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return
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}
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// Play refers (*mpegAudio).Read function, where the same mutex is used.
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// In order to avoid dead lock, use a different goroutine to start playing.
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// This issue happens especially on Windows where goroutines at Play are avoided in Oto (#1768).
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// TODO: Remove this hack in the future (ebitengine/oto#235).
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go p.audioPlayer.Play()
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return
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}
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if p.refTime != (time.Time{}) {
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return
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}
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p.refTime = time.Now()
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}
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type mpegAudio struct {
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audio *mpeg.Audio
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// leftovers is the remaining audio samples of the previous Read call.
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leftovers []byte
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// m is the mutex shared with the mpegPlayer.
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// As *mpeg.MPEG is not concurrent safe, this mutex is necessary.
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m *sync.Mutex
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}
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func (a *mpegAudio) Read(buf []byte) (int, error) {
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a.m.Lock()
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defer a.m.Unlock()
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var readBytes int
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if len(a.leftovers) > 0 {
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n := copy(buf, a.leftovers)
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readBytes += n
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buf = buf[n:]
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copy(a.leftovers, a.leftovers[n:])
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a.leftovers = a.leftovers[:len(a.leftovers)-n]
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}
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for len(buf) > 0 && !a.audio.HasEnded() {
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mpegSamples := a.audio.Decode()
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if mpegSamples == nil {
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break
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}
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bs := make([]byte, len(mpegSamples.S16)*2)
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for i, s := range mpegSamples.S16 {
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bs[i*2] = byte(s)
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bs[i*2+1] = byte(s >> 8)
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}
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n := copy(buf, bs)
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readBytes += n
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buf = buf[n:]
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if n < len(bs) {
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a.leftovers = append(a.leftovers, bs[n:]...)
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break
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}
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}
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if a.audio.HasEnded() {
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return readBytes, io.EOF
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}
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return readBytes, nil
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}
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