初始提交：短剧库源码（含转码优化 ultrafast）

internal/app/playback_process.go

@@ -0,0 +1,66 @@
+package app
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os/exec"
+)
+
+type playbackProcess struct {
+	command *exec.Cmd
+	cancel  context.CancelFunc
+	stdout  io.ReadCloser
+	log     *playbackLog
+	waited  bool
+	release func()
+}
+
+func (app *UIApp) startBudgetedPlaybackProcess(ctx context.Context, ffmpeg string, args []string, kind string) (*playbackProcess, error) {
+	optional, _ := ctx.Value(playbackPrefetchKey{}).(bool)
+	release, err := app.mediaResources().acquire(ctx, kind, optional)
+	if err != nil {
+		return nil, err
+	}
+	process, err := startPlaybackProcess(ctx, ffmpeg, args)
+	if err != nil {
+		release()
+		return nil, err
+	}
+	process.release = release
+	return process, nil
+}
+
+func startPlaybackProcess(ctx context.Context, ffmpeg string, args []string) (*playbackProcess, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	command := ffmpegMediaCommand(ctx, ffmpeg, args...)
+	stdout, err := command.StdoutPipe()
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	log := &playbackLog{text: cappedStringWriter{limit: 64 * 1024}, ready: make(chan struct{})}
+	command.Stderr = log
+	if err := command.Start(); err != nil {
+		cancel()
+		_ = stdout.Close()
+		return nil, fmt.Errorf("无法启动在线播放处理：%w", err)
+	}
+	return &playbackProcess{command: command, cancel: cancel, stdout: stdout, log: log}, nil
+}
+
+func (process *playbackProcess) Wait() error {
+	process.waited = true
+	if process.release != nil {
+		defer process.release()
+	}
+	return process.command.Wait()
+}
+
+func (process *playbackProcess) Close() {
+	process.cancel()
+	_ = process.stdout.Close()
+	if !process.waited {
+		_ = process.Wait()
+	}
+}