Add thumbnail.go with ffmpeg-based thumbnail generator

Co-authored-by: anacrolix <[email protected]>

Author: Copilot

.gitignore

@@ -1,5 +1,5 @@
 # Binaries for programs and plugins
-dms
+/dms
 *.exe
 *.exe~
 *.dll

dlna/dms/thumbnail.go

@@ -0,0 +1,107 @@
+package dms
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strconv"
+
+	"github.com/anacrolix/ffprobe"
+)
+
+// generateThumbnailFFmpeg generates a thumbnail using ffmpeg instead of ffmpegthumbnailer.
+// This provides better cross-platform compatibility, especially on Windows.
+func generateThumbnailFFmpeg(ctx context.Context, inputPath string) ([]byte, error) {
+	// Get video duration to calculate the seek position
+	ss, err := getThumbnailSeekPosition(ctx, inputPath)
+	if err != nil {
+		return nil, fmt.Errorf("determining seek position: %w", err)
+	}
+
+	// Build ffmpeg arguments for thumbnail generation
+	args := []string{
+		"-xerror",
+		"-loglevel", "warning",
+		"-ss", ss,
+		"-i", inputPath,
+		"-vf", "thumbnail",
+		"-frames:v", "1",
+		"-f", "image2",
+		"-c:v", "png",
+		"pipe:",
+	}
+
+	cmd := exec.Command("ffmpeg", args...)
+	cmd.Stderr = os.Stderr
+
+	// Start the command
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, fmt.Errorf("creating stdout pipe: %w", err)
+	}
+
+	if err := cmd.Start(); err != nil {
+		return nil, fmt.Errorf("starting ffmpeg: %w", err)
+	}
+
+	// Set up context cancellation
+	go func() {
+		<-ctx.Done()
+		if cmd.Process != nil {
+			cmd.Process.Kill()
+		}
+	}()
+
+	// Read the thumbnail data
+	thumbnailData, err := io.ReadAll(stdout)
+	if err != nil {
+		return nil, fmt.Errorf("reading thumbnail data: %w", err)
+	}
+
+	// Wait for command to finish
+	if err := cmd.Wait(); err != nil {
+		if ctx.Err() != nil {
+			return nil, ctx.Err()
+		}
+		return nil, fmt.Errorf("ffmpeg command failed: %w", err)
+	}
+
+	return thumbnailData, nil
+}
+
+// getThumbnailSeekPosition calculates the seek position for thumbnail extraction.
+// It seeks to 1/4 of the video duration by default.
+func getThumbnailSeekPosition(ctx context.Context, inputPath string) (string, error) {
+	// Use ffprobe to get video duration
+	pc, err := ffprobe.Start(inputPath)
+	if err != nil {
+		// If ffprobe fails, default to 10 seconds
+		return "10", nil
+	}
+
+	select {
+	case <-ctx.Done():
+		if pc.Cmd.Process != nil {
+			pc.Cmd.Process.Kill()
+		}
+		return "", ctx.Err()
+	case <-pc.Done:
+	}
+
+	if pc.Err != nil {
+		// If ffprobe fails, default to 10 seconds
+		return "10", nil
+	}
+
+	duration, err := pc.Info.Duration()
+	if err != nil {
+		// If duration cannot be determined, default to 10 seconds
+		return "10", nil
+	}
+
+	// Seek to 1/4 of the duration
+	seekDuration := duration / 4
+	return strconv.FormatFloat(seekDuration.Seconds(), 'f', -1, 64), nil
+}