use mediainfo to get duration for final subtitle entry

main.go

@@ -11,12 +11,16 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
+	"strings"
 )
 
 type config struct {
 	youtubeDl         string
 	mkvmerge          string
+	mediainfo         string
 	overrideOutput    string
+	subsOnly          bool
 	deleteTemporaries bool
 }
 
@@ -74,6 +78,16 @@ func performDownload(ctx context.Context, cfg *config, targetUrl string) error {
 	}
 
 	// Determine video's total length
+	minfo := exec.CommandContext(ctx, cfg.mediainfo, `--Inform="General;%Duration%"`, filepath.Join(tmpdir, "downloaded.mkv"))
+	minfo.Stderr = os.Stderr
+	ret, err := minfo.Output()
+	if err != nil {
+		return err
+	}
+	msecsDuration, err := strconv.ParseInt(strings.TrimSpace(string(ret)), 10, 64)
+	if err != nil {
+		return err
+	}
 
 	// Create the subtitle file (clamped to total length)
 
@@ -82,7 +96,7 @@ func performDownload(ctx context.Context, cfg *config, targetUrl string) error {
 		return err
 	}
 
-	err = ltc.WriteSRT(fh)
+	err = ltc.WriteSRT(fh, float64(msecsDuration)/1000)
 	fh.Close()
 	if err != nil {
 		return err
@@ -135,6 +149,7 @@ read equivalent loadtup.com HTML content from stdin.
 Options:
   --youtube-dl PATH          Override path to youtube-dl
   --mkvmerge PATH            Override path to mkvmerge
+  --mediainfo PATH           Override path to mediainfo
   --output PATH              Override output filename
                              (only valid for a single URL)
   --delete-temporary=false   Preserve temporary files
@@ -150,6 +165,7 @@ func main() {
 
 	flag.StringVar(&cfg.youtubeDl, "youtube-dl", "youtube-dl", "")
 	flag.StringVar(&cfg.mkvmerge, "mkvmerge", "mkvmerge", "")
+	flag.StringVar(&cfg.mediainfo, "mediainfo", "mediainfo", "")
 	flag.StringVar(&cfg.overrideOutput, "output", "", "")
 	flag.BoolVar(&cfg.deleteTemporaries, "delete-temporary", true, "")
 	flag.Usage = usage

writesubs.go

@@ -17,7 +17,7 @@ func secs_to_srt_time(secs float64) string {
 	return fmt.Sprintf("%02d:%02d:%02d,%03d", hh, mm, ss, ms)
 }
 
-func (ltc *loadTupContent) WriteSRT(w io.Writer) error {
+func (ltc *loadTupContent) WriteSRT(w io.Writer, totalVideoDurationSecs float64) error {
 	/*
 
 		SRT file format (example from Wikipedia):
@@ -44,11 +44,9 @@ func (ltc *loadTupContent) WriteSRT(w io.Writer) error {
 		if i < len(ltc.Caps)-1 {
 			end = secs_to_srt_time(ltc.Secs[i+1])
 		} else {
-			// The final subtitle. We don't know how long it should be displayed
-			// for since we don't know the entire video's duration
-			// FIXME supply
-			// Assume 3 seconds
-			end = secs_to_srt_time(ltc.Secs[i] + 3)
+			// The final subtitle. Loadtup displays these for the entire
+			// remaining video duration
+			end = secs_to_srt_time(totalVideoDurationSecs)
 		}
 
 		fmt.Fprintf(w, "%d\n%s --> %s\n%s\n\n",