diff --git a/server.js b/server.js
index d1a11f7..7794805 100644
--- a/server.js
+++ b/server.js
@@ -120,6 +120,29 @@ const probeFile = (filePath) => {
     });
 };
 
+const parseTimemarkToSeconds = (timemark) => {
+    if (typeof timemark !== 'string' || !timemark.trim()) {
+        return 0;
+    }
+
+    const parts = timemark.trim().split(':');
+    if (parts.length !== 3) {
+        const numericValue = parseFloat(timemark);
+        return Number.isFinite(numericValue) ? numericValue : 0;
+    }
+
+    const [hoursPart, minutesPart, secondsPart] = parts;
+    const hours = parseInt(hoursPart, 10);
+    const minutes = parseInt(minutesPart, 10);
+    const seconds = parseFloat(secondsPart);
+
+    if (![hours, minutes, seconds].every(Number.isFinite)) {
+        return 0;
+    }
+
+    return (hours * 3600) + (minutes * 60) + seconds;
+};
+
 const stopActiveTranscode = (progressKey) => {
     const activeCommand = transcodeProcesses.get(progressKey);
     if (!activeCommand) {
@@ -448,7 +471,7 @@ app.get('/api/stream', async (req, res) => {
             ffmpegCommand
                 .on('progress', (progress) => {
                     const effectiveDuration = Math.max(0, (progressMap[progressKey]?.duration || 0) - startSeconds);
-                    const timemarkSeconds = ffmpeg.timemarkToSeconds(progress.timemark || '0');
+                    const timemarkSeconds = parseTimemarkToSeconds(progress.timemark || '0');
                     const absoluteSeconds = startSeconds + (isFinite(timemarkSeconds) ? timemarkSeconds : 0);
                     const percent = effectiveDuration > 0
                         ? Math.min(Math.max(Math.round((absoluteSeconds / (progressMap[progressKey]?.duration || effectiveDuration)) * 100), 0), 100)