diff --git a/common/src/main/java/ctbrec/recorder/download/dash/DashDownload.java b/common/src/main/java/ctbrec/recorder/download/dash/DashDownload.java
index a9055d33..d5e72046 100644
--- a/common/src/main/java/ctbrec/recorder/download/dash/DashDownload.java
+++ b/common/src/main/java/ctbrec/recorder/download/dash/DashDownload.java
@@ -26,6 +26,8 @@ import javax.xml.bind.JAXBElement;
 import javax.xml.bind.JAXBException;
 import javax.xml.bind.Unmarshaller;
 
+import org.jcodec.containers.mp4.MP4Util;
+import org.jcodec.containers.mp4.boxes.MovieBox;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -63,6 +65,7 @@ public class DashDownload extends AbstractDownload {
     private ZonedDateTime splitRecStartTime;
 
     private File targetFile;
+    private File finalFile;
 
     public DashDownload(HttpClient httpClient, String manifestUrl) {
         this.httpClient = httpClient;
@@ -225,7 +228,7 @@ public class DashDownload extends AbstractDownload {
         this.config = config;
         this.model = model;
         this.startTime = startTime;
-        File finalFile = Config.getInstance().getFileForRecording(model, "mp4", startTime);
+        finalFile = Config.getInstance().getFileForRecording(model, "mp4", startTime);
         targetFile = new File(finalFile.getParentFile(), finalFile.getName() + ".part");
         downloadDir = targetFile.toPath();
     }
@@ -363,7 +366,14 @@ public class DashDownload extends AbstractDownload {
 
     @Override
     public Duration getLength() {
-        return Duration.between(startTime, Optional.ofNullable(endTime).orElse(Instant.now()));
+        try {
+            MovieBox movieBox = MP4Util.parseMovie(finalFile);
+            double lengthInSeconds = (double) movieBox.getDuration() / movieBox.getTimescale();
+            return Duration.ofSeconds((long) Math.ceil(lengthInSeconds));
+        } catch (IOException e) {
+            LOG.error("Couldn't determine length of MP4 file {}", getTarget(), e);
+            return Duration.between(startTime, Optional.ofNullable(endTime).orElse(Instant.now()));
+        }
     }
 
     @Override