diff --git a/render_mlt.py b/render_mlt.py
index d182675..ee05b39 100755
--- a/render_mlt.py
+++ b/render_mlt.py
@@ -185,6 +185,8 @@ for name, plist in (
         else:
             add_audio_clip(plist, clip['path'], frames)
 
+duration = sum(clip['duration'] for clip in data['clips'])
+
 save_xml(vocals, target_vocals)
 video.set("hide", 1)
 save_xml(video, target_source)
@@ -234,7 +236,6 @@ subprocess.call([
     'qmelt', target_audio, '-consumer', 'avformat:' + target_audio_wav,
 ])
 audiomix = mlt.Playlist()
-duration = sum(clip['duration'] for clip in data['clips'])
 add_audio_clip(audiomix, target_audio_wav, int(duration * fps))
 
 # mix video + audio