diff --git a/render.py b/render.py
index f7adb21..6c4db1d 100644
--- a/render.py
+++ b/render.py
@@ -56,6 +56,8 @@ def compose(clips, target=150, base=1024, voice_over=None):
         'back': {
             'V1': [],
             'V2': [],
+        },
+        'audio-back': {
             'A1': [],
         },
         'audio-center': {
@@ -225,7 +227,7 @@ def compose(clips, target=150, base=1024, voice_over=None):
             blur = seq() * 3
             if blur:
                 scene['back']['V1'][-1]['filter']['blur'] = blur
-        scene['back']['A1'].append({
+        scene['audio-back']['A1'].append({
             'duration': clip['duration'],
             'src': clip['original'],
         })
@@ -394,8 +396,8 @@ def render_all(options):
                 if ext == '.wav':
                     cmd += ['vn=1']
                 else:
-                    if not timeline.endswith("back.kdenlive"):
-                        cmd += ['an=1']
+                    #if not timeline.endswith("back.kdenlive"):
+                    cmd += ['an=1']
                     cmd += ['vcodec=libx264', 'x264opts=keyint=1', 'crf=15']
                 subprocess.call(cmd)
                 if ext == '.wav' and timeline.endswith('audio.kdenlive'):
@@ -445,18 +447,34 @@ def render_all(options):
                 "-c", "copy",
                 fragment_prefix / "front-5.1.mp4",
             ])
+            cmds.append([
+                "ffmpeg", "-y",
+                "-nostats", "-loglevel", "error",
+                "-i", fragment_prefix / "back.mp4",
+                "-i", fragment_prefix / "audio-back.wav",
+                "-c:v", "copy",
+                fragment_prefix / "back-audio.mp4",
+            ])
             for cmd in cmds:
                 #print(" ".join([str(x) for x in cmd]))
                 subprocess.call(cmd)
-            ft = ox.avinfo(str(fragment_prefix / "front-5.1.mp4"))['duration']
-            bt = ox.avinfo(str(fragment_prefix / "back.mp4"))['duration']
-            if ft != bt:
-                print(ft, fragment_prefix / "front-5.1.mp4")
-                print(bt, fragment_prefix / "back.mp4")
-                sys.exit(-1)
+
+            for a, b in (
+                ("back-audio.mp4", "back.mp4"),
+                ("front-5.1.mp4", "back.mp4"),
+            ):
+                duration_a = ox.avinfo(str(fragment_prefix / a))['duration']
+                duration_b = ox.avinfo(str(fragment_prefix / b))['duration']
+                if duration_a != duration_b:
+                    print('!!', duration_a, fragment_prefix / a)
+                    print('!!', duration_b, fragment_prefix / b)
+                    sys.exit(-1)
+            shutil.move(fragment_prefix / "back-audio.mp4", fragment_prefix / "back.mp4")
             shutil.move(fragment_prefix / "front-5.1.mp4", fragment_prefix / "front.mp4")
             for fn in (
-                "audio-5.1.mp4", "fl.wav", "fr.wav", "fc.wav", "lfe.wav", "bl.wav", "br.wav",
+                "audio-5.1.mp4",
+                "audio-back-wav", "back-audio.mp4",
+                "fl.wav", "fr.wav", "fc.wav", "lfe.wav", "bl.wav", "br.wav",
             ):
                 fn = fragment_prefix / fn
                 if os.path.exists(fn):