diff --git a/management/commands/generate_clips.py b/management/commands/generate_clips.py
index 23bc61c..e2ecca9 100644
--- a/management/commands/generate_clips.py
+++ b/management/commands/generate_clips.py
@@ -23,6 +23,9 @@ def resolve_roman(s):
         return s.replace(extra, new)
     return s
 
+def format_duration(duration, fps):
+    return float('%0.5f' % (round(duration * fps) / fps))
+
 
 class Command(BaseCommand):
     help = 'generate symlinks to clips and clips.json'
@@ -68,6 +71,10 @@ class Command(BaseCommand):
                 if not clip["duration"]:
                     print('!!', durations, clip)
                     continue
+                cd = format_duration(clip["duration"], 24)
+                #if cd != clip["duration"]:
+                #    print(clip["duration"], '->', cd, durations, clip)
+                clip["duration"] = cd
                 clip['tags'] = i.data.get('tags', [])
                 clip['editingtags'] = i.data.get('editingtags', [])
                 name = os.path.basename(clip['original'])
@@ -117,7 +124,7 @@ class Command(BaseCommand):
                 subs.append(sdata)
             voice_over[fragment_id][batch] = {
                 "src": target,
-                "duration": source.duration,
+                "duration": format_duration(source.duration, 24),
                 "subs": subs
             }
         with open(os.path.join(prefix, 'voice_over.json'), 'w') as fd:
diff --git a/render.py b/render.py
index 32d43a7..36518bf 100644
--- a/render.py
+++ b/render.py
@@ -11,8 +11,10 @@ import time
 from pathlib import Path
 
 import ox
+import lxml.etree
+
 from .pi import random
-from .render_kdenlive import KDEnliveProject, _CACHE
+from .render_kdenlive import KDEnliveProject, _CACHE, melt_xml, get_melt
 
 
 def random_int(seq, length):
@@ -64,6 +66,8 @@ def write_if_new(path, data, mode=''):
         with open(path, write_mode) as fd:
             fd.write(data)
 
+def format_duration(duration, fps):
+    return float('%0.5f' % (round(duration * fps) / fps))
 
 def compose(clips, target=150, base=1024, voice_over=None):
     fps = 24
@@ -120,7 +124,7 @@ def compose(clips, target=150, base=1024, voice_over=None):
         if vo_min > target:
             target = vo_min
         elif vo_min < target:
-            offset = int(((target - vo_min) / 2) * fps) / fps
+            offset = format_duration((target - vo_min) / 2, fps)
             scene['audio-center']['A1'].append({
                 'blank': True,
                 'duration': offset
@@ -188,7 +192,7 @@ def compose(clips, target=150, base=1024, voice_over=None):
         if length + clip['duration'] > target and length >= vo_min:
             break
         print('%06.3f %06.3f' % (length, clip['duration']), os.path.basename(clip['original']))
-        length += clip['duration']
+        length += int(clip['duration'] * fps) / fps
 
         if "foreground" not in clip and "animation" in clip:
             fg = clip['animation']
@@ -300,8 +304,11 @@ def compose(clips, target=150, base=1024, voice_over=None):
         })
         used.append(clip)
     print("scene duration %0.3f (target: %0.3f, vo_min: %0.3f)" % (length, target, vo_min))
-    if sub_offset < length:
-        delta = length - sub_offset
+    scene_duration = int(get_scene_duration(scene) * fps)
+    sub_offset = int(sub_offset * fps)
+    if sub_offset < scene_duration:
+        delta = format_duration((scene_duration - sub_offset) / fps, fps)
+        print(">> add %0.3f of silence.. %0.3f (scene_duration)" % (delta, scene_duration / fps))
         scene['audio-center']['A1'].append({
             'blank': True,
             'duration': delta
@@ -310,8 +317,24 @@ def compose(clips, target=150, base=1024, voice_over=None):
             'blank': True,
             'duration': delta
         })
+    elif sub_offset > scene_duration:
+        delta = format_duration((scene_duration - sub_offset) / fps, fps)
+        scene['audio-center']['A1'][-1]["duration"] += delta
+        scene['audio-rear']['A1'][-1]["duration"] += delta
+        print("WTF, needed to cut %s new duration: %s" % (delta, scene['audio-center']['A1'][-1]["duration"]))
+        print(scene['audio-center']['A1'][-1])
     return scene, used
 
+def get_track_duration(scene, k, n):
+    duration = 0
+    for key, value in scene.items():
+        if key == k:
+            for name, clips in value.items():
+                if name == n:
+                    for clip in clips:
+                        duration += int(clip['duration'] * 24)
+                    return duration / 24
+
 def get_scene_duration(scene):
     if isinstance(scene, str):
         with open(scene) as fd:
@@ -320,8 +343,8 @@ def get_scene_duration(scene):
     for key, value in scene.items():
         for name, clips in value.items():
             for clip in clips:
-                duration += clip['duration']
-            return duration
+                duration += int(clip['duration'] * 24)
+            return duration / 24
 
 def get_offset_duration(prefix):
     duration = 0
@@ -331,7 +354,8 @@ def get_offset_duration(prefix):
                 duration += get_scene_duration(scene)
     return duration
 
-def render(root, scene, prefix=''):
+def render(root, scene, prefix='', options=None):
+    if options is None: options = {}
     fps = 24
     files = []
     scene_duration = int(get_scene_duration(scene) * fps)
@@ -351,7 +375,7 @@ def render(root, scene, prefix=''):
             #print(track)
             for clip in clips:
                 project.append_clip(track, clip)
-            track_durations[track] = int(sum([c['duration'] for c in clips]) * fps)
+            track_durations[track] = sum([int(c['duration'] * fps) for c in clips])
         if timeline.startswith('audio-'):
             track_duration = project.get_duration()
             delta = scene_duration - track_duration
@@ -359,13 +383,34 @@ def render(root, scene, prefix=''):
                 for track in track_durations:
                     if track_durations[track] == track_duration:
                         project.append_clip(track, {'blank': True, "duration": delta/fps})
-                        break
+
         path = os.path.join(root, prefix + "%s.kdenlive" % timeline)
         project_xml = project.to_xml()
         write_if_new(path, project_xml)
+
+        if options["debug"]:
+            # check duration
+            out_duration = get_project_duration(path)
+            p_duration = project.get_duration()
+            print(path, 'out: %s, project: %s, scene: %s' %(out_duration, p_duration, scene_duration))
+            if p_duration != scene_duration:
+                print(path, 'FAIL project: %s, scene: %s' %(p_duration, scene_duration))
+                _cache = os.path.join(root, "cache.json")
+                with open(_cache, "w") as fd:
+                    json.dump(_CACHE, fd)
+                sys.exit(1)
+            if out_duration != p_duration:
+                print(path, 'fail got: %s expected: %s' %(out_duration, p_duration))
+                sys.exit(1)
+
         files.append(path)
     return files
 
+def get_project_duration(file):
+    out = melt_xml(file)
+    chain = lxml.etree.fromstring(out).xpath('producer')[0]
+    duration = int(chain.attrib['out']) + 1
+    return duration
 
 def get_fragments(clips, voice_over, prefix):
     import itemlist.models
@@ -415,8 +460,6 @@ def get_fragments(clips, voice_over, prefix):
     return fragments
 
 
-def render_timeline(options):
-
 def render_all(options):
     prefix = options['prefix']
     duration = int(options['duration'])
@@ -470,7 +513,7 @@ def render_all(options):
         elif position < target_position:
             target = target + 0.1 * fragment_target
 
-        timelines = render(prefix, scene, fragment_prefix[len(prefix) + 1:] + '/')
+        timelines = render(prefix, scene, fragment_prefix[len(prefix) + 1:] + '/', options)
 
         scene_json = json.dumps(scene, indent=2, ensure_ascii=False)
         write_if_new(os.path.join(fragment_prefix, 'scene.json'), scene_json)
@@ -481,9 +524,8 @@ def render_all(options):
                 ext = '.mp4'
                 if '/audio' in timeline:
                     ext = '.wav'
-                cmd = [
-                    'xvfb-run', '-a',
-                    'melt', timeline,
+                cmd = get_melt() + [
+                    timeline,
                     '-quiet',
                     '-consumer', 'avformat:%s' % timeline.replace('.kdenlive', ext),
                 ]
@@ -596,10 +638,7 @@ def render_all(options):
             if '/audio' in timelines[0]:
                 ext = '.wav'
             out = base_prefix / (timeline + ext)
-            cmd = [
-                'xvfb-run', '-a',
-                'melt'
-            ] + timelines + [
+            cmd = get_melt() + timelines + [
                 '-quiet',
                 '-consumer', 'avformat:%s' % out,
             ]
diff --git a/render_kdenlive.py b/render_kdenlive.py
index 2431500..cdf755b 100644
--- a/render_kdenlive.py
+++ b/render_kdenlive.py
@@ -4,6 +4,7 @@ import subprocess
 import lxml.etree
 import uuid
 import os
+import sys
 
 _CACHE = {}
 _IDS = defaultdict(int)
@@ -12,6 +13,14 @@ def get_propery(element, name):
     return element.xpath('property[@name="%s"]' % name)[0].text
 
 
+def get_melt():
+    cmd = ['melt']
+    if 'XDG_RUNTIME_DIR' not in os.environ:
+        os.environ['XDG_RUNTIME_DIR'] = '/tmp/runtime-pandora'
+    if 'DISPLAY' not in os.environ:
+        cmd = ['xvfb-run', '-a'] + cmd
+    return cmd
+
 def melt_xml(file):
     out = None
     real_path = os.path.realpath(file)
@@ -20,7 +29,8 @@ def melt_xml(file):
         if os.stat(real_path).st_mtime != ts:
             out = None
     if not out:
-        out = subprocess.check_output(['melt', file, '-consumer', 'xml']).decode()
+        cmd = get_melt() + [file, '-consumer', 'xml']
+        out = subprocess.check_output(cmd).decode()
         _CACHE[file] = [os.stat(real_path).st_mtime, out]
     return out