diff --git a/aux.py b/aux.py
index f651bf8..f259a7c 100644
--- a/aux.py
+++ b/aux.py
@@ -3,152 +3,12 @@
 
 import os
 import pathlib
-import queue
-import subprocess
-import sys
-import threading
-
-# --------------------------------------------------
-
-def capture_output(stream, fifo):
-	while True:
-		chunk = stream.read1(128)
-		
-		if chunk:
-			fifo.put(chunk)
-		else:
-			fifo.put(None) # indicates a process has terminated
-			break
-	
-	stream.close()
-
-class Command:
-	"""
-	A shell command with argument substitution and output capture.
-	
-	>>> c = Command(["process.sh", "-x", "ARGUMENT"])
-	>>> c.ARGUMENT = "file.txt"
-	>>> c.dump()
-	['process.sh', '-x', 'file.txt']
-	>>> c.run(stderr=False) # capture stdout
-	>>> c.get_output()
-	b'some output'
-	>>> c.get_output()
-	b'' # there was no output since the last call
-	>>> c.get_output()
-	b'more of it\nand some more'
-	>>> c.get_output()
-	None # indicates the process ended and there is no more output
-	
-	"""
-	
-	def __init__(self, *sequence):
-		self.__dict__["sequence_original"] = list(sequence)
-		self.reset()
-	
-	def __setattr__(self, name, value):
-		found = False
-		
-		for i, word in enumerate(self.sequence):
-			if word == name:
-				self.sequence[i] = value
-				found = True
-		
-		#if not found:
-			#raise AttributeError("Command has no attribute \'%s\'" %(name))
-	
-	def reset(self):
-		self.__dict__["sequence"] = list(self.sequence_original)
-		self.__dict__["thread"] = None
-		self.__dict__["fifo"] = None
-		self.__dict__["terminated"] = False
-	
-	def dump(self, sequence=None, pretty=False):
-		out = []
-		
-		if not sequence:
-			sequence = self.sequence
-		
-		for item in sequence:
-			if type(item) is list:
-				out += self.dump(item)
-			elif type(item) is Command:
-				out += item.dump()
-			elif item is not None:
-				out.append(str(item))
-		
-		if pretty:
-			return [('"%s"' %(a) if ' ' in a else a) for a in out]
-		else:
-			return out
-	
-	def run(self, stderr=False):
-		"""
-		Executes the command in the current environment.
-		
-		stderr    capture stderr instead of stdout
-		"""
-		
-		self.__dict__["process"] = subprocess.Popen(self.dump(), stdout=subprocess.PIPE, stderr=subprocess.PIPE, bufsize=1)
-		self.__dict__["fifo"] = queue.Queue()
-		self.__dict__["thread"] = threading.Thread(
-			target=capture_output,
-			args=(self.process.stderr if stderr else self.process.stdout, self.fifo)
-		)
-		self.__dict__["terminated"] = False
-		self.thread.daemon = True # thread dies with the program
-		self.thread.start()
-	
-	def get_output(self, blocking=False):
-		"""
-		Returns the output of a currently running process and clears the buffer.
-		
-		Returns None if no process is running and no more output is available.
-		
-		blocking    block until some output is available or the process terminates
-		"""
-		
-		buffer = []
-		
-		if self.terminated:
-			return None
-		
-		if blocking:
-			buffer.append(self.fifo.get())
-		
-		while not self.fifo.empty():
-			buffer.append(self.fifo.get_nowait()) # FIXME nowait needed?
-		
-		if None in buffer:
-			self.__dict__["terminated"] = True
-			self.__dict__["returncode"] = self.process.poll()
-			
-			if len(buffer) == 1:
-				return None
-			else:
-				assert(buffer[-1] is None)
-				del buffer[-1]
-		
-		return b"".join(buffer)
-	
-	def get_all_output(self):
-		buffer = []
-		
-		while True:
-			chunk = self.get_output(blocking=True)
-			
-			if chunk is None:
-				break
-			else:
-				buffer.append(chunk)
-		
-		return b''.join(buffer) if buffer else None
 
 # --------------------------------------------------
 
 def parse_fps(raw):
-	if "/" in raw:
-		num, den = (int(x) for x in raw.split("/"))
+	if '/' in raw:
+		num, den = (int(x) for x in raw.split('/'))
 		
 		return float(num) / float(den)
 	
@@ -158,7 +18,7 @@ def parse_fps(raw):
 
 def to_Path(raw_path):
 	'''
-	Returns pathlib.Path pointing to raw_path, handling "~/" correctly.
+	Returns pathlib.Path pointing to raw_path, handling '~/' correctly.
 	
 	To be removed after python:3.5 move.
 	'''
diff --git a/over-video.py b/over-video.py
index bb59a9f..f541ae0 100755
--- a/over-video.py
+++ b/over-video.py
@@ -6,13 +6,14 @@ import os
 import over
 import pathlib
 import re
-import subprocess
 import tempfile
 import time
 
-from aux import Command, parse_fps, to_Path
+from aux import parse_fps, to_Path
 from version import _version
 
+Command = over.core.cmd.Command
+
 # --------------------------------------------------
 
 prefix = over.core.textui.prefix