diff --git a/python/c4fm-demod.py b/python/c4fm-demod.py
index 7e995a7..b951342 100755
--- a/python/c4fm-demod.py
+++ b/python/c4fm-demod.py
@@ -1,4 +1,7 @@
 #!/usr/bin/env python
+from gnuradio import gr, gru, blks
+from gnuradio.eng_option import eng_option
+from optparse import OptionParser
 
 """
 simple frequency demodulator for captured P25 C4FM signals
@@ -7,47 +10,46 @@ input: complex sample captured by USRP
 output: real baseband sample at 48 ksps
 """
 
-from gnuradio import gr, gru, blks
-import math
-
-class my_graph(gr.flow_graph):
-
-	def __init__(self):
+class app_flow_graph(gr.flow_graph):
+	def __init__(self, options):
 		gr.flow_graph.__init__(self)
 
-		### set these manually for target sample
-		input_sample_rate = 500e3	# trunk control channel sample
-		# frequency is relative to input sample
-		#frequency = 87.5e3			# lower band of trunk control channel sample
-		frequency = 100e3			# higher band of trunk control channel sample
-		#input_sample_rate = 256e3	# *-256KSS.dat samples
-		#frequency = 0				# baseband-complex-256KSS.dat
-		#frequency = 30e3			# sample-complex-256KSS.dat
 		bandwidth = 12.5e3
-		###
-		src = gr.file_source(gr.sizeof_gr_complex, "infile")
 		symbol_rate = 4800
-		output_samples_per_symbol = 10
-		output_sample_rate = output_samples_per_symbol * symbol_rate
-		lcm = gru.lcm(input_sample_rate, output_sample_rate)
-		intrp = int(lcm // input_sample_rate)
+
+		output_sample_rate = options.samples_per_symbol * symbol_rate
+		lcm = gru.lcm(options.sample_rate, output_sample_rate)
+		intrp = int(lcm // options.sample_rate)
 		decim = int(lcm // output_sample_rate)
+
+		src = gr.file_source(gr.sizeof_gr_complex, options.input_file)
 		ddc_coeffs = \
 			gr.firdes.low_pass (1.0,
-				input_sample_rate,
+				options.sample_rate,
 				bandwidth/2,
 				bandwidth/2,
 				gr.firdes.WIN_HANN)
-		ddc =  gr.freq_xlating_fir_filter_ccf (1,ddc_coeffs,-frequency,input_sample_rate)
+		ddc =  gr.freq_xlating_fir_filter_ccf (1,ddc_coeffs,-options.frequency,options.sample_rate)
 		resampler = blks.rational_resampler_ccc(self, intrp, decim)
 		qdemod = gr.quadrature_demod_cf(1.0)
-		f2c = gr.float_to_complex()
-		sink = gr.file_sink(gr.sizeof_float, "demod")
+		sink = gr.file_sink(gr.sizeof_float, options.output_file)
 
 		self.connect(src,ddc,resampler,qdemod,sink)
 
-if __name__ == '__main__':
+def main():
+	parser = OptionParser(option_class=eng_option)
+	parser.add_option("-i", "--input-file", type="string", default="in.dat", help="specify the input file")
+	parser.add_option("-o", "--output-file", type="string", default="demod.dat", help="specify the output file")
+	parser.add_option("-r", "--sample-rate", type="eng_float", default=500e3, help="sample rate of input file", metavar="Hz")
+	parser.add_option("-f", "--frequency", type="eng_float", default=0, help="frequency of signal to demodulate", metavar="Hz")
+	parser.add_option("-s", "--samples-per-symbol", type="int", default=10, help="samples per symbol in output file")
+	(options, args) = parser.parse_args()
+
+	fg = app_flow_graph(options)
 	try:
-		my_graph().run()
+		fg.run()
 	except KeyboardInterrupt:
 		pass
+
+if __name__ == "__main__":
+	main()