diff --git a/.gitignore b/.gitignore
index 0d0c7da..0d20b64 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1 @@
-*.int16
 *.pyc
diff --git a/common.py b/common.py
index 6a3f963..de9cdc3 100644
--- a/common.py
+++ b/common.py
@@ -34,7 +34,11 @@ def to_bytes(bits):
     return chr(byte)
 
 def load(fname):
-    x = np.fromfile(open(fname, 'rb'), dtype='int16')
+    data = open(fname, 'rb').read()
+    return loads(data)
+
+def loads(data):
+    x = np.fromstring(data, dtype='int16')
     x = x / scaling
     t = np.arange(len(x)) / Fs
     return t, x
@@ -45,6 +49,9 @@ def dumps(sym, n=1):
     data = sym.tostring()
     return data * n
 
+def norm(x):
+    return np.sqrt(np.dot(x.conj(), x).real)
+
 if __name__ == '__main__':
 
     import pylab
diff --git a/ecc.py b/ecc.py
index 4a4d43c..5781e6b 100644
--- a/ecc.py
+++ b/ecc.py
@@ -34,6 +34,10 @@ def decode(data, nsym=DEFAULT_NSYM):
         except ReedSolomonError:
             break
 
+    overhead = (i - len(dec)) / float(i)
+    blocks = i / BLOCK_SIZE
+    log.debug('Decoded %d blocks = %d bytes (ECC overhead %.1f%%)', blocks, len(dec), overhead * 100)
+
     n = struct.calcsize(LEN_FMT)
     payload, length = dec[n:], dec[:n]
     length, = struct.unpack(LEN_FMT, length)
diff --git a/recv.py b/recv.py
index 75cc5a4..3a868e6 100644
--- a/recv.py
+++ b/recv.py
@@ -15,9 +15,6 @@ COHERENCE_THRESHOLD = 0.9
 CARRIER_DURATION = 300
 CARRIER_THRESHOLD = int(0.9 * CARRIER_DURATION)
 
-def norm(x):
-    return np.sqrt(np.dot(x.conj(), x).real)
-
 def power(x):
     return np.dot(x.conj(), x).real / len(x)
 
@@ -38,7 +35,7 @@ def exp_iwt(freq, n):
 
 def coherence(x, freq):
     n = len(x)
-    Hc = exp_iwt(freq, n) / np.sqrt(0.5*n)
+    Hc = exp_iwt(-freq, n) / np.sqrt(0.5*n)
     return np.dot(Hc, x) / norm(x)
 
 def detect(freq):
diff --git a/send.py b/send.py
index 0a6f93a..6826d4b 100644
--- a/send.py
+++ b/send.py
@@ -62,7 +62,8 @@ if __name__ == '__main__':
 
     r = record('rx.int16')
     start = time.time()
-    p = play(fd)
+    p = play(fd.name)
+    p.wait()
     log.debug('Took %.2f seconds', time.time() - start)
     time.sleep(0.1)
     r.stop()
diff --git a/sigproc.py b/sigproc.py
index 0839e24..04b0945 100644
--- a/sigproc.py
+++ b/sigproc.py
@@ -61,7 +61,7 @@ class QAM(object):
             index = np.argmin(np.abs(s - keys))
             yield self._dec[ keys[index] ]
 
-modulator = QAM(bits_per_symbol=4, radii=[0.6, 1.0])
+modulator = QAM(bits_per_symbol=2, radii=[1.0])
 
 def test():
     q = QAM(bits_per_symbol=8, radii=[0.25, 0.5, 0.75, 1.0])
diff --git a/wave.py b/wave.py
index e0cb5e6..8385f47 100644
--- a/wave.py
+++ b/wave.py
@@ -4,15 +4,14 @@ import subprocess as sp
 
 from common import Fs
 
-def play(fd):
-    args = ['aplay', fd.name, '-q', '-f', 'S16_LE', '-c', '1', '-r', str(int(Fs))]
-    ret = sp.call(args=args)
-    assert ret == 0
+def play(fname, **kwargs):
+    return launch('aplay', fname, '-q', '-f', 'S16_LE', '-c', '1', '-r', str(int(Fs)), **kwargs)
 
-def record(fname):
-    args = ['arecord', fname, '-q', '-f', 'S16_LE', '-c', '1', '-r', str(int(Fs))]
-    p = sp.Popen(args=args)
+def record(fname, **kwargs):
+    return launch('arecord', fname, '-q', '-f', 'S16_LE', '-c', '1', '-r', str(int(Fs)), **kwargs)
+
+def launch(*args, **kwargs):
+    print args
+    p = sp.Popen(args=args, **kwargs)
     p.stop = lambda: os.kill(p.pid, signal.SIGINT)
     return p
-
-