send should work with stdin and stdout

send.py

@@ -36,7 +36,6 @@ write = Writer().write
 
 
 def start(fd, c):
-    write(fd, c*0, n=50)
     write(fd, c*1, n=400)
     write(fd, c*0, n=50)
 
@@ -54,7 +53,7 @@ def modulate(fd, bits):
         symbols = itertools.islice(symbols_iter, len(sym.carrier))
         symbols = np.array(list(symbols))
         write(fd, np.dot(symbols, carriers))
-        if all(symbols == 0):
+        if all(symbols == 0):  # EOF marker
             break
 
 
@@ -76,11 +75,15 @@ class Reader(object):
         return self
 
 
-def main(fname):
+def main(args):
     import ecc
     log.info('Running MODEM @ {:.1f} kbps'.format(sigproc.modem_bps / 1e3))
 
-    with open(fname, 'wb') as fd:
+    fd = sys.stdout
+
+    # padding audio with silence
+    write(fd, np.zeros(int(Fs * args.silence_start)))
+
     start(fd, sym.carrier[carrier_index])
     for c in sym.carrier:
         training(fd, c)
@@ -96,8 +99,9 @@ def main(fname):
     data_size = fd.tell() - training_size
     log.info('%.3f seconds of data audio, for %.3f kB of data',
              data_size / wave.bytes_per_second, reader.total / 1e3)
+
     # padding audio with silence
-        fd.write('\x00' * int(wave.bytes_per_second))
+    write(fd, np.zeros(int(Fs * args.silence_stop)))
 
 if __name__ == '__main__':
     logging.basicConfig(level=logging.DEBUG,
@@ -105,6 +109,7 @@ if __name__ == '__main__':
 
     import argparse
     p = argparse.ArgumentParser()
-    p.add_argument('fname')
+    p.add_argument('--silence-start', type=float, default=1.0)
+    p.add_argument('--silence-stop', type=float, default=1.0)
     args = p.parse_args()
-    main(fname=args.fname)
+    main(args)