diff --git a/csdr.py b/csdr.py
index b4512b0..c35cc3e 100755
--- a/csdr.py
+++ b/csdr.py
@@ -26,7 +26,6 @@ import os
 import code
 import signal
 import fcntl
-import select
 
 class dsp:
 
@@ -394,6 +393,10 @@ class dsp:
         if self.csdr_dynamic_bufsize: my_env["CSDR_DYNAMIC_BUFSIZE_ON"]="1";
         if self.csdr_print_bufsizes: my_env["CSDR_PRINT_BUFSIZES"]="1";
         self.process = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True, preexec_fn=os.setpgrp, env=my_env)
+
+        #set stdout to non-blocking to avoid blocking the main loop when no audio was decoded in digital modes
+        self.set_pipe_nonblocking(self.process.stdout)
+
         self.running = True
 
         #open control pipes for csdr and send initialization data
@@ -419,9 +422,9 @@ class dsp:
         return self.process.stdout.read(size)
 
     def read_async(self, size):
-        if (select.select([self.process.stdout], [], [], 0)[0] != []):
+        try:
             return self.process.stdout.read(size)
-        else:
+        except IOError:
             return None
 
     def stop(self):
diff --git a/openwebrx.py b/openwebrx.py
index ee59b87..b2adddc 100755
--- a/openwebrx.py
+++ b/openwebrx.py
@@ -306,13 +306,16 @@ def spectrum_thread_function():
     print "[openwebrx-spectrum] Spectrum thread initialized successfully."
     dsp.start()
     if cfg.csdr_dynamic_bufsize:
-        dsp.read(8) #dummy read to skip bufsize & preamble
+        dsp.read_async(8) #dummy read to skip bufsize & preamble
         print "[openwebrx-spectrum] Note: CSDR_DYNAMIC_BUFSIZE_ON = 1"
     print "[openwebrx-spectrum] Spectrum thread started."
     bytes_to_read=int(dsp.get_fft_bytes_to_read())
     spectrum_thread_counter=0
     while True:
-        data=dsp.read(bytes_to_read)
+        data=dsp.read_async(bytes_to_read)
+        if data is None:
+            time.sleep(.01)
+            continue
         #print "gotcha",len(data),"bytes of spectrum data via spectrum_thread_function()"
         if spectrum_thread_counter >= cfg.fft_fps:
             spectrum_thread_counter=0