Zerofill for AudioDeviceUDP

AudioDeviceUDP can now write zeros to the UDP connection on underflow.
That is, when the "audio device" is open but there is no audio to write
zeros will be written instead. Enable this behavior by setting the
environment variable ASYNC_AUDIO_UDP_ZEROFILL=1.

src/async/ChangeLog

@@ -1,4 +1,4 @@
- 1.6.1 -- ?? ??? 2020
+ 1.6.1 -- ?? ??? 2021
 ----------------------
 
 * ASYNC_AUDIO_ALSA_ZEROFILL is now enabled by default.
@@ -39,6 +39,11 @@
 
 * The Async::Serial class now support all extended baudrates.
 
+* AudioDeviceUDP can now write zeros to the UDP connection on underflow. That
+  is, when the "audio device" is open but there is no audio to write zeros
+  will be written instead. Enable this behavior by setting the environment
+  variable ASYNC_AUDIO_UDP_ZEROFILL=1.
+
 
 
  1.6.0 -- 01 Sep 2019

src/async/audio/AsyncAudioDeviceUDP.cpp

@@ -40,6 +40,8 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 #include <cassert>
 #include <cstdio>
+#include <cstring>
+#include <cstdlib>
 #include <vector>
 #include <sstream>
 
@@ -190,7 +192,7 @@ int AudioDeviceUDP::samplesToWrite(void) const
 
 AudioDeviceUDP::AudioDeviceUDP(const string& dev_name)
   : AudioDevice(dev_name), block_size(0), sock(0), read_buf(0),
-    read_buf_pos(0), port(0)
+    read_buf_pos(0), port(0), zerofill_on_underflow(false)
 {
   assert(AudioDeviceUDP_creator_registered);
   assert(sampleRate() > 0);
@@ -202,6 +204,12 @@ AudioDeviceUDP::AudioDeviceUDP(const string& dev_name)
   pace_timer->setEnable(false);
   pace_timer->expired.connect(
       sigc::hide(mem_fun(*this, &AudioDeviceUDP::audioWriteHandler)));
+
+  char *zerofill_str = std::getenv("ASYNC_AUDIO_UDP_ZEROFILL");
+  if (zerofill_str != 0)
+  {
+    std::istringstream(zerofill_str) >> zerofill_on_underflow;
+  }
 } /* AudioDeviceUDP::AudioDeviceUDP */
 
 
@@ -347,8 +355,16 @@ void AudioDeviceUDP::audioWriteHandler(void)
   frags_read = getBlocks(buf, 1);
   if (frags_read == 0)
   {
-    pace_timer->setEnable(false);
+    if (zerofill_on_underflow)
-    return;
+    {
+      frags_read = 1;
+      std::memset(buf, 0, block_size * channels);
+    }
+    else
+    {
+      pace_timer->setEnable(false);
+      return;
+    }
   }
 
     // Write the samples to the socket

src/async/audio/AsyncAudioDeviceUDP.h

@@ -199,7 +199,8 @@ class AudioDeviceUDP : public Async::AudioDevice
     IpAddress           ip_addr;
     uint16_t            port;
     Async::Timer        *pace_timer;
-    
+    bool                zerofill_on_underflow;
+
     void audioReadHandler(const Async::IpAddress &ip, uint16_t port,
                           void *buf, int count);
     void audioWriteHandler(void);

src/doc/man/devcal.1

@@ -1,4 +1,4 @@
-.TH DEVCAL 1 "APRIL 2021" Linux "User Manuals"
+.TH DEVCAL 1 "AUGUST 2021" Linux "User Manuals"
 .
 .SH NAME
 .
@@ -245,6 +245,9 @@ during devcal startup when using OSS audio.
 ASYNC_AUDIO_ALSA_ZEROFILL
 Set this environment variable to 0 to stop the Alsa audio code from writing
 zeros to the audio device when there is no audio to write available.
+ASYNC_AUDIO_UDP_ZEROFILL
+Set this environment variable to 1 to enable the UDP audio code to write zeros
+to the UDP connection when there is no audio to write available.
 .
 .SH AUTHOR
 .

src/doc/man/qtel.1

@@ -1,4 +1,4 @@
-.TH QTEL "1" "APRIL 2021" Linux "User Manuals"
+.TH QTEL "1" "AUGUST 2021" Linux "User Manuals"
 .
 .SH NAME
 .
@@ -61,6 +61,9 @@ during qtel startup when using OSS audio.
 ASYNC_AUDIO_ALSA_ZEROFILL
 Set this environment variable to 0 to stop the Alsa audio code from writing
 zeros to the audio device when there is no audio to write available.
+ASYNC_AUDIO_UDP_ZEROFILL
+Set this environment variable to 1 to enable the UDP audio code to write zeros
+to the UDP connection when there is no audio to write available.
 .
 .SH AUTHOR
 .

src/doc/man/remotetrx.1

@@ -1,4 +1,4 @@
-.TH REMOTETRX 1 "APRIL 2021" Linux "User Manuals"
+.TH REMOTETRX 1 "AUGUST 2021" Linux "User Manuals"
 .
 .SH NAME
 .
@@ -86,6 +86,9 @@ during remotetrx server startup when using OSS audio.
 ASYNC_AUDIO_ALSA_ZEROFILL
 Set this environment variable to 0 to stop the Alsa audio code from writing
 zeros to the audio device when there is no audio to write available.
+ASYNC_AUDIO_UDP_ZEROFILL
+Set this environment variable to 1 to enable the UDP audio code to write zeros
+to the UDP connection when there is no audio to write available.
 .TP
 HOME
 Used to find the per user configuration file.

src/doc/man/siglevdetcal.1

@@ -1,4 +1,4 @@
-.TH SIGLEVDETCAL 1 "APRIL 2021" Linux "User Manuals"
+.TH SIGLEVDETCAL 1 "AUGUST 2021" Linux "User Manuals"
 .
 .SH NAME
 .
@@ -60,6 +60,9 @@ when the remotetrx server starts.
 ASYNC_AUDIO_ALSA_ZEROFILL
 Set this environment variable to 0 to stop the Alsa audio code from writing
 zeros to the audio device when there is no audio to write available.
+ASYNC_AUDIO_UDP_ZEROFILL
+Set this environment variable to 1 to enable the UDP audio code to write zeros
+to the UDP connection when there is no audio to write available.
 .
 .SH AUTHOR
 .

src/doc/man/svxlink.1

@@ -1,4 +1,4 @@
-.TH SVXLINK 1 "APRIL 2021" Linux "User Manuals"
+.TH SVXLINK 1 "AUGUST 2021" Linux "User Manuals"
 .
 .SH NAME
 .
@@ -65,6 +65,9 @@ during startup of the SvxLink server when using OSS audio.
 ASYNC_AUDIO_ALSA_ZEROFILL
 Set this environment variable to 0 to stop the Alsa audio code from writing
 zeros to the audio device when there is no audio to write available.
+ASYNC_AUDIO_UDP_ZEROFILL
+Set this environment variable to 1 to enable the UDP audio code to write zeros
+to the UDP connection when there is no audio to write available.
 .TP
 HOME
 Used to find the per user configuration file.

src/svxlink/systemd/remotetrx.default.in

@@ -18,3 +18,6 @@ PIDFILE=/run/remotetrx.pid
 
 # Disable Alsa zerofill if set to 0 (see manual page)
 #ASYNC_AUDIO_ALSA_ZEROFILL=1
+
+# Enable UDP zerofill if set to 1 (see manual page)
+#ASYNC_AUDIO_UDP_ZEROFILL=0

src/svxlink/systemd/svxlink.default.in

@@ -18,3 +18,6 @@ PIDFILE=/run/svxlink.pid
 
 # Disable Alsa zerofill if set to 0 (see manual page)
 #ASYNC_AUDIO_ALSA_ZEROFILL=1
+
+# Enable UDP zerofill if set to 1 (see manual page)
+#ASYNC_AUDIO_UDP_ZEROFILL=0

src/versions

@@ -8,7 +8,7 @@ QTEL=1.2.4.99.5
 LIBECHOLIB=1.3.3.99.0
 
 # Version for the Async library
-LIBASYNC=1.6.99.15
+LIBASYNC=1.6.99.16
 
 # SvxLink versions
 SVXLINK=1.7.99.52