Add stdout option for audio output

src/audio.c

@@ -129,6 +129,7 @@ static struct adev_s {
 	int outbuf_len;
 
 	enum audio_in_type_e g_audio_in_type;
+	enum audio_out_type_e g_audio_out_type;
 
 	int udp_sock;			/* UDP socket for receiving data */
 
@@ -453,9 +454,20 @@ int audio_open (struct audio_s *pa)
   	    }
 
 /*
- * Output device.  Only "soundcard" is supported at this time. 
+ * Output device.  Only "soundcard" and "stdout" are supported at this time.
  */
+	    if (strcasecmp(pa->adev[a].adevice_out, "stdout") == 0 || strcmp(pa->adev[a].adevice_out, "-") == 0) {
+	      adev[a].g_audio_out_type = AUDIO_OUT_TYPE_STDOUT;
+	    } else {
+	      adev[a].g_audio_out_type = AUDIO_OUT_TYPE_SOUNDCARD;
+	    }
 
+	    switch (adev[a].g_audio_out_type) {
+	      case AUDIO_OUT_TYPE_STDOUT:
+	        adev[a].outbuf_size_in_bytes = 1024;
+	        break;
+
+	      case AUDIO_OUT_TYPE_SOUNDCARD:
 #if USE_ALSA
 	        err = snd_pcm_open (&(adev[a].audio_out_handle), audio_out_name, SND_PCM_STREAM_PLAYBACK, 0);
 
@@ -498,7 +510,7 @@ int audio_open (struct audio_s *pa)
 	          return (-1);
 	        }
 #endif
-
+	    }
 /*
  * Finally allocate buffer for each direction.
  */
@@ -1333,6 +1345,29 @@ int audio_put (int a, int c)
 
 int audio_flush (int a)
 {
+	switch (adev[a].g_audio_out_type) {
+	  case AUDIO_OUT_TYPE_STDOUT:;
+	    int res;
+	    unsigned char *ptr;
+	    int len;
+
+	    ptr = adev[a].outbuf_ptr;
+	    len = adev[a].outbuf_len;
+
+	    while (len > 0) {
+	      res = write(STDOUT_FILENO, ptr, (size_t) len);
+	      if (res <= 0) {
+	        text_color_set(DW_COLOR_INFO);
+	        dw_printf ("\nError writing to stdout.  Exiting.\n");
+	        exit (0);
+	      }
+	      ptr += res;
+	      len -= res;
+	    }
+	    adev[a].outbuf_len = 0;
+	    return 0;
+
+	  case AUDIO_OUT_TYPE_SOUNDCARD:;
 #if USE_ALSA
 	    int k;
 	    unsigned char *psound;
@@ -1504,7 +1539,8 @@ int audio_flush (int a)
 	    adev[a].outbuf_len = 0;
 	    return (0);
 #endif
-
+	}
+	return (0);
 } /* end audio_flush */
 
 
@@ -1546,9 +1582,12 @@ int audio_flush (int a)
 
 void audio_wait (int a)
 {	
-
 	audio_flush (a);
 
+	if (adev[a].g_audio_out_type == AUDIO_OUT_TYPE_STDOUT) {
+	  return;
+	}
+
 #if USE_ALSA
 
 	/* For playback, this should wait for all pending frames */

src/audio.h

@@ -43,6 +43,10 @@ enum audio_in_type_e {
 	AUDIO_IN_TYPE_SDR_UDP,
 	AUDIO_IN_TYPE_STDIN };
 
+enum audio_out_type_e {
+	AUDIO_OUT_TYPE_SOUNDCARD,
+	AUDIO_OUT_TYPE_STDOUT };
+
 /* For option to try fixing frames with bad CRC. */
 
 typedef enum retry_e {