Merge pull request #743 from mLupine/pa_sink

Add configuration option to specify PulseAudio output sink. Many thanks!

README.md

@@ -326,7 +326,15 @@ alsa =
 };
 ```
 
-The `pa` group is used to specify settings relevant to the PulseAudio backend. You can set the "Application Name" that will appear in the "Sound" control panel.
+The `pa` group is used to specify settings relevant to the PulseAudio backend. You can set the "Application Name" that will appear in the "Sound" control panel. You can also set the sink name that audio will be pushed to. Here's an example `pa` group configuration:
+
+```
+pa = 
+{
+  application_name = "Shairport Sync - Bedroom";
+  sink = "server_bedroom"; // Sink name or ID. If not specified, the default sink will be used.
+};
+```
 
 Shairport Sync can run programs just before it starts to play an audio stream and just after it finishes. You specify them using the `sessioncontrol` group settings `run_this_before_play_begins` and `run_this_after_play_ends`. This is to facilitate situations where something has to be done before and after playing, e.g. switching on an amplifier beforehand and switching it off afterwards. Set the `wait_for_completion` value to `"yes"` for Shairport Sync to wait until the respective commands have been completed before continuing.
 

audio_pa.c

@@ -85,6 +85,11 @@ static int init(__attribute__((unused)) int argc, __attribute__((unused)) char *
     if (config_lookup_string(config.cfg, "pa.application_name", &str)) {
       config.pa_application_name = (char *)str;
     }
+
+    /* Get the PulseAudio sink name. */
+    if (config_lookup_string(config.cfg, "pa.sink", &str)) {
+      config.pa_sink = (char *)str;
+    }
   }
 
   // finish collecting settings
@@ -178,8 +183,17 @@ static void start(__attribute__((unused)) int sample_rate,
                  //        PA_STREAM_AUTO_TIMING_UPDATE;
                  PA_STREAM_AUTO_TIMING_UPDATE | PA_STREAM_ADJUST_LATENCY;
 
-  // Connect stream to the default audio output sink
-  if (pa_stream_connect_playback(stream, NULL, &buffer_attr, stream_flags, NULL, NULL) != 0)
+  int connect_result;
+
+  if (config.pa_sink) {
+    // Connect stream to the sink specified in the config
+    connect_result = pa_stream_connect_playback(stream, config.pa_sink, &buffer_attr, stream_flags, NULL, NULL);
+  } else {
+    // Connect stream to the default audio output sink
+    connect_result = pa_stream_connect_playback(stream, NULL, &buffer_attr, stream_flags, NULL, NULL);
+  }
+  
+  if (connect_result != 0)
     die("could not connect to the pulseaudio playback stream -- the error message is \"%s\".",
         pa_strerror(pa_context_errno(context)));
 

common.h

@@ -84,7 +84,9 @@ typedef struct {
 #ifdef CONFIG_PA
   char *pa_application_name; // the name under which Shairport Sync shows up as an "Application" in
                              // the Sound Preferences in most desktop Linuxes.
-// Defaults to "Shairport Sync". Shairport Sync must be playing to see it.
+                             // Defaults to "Shairport Sync". Shairport Sync must be playing to see it.
+
+  char *pa_sink;    // the name (or id) of the sink that Shairport Sync will play on.
 #endif
 #ifdef CONFIG_METADATA
   int metadata_enabled;