output: added option "always_on" for radio stations

Did you ever accidently click "stop" while feeding a radio station?
This option sets the output device to "pause" to disable the "close"
method.  It falls back to "pause" then, which is specific to the
plugin.  Some plugins implement it by feeding silence.

8 files changed, 73 insertions, 2 deletions

diff --git a/doc/user.xml b/doc/user.xml
index 30fcae69..e1e62eb9 100644
--- a/doc/user.xml
+++ b/doc/user.xml
@@ -339,6 +339,18 @@ cd mpd-version</programlisting>
             </row>
             <row>
               <entry>
+                <varname>always_on</varname>
+                  <parameter>yes|no</parameter>
+              </entry>
+              <entry>
+                If set to "yes", then MPD attempts to keep this audio
+                output always open.  This may be useful for streaming
+                servers, when you don't want to disconnect all
+                listeners even when playback is accidently stopped.
+              </entry>
+            </row>
+            <row>
+              <entry>
                 <varname>mixer_type</varname>
                 <parameter>hardware|software|none</parameter>
               </entry>
diff --git a/src/output_all.c b/src/output_all.c
index 4b770114..dbd5a6ce 100644
--- a/src/output_all.c
+++ b/src/output_all.c
@@ -559,6 +559,29 @@ audio_output_all_close(void)
 }
 
 void
+audio_output_all_release(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < num_audio_outputs; ++i)
+		audio_output_release(&audio_outputs[i]);
+
+	if (g_mp != NULL) {
+		assert(g_music_buffer != NULL);
+
+		music_pipe_clear(g_mp, g_music_buffer);
+		music_pipe_free(g_mp);
+		g_mp = NULL;
+	}
+
+	g_music_buffer = NULL;
+
+	audio_format_clear(&input_audio_format);
+
+	audio_output_all_elapsed_time = -1.0;
+}
+
+void
 audio_output_all_song_border(void)
 {
 	/* clear the elapsed_time pointer at the beginning of a new
diff --git a/src/output_all.h b/src/output_all.h
index 8c3f1e80..a579bf5f 100644
--- a/src/output_all.h
+++ b/src/output_all.h
@@ -92,6 +92,13 @@ void
 audio_output_all_close(void);
 
 /**
+ * Closes all audio outputs.  Outputs with the "always_on" flag are
+ * put into pause mode.
+ */
+void
+audio_output_all_release(void);
+
+/**
  * Enqueue a #music_chunk object for playing, i.e. pushes it to a
  * #music_pipe.
  *
diff --git a/src/output_control.c b/src/output_control.c
index b5d983ae..17edc3d7 100644
--- a/src/output_control.c
+++ b/src/output_control.c
@@ -118,9 +118,13 @@ audio_output_open(struct audio_output *ao,
 
 	if (ao->open &&
 	    audio_format_equals(audio_format, &ao->in_audio_format)) {
-		assert(ao->pipe == mp);
+		assert(ao->pipe == mp ||
+		       (ao->always_on && ao->pause));
 
 		if (ao->pause) {
+			ao->chunk = NULL;
+			ao->pipe = mp;
+
 			/* unpause with the CANCEL command; this is a
 			   hack, but suits well for forcing the thread
 			   to leave the ao_pause() thread, and we need
@@ -266,6 +270,15 @@ void audio_output_close(struct audio_output *ao)
 	g_mutex_unlock(ao->mutex);
 }
 
+void
+audio_output_release(struct audio_output *ao)
+{
+	if (ao->always_on)
+		audio_output_pause(ao);
+	else
+		audio_output_close(ao);
+}
+
 void audio_output_finish(struct audio_output *ao)
 {
 	audio_output_close(ao);
diff --git a/src/output_control.h b/src/output_control.h
index 9c2171a4..7f4f4a53 100644
--- a/src/output_control.h
+++ b/src/output_control.h
@@ -71,7 +71,16 @@ void
 audio_output_drain_async(struct audio_output *ao);
 
 void audio_output_cancel(struct audio_output *ao);
+
 void audio_output_close(struct audio_output *ao);
+
+/**
+ * Closes the audio output, but if the "always_on" flag is set, put it
+ * into pause mode instead.
+ */
+void
+audio_output_release(struct audio_output *ao);
+
 void audio_output_finish(struct audio_output *ao);
 
 #endif
diff --git a/src/output_init.c b/src/output_init.c
index f3d22ace..6ee340ed 100644
--- a/src/output_init.c
+++ b/src/output_init.c
@@ -184,6 +184,7 @@ audio_output_init(struct audio_output *ao, const struct config_param *param,
 	}
 
 	ao->plugin = plugin;
+	ao->always_on = config_get_block_bool(param, "always_on", false);
 	ao->enabled = config_get_block_bool(param, "enabled", true);
 	ao->really_enabled = false;
 	ao->open = false;
diff --git a/src/output_internal.h b/src/output_internal.h
index 2a438c62..06df9531 100644
--- a/src/output_internal.h
+++ b/src/output_internal.h
@@ -76,6 +76,12 @@ struct audio_output {
 	struct mixer *mixer;
 
 	/**
+	 * Shall this output always play something (i.e. silence),
+	 * even when playback is stopped?
+	 */
+	bool always_on;
+
+	/**
 	 * Has the user enabled this device?
 	 */
 	bool enabled;
diff --git a/src/player_thread.c b/src/player_thread.c
index 3e234c4f..2496f0cd 100644
--- a/src/player_thread.c
+++ b/src/player_thread.c
@@ -978,7 +978,7 @@ static gpointer player_task(G_GNUC_UNUSED gpointer arg)
 		case PLAYER_COMMAND_CLOSE_AUDIO:
 			player_unlock();
 
-			audio_output_all_close();
+			audio_output_all_release();
 
 			player_lock();
 			player_command_finished_locked();