output: added command REOPEN

REOPEN is called when the input audio format changes.  The output
thread may be reconfigure the PCM converter.

src/output_control.c

@@ -82,26 +82,13 @@ audio_output_open(struct audio_output *ao,
 	ao->in_audio_format = *audio_format;
 	ao->chunk = NULL;
 
-	if (!ao->config_audio_format) {
-		if (ao->open)
-			audio_output_close(ao);
-
-		/* no audio format is configured: copy in->out, let
-		   the output's open() method determine the effective
-		   out_audio_format */
-		ao->out_audio_format = ao->in_audio_format;
-	}
-
 	ao->pipe = mp;
 
 	if (ao->thread == NULL)
 		audio_output_thread_start(ao);
 
+	ao_command(ao, ao->open ? AO_COMMAND_REOPEN : AO_COMMAND_OPEN);
 	open = ao->open;
-	if (!open) {
-		ao_command(ao, AO_COMMAND_OPEN);
-		open = ao->open;
-	}
 
 	if (open && ao->mixer != NULL)
 		mixer_open(ao->mixer);

src/output_internal.h

@@ -29,6 +29,13 @@
 enum audio_output_command {
 	AO_COMMAND_NONE = 0,
 	AO_COMMAND_OPEN,
+
+	/**
+	 * This command is invoked when the input audio format
+	 * changes.
+	 */
+	AO_COMMAND_REOPEN,
+
 	AO_COMMAND_CLOSE,
 	AO_COMMAND_PAUSE,
 	AO_COMMAND_CANCEL,

src/output_thread.c

@@ -105,6 +105,26 @@ ao_close(struct audio_output *ao)
 	g_debug("closed plugin=%s name=\"%s\"", ao->plugin->name, ao->name);
 }
 
+static void
+ao_reopen(struct audio_output *ao)
+{
+	if (!ao->config_audio_format) {
+		if (ao->open) {
+			const struct music_pipe *mp = ao->pipe;
+			ao_close(ao);
+			ao->pipe = mp;
+		}
+
+		/* no audio format is configured: copy in->out, let
+		   the output's open() method determine the effective
+		   out_audio_format */
+		ao->out_audio_format = ao->in_audio_format;
+	}
+
+	if (!ao->open)
+		ao_open(ao);
+}
+
 static bool
 ao_play_chunk(struct audio_output *ao, const struct music_chunk *chunk)
 {
@@ -237,6 +257,11 @@ static gpointer audio_output_task(gpointer arg)
 			ao_command_finished(ao);
 			break;
 
+		case AO_COMMAND_REOPEN:
+			ao_reopen(ao);
+			ao_command_finished(ao);
+			break;
+
 		case AO_COMMAND_CLOSE:
 			assert(ao->open);
 			assert(ao->pipe != NULL);