pipe: new audio output plugin which runs a command

Makefile.am

@@ -450,6 +450,10 @@ if HAVE_FIFO
 OUTPUT_SRC += src/output/fifo_plugin.c
 endif
 
+if ENABLE_PIPE_OUTPUT
+OUTPUT_SRC += src/output/pipe_output_plugin.c
+endif
+
 if HAVE_JACK
 OUTPUT_SRC += src/output/jack_plugin.c
 endif

NEWS

@@ -22,6 +22,7 @@ ver 0.15 - (200?/??/??)
   - mvp: fall back to 16 bit audio samples
   - mvp: check for reopen errors
   - mvp: fixed default device detection
+  - pipe: new audio output plugin which runs a command
 * commands:
   - "playlistinfo" supports a range now
   - added "sticker database", command "sticker", which allows clients

configure.ac

@@ -497,6 +497,16 @@ AC_ARG_ENABLE(fifo,
 	enable_fifo=$enableval,
 	enable_fifo=yes)
 
+AC_ARG_ENABLE(pipe-output,
+	AS_HELP_STRING([--enable-pipe-output],
+		[disable support for writing audio to a pipe (default: disable)]),,
+	enable_pipe_output=no)
+
+if test x$enable_pipe_output = xyes; then
+	AC_DEFINE([ENABLE_PIPE_OUTPUT], 1, [Define to enable support for writing audio to a pipe])
+fi
+AM_CONDITIONAL(ENABLE_PIPE_OUTPUT, test x$enable_pipe_output = xyes)
+
 AC_ARG_ENABLE(jack,
 	AS_HELP_STRING([--disable-jack],
 		[disable jack support (default: enable)]),

doc/mpdconf.example

@@ -207,6 +207,19 @@ log_file			"~/.mpd/log"
 #	sink			"remote_server_sink"
 #}
 #
+## Example "pipe" output:
+#
+#audio_output {
+#	type		"pipe"
+#	name		"my pipe"
+#	command		"aplay -f cd 2>/dev/null"
+## Or if you're want to use AudioCompress
+#	command		"AudioCompress -m | aplay -f cd 2>/dev/null"
+## Or to send raw PCM stream through PCM:
+#	command		"nc example.org 8765"
+#	format		"44100:16:2"
+#}
+#
 ## An example of a null output (for no audio output):
 #
 #audio_output {

src/output/pipe_output_plugin.c

+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "output_api.h"
+
+#include <stdio.h>
+#include <errno.h>
+
+struct pipe_output {
+	char *cmd;
+	FILE *fh;
+};
+
+/**
+ * The quark used for GError.domain.
+ */
+static inline GQuark
+pipe_output_quark(void)
+{
+	return g_quark_from_static_string("pipe_output");
+}
+
+static void *
+pipe_output_init(G_GNUC_UNUSED const struct audio_format *audio_format,
+		 const struct config_param *param,
+		 GError **error)
+{
+	struct pipe_output *pd = g_new(struct pipe_output, 1);
+
+	pd->cmd = config_dup_block_string(param, "command", NULL);
+	if (pd->cmd == NULL) {
+		g_set_error(error, pipe_output_quark(), 0,
+			    "No \"command\" parameter specified");
+		return NULL;
+	}
+
+	return pd;
+}
+
+static void
+pipe_output_finish(void *data)
+{
+	struct pipe_output *pd = data;
+
+	g_free(pd->cmd);
+	g_free(pd);
+}
+
+static bool
+pipe_output_open(void *data, G_GNUC_UNUSED struct audio_format *audio_format,
+		 G_GNUC_UNUSED GError **error)
+{
+	struct pipe_output *pd = data;
+
+	pd->fh = popen(pd->cmd, "w");
+	if (pd->fh == NULL) {
+		g_set_error(error, pipe_output_quark(), errno,
+			    "Error opening pipe \"%s\": %s",
+			    pd->cmd, g_strerror(errno));
+		return false;
+	}
+
+	return true;
+}
+
+static void
+pipe_output_close(void *data)
+{
+	struct pipe_output *pd = data;
+
+	pclose(pd->fh);
+}
+
+static size_t
+pipe_output_play(void *data, const void *chunk, size_t size, GError **error)
+{
+	struct pipe_output *pd = data;
+	size_t ret;
+
+	ret = fwrite(chunk, 1, size, pd->fh);
+	if (ret == 0)
+		g_set_error(error, pipe_output_quark(), errno,
+			    "Write error on pipe: %s", g_strerror(errno));
+
+	return ret;
+}
+
+const struct audio_output_plugin pipe_output_plugin = {
+	.name = "pipe",
+	.init = pipe_output_init,
+	.finish = pipe_output_finish,
+	.open = pipe_output_open,
+	.close = pipe_output_close,
+	.play = pipe_output_play,
+};

src/output_list.c

@@ -23,6 +23,7 @@
 extern const struct audio_output_plugin shoutPlugin;
 extern const struct audio_output_plugin null_output_plugin;
 extern const struct audio_output_plugin fifo_output_plugin;
+extern const struct audio_output_plugin pipe_output_plugin;
 extern const struct audio_output_plugin alsaPlugin;
 extern const struct audio_output_plugin ao_output_plugin;
 extern const struct audio_output_plugin oss_output_plugin;
@@ -39,6 +40,9 @@ const struct audio_output_plugin *audio_output_plugins[] = {
 #ifdef HAVE_FIFO
 	&fifo_output_plugin,
 #endif
+#ifdef ENABLE_PIPE_OUTPUT
+	&pipe_output_plugin,
+#endif
 #ifdef HAVE_ALSA
 	&alsaPlugin,
 #endif