output: attach a filter chain to each audio_output

Makefile.am

@@ -739,6 +739,8 @@ test_run_output_SOURCES = test/run_output.c \
 	src/mixer_api.c \
 	src/mixer_control.c \
 	$(MIXER_SRC) \
+	src/filter_plugin.c src/filter/chain_filter_plugin.c \
+	src/filter/convert_filter_plugin.c \
 	$(OUTPUT_SRC)
 
 test_read_mixer_CPPFLAGS = $(AM_CPPFLAGS) \

src/output_control.c

@@ -23,6 +23,7 @@
 #include "output_thread.h"
 #include "mixer_control.h"
 #include "mixer_plugin.h"
+#include "filter_plugin.h"
 
 #include <assert.h>
 #include <stdlib.h>
@@ -171,4 +172,6 @@ void audio_output_finish(struct audio_output *ao)
 
 	notify_deinit(&ao->notify);
 	g_mutex_free(ao->mutex);
+
+	filter_free(ao->filter);
 }

src/output_init.c

@@ -23,9 +23,14 @@
 #include "output_list.h"
 #include "audio_parser.h"
 #include "mixer_control.h"
+#include "filter_plugin.h"
+#include "filter_registry.h"
+#include "filter/chain_filter_plugin.h"
 
 #include <glib.h>
 
+#include <assert.h>
+
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "output"
 
@@ -124,7 +129,15 @@ audio_output_init(struct audio_output *ao, const struct config_param *param,
 	ao->open = false;
 	ao->fail_timer = NULL;
 
-	pcm_convert_init(&ao->convert_state);
+	/* set up the filter chain */
+
+	ao->filter = filter_chain_new();
+	assert(ao->filter != NULL);
+
+	ao->convert_filter = filter_new(&convert_filter_plugin, NULL, NULL);
+	assert(ao->convert_filter != NULL);
+
+	filter_chain_append(ao->filter, ao->convert_filter);
 
 	ao->config_audio_format = format != NULL;
 	if (ao->config_audio_format) {

src/output_internal.h

@@ -21,7 +21,6 @@
 #define MPD_OUTPUT_INTERNAL_H
 
 #include "audio_format.h"
-#include "pcm_convert.h"
 #include "notify.h"
 
 #include <time.h>
@@ -108,7 +107,19 @@ struct audio_output {
 	 */
 	struct audio_format out_audio_format;
 
-	struct pcm_convert_state convert_state;
+	/**
+	 * The filter object of this audio output.  This is an
+	 * instance of chain_filter_plugin.
+	 */
+	struct filter *filter;
+
+	/**
+	 * The convert_filter_plugin instance of this audio output.
+	 * It is the last item in the filter chain, and is responsible
+	 * for converting the input data into the appropriate format
+	 * for this audio output.
+	 */
+	struct filter *convert_filter;
 
 	/**
 	 * The thread handle, or NULL if the output thread isn't

src/output_thread.c

@@ -23,6 +23,8 @@
 #include "chunk.h"
 #include "pipe.h"
 #include "player_control.h"
+#include "filter_plugin.h"
+#include "filter/convert_filter_plugin.h"
 
 #include <glib.h>
 
@@ -45,12 +47,29 @@ ao_open(struct audio_output *ao)
 {
 	bool success;
 	GError *error = NULL;
+	const struct audio_format *filter_audio_format;
 
 	assert(!ao->open);
 	assert(ao->fail_timer == NULL);
 	assert(ao->pipe != NULL);
 	assert(ao->chunk == NULL);
 
+	/* open the filter */
+
+	filter_audio_format = filter_open(ao->filter, &ao->in_audio_format,
+					  &error);
+	if (filter_audio_format == NULL) {
+		g_warning("Failed to open filter for \"%s\" [%s]: %s",
+			  ao->name, ao->plugin->name, error->message);
+		g_error_free(error);
+
+		ao->fail_timer = g_timer_new();
+		return;
+	}
+
+	if (!ao->config_audio_format)
+		ao->out_audio_format = *filter_audio_format;
+
 	success = ao_plugin_open(ao->plugin, ao->data,
 				 &ao->out_audio_format,
 				 &error);
@@ -62,11 +81,12 @@ ao_open(struct audio_output *ao)
 			  ao->name, ao->plugin->name, error->message);
 		g_error_free(error);
 
+		filter_close(ao->filter);
 		ao->fail_timer = g_timer_new();
 		return;
 	}
 
-	pcm_convert_init(&ao->convert_state);
+	convert_filter_set(ao->convert_filter, &ao->out_audio_format);
 
 	g_mutex_lock(ao->mutex);
 	ao->open = true;
@@ -100,12 +120,46 @@ ao_close(struct audio_output *ao)
 	g_mutex_unlock(ao->mutex);
 
 	ao_plugin_close(ao->plugin, ao->data);
-	pcm_convert_deinit(&ao->convert_state);
+	filter_close(ao->filter);
 
 	g_debug("closed plugin=%s name=\"%s\"", ao->plugin->name, ao->name);
 }
 
 static void
+ao_reopen_filter(struct audio_output *ao)
+{
+	const struct audio_format *filter_audio_format;
+	GError *error = NULL;
+
+	filter_close(ao->filter);
+	filter_audio_format = filter_open(ao->filter, &ao->in_audio_format,
+					  &error);
+	if (filter_audio_format == NULL) {
+		g_warning("Failed to open filter for \"%s\" [%s]: %s",
+			  ao->name, ao->plugin->name, error->message);
+		g_error_free(error);
+
+		/* this is a little code duplication fro ao_close(),
+		   but we cannot call this function because we must
+		   not call filter_close(ao->filter) again */
+
+		ao->pipe = NULL;
+
+		g_mutex_lock(ao->mutex);
+		ao->chunk = NULL;
+		ao->open = false;
+		g_mutex_unlock(ao->mutex);
+
+		ao_plugin_close(ao->plugin, ao->data);
+
+		ao->fail_timer = g_timer_new();
+		return;
+	}
+
+	convert_filter_set(ao->convert_filter, &ao->out_audio_format);
+}
+
+static void
 ao_reopen(struct audio_output *ao)
 {
 	if (!ao->config_audio_format) {
@@ -121,7 +175,11 @@ ao_reopen(struct audio_output *ao)
 		ao->out_audio_format = ao->in_audio_format;
 	}
 
-	if (!ao->open)
+	if (ao->open)
+		/* the audio format has changed, and all filters have
+		   to be reconfigured */
+		ao_reopen_filter(ao);
+	else
 		ao_open(ao);
 }
 
@@ -132,6 +190,8 @@ ao_play_chunk(struct audio_output *ao, const struct music_chunk *chunk)
 	size_t size = chunk->length;
 	GError *error = NULL;
 
+	assert(ao != NULL);
+	assert(ao->filter != NULL);
 	assert(!music_chunk_is_empty(chunk));
 	assert(music_chunk_check_format(chunk, &ao->in_audio_format));
 	assert(size % audio_format_frame_size(&ao->in_audio_format) == 0);
@@ -142,18 +202,19 @@ ao_play_chunk(struct audio_output *ao, const struct music_chunk *chunk)
 	if (size == 0)
 		return true;
 
-	if (!audio_format_equals(&ao->in_audio_format,
-				 &ao->out_audio_format)) {
-		data = pcm_convert(&ao->convert_state,
-				   &ao->in_audio_format, data, size,
-				   &ao->out_audio_format, &size);
-
-		/* under certain circumstances, pcm_convert() may
-		   return an empty buffer - this condition should be
-		   investigated further, but for now, do this check as
-		   a workaround: */
-		if (data == NULL)
-			return true;
+	data = filter_filter(ao->filter, data, size, &size, &error);
+	if (data == NULL) {
+		g_warning("\"%s\" [%s] failed to filter: %s",
+			  ao->name, ao->plugin->name, error->message);
+		g_error_free(error);
+
+		ao_plugin_cancel(ao->plugin, ao->data);
+		ao_close(ao);
+
+		/* don't automatically reopen this device for 10
+		   seconds */
+		ao->fail_timer = g_timer_new();
+		return false;
 	}
 
 	while (size > 0 && ao->command == AO_COMMAND_NONE) {
@@ -271,6 +332,7 @@ static gpointer audio_output_task(gpointer arg)
 
 			ao_plugin_cancel(ao->plugin, ao->data);
 			ao_close(ao);
+			filter_close(ao->filter);
 			ao_command_finished(ao);
 			break;
 

test/run_output.c

@@ -22,6 +22,8 @@
 #include "output_control.h"
 #include "conf.h"
 #include "audio_parser.h"
+#include "filter_registry.h"
+#include "pcm_convert.h"
 
 #include <glib.h>
 
@@ -33,10 +35,31 @@ void pcm_convert_init(G_GNUC_UNUSED struct pcm_convert_state *state)
 {
 }
 
+void pcm_convert_deinit(G_GNUC_UNUSED struct pcm_convert_state *state)
+{
+}
+
+const void *
+pcm_convert(G_GNUC_UNUSED struct pcm_convert_state *state,
+	    G_GNUC_UNUSED const struct audio_format *src_format,
+	    G_GNUC_UNUSED const void *src, G_GNUC_UNUSED size_t src_size,
+	    G_GNUC_UNUSED const struct audio_format *dest_format,
+	    G_GNUC_UNUSED size_t *dest_size_r)
+{
+	return NULL;
+}
+
 void notify_init(G_GNUC_UNUSED struct notify *notify)
 {
 }
 
+const struct filter_plugin *
+filter_plugin_by_name(G_GNUC_UNUSED const char *name)
+{
+	assert(false);
+	return NULL;
+}
+
 static const struct config_param *
 find_named_config_block(const char *block, const char *name)
 {