replay_gain: reimplement as a filter plugin

Apply the replay gain in the output thread.  This means a new setting
will be active instantly, without going through the whole music pipe.
And we might have different replay gain settings for each audio output
device.

src/filter/replay_gain_filter_plugin.c

@@ -0,0 +1,193 @@
+/*
+ * Copyright (C) 2003-2010 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.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "filter/replay_gain_filter_plugin.h"
+#include "filter_plugin.h"
+#include "filter_internal.h"
+#include "filter_registry.h"
+#include "audio_format.h"
+#include "pcm_buffer.h"
+#include "pcm_volume.h"
+#include "replay_gain_info.h"
+#include "replay_gain_config.h"
+
+#include <string.h>
+
+#undef G_LOG_DOMAIN
+#define G_LOG_DOMAIN "replay_gain"
+
+struct replay_gain_filter {
+	struct filter filter;
+
+	enum replay_gain_mode mode;
+
+	struct replay_gain_info info;
+
+	/**
+	 * The current volume, between 0 and #PCM_VOLUME_1 (both
+	 * including).
+	 */
+	unsigned volume;
+
+	struct audio_format audio_format;
+
+	struct pcm_buffer buffer;
+};
+
+static inline GQuark
+replay_gain_quark(void)
+{
+	return g_quark_from_static_string("replay_gain");
+}
+
+/**
+ * Recalculates the new volume after a property was changed.
+ */
+static void
+replay_gain_filter_update(struct replay_gain_filter *filter)
+{
+	if (filter->mode != REPLAY_GAIN_OFF) {
+		const struct replay_gain_tuple *tuple =
+			&filter->info.tuples[filter->mode];
+		float scale = replay_gain_tuple_defined(tuple)
+			? replay_gain_tuple_scale(tuple, replay_gain_preamp)
+			: replay_gain_missing_preamp;
+		g_debug("scale=%f\n", (double)scale);
+
+		filter->volume = pcm_float_to_volume(scale);
+	} else
+		filter->volume = PCM_VOLUME_1;
+}
+
+static struct filter *
+replay_gain_filter_init(G_GNUC_UNUSED const struct config_param *param,
+			G_GNUC_UNUSED GError **error_r)
+{
+	struct replay_gain_filter *filter = g_new(struct replay_gain_filter, 1);
+
+	filter_init(&filter->filter, &replay_gain_filter_plugin);
+
+	filter->mode = replay_gain_mode;
+	replay_gain_info_init(&filter->info);
+	filter->volume = PCM_VOLUME_1;
+
+	return &filter->filter;
+}
+
+static void
+replay_gain_filter_finish(struct filter *filter)
+{
+	g_free(filter);
+}
+
+static const struct audio_format *
+replay_gain_filter_open(struct filter *_filter,
+			struct audio_format *audio_format,
+			G_GNUC_UNUSED GError **error_r)
+{
+	struct replay_gain_filter *filter =
+		(struct replay_gain_filter *)_filter;
+
+	audio_format->reverse_endian = false;
+
+	filter->audio_format = *audio_format;
+	pcm_buffer_init(&filter->buffer);
+
+	return &filter->audio_format;
+}
+
+static void
+replay_gain_filter_close(struct filter *_filter)
+{
+	struct replay_gain_filter *filter =
+		(struct replay_gain_filter *)_filter;
+
+	pcm_buffer_deinit(&filter->buffer);
+}
+
+static const void *
+replay_gain_filter_filter(struct filter *_filter,
+			  const void *src, size_t src_size,
+			  size_t *dest_size_r, GError **error_r)
+{
+	struct replay_gain_filter *filter =
+		(struct replay_gain_filter *)_filter;
+	bool success;
+	void *dest;
+
+	/* check if the mode has been changed since the last call */
+	if (filter->mode != replay_gain_mode) {
+		filter->mode = replay_gain_mode;
+		replay_gain_filter_update(filter);
+	}
+
+	*dest_size_r = src_size;
+
+	if (filter->volume >= PCM_VOLUME_1)
+		/* optimized special case: 100% volume = no-op */
+		return src;
+
+	dest = pcm_buffer_get(&filter->buffer, src_size);
+	*dest_size_r = src_size;
+
+	if (filter->volume <= 0) {
+		/* optimized special case: 0% volume = memset(0) */
+		/* XXX is this valid for all sample formats? What
+		   about floating point? */
+		memset(dest, 0, src_size);
+		return dest;
+	}
+
+	memcpy(dest, src, src_size);
+
+	success = pcm_volume(dest, src_size, &filter->audio_format,
+			     filter->volume);
+	if (!success) {
+		g_set_error(error_r, replay_gain_quark(), 0,
+			    "pcm_volume() has failed");
+		return NULL;
+	}
+
+	return dest;
+}
+
+const struct filter_plugin replay_gain_filter_plugin = {
+	.name = "replay_gain",
+	.init = replay_gain_filter_init,
+	.finish = replay_gain_filter_finish,
+	.open = replay_gain_filter_open,
+	.close = replay_gain_filter_close,
+	.filter = replay_gain_filter_filter,
+};
+
+void
+replay_gain_filter_set_info(struct filter *_filter,
+			    const struct replay_gain_info *info)
+{
+	struct replay_gain_filter *filter =
+		(struct replay_gain_filter *)_filter;
+
+	if (info != NULL)
+		filter->info = *info;
+	else
+		replay_gain_info_init(&filter->info);
+
+	replay_gain_filter_update(filter);
+}

src/filter/replay_gain_filter_plugin.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2003-2010 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.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef REPLAY_GAIN_FILTER_PLUGIN_H
+#define REPLAY_GAIN_FILTER_PLUGIN_H
+
+#include "replay_gain_info.h"
+
+struct filter;
+
+/**
+ * Sets a new #replay_gain_info at the beginning of a new song.
+ *
+ * @param info the new #replay_gain_info value, or NULL if no replay
+ * gain data is available for the current song
+ */
+void
+replay_gain_filter_set_info(struct filter *filter,
+			    const struct replay_gain_info *info);
+
+#endif