filter/Plugin: return std::unique_ptr<PreparedFilter>

src/output/Filtered.hxx

@@ -93,7 +93,7 @@ public:
 	 * The filter object of this audio output.  This is an
 	 * instance of chain_filter_plugin.
 	 */
-	PreparedFilter *prepared_filter = nullptr;
+	std::unique_ptr<PreparedFilter> prepared_filter;
 
 	/**
 	 * The #VolumeFilter instance of this audio output.  It is
@@ -105,14 +105,14 @@ public:
 	 * The replay_gain_filter_plugin instance of this audio
 	 * output.
 	 */
-	PreparedFilter *prepared_replay_gain_filter = nullptr;
+	std::unique_ptr<PreparedFilter> prepared_replay_gain_filter;
 
 	/**
 	 * The replay_gain_filter_plugin instance of this audio
 	 * output, to be applied to the second chunk during
 	 * cross-fading.
 	 */
-	PreparedFilter *prepared_other_replay_gain_filter = nullptr;
+	std::unique_ptr<PreparedFilter> prepared_other_replay_gain_filter;
 
 	/**
 	 * The convert_filter_plugin instance of this audio output.

src/output/Finish.cxx

@@ -27,10 +27,6 @@ FilteredAudioOutput::~FilteredAudioOutput()
 {
 	if (mixer != nullptr)
 		mixer_free(mixer);
-
-	delete prepared_replay_gain_filter;
-	delete prepared_other_replay_gain_filter;
-	delete prepared_filter;
 }
 
 void

src/output/Init.cxx

@@ -22,12 +22,13 @@
 #include "Registry.hxx"
 #include "Domain.hxx"
 #include "OutputAPI.hxx"
-#include "filter/FilterConfig.hxx"
 #include "AudioParser.hxx"
 #include "mixer/MixerList.hxx"
 #include "mixer/MixerType.hxx"
 #include "mixer/MixerControl.hxx"
 #include "mixer/plugins/SoftwareMixerPlugin.hxx"
+#include "filter/FilterConfig.hxx"
+#include "filter/FilterInternal.hxx"
 #include "filter/plugins/AutoConvertFilterPlugin.hxx"
 #include "filter/plugins/ConvertFilterPlugin.hxx"
 #include "filter/plugins/ReplayGainFilterPlugin.hxx"

src/output/Thread.cxx

@@ -146,8 +146,8 @@ AudioOutputControl::InternalOpen(const AudioFormat in_audio_format,
 	try {
 		try {
 			f = source.Open(in_audio_format, pipe,
-					output->prepared_replay_gain_filter,
-					output->prepared_other_replay_gain_filter,
+					output->prepared_replay_gain_filter.get(),
+					output->prepared_other_replay_gain_filter.get(),
 					*output->prepared_filter);
 		} catch (...) {
 			std::throw_with_nested(FormatRuntimeError("Failed to open filter for %s",