output/Interface: convert need_fully_defined_audio_format to flag

src/output/Interface.hxx

@@ -28,12 +28,16 @@ struct Tag;
 class AudioOutput {
 	const unsigned flags;
 
-	bool need_fully_defined_audio_format = false;
-
 protected:
 	static constexpr unsigned FLAG_ENABLE_DISABLE = 0x1;
 	static constexpr unsigned FLAG_PAUSE = 0x2;
 
+	/**
+	 * This output requires an "audio_format" setting which
+	 * evaluates AudioFormat::IsFullyDefined().
+	 */
+	static constexpr unsigned FLAG_NEED_FULLY_DEFINED_AUDIO_FORMAT = 0x4;
+
 public:
 	explicit AudioOutput(unsigned _flags):flags(_flags) {}
 	virtual ~AudioOutput() = default;
@@ -50,16 +54,7 @@ public:
 	}
 
 	bool GetNeedFullyDefinedAudioFormat() const {
-		return need_fully_defined_audio_format;
-	}
-
-	/**
-	 * Plugins shall call this method if they require an
-	 * "audio_format" setting which evaluates
-	 * AudioFormat::IsFullyDefined().
-	 */
-	void NeedFullyDefinedAudioFormat() {
-		need_fully_defined_audio_format = true;
+		return flags & FLAG_NEED_FULLY_DEFINED_AUDIO_FORMAT;
 	}
 
 	/**

src/output/plugins/ShoutOutputPlugin.cxx

@@ -97,12 +97,10 @@ ShoutSetAudioInfo(shout_t *shout_conn, const AudioFormat &audio_format)
 }
 
 ShoutOutput::ShoutOutput(const ConfigBlock &block)
-	:AudioOutput(FLAG_PAUSE),
+	:AudioOutput(FLAG_PAUSE|FLAG_NEED_FULLY_DEFINED_AUDIO_FORMAT),
 	 shout_conn(shout_new()),
 	 prepared_encoder(CreateConfiguredEncoder(block, true))
 {
-	NeedFullyDefinedAudioFormat();
-
 	const char *host = require_block_string(block, "host");
 	const char *mount = require_block_string(block, "mount");
 	unsigned port = block.GetBlockValue("port", 0u);