filter/convert: add method IsActive()

src/filter/plugins/ConvertFilterPlugin.cxx

@@ -57,6 +57,11 @@ public:
 	}
 
 	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+
+private:
+	bool IsActive() const noexcept {
+		return out_audio_format != in_audio_format;
+	}
 };
 
 class PreparedConvertFilter final : public PreparedFilter {
@@ -80,7 +85,7 @@ ConvertFilter::Set(const AudioFormat &_out_audio_format)
 		/* no change */
 		return;
 
-	if (out_audio_format != in_audio_format) {
+	if (IsActive()) {
 		out_audio_format = in_audio_format;
 		state.Close();
 	}
@@ -111,7 +116,7 @@ ConvertFilter::~ConvertFilter()
 {
 	assert(in_audio_format.IsValid());
 
-	if (out_audio_format != in_audio_format)
+	if (IsActive())
 		state.Close();
 }
 
@@ -120,11 +125,10 @@ ConvertFilter::FilterPCM(ConstBuffer<void> src)
 {
 	assert(in_audio_format.IsValid());
 
-	if (out_audio_format == in_audio_format)
+	return IsActive()
+		? state.Convert(src)
 		/* optimized special case: no-op */
-		return src;
-
-	return state.Convert(src);
+		: src;
 }
 
 const FilterPlugin convert_filter_plugin = {