5 files changed, 35 insertions, 3 deletions

diff --git a/src/lib/dcp_content.cc b/src/lib/dcp_content.cc
index 87e59de50..e2b19fb8e 100644
--- a/src/lib/dcp_content.cc
+++ b/src/lib/dcp_content.cc
@@ -160,6 +160,8 @@ DCPContent::DCPContent (cxml::ConstNodePtr node, int version)
 	for (auto i: node->node_children("ContentVersion")) {
 		_content_versions.push_back (i->content());
 	}
+
+	_active_audio_channels = node->optional_number_child<int>("ActiveAudioChannels");
 }
 
 void
@@ -252,6 +254,8 @@ DCPContent::examine (shared_ptr<const Film> film, shared_ptr<Job> job)
 		auto m = as->mapping ();
 		m.make_default (film ? film->audio_processor() : 0);
 		as->set_mapping (m);
+
+		_active_audio_channels = examiner->active_audio_channels();
 	}
 
 	if (examiner->has_atmos()) {
@@ -413,6 +417,10 @@ DCPContent::as_xml (xmlpp::Node* node, bool with_paths) const
 	for (auto i: _content_versions) {
 		node->add_child("ContentVersion")->add_child_text(i);
 	}
+
+	if (_active_audio_channels) {
+		node->add_child("ActiveAudioChannels")->add_child_text(raw_convert<string>(*_active_audio_channels));
+	}
 }
 
 DCPTime
@@ -862,3 +870,12 @@ DCPContent::check_font_ids()
 	add_fonts_from_examiner(text.front(), examiner.fonts());
 }
 
+
+int
+DCPContent::active_audio_channels() const
+{
+	return _active_audio_channels.get_value_or(
+		(audio && audio->stream()) ? audio->stream()->channels() : 0
+		);
+}
+
diff --git a/src/lib/dcp_content.h b/src/lib/dcp_content.h
index 96ae09521..fd78cd0ac 100644
--- a/src/lib/dcp_content.h
+++ b/src/lib/dcp_content.h
@@ -174,6 +174,8 @@ public:
 		return _content_versions;
 	}
 
+	int active_audio_channels() const;
+
 	void check_font_ids();
 
 private:
@@ -225,6 +227,8 @@ private:
 	std::map<dcp::Marker, dcpomatic::ContentTime> _markers;
 	std::vector<dcp::Rating> _ratings;
 	std::vector<std::string> _content_versions;
+
+	boost::optional<int> _active_audio_channels;
 };
 
 
diff --git a/src/lib/dcp_examiner.cc b/src/lib/dcp_examiner.cc
index 50b19e2fd..e369b46ff 100644
--- a/src/lib/dcp_examiner.cc
+++ b/src/lib/dcp_examiner.cc
@@ -175,11 +175,17 @@ DCPExaminer::DCPExaminer (shared_ptr<const DCPContent> content, bool tolerant)
 			auto asset = reel->main_sound()->asset();
 
 			if (!_audio_channels) {
-				_audio_channels = asset->active_channels();
-			} else if (_audio_channels.get() != asset->active_channels()) {
+				_audio_channels = asset->channels();
+			} else if (_audio_channels.get() != asset->channels()) {
 				throw DCPError (_("Mismatched audio channel counts in DCP"));
 			}
 
+			if (!_active_audio_channels) {
+				_active_audio_channels = asset->active_channels();
+			} else if (_active_audio_channels.get() != asset->active_channels()) {
+				throw DCPError(_("Mismatched active audio channel counts in DCP"));
+			}
+
 			if (!_audio_frame_rate) {
 				_audio_frame_rate = asset->sampling_rate ();
 			} else if (_audio_frame_rate.get() != asset->sampling_rate ()) {
diff --git a/src/lib/dcp_examiner.h b/src/lib/dcp_examiner.h
index b51e7ae7a..1a3615867 100644
--- a/src/lib/dcp_examiner.h
+++ b/src/lib/dcp_examiner.h
@@ -90,6 +90,10 @@ public:
 		return _audio_channels.get_value_or (0);
 	}
 
+	int active_audio_channels() const {
+		return _active_audio_channels.get_value_or(0);
+	}
+
 	Frame audio_length () const override {
 		return _audio_length;
 	}
@@ -179,6 +183,7 @@ private:
 	boost::optional<dcp::Size> _video_size;
 	Frame _video_length = 0;
 	boost::optional<int> _audio_channels;
+	boost::optional<int> _active_audio_channels;
 	boost::optional<int> _audio_frame_rate;
 	Frame _audio_length = 0;
 	std::string _name;
diff --git a/src/wx/player_information.cc b/src/wx/player_information.cc
index 4e95e0956..806611140 100644
--- a/src/wx/player_information.cc
+++ b/src/wx/player_information.cc
@@ -166,7 +166,7 @@ PlayerInformation::triggered_update ()
 		checked_set (_dcp[r++], wxString::Format(_("Frame rate: %d"), (int) lrint(*dcp->video_frame_rate())));
 	}
 	if (dcp->audio && !dcp->audio->streams().empty()) {
-		checked_set (_dcp[r++], wxString::Format(_("Audio channels: %d"), dcp->audio->streams().front()->channels()));
+		checked_set(_dcp[r++], wxString::Format(_("Audio channels: %d"), dcp->active_audio_channels()));
 	}
 	if (!dcp->text.empty()) {
 		checked_set (_dcp[r++], _("Subtitles: yes"));