Try to tidy up channel mapping a bit.

4 files changed, 84 insertions, 28 deletions

diff --git a/src/lib/encoder.cc b/src/lib/encoder.cc
index f25256379..07139968d 100644
--- a/src/lib/encoder.cc
+++ b/src/lib/encoder.cc
@@ -423,18 +423,20 @@ Encoder::encoder_thread (ServerDescription* server)
 void
 Encoder::write_audio (shared_ptr<const AudioBuffers> data)
 {
-	if (_film->audio_channels() == 1) {
-		/* We need to switch things around so that the mono channel is on
-		   the centre channel of a 5.1 set (with other channels silent).
-		*/
-
-		shared_ptr<AudioBuffers> b (new AudioBuffers (6, data->frames ()));
-		b->make_silent (libdcp::LEFT);
-		b->make_silent (libdcp::RIGHT);
-		memcpy (b->data()[libdcp::CENTRE], data->data()[0], data->frames() * sizeof(float));
-		b->make_silent (libdcp::LFE);
-		b->make_silent (libdcp::LS);
-		b->make_silent (libdcp::RS);
+	AudioMapping m (_film->audio_channels ());
+	if (m.dcp_channels() != _film->audio_channels()) {
+
+		/* Remap (currently just for mono -> 5.1) */
+
+		shared_ptr<AudioBuffers> b (new AudioBuffers (m.dcp_channels(), data->frames ()));
+		for (int i = 0; i < m.dcp_channels(); ++i) {
+			optional<int> s = m.dcp_to_source (static_cast<libdcp::Channel> (i));
+			if (!s) {
+				b->make_silent (i);
+			} else {
+				memcpy (b->data()[i], data->data()[s.get()], data->frames() * sizeof(float));
+			}
+		}
 
 		data = b;
 	}
diff --git a/src/lib/util.cc b/src/lib/util.cc
index f807bf329..8ad980361 100644
--- a/src/lib/util.cc
+++ b/src/lib/util.cc
@@ -445,19 +445,6 @@ dcp_audio_sample_rate (int fs)
 	return 96000;
 }
 
-int
-dcp_audio_channels (int f)
-{
-	if (f == 1) {
-		/* The source is mono, so to put the mono channel into
-		   the centre we need to generate a 5.1 soundtrack.
-		*/
-		return 6;
-	}
-
-	return f;
-}
-
 bool operator== (Crop const & a, Crop const & b)
 {
 	return (a.left == b.left && a.right == b.right && a.top == b.top && a.bottom == b.bottom);
@@ -918,3 +905,55 @@ audio_channel_name (int c)
 
 	return channels[c];
 }
+
+AudioMapping::AudioMapping (int c)
+	: _source_channels (c)
+{
+
+}
+
+optional<libdcp::Channel>
+AudioMapping::source_to_dcp (int c) const
+{
+	if (c >= _source_channels) {
+		return optional<libdcp::Channel> ();
+	}
+
+	if (_source_channels == 1) {
+		/* mono sources to centre */
+		return libdcp::CENTRE;
+	}
+	
+	return static_cast<libdcp::Channel> (c);
+}
+
+optional<int>
+AudioMapping::dcp_to_source (libdcp::Channel c) const
+{
+	if (_source_channels == 1) {
+		if (c == libdcp::CENTRE) {
+			return 0;
+		} else {
+			return optional<int> ();
+		}
+	}
+
+	if (static_cast<int> (c) >= _source_channels) {
+		return optional<int> ();
+	}
+	
+	return static_cast<int> (c);
+}
+
+int
+AudioMapping::dcp_channels () const
+{
+	if (_source_channels == 1) {
+		/* The source is mono, so to put the mono channel into
+		   the centre we need to generate a 5.1 soundtrack.
+		*/
+		return 6;
+	}
+
+	return _source_channels;
+}
diff --git a/src/lib/util.h b/src/lib/util.h
index b76aead41..22c6ea95b 100644
--- a/src/lib/util.h
+++ b/src/lib/util.h
@@ -29,6 +29,7 @@
 #include <vector>
 #include <boost/shared_ptr.hpp>
 #include <boost/asio.hpp>
+#include <boost/optional.hpp>
 #include <libdcp/util.h>
 extern "C" {
 #include <libavcodec/avcodec.h>
@@ -179,7 +180,6 @@ struct Rect
 
 extern std::string crop_string (Position, libdcp::Size);
 extern int dcp_audio_sample_rate (int);
-extern int dcp_audio_channels (int);
 extern std::string colour_lut_index_to_name (int index);
 extern int stride_round_up (int, int const *, int);
 extern int stride_lookup (int c, int const * stride);
@@ -269,6 +269,19 @@ private:
 	float** _data;
 };
 
+class AudioMapping
+{
+public:
+	AudioMapping (int);
+
+	boost::optional<libdcp::Channel> source_to_dcp (int c) const;
+	boost::optional<int> dcp_to_source (libdcp::Channel c) const;
+	int dcp_channels () const;
+
+private:
+	int _source_channels;
+};
+
 extern int64_t video_frames_to_audio_frames (SourceFrame v, float audio_sample_rate, float frames_per_second);
 extern bool still_image_file (std::string);
 extern std::pair<std::string, int> cpu_info ();
diff --git a/src/lib/writer.cc b/src/lib/writer.cc
index c2cc00328..1dad4357d 100644
--- a/src/lib/writer.cc
+++ b/src/lib/writer.cc
@@ -72,13 +72,15 @@ Writer::Writer (shared_ptr<Film> f)
 
 	_picture_asset_writer = _picture_asset->start_write (_first_nonexistant_frame > 0);
 
-	if (dcp_audio_channels (_film->audio_channels()) > 0) {
+	AudioMapping m (_film->audio_channels ());
+	
+	if (m.dcp_channels() > 0) {
 		_sound_asset.reset (
 			new libdcp::SoundAsset (
 				_film->dir (_film->dcp_name()),
 				"audio.mxf",
 				DCPFrameRate (_film->frames_per_second()).frames_per_second,
-				dcp_audio_channels (_film->audio_channels()),
+				m.dcp_channels (),
 				dcp_audio_sample_rate (_film->audio_stream()->sample_rate())
 				)
 			);