Split audio; builds.

33 files changed, 296 insertions, 342 deletions

diff --git a/src/lib/analyse_audio_job.cc b/src/lib/analyse_audio_job.cc
index 7a1a993e7..9a24a9188 100644
--- a/src/lib/analyse_audio_job.cc
+++ b/src/lib/analyse_audio_job.cc
@@ -106,7 +106,7 @@ AnalyseAudioJob::run ()
 
 	bool has_any_audio = false;
 	BOOST_FOREACH (shared_ptr<Content> c, _playlist->content ()) {
-		if (dynamic_pointer_cast<AudioContent> (c)) {
+		if (c->audio) {
 			has_any_audio = true;
 		}
 	}
@@ -145,7 +145,7 @@ AnalyseAudioJob::run ()
 		/* If there was only one piece of content in this analysis we may later need to know what its
 		   gain was when we analysed it.
 		*/
-		shared_ptr<const AudioContent> ac = dynamic_pointer_cast<const AudioContent> (_playlist->content().front ());
+		shared_ptr<const AudioContent> ac = _playlist->content().front()->audio;
 		DCPOMATIC_ASSERT (ac);
 		_analysis->set_analysis_gain (ac->audio_gain ());
 	}
diff --git a/src/lib/audio_analysis.cc b/src/lib/audio_analysis.cc
index 03f35d84e..d99b01ce6 100644
--- a/src/lib/audio_analysis.cc
+++ b/src/lib/audio_analysis.cc
@@ -153,9 +153,8 @@ AudioAnalysis::gain_correction (shared_ptr<const Playlist> playlist)
 		   we know that content's gain when the analysis was run.  Hence we can work out
 		   what correction is now needed to make it look `right'.
 		*/
-		shared_ptr<const AudioContent> ac = dynamic_pointer_cast<const AudioContent> (playlist->content().front ());
-		DCPOMATIC_ASSERT (ac);
-		return ac->audio_gain() - analysis_gain().get ();
+		DCPOMATIC_ASSERT (playlist->content().front()->audio);
+		return playlist->content().front()->audio->audio_gain() - analysis_gain().get ();
 	}
 
 	return 0.0f;
diff --git a/src/lib/audio_content.cc b/src/lib/audio_content.cc
index bd4bb565f..2832e2575 100644
--- a/src/lib/audio_content.cc
+++ b/src/lib/audio_content.cc
@@ -49,52 +49,34 @@ int const AudioContentProperty::AUDIO_GAIN = 201;
 int const AudioContentProperty::AUDIO_DELAY = 202;
 int const AudioContentProperty::AUDIO_VIDEO_FRAME_RATE = 203;
 
-AudioContent::AudioContent (shared_ptr<const Film> film)
-	: Content (film)
+AudioContent::AudioContent (Content* parent, shared_ptr<const Film> film)
+	: ContentPart (parent, film)
 	, _audio_gain (0)
 	, _audio_delay (Config::instance()->default_audio_delay ())
 {
 
 }
 
-AudioContent::AudioContent (shared_ptr<const Film> film, DCPTime s)
-	: Content (film, s)
-	, _audio_gain (0)
-	, _audio_delay (Config::instance()->default_audio_delay ())
-{
-
-}
-
-AudioContent::AudioContent (shared_ptr<const Film> film, boost::filesystem::path p)
-	: Content (film, p)
-	, _audio_gain (0)
-	, _audio_delay (Config::instance()->default_audio_delay ())
-{
-
-}
-
-AudioContent::AudioContent (shared_ptr<const Film> film, cxml::ConstNodePtr node)
-	: Content (film, node)
+AudioContent::AudioContent (Content* parent, shared_ptr<const Film> film, cxml::ConstNodePtr node)
+	: ContentPart (parent, film)
 {
 	_audio_gain = node->number_child<double> ("AudioGain");
 	_audio_delay = node->number_child<int> ("AudioDelay");
 	_audio_video_frame_rate = node->optional_number_child<double> ("AudioVideoFrameRate");
 }
 
-AudioContent::AudioContent (shared_ptr<const Film> film, vector<shared_ptr<Content> > c)
-	: Content (film, c)
+AudioContent::AudioContent (Content* parent, shared_ptr<const Film> film, vector<shared_ptr<Content> > c)
+	: ContentPart (parent, film)
 {
-	shared_ptr<AudioContent> ref = dynamic_pointer_cast<AudioContent> (c[0]);
+	shared_ptr<AudioContent> ref = c[0]->audio;
 	DCPOMATIC_ASSERT (ref);
 
-	for (size_t i = 0; i < c.size(); ++i) {
-		shared_ptr<AudioContent> ac = dynamic_pointer_cast<AudioContent> (c[i]);
-
-		if (ac->audio_gain() != ref->audio_gain()) {
+	for (size_t i = 1; i < c.size(); ++i) {
+		if (c[i]->audio->audio_gain() != ref->audio_gain()) {
 			throw JoinError (_("Content to be joined must have the same audio gain."));
 		}
 
-		if (ac->audio_delay() != ref->audio_delay()) {
+		if (c[i]->audio->audio_delay() != ref->audio_delay()) {
 			throw JoinError (_("Content to be joined must have the same audio delay."));
 		}
 
@@ -107,6 +89,7 @@ AudioContent::AudioContent (shared_ptr<const Film> film, vector<shared_ptr<Conte
 	_audio_delay = ref->audio_delay ();
 	/* Preserve the optional<> part of this */
 	_audio_video_frame_rate = ref->_audio_video_frame_rate;
+	_streams = ref->streams ();
 }
 
 void
@@ -120,34 +103,23 @@ AudioContent::as_xml (xmlpp::Node* node) const
 	}
 }
 
-
 void
 AudioContent::set_audio_gain (double g)
 {
-	{
-		boost::mutex::scoped_lock lm (_mutex);
-		_audio_gain = g;
-	}
-
-	signal_changed (AudioContentProperty::AUDIO_GAIN);
+	maybe_set (_audio_gain, g, AudioContentProperty::AUDIO_GAIN);
 }
 
 void
 AudioContent::set_audio_delay (int d)
 {
-	{
-		boost::mutex::scoped_lock lm (_mutex);
-		_audio_delay = d;
-	}
-
-	signal_changed (AudioContentProperty::AUDIO_DELAY);
+	maybe_set (_audio_delay, d, AudioContentProperty::AUDIO_DELAY);
 }
 
 string
 AudioContent::technical_summary () const
 {
 	string s = "audio :";
-	BOOST_FOREACH (AudioStreamPtr i, audio_streams ()) {
+	BOOST_FOREACH (AudioStreamPtr i, streams ()) {
 		s += String::compose ("stream channels %1 rate %2", i->channels(), i->frame_rate());
 	}
 
@@ -158,7 +130,7 @@ void
 AudioContent::set_audio_mapping (AudioMapping mapping)
 {
 	int c = 0;
-	BOOST_FOREACH (AudioStreamPtr i, audio_streams ()) {
+	BOOST_FOREACH (AudioStreamPtr i, streams ()) {
 		AudioMapping stream_mapping (i->channels (), MAX_DCP_AUDIO_CHANNELS);
 		for (int j = 0; j < i->channels(); ++j) {
 			for (int k = 0; k < MAX_DCP_AUDIO_CHANNELS; ++k) {
@@ -169,14 +141,14 @@ AudioContent::set_audio_mapping (AudioMapping mapping)
 		i->set_mapping (stream_mapping);
 	}
 
-	signal_changed (AudioContentProperty::AUDIO_STREAMS);
+	_parent->signal_changed (AudioContentProperty::AUDIO_STREAMS);
 }
 
 AudioMapping
 AudioContent::audio_mapping () const
 {
 	int channels = 0;
-	BOOST_FOREACH (AudioStreamPtr i, audio_streams ()) {
+	BOOST_FOREACH (AudioStreamPtr i, streams ()) {
 		channels += i->channels ();
 	}
 
@@ -185,7 +157,7 @@ AudioContent::audio_mapping () const
 
 	int c = 0;
 	int s = 0;
-	BOOST_FOREACH (AudioStreamPtr i, audio_streams ()) {
+	BOOST_FOREACH (AudioStreamPtr i, streams ()) {
 		AudioMapping mapping = i->mapping ();
 		for (int j = 0; j < mapping.input_channels(); ++j) {
 			for (int k = 0; k < MAX_DCP_AUDIO_CHANNELS; ++k) {
@@ -210,7 +182,9 @@ AudioContent::resampled_audio_frame_rate () const
 	/* Resample to a DCI-approved sample rate */
 	double t = has_rate_above_48k() ? 96000 : 48000;
 
-	FrameRateChange frc (audio_video_frame_rate(), film()->video_frame_rate());
+	shared_ptr<const Film> film = _film.lock ();
+	DCPOMATIC_ASSERT (film);
+	FrameRateChange frc (audio_video_frame_rate(), film->video_frame_rate());
 
 	/* Compensate if the DCP is being run at a different frame rate
 	   to the source; that is, if the video is run such that it will
@@ -227,8 +201,7 @@ AudioContent::resampled_audio_frame_rate () const
 string
 AudioContent::processing_description () const
 {
-	vector<AudioStreamPtr> streams = audio_streams ();
-	if (streams.empty ()) {
+	if (streams().empty ()) {
 		return "";
 	}
 
@@ -244,7 +217,7 @@ AudioContent::processing_description () const
 	bool same = true;
 
 	optional<int> common_frame_rate;
-	BOOST_FOREACH (AudioStreamPtr i, streams) {
+	BOOST_FOREACH (AudioStreamPtr i, streams()) {
 		if (i->frame_rate() != resampled_audio_frame_rate()) {
 			resampled = true;
 		} else {
@@ -280,7 +253,7 @@ AudioContent::processing_description () const
 bool
 AudioContent::has_rate_above_48k () const
 {
-	BOOST_FOREACH (AudioStreamPtr i, audio_streams ()) {
+	BOOST_FOREACH (AudioStreamPtr i, streams ()) {
 		if (i->frame_rate() > 48000) {
 			return true;
 		}
@@ -296,7 +269,7 @@ AudioContent::audio_channel_names () const
 	vector<string> n;
 
 	int t = 1;
-	BOOST_FOREACH (AudioStreamPtr i, audio_streams ()) {
+	BOOST_FOREACH (AudioStreamPtr i, streams ()) {
 		for (int j = 0; j < i->channels(); ++j) {
 			n.push_back (String::compose ("%1:%2", t, j + 1));
 		}
@@ -310,8 +283,8 @@ void
 AudioContent::add_properties (list<UserProperty>& p) const
 {
 	shared_ptr<const AudioStream> stream;
-	if (audio_streams().size() == 1) {
-		stream = audio_streams().front ();
+	if (streams().size() == 1) {
+		stream = streams().front ();
 	}
 
 	if (stream) {
@@ -319,8 +292,11 @@ AudioContent::add_properties (list<UserProperty>& p) const
 		p.push_back (UserProperty (_("Audio"), _("Content audio frame rate"), stream->frame_rate(), _("Hz")));
 	}
 
-	FrameRateChange const frc (audio_video_frame_rate(), film()->video_frame_rate());
-	ContentTime const c (full_length(), frc);
+	shared_ptr<const Film> film = _film.lock ();
+	DCPOMATIC_ASSERT (film);
+
+	FrameRateChange const frc (audio_video_frame_rate(), film->video_frame_rate());
+	ContentTime const c (_parent->full_length(), frc);
 
 	p.push_back (
 		UserProperty (_("Length"), _("Full length in video frames at content rate"), c.frames_round(frc.source))
@@ -376,3 +352,44 @@ AudioContent::audio_video_frame_rate () const
 	*/
 	return film()->active_frame_rate_change(position()).source;
 }
+
+AudioContent::set_streams (vector<AudioStreamPtr> streams)
+{
+	{
+		boost::mutex::scoped_lock lm (_mutex);
+		_streams = streams;
+	}
+
+	_parent->signal_changed (AudioContentProperty::AUDIO_STREAMS);
+}
+
+AudioStreamPtr
+AudioContent::stream () const
+{
+	boost::mutex::scoped_lock lm (_mutex);
+	DCPOMATIC_ASSERT (_streams.size() == 1);
+	return _streams.front ();
+}
+
+void
+AudioContent::add_stream (AudioStreamPtr stream)
+{
+	{
+		boost::mutex::scoped_lock lm (_mutex);
+		_streams.push_back (stream);
+	}
+
+	_parent->signal_changed (AudioContentProperty::AUDIO_STREAMS);
+}
+
+void
+AudioContent::set_stream (AudioStreamPtr stream)
+{
+	{
+		boost::mutex::scoped_lock lm (_mutex);
+		_streams.clear ();
+		_streams.push_back (stream);
+	}
+
+	_parent->signal_changed (AudioContentProperty::AUDIO_STREAMS);
+}
diff --git a/src/lib/audio_content.h b/src/lib/audio_content.h
index ac91da595..3aa9678b0 100644
--- a/src/lib/audio_content.h
+++ b/src/lib/audio_content.h
@@ -24,7 +24,7 @@
 #ifndef DCPOMATIC_AUDIO_CONTENT_H
 #define DCPOMATIC_AUDIO_CONTENT_H
 
-#include "content.h"
+#include "content_part.h"
 #include "audio_stream.h"
 #include "audio_mapping.h"
 
@@ -40,23 +40,16 @@ public:
 	static int const AUDIO_VIDEO_FRAME_RATE;
 };
 
-/** @class AudioContent
- *  @brief Parent class for content which may contain audio data.
- */
-class AudioContent : public virtual Content
+class AudioContent : public ContentPart
 {
 public:
-	AudioContent (boost::shared_ptr<const Film>);
-	AudioContent (boost::shared_ptr<const Film>, DCPTime);
-	AudioContent (boost::shared_ptr<const Film>, boost::filesystem::path);
-	AudioContent (boost::shared_ptr<const Film>, cxml::ConstNodePtr);
-	AudioContent (boost::shared_ptr<const Film>, std::vector<boost::shared_ptr<Content> >);
+	AudioContent (Content* parent, boost::shared_ptr<const Film>);
+	AudioContent (Content* parent, boost::shared_ptr<const Film>, cxml::ConstNodePtr);
+	AudioContent (Content* parent, boost::shared_ptr<const Film>, std::vector<boost::shared_ptr<Content> >);
 
 	void as_xml (xmlpp::Node *) const;
 	std::string technical_summary () const;
 
-	virtual std::vector<AudioStreamPtr> audio_streams () const = 0;
-
 	AudioMapping audio_mapping () const;
 	void set_audio_mapping (AudioMapping);
 	int resampled_audio_frame_rate () const;
@@ -81,16 +74,26 @@ public:
 
 	std::string processing_description () const;
 
-protected:
+	std::vector<AudioStreamPtr> streams () const {
+		boost::mutex::scoped_lock lm (_mutex);
+		return _streams;
+	}
+
+	void add_stream (AudioStreamPtr stream);
+	void set_stream (AudioStreamPtr stream);
+	void set_streams (std::vector<AudioStreamPtr> streams);
+	AudioStreamPtr stream () const;
 
 	void add_properties (std::list<UserProperty> &) const;
 
 private:
+
 	/** Gain to apply to audio in dB */
 	double _audio_gain;
 	/** Delay to apply to audio (positive moves audio later) in milliseconds */
 	int _audio_delay;
 	boost::optional<double> _audio_video_frame_rate;
+	std::vector<AudioStreamPtr> _streams;
 };
 
 #endif
diff --git a/src/lib/audio_decoder.cc b/src/lib/audio_decoder.cc
index 2944357ba..705fdbef1 100644
--- a/src/lib/audio_decoder.cc
+++ b/src/lib/audio_decoder.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -30,13 +30,13 @@ using std::cout;
 using std::map;
 using boost::shared_ptr;
 
-AudioDecoder::AudioDecoder (shared_ptr<const AudioContent> content, bool fast)
+AudioDecoder::AudioDecoder (shared_ptr<const AudioContent> content, bool fast, shared_ptr<Log> log)
 	: _audio_content (content)
 	, _ignore_audio (false)
 	, _fast (fast)
 {
-	BOOST_FOREACH (AudioStreamPtr i, content->audio_streams ()) {
-		_streams[i] = shared_ptr<AudioDecoderStream> (new AudioDecoderStream (_audio_content, i, this));
+	BOOST_FOREACH (AudioStreamPtr i, content->streams ()) {
+		_streams[i] = shared_ptr<AudioDecoderStream> (new AudioDecoderStream (_audio_content, i, this, log));
 	}
 }
 
diff --git a/src/lib/audio_decoder.h b/src/lib/audio_decoder.h
index 716b37969..679cdd5c5 100644
--- a/src/lib/audio_decoder.h
+++ b/src/lib/audio_decoder.h
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2014 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -32,6 +32,7 @@
 class AudioBuffers;
 class AudioContent;
 class AudioDecoderStream;
+class Log;
 
 /** @class AudioDecoder.
  *  @brief Parent class for audio decoders.
@@ -39,7 +40,7 @@ class AudioDecoderStream;
 class AudioDecoder : public virtual Decoder, public boost::enable_shared_from_this<AudioDecoder>
 {
 public:
-	AudioDecoder (boost::shared_ptr<const AudioContent>, bool fast);
+	AudioDecoder (boost::shared_ptr<const AudioContent>, bool fast, boost::shared_ptr<Log> log);
 
 	boost::shared_ptr<const AudioContent> audio_content () const {
 		return _audio_content;
diff --git a/src/lib/audio_decoder_stream.cc b/src/lib/audio_decoder_stream.cc
index cb0372231..7037d9f47 100644
--- a/src/lib/audio_decoder_stream.cc
+++ b/src/lib/audio_decoder_stream.cc
@@ -39,10 +39,11 @@ using std::max;
 using boost::optional;
 using boost::shared_ptr;
 
-AudioDecoderStream::AudioDecoderStream (shared_ptr<const AudioContent> content, AudioStreamPtr stream, AudioDecoder* decoder)
+AudioDecoderStream::AudioDecoderStream (shared_ptr<const AudioContent> content, AudioStreamPtr stream, AudioDecoder* decoder, shared_ptr<Log> log)
 	: _content (content)
 	, _stream (stream)
 	, _decoder (decoder)
+	, _log (log)
 {
 	if (content->resampled_audio_frame_rate() != _stream->frame_rate() && _stream->channels() > 0) {
 		_resampler.reset (new Resampler (_stream->frame_rate(), content->resampled_audio_frame_rate(), _stream->channels (), decoder->fast ()));
@@ -62,7 +63,7 @@ AudioDecoderStream::get (Frame frame, Frame length, bool accurate)
 {
 	shared_ptr<ContentAudio> dec;
 
-	_content->film()->log()->log (String::compose ("-> ADS has request for %1 %2", frame, length), LogEntry::TYPE_DEBUG_DECODE);
+	_log->log (String::compose ("-> ADS has request for %1 %2", frame, length), LogEntry::TYPE_DEBUG_DECODE);
 
 	Frame const end = frame + length - 1;
 
@@ -93,7 +94,7 @@ AudioDecoderStream::get (Frame frame, Frame length, bool accurate)
 
 		decoded_offset = frame - _decoded.frame;
 
-		_content->film()->log()->log (
+		_log->log (
 			String::compose ("Accurate ADS::get has offset %1 from request %2 and available %3", decoded_offset, frame, _decoded.frame),
 			LogEntry::TYPE_DEBUG_DECODE
 			);
@@ -141,7 +142,7 @@ AudioDecoderStream::get (Frame frame, Frame length, bool accurate)
 void
 AudioDecoderStream::audio (shared_ptr<const AudioBuffers> data, ContentTime time)
 {
-	_content->film()->log()->log (String::compose ("ADS receives %1 %2", time, data->frames ()), LogEntry::TYPE_DEBUG_DECODE);
+	_log->log (String::compose ("ADS receives %1 %2", time, data->frames ()), LogEntry::TYPE_DEBUG_DECODE);
 
 	if (_resampler) {
 		data = _resampler->run (data);
diff --git a/src/lib/audio_decoder_stream.h b/src/lib/audio_decoder_stream.h
index 3503a46d1..90269a0f4 100644
--- a/src/lib/audio_decoder_stream.h
+++ b/src/lib/audio_decoder_stream.h
@@ -28,11 +28,12 @@
 class AudioContent;
 class AudioDecoder;
 class Resampler;
+class Log;
 
 class AudioDecoderStream
 {
 public:
-	AudioDecoderStream (boost::shared_ptr<const AudioContent>, AudioStreamPtr, AudioDecoder* decoder);
+	AudioDecoderStream (boost::shared_ptr<const AudioContent>, AudioStreamPtr, AudioDecoder* decoder, boost::shared_ptr<Log> log);
 
 	ContentAudio get (Frame time, Frame length, bool accurate);
 	void audio (boost::shared_ptr<const AudioBuffers>, ContentTime);
@@ -47,6 +48,7 @@ private:
 	boost::shared_ptr<const AudioContent> _content;
 	AudioStreamPtr _stream;
 	AudioDecoder* _decoder;
+	boost::shared_ptr<Log> _log;
 	boost::shared_ptr<Resampler> _resampler;
 	boost::optional<Frame> _position;
 	/** Currently-available decoded audio data */
diff --git a/src/lib/audio_stream.h b/src/lib/audio_stream.h
index 506a3c02d..8d05df268 100644
--- a/src/lib/audio_stream.h
+++ b/src/lib/audio_stream.h
@@ -30,6 +30,7 @@ class AudioStream
 public:
 	AudioStream (int frame_rate, int channels);
 	AudioStream (int frame_rate, AudioMapping mapping);
+	virtual ~AudioStream () {}
 
 	void set_mapping (AudioMapping mapping);
 
diff --git a/src/lib/content.cc b/src/lib/content.cc
index 28103e9c0..499f90dd1 100644
--- a/src/lib/content.cc
+++ b/src/lib/content.cc
@@ -155,6 +155,7 @@ Content::examine (shared_ptr<Job> job)
 void
 Content::signal_changed (int p)
 {
+	changed (p);
 	emit (boost::bind (boost::ref (Changed), shared_from_this (), p, _change_signals_frequent));
 }
 
diff --git a/src/lib/content.h b/src/lib/content.h
index f488962b3..60dd89b97 100644
--- a/src/lib/content.h
+++ b/src/lib/content.h
@@ -93,6 +93,8 @@ public:
 	 */
 	virtual std::list<DCPTime> reel_split_points () const;
 
+	virtual void changed (int) {}
+
 	boost::shared_ptr<Content> clone () const;
 
 	void set_path (boost::filesystem::path);
@@ -167,6 +169,7 @@ public:
 	boost::signals2::signal<void (boost::weak_ptr<Content>, int, bool)> Changed;
 
 	boost::shared_ptr<VideoContent> video;
+	boost::shared_ptr<AudioContent> audio;
 	boost::shared_ptr<SubtitleContent> subtitle;
 
 	void signal_changed (int);
diff --git a/src/lib/dcp_content.cc b/src/lib/dcp_content.cc
index a81a152c1..cfd19fe31 100644
--- a/src/lib/dcp_content.cc
+++ b/src/lib/dcp_content.cc
@@ -19,6 +19,7 @@
 
 #include "dcp_content.h"
 #include "video_content.h"
+#include "audio_content.h"
 #include "dcp_examiner.h"
 #include "job.h"
 #include "film.h"
@@ -55,7 +56,6 @@ int const DCPContentProperty::REFERENCE_SUBTITLE = 603;
 
 DCPContent::DCPContent (shared_ptr<const Film> film, boost::filesystem::path p)
 	: Content (film)
-	, AudioContent (film)
 	, _has_subtitles (false)
 	, _encrypted (false)
 	, _kdm_valid (false)
@@ -64,6 +64,7 @@ DCPContent::DCPContent (shared_ptr<const Film> film, boost::filesystem::path p)
 	, _reference_subtitle (false)
 {
 	video.reset (new VideoContent (this, film));
+	audio.reset (new AudioContent (this, film));
 	subtitle.reset (new SubtitleContent (this, film));
 
 	read_directory (p);
@@ -72,10 +73,14 @@ DCPContent::DCPContent (shared_ptr<const Film> film, boost::filesystem::path p)
 
 DCPContent::DCPContent (shared_ptr<const Film> film, cxml::ConstNodePtr node, int version)
 	: Content (film, node)
-	, AudioContent (film, node)
-	, _audio_stream (new AudioStream (node->number_child<int> ("AudioFrameRate"), AudioMapping (node->node_child ("AudioMapping"), version)))
 {
 	video.reset (new VideoContent (this, film, node, version));
+	audio.reset (new AudioContent (this, film, node));
+	audio->set_stream (
+		AudioStreamPtr (
+			new AudioStream (node->number_child<int> ("AudioFrameRate"), AudioMapping (node->node_child ("AudioMapping"), version))
+			)
+		);
 	subtitle.reset (new SubtitleContent (this, film, node, version));
 
 	_name = node->string_child ("Name");
@@ -116,10 +121,12 @@ DCPContent::examine (shared_ptr<Job> job)
 
 	{
 		boost::mutex::scoped_lock lm (_mutex);
-		_audio_stream.reset (new AudioStream (examiner->audio_frame_rate(), examiner->audio_channels ()));
-		AudioMapping m = _audio_stream->mapping ();
+
+		AudioStreamPtr as (new AudioStream (examiner->audio_frame_rate(), examiner->audio_channels ()));
+		audio->set_stream (as);
+		AudioMapping m = as->mapping ();
 		film()->make_audio_mapping_default (m);
-		_audio_stream->set_mapping (m);
+		as->set_mapping (m);
 	}
 
 	signal_changed (AudioContentProperty::AUDIO_STREAMS);
@@ -149,7 +156,7 @@ DCPContent::technical_summary () const
 {
 	return Content::technical_summary() + " - "
 		+ video->technical_summary() + " - "
-		+ AudioContent::technical_summary() + " - ";
+		+ audio->technical_summary() + " - ";
 }
 
 void
@@ -159,9 +166,9 @@ DCPContent::as_xml (xmlpp::Node* node) const
 
 	Content::as_xml (node);
 	video->as_xml (node);
-	AudioContent::as_xml (node);
-	node->add_child("AudioFrameRate")->add_child_text (raw_convert<string> (audio_stream()->frame_rate ()));
-	audio_stream()->mapping().as_xml (node->add_child("AudioMapping"));
+	audio->as_xml (node);
+	node->add_child("AudioFrameRate")->add_child_text (raw_convert<string> (audio->stream()->frame_rate()));
+	audio->stream()->mapping().as_xml (node->add_child("AudioMapping"));
 	subtitle->as_xml (node);
 
 	boost::mutex::scoped_lock lm (_mutex);
@@ -226,7 +233,7 @@ DCPContent::directory () const
 void
 DCPContent::add_properties (list<UserProperty>& p) const
 {
-	AudioContent::add_properties (p);
+	audio->add_properties (p);
 }
 
 void
@@ -337,15 +344,8 @@ DCPContent::can_reference_video (list<string>& why_not) const
 bool
 DCPContent::can_reference_audio (list<string>& why_not) const
 {
-	DCPDecoder decoder (shared_from_this(), film()->log(), false);
-	BOOST_FOREACH (shared_ptr<dcp::Reel> i, decoder.reels()) {
-		if (!i->main_sound()) {
-			why_not.push_back (_("The DCP does not have sound in all reels."));
-			return false;
-		}
-	}
-
-	return can_reference<AudioContent> (_("There is other audio content overlapping this DCP; remove it."), why_not);
+	/* XXX: this needs to be fixed */
+	return true;
 }
 
 bool
@@ -355,16 +355,10 @@ DCPContent::can_reference_subtitle (list<string>& why_not) const
 	return true;
 }
 
-double
-DCPContent::subtitle_video_frame_rate () const
-{
-	return video->video_frame_rate ();
-}
-
-vector<AudioStreamPtr>
-DCPContent::audio_streams () const
+void
+DCPContent::changed (int property)
 {
-	vector<AudioStreamPtr> s;
-	s.push_back (_audio_stream);
-	return s;
+	if (property == VideoContentProperty::VIDEO_FRAME_RATE && subtitle) {
+		subtitle->set_subtitle_video_frame_rate (video->video_frame_rate ());
+	}
 }
diff --git a/src/lib/dcp_content.h b/src/lib/dcp_content.h
index f3cd6bf65..b2bc90ebd 100644
--- a/src/lib/dcp_content.h
+++ b/src/lib/dcp_content.h
@@ -24,7 +24,7 @@
  *  @brief DCPContent class.
  */
 
-#include "audio_content.h"
+#include "content.h"
 #include <libcxml/cxml.h>
 #include <dcp/encrypted_kdm.h>
 
@@ -40,7 +40,7 @@ public:
 /** @class DCPContent
  *  @brief An existing DCP used as input.
  */
-class DCPContent : public AudioContent
+class DCPContent : public Content
 {
 public:
 	DCPContent (boost::shared_ptr<const Film>, boost::filesystem::path p);
@@ -65,8 +65,6 @@ public:
 	void set_default_colour_conversion ();
 	std::list<DCPTime> reel_split_points () const;
 
-	/* SubtitleContent */
-
 	bool has_text_subtitles () const {
 		boost::mutex::scoped_lock lm (_mutex);
 		return _has_subtitles;
@@ -76,7 +74,7 @@ public:
 		return false;
 	}
 
-	double subtitle_video_frame_rate () const;
+	void changed (int property);
 
 	boost::filesystem::path directory () const;
 
@@ -120,16 +118,9 @@ public:
 
 	bool can_reference_subtitle (std::list<std::string> &) const;
 
-	std::vector<AudioStreamPtr> audio_streams () const;
-
-	AudioStreamPtr audio_stream () const {
-		return _audio_stream;
-	}
-
-protected:
+private:
 	void add_properties (std::list<UserProperty>& p) const;
 
-private:
 	void read_directory (boost::filesystem::path);
 	std::list<DCPTimePeriod> reels () const;
 	template <class T> bool can_reference (std::string overlapping, std::list<std::string>& why_not) const;
@@ -153,8 +144,6 @@ private:
 	 *  rather than by rewrapping.
 	 */
 	bool _reference_subtitle;
-
-	boost::shared_ptr<AudioStream> _audio_stream;
 };
 
 #endif
diff --git a/src/lib/dcp_decoder.cc b/src/lib/dcp_decoder.cc
index f032ee661..4e28dc758 100644
--- a/src/lib/dcp_decoder.cc
+++ b/src/lib/dcp_decoder.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2014-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2014-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,6 +19,7 @@
 
 #include "dcp_decoder.h"
 #include "dcp_content.h"
+#include "audio_content.h"
 #include "j2k_image_proxy.h"
 #include "image.h"
 #include "config.h"
@@ -44,7 +45,7 @@ using boost::dynamic_pointer_cast;
 
 DCPDecoder::DCPDecoder (shared_ptr<const DCPContent> c, shared_ptr<Log> log, bool fast)
 	: VideoDecoder (c->video, log)
-	, AudioDecoder (c, fast)
+	, AudioDecoder (c->audio, fast, log)
 	, SubtitleDecoder (c->subtitle)
 	, _dcp_content (c)
 {
@@ -103,7 +104,7 @@ DCPDecoder::pass (PassReason reason, bool)
 		shared_ptr<const dcp::SoundFrame> sf = (*_reel)->main_sound()->asset()->get_frame (entry_point + frame);
 		uint8_t const * from = sf->data ();
 
-		int const channels = _dcp_content->audio_stream()->channels ();
+		int const channels = _dcp_content->audio->stream()->channels ();
 		int const frames = sf->size() / (3 * channels);
 		shared_ptr<AudioBuffers> data (new AudioBuffers (channels, frames));
 		for (int i = 0; i < frames; ++i) {
@@ -113,7 +114,7 @@ DCPDecoder::pass (PassReason reason, bool)
 			}
 		}
 
-		audio (_dcp_content->audio_stream(), data, ContentTime::from_frames (offset, vfr) + _next);
+		audio (_dcp_content->audio->stream(), data, ContentTime::from_frames (offset, vfr) + _next);
 	}
 
 	if ((*_reel)->main_subtitle ()) {
diff --git a/src/lib/dcp_subtitle_content.cc b/src/lib/dcp_subtitle_content.cc
index b38c0c6a7..3feb8947a 100644
--- a/src/lib/dcp_subtitle_content.cc
+++ b/src/lib/dcp_subtitle_content.cc
@@ -44,7 +44,6 @@ DCPSubtitleContent::DCPSubtitleContent (shared_ptr<const Film> film, boost::file
 DCPSubtitleContent::DCPSubtitleContent (shared_ptr<const Film> film, cxml::ConstNodePtr node, int version)
 	: Content (film, node)
 	, _length (node->number_child<ContentTime::Type> ("Length"))
-	, _frame_rate (node->optional_number_child<int>("SubtitleFrameRate"))
 {
 	subtitle.reset (new SubtitleContent (this, film, node, version));
 }
@@ -68,7 +67,7 @@ DCPSubtitleContent::examine (shared_ptr<Job> job)
 	shared_ptr<dcp::SMPTESubtitleAsset> smpte = dynamic_pointer_cast<dcp::SMPTESubtitleAsset> (sc);
 	if (smpte) {
 		subtitle->set_subtitle_language (smpte->language().get_value_or (""));
-		_frame_rate = smpte->edit_rate().numerator;
+		subtitle->set_subtitle_video_frame_rate (smpte->edit_rate().numerator);
 	}
 
 	_length = ContentTime::from_seconds (sc->latest_subtitle_out().as_seconds ());
@@ -81,7 +80,7 @@ DCPSubtitleContent::examine (shared_ptr<Job> job)
 DCPTime
 DCPSubtitleContent::full_length () const
 {
-	FrameRateChange const frc (subtitle_video_frame_rate(), film()->video_frame_rate());
+	FrameRateChange const frc (subtitle->subtitle_video_frame_rate(), film()->video_frame_rate());
 	return DCPTime (_length, frc);
 }
 
@@ -105,30 +104,3 @@ DCPSubtitleContent::as_xml (xmlpp::Node* node) const
 	subtitle->as_xml (node);
 	node->add_child("Length")->add_child_text (raw_convert<string> (_length.get ()));
 }
-
-void
-DCPSubtitleContent::set_subtitle_video_frame_rate (int r)
-{
-	{
-		boost::mutex::scoped_lock lm (_mutex);
-		_frame_rate = r;
-	}
-
-	signal_changed (SubtitleContentProperty::SUBTITLE_VIDEO_FRAME_RATE);
-}
-
-double
-DCPSubtitleContent::subtitle_video_frame_rate () const
-{
-	{
-		boost::mutex::scoped_lock lm (_mutex);
-		if (_frame_rate) {
-			return _frame_rate.get ();
-		}
-	}
-
-	/* No frame rate specified, so assume this content has been
-	   prepared for any concurrent video content.
-	*/
-	return film()->active_frame_rate_change(position()).source;
-}
diff --git a/src/lib/dcp_subtitle_content.h b/src/lib/dcp_subtitle_content.h
index de9fa68ec..211765796 100644
--- a/src/lib/dcp_subtitle_content.h
+++ b/src/lib/dcp_subtitle_content.h
@@ -43,11 +43,6 @@ public:
 		return false;
 	}
 
-	double subtitle_video_frame_rate () const;
-	void set_subtitle_video_frame_rate (int r);
-
 private:
 	ContentTime _length;
-	/** Video frame rate that this content has been prepared for, if known */
-	boost::optional<double> _frame_rate;
 };
diff --git a/src/lib/ffmpeg_content.cc b/src/lib/ffmpeg_content.cc
index f276a16a3..c67d643a5 100644
--- a/src/lib/ffmpeg_content.cc
+++ b/src/lib/ffmpeg_content.cc
@@ -19,6 +19,7 @@
 
 #include "ffmpeg_content.h"
 #include "video_content.h"
+#include "audio_content.h"
 #include "ffmpeg_examiner.h"
 #include "ffmpeg_subtitle_stream.h"
 #include "ffmpeg_audio_stream.h"
@@ -62,9 +63,9 @@ int const FFmpegContentProperty::FILTERS = 102;
 
 FFmpegContent::FFmpegContent (shared_ptr<const Film> film, boost::filesystem::path p)
 	: Content (film, p)
-	, AudioContent (film, p)
 {
 	video.reset (new VideoContent (this, film));
+	audio.reset (new AudioContent (this, film));
 	subtitle.reset (new SubtitleContent (this, film));
 
 	set_default_colour_conversion ();
@@ -72,9 +73,9 @@ FFmpegContent::FFmpegContent (shared_ptr<const Film> film, boost::filesystem::pa
 
 FFmpegContent::FFmpegContent (shared_ptr<const Film> film, cxml::ConstNodePtr node, int version, list<string>& notes)
 	: Content (film, node)
-	, AudioContent (film, node)
 {
 	video.reset (new VideoContent (this, film, node, version));
+	audio.reset (new AudioContent (this, film, node));
 	subtitle.reset (new SubtitleContent (this, film, node, version));
 
 	list<cxml::NodePtr> c = node->node_children ("SubtitleStream");
@@ -87,10 +88,11 @@ FFmpegContent::FFmpegContent (shared_ptr<const Film> film, cxml::ConstNodePtr no
 
 	c = node->node_children ("AudioStream");
 	for (list<cxml::NodePtr>::const_iterator i = c.begin(); i != c.end(); ++i) {
-		_audio_streams.push_back (shared_ptr<FFmpegAudioStream> (new FFmpegAudioStream (*i, version)));
+		shared_ptr<FFmpegAudioStream> as (new FFmpegAudioStream (*i, version));
+		audio->add_stream (as);
 		if (version < 11 && !(*i)->optional_node_child ("Selected")) {
 			/* This is an old file and this stream is not selected, so un-map it */
-			_audio_streams.back()->set_mapping (AudioMapping (_audio_streams.back()->channels (), MAX_DCP_AUDIO_CHANNELS));
+			as->set_mapping (AudioMapping (_audio_streams.back()->channels (), MAX_DCP_AUDIO_CHANNELS));
 		}
 	}
 
@@ -121,9 +123,9 @@ FFmpegContent::FFmpegContent (shared_ptr<const Film> film, cxml::ConstNodePtr no
 
 FFmpegContent::FFmpegContent (shared_ptr<const Film> film, vector<boost::shared_ptr<Content> > c)
 	: Content (film, c)
-	, AudioContent (film, c)
 {
 	video.reset (new VideoContent (this, film, c));
+	audio.reset (new AudioContent (this, film, c));
 	subtitle.reset (new SubtitleContent (this, film, c));
 
 	shared_ptr<FFmpegContent> ref = dynamic_pointer_cast<FFmpegContent> (c[0]);
@@ -140,7 +142,6 @@ FFmpegContent::FFmpegContent (shared_ptr<const Film> film, vector<boost::shared_
 
 	_subtitle_streams = ref->subtitle_streams ();
 	_subtitle_stream = ref->subtitle_stream ();
-	_audio_streams = ref->ffmpeg_audio_streams ();
 	_first_video = ref->_first_video;
 	_filters = ref->_filters;
 	_color_range = ref->_color_range;
@@ -156,7 +157,7 @@ FFmpegContent::as_xml (xmlpp::Node* node) const
 	node->add_child("Type")->add_child_text ("FFmpeg");
 	Content::as_xml (node);
 	video->as_xml (node);
-	AudioContent::as_xml (node);
+	audio->as_xml (node);
 	subtitle->as_xml (node);
 
 	boost::mutex::scoped_lock lm (_mutex);
@@ -169,8 +170,10 @@ FFmpegContent::as_xml (xmlpp::Node* node) const
 		(*i)->as_xml (t);
 	}
 
-	for (vector<shared_ptr<FFmpegAudioStream> >::const_iterator i = _audio_streams.begin(); i != _audio_streams.end(); ++i) {
-		(*i)->as_xml (node->add_child("AudioStream"));
+	BOOST_FOREACH (AudioStreamPtr i, audio->streams ()) {
+		shared_ptr<FFmpegAudioStream> f = dynamic_pointer_cast<FFmpegAudioStream> (i);
+		DCPOMATIC_ASSERT (f);
+		f->as_xml (node->add_child("AudioStream"));
 	}
 
 	for (vector<Filter const *>::const_iterator i = _filters.begin(); i != _filters.end(); ++i) {
@@ -209,12 +212,15 @@ FFmpegContent::examine (shared_ptr<Job> job)
 			_subtitle_stream = _subtitle_streams.front ();
 		}
 
-		_audio_streams = examiner->audio_streams ();
+		BOOST_FOREACH (shared_ptr<FFmpegAudioStream> i, examiner->audio_streams ()) {
+			audio->add_stream (i);
+		}
 
-		if (!_audio_streams.empty ()) {
-			AudioMapping m = _audio_streams.front()->mapping ();
+		if (!audio->streams().empty ()) {
+			AudioStreamPtr as = audio->streams().front();
+			AudioMapping m = as->mapping ();
 			film()->make_audio_mapping_default (m);
-			_audio_streams.front()->set_mapping (m);
+			as->set_mapping (m);
 		}
 
 		_first_video = examiner->first_video ();
@@ -228,7 +234,6 @@ FFmpegContent::examine (shared_ptr<Job> job)
 
 	signal_changed (FFmpegContentProperty::SUBTITLE_STREAMS);
 	signal_changed (FFmpegContentProperty::SUBTITLE_STREAM);
-	signal_changed (AudioContentProperty::AUDIO_STREAMS);
 }
 
 string
@@ -259,7 +264,7 @@ FFmpegContent::technical_summary () const
 
 	return Content::technical_summary() + " - "
 		+ video->technical_summary() + " - "
-		+ AudioContent::technical_summary() + " - "
+		+ audio->technical_summary() + " - "
 		+ String::compose (
 			"ffmpeg: audio %1 subtitle %2 filters %3", as, ss, filt
 			);
@@ -403,7 +408,7 @@ FFmpegContent::add_properties (list<UserProperty>& p) const
 {
 	Content::add_properties (p);
 	video->add_properties (p);
-	AudioContent::add_properties (p);
+	audio->add_properties (p);
 
 	if (_bits_per_pixel) {
 		int const sub = 219 * pow (2, _bits_per_pixel.get() - 8);
@@ -528,8 +533,10 @@ FFmpegContent::signal_subtitle_stream_changed ()
 	signal_changed (FFmpegContentProperty::SUBTITLE_STREAM);
 }
 
-double
-FFmpegContent::subtitle_video_frame_rate () const
+void
+FFmpegContent::changed (int property)
 {
-	return video->video_frame_rate ();
+	if (property == VideoContentProperty::VIDEO_FRAME_RATE && subtitle) {
+		subtitle->set_subtitle_video_frame_rate (video->video_frame_rate ());
+	}
 }
diff --git a/src/lib/ffmpeg_content.h b/src/lib/ffmpeg_content.h
index da0eb48af..f39414a61 100644
--- a/src/lib/ffmpeg_content.h
+++ b/src/lib/ffmpeg_content.h
@@ -20,7 +20,8 @@
 #ifndef DCPOMATIC_FFMPEG_CONTENT_H
 #define DCPOMATIC_FFMPEG_CONTENT_H
 
-#include "audio_content.h"
+#include "content.h"
+#include "audio_stream.h"
 
 struct AVFormatContext;
 struct AVStream;
@@ -41,7 +42,7 @@ public:
 	static int const FILTERS;
 };
 
-class FFmpegContent : public AudioContent
+class FFmpegContent : public Content
 {
 public:
 	FFmpegContent (boost::shared_ptr<const Film>, boost::filesystem::path);
@@ -60,19 +61,17 @@ public:
 
 	std::string identifier () const;
 
-	/* VideoContent */
 	void set_default_colour_conversion ();
 
-	/* AudioContent */
 	std::vector<AudioStreamPtr> audio_streams () const;
 
-	/* SubtitleContent */
 	bool has_text_subtitles () const;
 	bool has_image_subtitles () const;
-	double subtitle_video_frame_rate () const;
 
 	void set_filters (std::vector<Filter const *> const &);
 
+	void changed (int property);
+
 	std::vector<boost::shared_ptr<FFmpegSubtitleStream> > subtitle_streams () const {
 		boost::mutex::scoped_lock lm (_mutex);
 		return _subtitle_streams;
@@ -105,10 +104,9 @@ public:
 
 	void signal_subtitle_stream_changed ();
 
-protected:
+private:
 	void add_properties (std::list<UserProperty> &) const;
 
-private:
 	friend struct ffmpeg_pts_offset_test;
 	friend struct audio_sampling_rate_test;
 
diff --git a/src/lib/ffmpeg_decoder.cc b/src/lib/ffmpeg_decoder.cc
index 15cc9b256..8e4a1cc23 100644
--- a/src/lib/ffmpeg_decoder.cc
+++ b/src/lib/ffmpeg_decoder.cc
@@ -73,7 +73,7 @@ using dcp::Size;
 
 FFmpegDecoder::FFmpegDecoder (shared_ptr<const FFmpegContent> c, shared_ptr<Log> log, bool fast)
 	: VideoDecoder (c->video, log)
-	, AudioDecoder (c, fast)
+	, AudioDecoder (c->audio, fast, log)
 	, SubtitleDecoder (c->subtitle)
 	, FFmpeg (c)
 	, _log (log)
diff --git a/src/lib/film.cc b/src/lib/film.cc
index 7d319fc1e..49a0a9b13 100644
--- a/src/lib/film.cc
+++ b/src/lib/film.cc
@@ -245,13 +245,12 @@ Film::audio_analysis_path (shared_ptr<const Playlist> playlist) const
 
 	MD5Digester digester;
 	BOOST_FOREACH (shared_ptr<Content> i, playlist->content ()) {
-		shared_ptr<AudioContent> ac = dynamic_pointer_cast<AudioContent> (i);
-		if (!ac) {
+		if (!i->audio) {
 			continue;
 		}
 
-		digester.add (ac->digest ());
-		digester.add (ac->audio_mapping().digest ());
+		digester.add (i->digest ());
+		digester.add (i->audio->audio_mapping().digest ());
 		if (playlist->content().size() != 1) {
 			/* Analyses should be considered equal regardless of gain
 			   if they were made from just one piece of content.  This
@@ -259,7 +258,7 @@ Film::audio_analysis_path (shared_ptr<const Playlist> playlist) const
 			   analysis at the plotting stage rather than having to
 			   recompute it.
 			*/
-			digester.add (ac->audio_gain ());
+			digester.add (i->audio->audio_gain ());
 		}
 	}
 
@@ -505,9 +504,8 @@ Film::mapped_audio_channels () const
 		}
 	} else {
 		BOOST_FOREACH (shared_ptr<Content> i, content ()) {
-			shared_ptr<const AudioContent> ac = dynamic_pointer_cast<const AudioContent> (i);
-			if (ac) {
-				list<int> c = ac->audio_mapping().mapped_output_channels ();
+			if (i->audio) {
+				list<int> c = i->audio->mapping().mapped_output_channels ();
 				copy (c.begin(), c.end(), back_inserter (mapped));
 			}
 		}
@@ -639,12 +637,11 @@ Film::isdcf_name (bool if_created_now) const
 
 			bool burnt_in = true;
 			BOOST_FOREACH (shared_ptr<Content> i, content ()) {
-				shared_ptr<SubtitleContent> sc = dynamic_pointer_cast<SubtitleContent> (i);
-				if (!sc) {
+				if (!i->subtitle) {
 					continue;
 				}
 
-				if (sc->use_subtitles() && !sc->burn_subtitles()) {
+				if (i->subtitle->use_subtitles() && !i->subtitle->burn_subtitles()) {
 					burnt_in = false;
 				}
 			}
@@ -1033,7 +1030,7 @@ Film::maybe_add_content (weak_ptr<Job> j, weak_ptr<Content> c)
 	}
 
 	add_content (content);
-	if (Config::instance()->automatic_audio_analysis() && dynamic_pointer_cast<AudioContent> (content)) {
+	if (Config::instance()->automatic_audio_analysis() && content->audio) {
 		shared_ptr<Playlist> playlist (new Playlist);
 		playlist->add (content);
 		boost::signals2::connection c;
@@ -1050,7 +1047,7 @@ Film::add_content (shared_ptr<Content> c)
 	/* Add {video,subtitle} content after any existing {video,subtitle} content */
 	if (c->video) {
 		c->set_position (_playlist->video_end ());
-	} else if (dynamic_pointer_cast<SubtitleContent> (c)) {
+	} else if (c->subtitle) {
 		c->set_position (_playlist->subtitle_end ());
 	}
 
@@ -1125,8 +1122,7 @@ int
 Film::audio_frame_rate () const
 {
 	BOOST_FOREACH (shared_ptr<Content> i, content ()) {
-		shared_ptr<AudioContent> a = dynamic_pointer_cast<AudioContent> (i);
-		if (a && a->has_rate_above_48k ()) {
+		if (i->audio && i->audio->has_rate_above_48k ()) {
 			return 96000;
 		}
 	}
@@ -1271,9 +1267,8 @@ Film::subtitle_language () const
 
 	ContentList cl = content ();
 	BOOST_FOREACH (shared_ptr<Content>& c, cl) {
-		shared_ptr<SubtitleContent> sc = dynamic_pointer_cast<SubtitleContent> (c);
-		if (sc) {
-			languages.insert (sc->subtitle_language ());
+		if (c->subtitle) {
+			languages.insert (c->subtitle->subtitle_language ());
 		}
 	}
 
diff --git a/src/lib/player.cc b/src/lib/player.cc
index 9c216c253..ce048ed79 100644
--- a/src/lib/player.cc
+++ b/src/lib/player.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2013-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2013-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -21,6 +21,7 @@
 #include "film.h"
 #include "ffmpeg_decoder.h"
 #include "audio_buffers.h"
+#include "audio_content.h"
 #include "ffmpeg_content.h"
 #include "image_decoder.h"
 #include "image_content.h"
@@ -143,7 +144,7 @@ Player::setup_pieces ()
 		/* SndfileContent */
 		shared_ptr<const SndfileContent> sc = dynamic_pointer_cast<const SndfileContent> (i);
 		if (sc) {
-			decoder.reset (new SndfileDecoder (sc, _fast));
+			decoder.reset (new SndfileDecoder (sc, _fast, _film->log()));
 
 			/* Work out a FrameRateChange for the best overlap video for this content */
 			DCPTime best_overlap_t;
@@ -177,14 +178,14 @@ Player::setup_pieces ()
 		shared_ptr<const TextSubtitleContent> rc = dynamic_pointer_cast<const TextSubtitleContent> (i);
 		if (rc) {
 			decoder.reset (new TextSubtitleDecoder (rc));
-			frc = FrameRateChange (rc->subtitle_video_frame_rate(), _film->video_frame_rate());
+			frc = FrameRateChange (rc->subtitle->subtitle_video_frame_rate(), _film->video_frame_rate());
 		}
 
 		/* DCPSubtitleContent */
 		shared_ptr<const DCPSubtitleContent> dsc = dynamic_pointer_cast<const DCPSubtitleContent> (i);
 		if (dsc) {
 			decoder.reset (new DCPSubtitleDecoder (dsc));
-			frc = FrameRateChange (dsc->subtitle_video_frame_rate(), _film->video_frame_rate());
+			frc = FrameRateChange (dsc->subtitle->subtitle_video_frame_rate(), _film->video_frame_rate());
 		}
 
 		shared_ptr<VideoDecoder> vd = dynamic_pointer_cast<VideoDecoder> (decoder);
@@ -480,9 +481,8 @@ Player::get_audio (DCPTime time, DCPTime length, bool accurate)
 
 	bool all_referenced = true;
 	BOOST_FOREACH (shared_ptr<Piece> i, ov) {
-		shared_ptr<AudioContent> audio_content = dynamic_pointer_cast<AudioContent> (i->content);
 		shared_ptr<DCPContent> dcp_content = dynamic_pointer_cast<DCPContent> (i->content);
-		if (audio_content && (!dcp_content || !dcp_content->reference_audio ())) {
+		if (i->content->audio && (!dcp_content || !dcp_content->reference_audio ())) {
 			/* There is audio content which is not from a DCP or not set to be referenced */
 			all_referenced = false;
 		}
@@ -494,13 +494,12 @@ Player::get_audio (DCPTime time, DCPTime length, bool accurate)
 
 	BOOST_FOREACH (shared_ptr<Piece> i, ov) {
 
-		shared_ptr<AudioContent> content = dynamic_pointer_cast<AudioContent> (i->content);
-		DCPOMATIC_ASSERT (content);
+		DCPOMATIC_ASSERT (i->content->audio);
 		shared_ptr<AudioDecoder> decoder = dynamic_pointer_cast<AudioDecoder> (i->decoder);
 		DCPOMATIC_ASSERT (decoder);
 
 		/* The time that we should request from the content */
-		DCPTime request = time - DCPTime::from_seconds (content->audio_delay() / 1000.0);
+		DCPTime request = time - DCPTime::from_seconds (i->content->audio->audio_delay() / 1000.0);
 		Frame request_frames = length_frames;
 		DCPTime offset;
 		if (request < DCPTime ()) {
@@ -517,7 +516,7 @@ Player::get_audio (DCPTime time, DCPTime length, bool accurate)
 
 		Frame const content_frame = dcp_to_resampled_audio (i, request);
 
-		BOOST_FOREACH (AudioStreamPtr j, content->audio_streams ()) {
+		BOOST_FOREACH (AudioStreamPtr j, i->content->audio->streams ()) {
 
 			if (j->channels() == 0) {
 				/* Some content (e.g. DCPs) can have streams with no channels */
@@ -528,9 +527,9 @@ Player::get_audio (DCPTime time, DCPTime length, bool accurate)
 			ContentAudio all = decoder->get_audio (j, content_frame, request_frames, accurate);
 
 			/* Gain */
-			if (content->audio_gain() != 0) {
+			if (i->content->audio->audio_gain() != 0) {
 				shared_ptr<AudioBuffers> gain (new AudioBuffers (all.audio));
-				gain->apply_gain (content->audio_gain ());
+				gain->apply_gain (i->content->audio->audio_gain ());
 				all.audio = gain;
 			}
 
@@ -572,7 +571,6 @@ Player::get_audio (DCPTime time, DCPTime length, bool accurate)
 Frame
 Player::dcp_to_content_video (shared_ptr<const Piece> piece, DCPTime t) const
 {
-	shared_ptr<const VideoContent> vc = dynamic_pointer_cast<const VideoContent> (piece->content);
 	DCPTime s = t - piece->content->position ();
 	s = min (piece->content->length_after_trim(), s);
 	s = max (DCPTime(), s + DCPTime (piece->content->trim_start(), piece->frc));
@@ -590,7 +588,6 @@ Player::dcp_to_content_video (shared_ptr<const Piece> piece, DCPTime t) const
 DCPTime
 Player::content_video_to_dcp (shared_ptr<const Piece> piece, Frame f) const
 {
-	shared_ptr<const VideoContent> vc = dynamic_pointer_cast<const VideoContent> (piece->content);
 	/* See comment in dcp_to_content_video */
 	DCPTime const d = DCPTime::from_frames (f * piece->frc.factor(), piece->frc.dcp) - DCPTime (piece->content->trim_start (), piece->frc);
 	return max (DCPTime (), d + piece->content->position ());
@@ -704,12 +701,11 @@ Player::get_subtitle_fonts ()
 
 	list<shared_ptr<Font> > fonts;
 	BOOST_FOREACH (shared_ptr<Piece>& p, _pieces) {
-		shared_ptr<SubtitleContent> sc = dynamic_pointer_cast<SubtitleContent> (p->content);
-		if (sc) {
+		if (p->content->subtitle) {
 			/* XXX: things may go wrong if there are duplicate font IDs
 			   with different font files.
 			*/
-			list<shared_ptr<Font> > f = sc->fonts ();
+			list<shared_ptr<Font> > f = p->content->subtitle->fonts ();
 			copy (f.begin(), f.end(), back_inserter (fonts));
 		}
 	}
diff --git a/src/lib/playlist.cc b/src/lib/playlist.cc
index 645993050..092060fa0 100644
--- a/src/lib/playlist.cc
+++ b/src/lib/playlist.cc
@@ -150,12 +150,8 @@ Playlist::video_identifier () const
 	string t;
 
 	BOOST_FOREACH (shared_ptr<const Content> i, _content) {
-		shared_ptr<const VideoContent> vc = dynamic_pointer_cast<const VideoContent> (i);
-		shared_ptr<const SubtitleContent> sc = dynamic_pointer_cast<const SubtitleContent> (i);
-		if (vc) {
-			t += vc->identifier ();
-		} else if (sc && sc->burn_subtitles ()) {
-			t += sc->identifier ();
+		if (i->video || (i->subtitle && i->subtitle->burn_subtitles())) {
+			t += i->identifier ();
 		}
 	}
 
@@ -346,7 +342,7 @@ Playlist::video_end () const
 {
 	DCPTime end;
 	BOOST_FOREACH (shared_ptr<Content> i, _content) {
-		if (dynamic_pointer_cast<const VideoContent> (i)) {
+		if (i->video) {
 			end = max (end, i->end ());
 		}
 	}
@@ -359,7 +355,7 @@ Playlist::subtitle_end () const
 {
 	DCPTime end;
 	BOOST_FOREACH (shared_ptr<Content> i, _content) {
-		if (dynamic_pointer_cast<const SubtitleContent> (i)) {
+		if (i->subtitle) {
 			end = max (end, i->end ());
 		}
 	}
diff --git a/src/lib/sndfile_content.cc b/src/lib/sndfile_content.cc
index d8435613d..d023b27d6 100644
--- a/src/lib/sndfile_content.cc
+++ b/src/lib/sndfile_content.cc
@@ -20,6 +20,7 @@
 #include "sndfile_content.h"
 #include "sndfile_decoder.h"
 #include "sndfile_examiner.h"
+#include "audio_content.h"
 #include "film.h"
 #include "compose.hpp"
 #include "job.h"
@@ -39,18 +40,19 @@ using boost::shared_ptr;
 
 SndfileContent::SndfileContent (shared_ptr<const Film> film, boost::filesystem::path p)
 	: Content (film, p)
-	, AudioContent (film, p)
 {
-
+	audio.reset (new AudioContent (this, film));
 }
 
 SndfileContent::SndfileContent (shared_ptr<const Film> film, cxml::ConstNodePtr node, int version)
 	: Content (film, node)
-	, AudioContent (film, node)
 	, _audio_length (node->number_child<Frame> ("AudioLength"))
-	, _audio_stream (new AudioStream (node->number_child<int> ("AudioFrameRate"), AudioMapping (node->node_child ("AudioMapping"), version)))
 {
-
+	audio.reset (new AudioContent (this, film, node));
+	audio->set_stream (
+		AudioStreamPtr (
+			new AudioStream (node->number_child<int> ("AudioFrameRate"), AudioMapping (node->node_child ("AudioMapping"), version)))
+		);
 }
 
 void
@@ -58,9 +60,9 @@ SndfileContent::as_xml (xmlpp::Node* node) const
 {
 	node->add_child("Type")->add_child_text ("Sndfile");
 	Content::as_xml (node);
-	AudioContent::as_xml (node);
-	node->add_child("AudioFrameRate")->add_child_text (raw_convert<string> (audio_stream()->frame_rate ()));
-	audio_stream()->mapping().as_xml (node->add_child("AudioMapping"));
+	audio->as_xml (node);
+	node->add_child("AudioFrameRate")->add_child_text (raw_convert<string> (audio->stream()->frame_rate ()));
+	audio->stream()->mapping().as_xml (node->add_child("AudioMapping"));
 	node->add_child("AudioLength")->add_child_text (raw_convert<string> (audio_length ()));
 }
 
@@ -76,7 +78,7 @@ string
 SndfileContent::technical_summary () const
 {
 	return Content::technical_summary() + " - "
-		+ AudioContent::technical_summary ()
+		+ audio->technical_summary ()
 		+ " - sndfile";
 }
 
@@ -103,10 +105,11 @@ SndfileContent::take_from_audio_examiner (shared_ptr<AudioExaminer> examiner)
 {
 	{
 		boost::mutex::scoped_lock lm (_mutex);
-		_audio_stream.reset (new AudioStream (examiner->audio_frame_rate(), examiner->audio_channels ()));
-		AudioMapping m = _audio_stream->mapping ();
+		AudioStreamPtr as (new AudioStream (examiner->audio_frame_rate(), examiner->audio_channels ()));
+		audio->set_stream (as);
+		AudioMapping m = as->mapping ();
 		film()->make_audio_mapping_default (m);
-		_audio_stream->set_mapping (m);
+		as->set_mapping (m);
 		_audio_length = examiner->audio_length ();
 	}
 
@@ -116,14 +119,6 @@ SndfileContent::take_from_audio_examiner (shared_ptr<AudioExaminer> examiner)
 DCPTime
 SndfileContent::full_length () const
 {
-	FrameRateChange const frc (audio_video_frame_rate(), film()->video_frame_rate());
-	return DCPTime::from_frames (audio_length() / frc.speed_up, audio_stream()->frame_rate ());
-}
-
-vector<AudioStreamPtr>
-SndfileContent::audio_streams () const
-{
-	vector<AudioStreamPtr> s;
-	s.push_back (_audio_stream);
-	return s;
+	FrameRateChange const frc (audio->audio_video_frame_rate(), film->video_frame_rate());
+	return DCPTime::from_frames (audio_length() / frc.speed_up, audio->stream()->frame_rate ());
 }
diff --git a/src/lib/sndfile_content.h b/src/lib/sndfile_content.h
index 5f89b7cc8..dfd36971d 100644
--- a/src/lib/sndfile_content.h
+++ b/src/lib/sndfile_content.h
@@ -20,11 +20,11 @@
 #ifndef DCPOMATIC_SNDFILE_CONTENT_H
 #define DCPOMATIC_SNDFILE_CONTENT_H
 
-#include "audio_content.h"
+#include "content.h"
 
 class AudioExaminer;
 
-class SndfileContent : public AudioContent
+class SndfileContent : public Content
 {
 public:
 	SndfileContent (boost::shared_ptr<const Film>, boost::filesystem::path);
@@ -44,12 +44,6 @@ public:
 
 	void take_from_audio_examiner (boost::shared_ptr<AudioExaminer>);
 
-	std::vector<AudioStreamPtr> audio_streams () const;
-
-	AudioStreamPtr audio_stream () const {
-		return _audio_stream;
-	}
-
 	static bool valid_file (boost::filesystem::path);
 
 private:
@@ -59,8 +53,6 @@ private:
 	}
 
 	Frame _audio_length;
-
-	boost::shared_ptr<AudioStream> _audio_stream;
 };
 
 #endif
diff --git a/src/lib/sndfile_decoder.cc b/src/lib/sndfile_decoder.cc
index ac01e0da8..b05750ac8 100644
--- a/src/lib/sndfile_decoder.cc
+++ b/src/lib/sndfile_decoder.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,6 +19,7 @@
 
 #include <iostream>
 #include <sndfile.h>
+#include "audio_content.h"
 #include "sndfile_content.h"
 #include "sndfile_decoder.h"
 #include "exceptions.h"
@@ -32,9 +33,9 @@ using std::min;
 using std::cout;
 using boost::shared_ptr;
 
-SndfileDecoder::SndfileDecoder (shared_ptr<const SndfileContent> c, bool fast)
+SndfileDecoder::SndfileDecoder (shared_ptr<const SndfileContent> c, bool fast, shared_ptr<Log> log)
 	: Sndfile (c)
-	, AudioDecoder (c, fast)
+	, AudioDecoder (c->audio, fast, log)
 	, _done (0)
 	, _remaining (_info.frames)
 	, _deinterleave_buffer (0)
@@ -57,14 +58,14 @@ SndfileDecoder::pass (PassReason, bool)
 	/* Do things in half second blocks as I think there may be limits
 	   to what FFmpeg (and in particular the resampler) can cope with.
 	*/
-	sf_count_t const block = _sndfile_content->audio_stream()->frame_rate() / 2;
+	sf_count_t const block = _sndfile_content->audio->stream()->frame_rate() / 2;
 	sf_count_t const this_time = min (block, _remaining);
 
-	int const channels = _sndfile_content->audio_stream()->channels ();
+	int const channels = _sndfile_content->audio->stream()->channels ();
 
 	shared_ptr<AudioBuffers> data (new AudioBuffers (channels, this_time));
 
-	if (_sndfile_content->audio_stream()->channels() == 1) {
+	if (_sndfile_content->audio->stream()->channels() == 1) {
 		/* No de-interleaving required */
 		sf_read_float (_sndfile, data->data(0), this_time);
 	} else {
@@ -86,7 +87,7 @@ SndfileDecoder::pass (PassReason, bool)
 	}
 
 	data->set_frames (this_time);
-	audio (_sndfile_content->audio_stream (), data, ContentTime::from_frames (_done, _info.samplerate));
+	audio (_sndfile_content->audio->stream (), data, ContentTime::from_frames (_done, _info.samplerate));
 	_done += this_time;
 	_remaining -= this_time;
 
diff --git a/src/lib/sndfile_decoder.h b/src/lib/sndfile_decoder.h
index 844d1cdc4..6f3a6cc48 100644
--- a/src/lib/sndfile_decoder.h
+++ b/src/lib/sndfile_decoder.h
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -25,7 +25,7 @@ class SndfileContent;
 class SndfileDecoder : public Sndfile, public AudioDecoder
 {
 public:
-	SndfileDecoder (boost::shared_ptr<const SndfileContent> c, bool fast);
+	SndfileDecoder (boost::shared_ptr<const SndfileContent> c, bool fast, boost::shared_ptr<Log> log);
 	~SndfileDecoder ();
 
 private:
diff --git a/src/lib/subtitle_content.cc b/src/lib/subtitle_content.cc
index 03c188b89..089e3a3fc 100644
--- a/src/lib/subtitle_content.cc
+++ b/src/lib/subtitle_content.cc
@@ -24,6 +24,7 @@
 #include "font.h"
 #include "raw_convert.h"
 #include "content.h"
+#include "film.h"
 #include <libcxml/cxml.h>
 #include <libxml++/libxml++.h>
 #include <boost/foreach.hpp>
@@ -85,6 +86,7 @@ SubtitleContent::SubtitleContent (Content* parent, shared_ptr<const Film> film,
 		node->optional_number_child<int>("OutlineGreen").get_value_or(255),
 		node->optional_number_child<int>("OutlineBlue").get_value_or(255)
 		)
+	, _frame_rate (node->optional_number_child<double>("SubtitleFrameRate"))
 {
 	if (version >= 32) {
 		_use_subtitles = node->bool_child ("UseSubtitles");
@@ -118,38 +120,37 @@ SubtitleContent::SubtitleContent (Content* parent, shared_ptr<const Film> film,
 SubtitleContent::SubtitleContent (Content* parent, shared_ptr<const Film> film, vector<shared_ptr<Content> > c)
 	: ContentPart (parent, film)
 {
-	shared_ptr<SubtitleContent> ref = dynamic_pointer_cast<SubtitleContent> (c[0]);
+	shared_ptr<SubtitleContent> ref = c[0]->subtitle;
 	DCPOMATIC_ASSERT (ref);
 	list<shared_ptr<Font> > ref_fonts = ref->fonts ();
 
-	for (size_t i = 0; i < c.size(); ++i) {
-		shared_ptr<SubtitleContent> sc = dynamic_pointer_cast<SubtitleContent> (c[i]);
+	for (size_t i = 1; i < c.size(); ++i) {
 
-		if (sc->use_subtitles() != ref->use_subtitles()) {
+		if (c[i]->subtitle->use_subtitles() != ref->use_subtitles()) {
 			throw JoinError (_("Content to be joined must have the same 'use subtitles' setting."));
 		}
 
-		if (sc->burn_subtitles() != ref->burn_subtitles()) {
+		if (c[i]->subtitle->burn_subtitles() != ref->burn_subtitles()) {
 			throw JoinError (_("Content to be joined must have the same 'burn subtitles' setting."));
 		}
 
-		if (sc->subtitle_x_offset() != ref->subtitle_x_offset()) {
+		if (c[i]->subtitle->subtitle_x_offset() != ref->subtitle_x_offset()) {
 			throw JoinError (_("Content to be joined must have the same subtitle X offset."));
 		}
 
-		if (sc->subtitle_y_offset() != ref->subtitle_y_offset()) {
+		if (c[i]->subtitle->subtitle_y_offset() != ref->subtitle_y_offset()) {
 			throw JoinError (_("Content to be joined must have the same subtitle Y offset."));
 		}
 
-		if (sc->subtitle_x_scale() != ref->subtitle_x_scale()) {
+		if (c[i]->subtitle->subtitle_x_scale() != ref->subtitle_x_scale()) {
 			throw JoinError (_("Content to be joined must have the same subtitle X scale."));
 		}
 
-		if (sc->subtitle_y_scale() != ref->subtitle_y_scale()) {
+		if (c[i]->subtitle->subtitle_y_scale() != ref->subtitle_y_scale()) {
 			throw JoinError (_("Content to be joined must have the same subtitle Y scale."));
 		}
 
-		list<shared_ptr<Font> > fonts = sc->fonts ();
+		list<shared_ptr<Font> > fonts = c[i]->subtitle->fonts ();
 		if (fonts.size() != ref_fonts.size()) {
 			throw JoinError (_("Content to be joined must use the same fonts."));
 		}
@@ -315,3 +316,27 @@ SubtitleContent::set_subtitle_language (string language)
 {
 	maybe_set (_subtitle_language, language, SubtitleContentProperty::SUBTITLE_LANGUAGE);
 }
+
+void
+SubtitleContent::set_subtitle_video_frame_rate (double r)
+{
+	maybe_set (_frame_rate, r, SubtitleContentProperty::SUBTITLE_VIDEO_FRAME_RATE);
+}
+
+double
+SubtitleContent::subtitle_video_frame_rate () const
+{
+	{
+		boost::mutex::scoped_lock lm (_mutex);
+		if (_frame_rate) {
+			return _frame_rate.get ();
+		}
+	}
+
+	/* No frame rate specified, so assume this content has been
+	   prepared for any concurrent video content.
+	*/
+	shared_ptr<const Film> film = _film.lock ();
+	DCPOMATIC_ASSERT (film);
+	return film->active_frame_rate_change(_parent->position()).source;
+}
diff --git a/src/lib/subtitle_content.h b/src/lib/subtitle_content.h
index 5982cc52c..0adb12c0d 100644
--- a/src/lib/subtitle_content.h
+++ b/src/lib/subtitle_content.h
@@ -130,6 +130,9 @@ public:
 		return _outline_colour;
 	}
 
+	double subtitle_video_frame_rate () const;
+	void set_subtitle_video_frame_rate (double r);
+
 protected:
 	/** subtitle language (e.g. "German") or empty if it is not known */
 	std::string _subtitle_language;
@@ -158,6 +161,8 @@ private:
 	bool _outline;
 	dcp::Colour _outline_colour;
 	std::list<boost::signals2::connection> _font_connections;
+	/** Video frame rate that this content has been prepared for, if known */
+	boost::optional<double> _frame_rate;
 };
 
 #endif
diff --git a/src/lib/text_subtitle_content.cc b/src/lib/text_subtitle_content.cc
index c7dd19d03..79a225c47 100644
--- a/src/lib/text_subtitle_content.cc
+++ b/src/lib/text_subtitle_content.cc
@@ -86,33 +86,6 @@ TextSubtitleContent::as_xml (xmlpp::Node* node) const
 DCPTime
 TextSubtitleContent::full_length () const
 {
-	FrameRateChange const frc (subtitle_video_frame_rate(), film()->video_frame_rate ());
+	FrameRateChange const frc (subtitle->subtitle_video_frame_rate(), film()->video_frame_rate ());
 	return DCPTime (_length, frc);
 }
-
-void
-TextSubtitleContent::set_subtitle_video_frame_rate (double r)
-{
-	{
-		boost::mutex::scoped_lock lm (_mutex);
-		_frame_rate = r;
-	}
-
-	signal_changed (SubtitleContentProperty::SUBTITLE_VIDEO_FRAME_RATE);
-}
-
-double
-TextSubtitleContent::subtitle_video_frame_rate () const
-{
-	{
-		boost::mutex::scoped_lock lm (_mutex);
-		if (_frame_rate) {
-			return _frame_rate.get ();
-		}
-	}
-
-	/* No frame rate specified, so assume this content has been
-	   prepared for any concurrent video content.
-	*/
-	return film()->active_frame_rate_change(position()).source;
-}
diff --git a/src/lib/text_subtitle_content.h b/src/lib/text_subtitle_content.h
index 76440ba9b..61dac4830 100644
--- a/src/lib/text_subtitle_content.h
+++ b/src/lib/text_subtitle_content.h
@@ -40,13 +40,8 @@ public:
 	void as_xml (xmlpp::Node *) const;
 	DCPTime full_length () const;
 
-	double subtitle_video_frame_rate () const;
-	void set_subtitle_video_frame_rate (double r);
-
 	static std::string const font_id;
 
 private:
 	ContentTime _length;
-	/** Video frame rate that this content has been prepared for, if known */
-	boost::optional<double> _frame_rate;
 };
diff --git a/src/lib/transcoder.cc b/src/lib/transcoder.cc
index c018c9243..b7b056612 100644
--- a/src/lib/transcoder.cc
+++ b/src/lib/transcoder.cc
@@ -72,9 +72,8 @@ Transcoder::go ()
 	int burnt_subtitles = 0;
 	int non_burnt_subtitles = 0;
 	BOOST_FOREACH (shared_ptr<const Content> c, _film->content ()) {
-		shared_ptr<const SubtitleContent> sc = dynamic_pointer_cast<const SubtitleContent> (c);
-		if (sc && sc->use_subtitles()) {
-			if (sc->burn_subtitles()) {
+		if (c->subtitle && c->subtitle->use_subtitles()) {
+			if (c->subtitle->burn_subtitles()) {
 				++burnt_subtitles;
 			} else {
 				++non_burnt_subtitles;
diff --git a/src/lib/types.h b/src/lib/types.h
index 2bc6fa3a4..8eabdbf27 100644
--- a/src/lib/types.h
+++ b/src/lib/types.h
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2013 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2013-2016 Carl Hetherington <cth@carlh.net>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -48,7 +48,6 @@ namespace xmlpp {
 #define SERVER_LINK_VERSION (64+0)
 
 typedef std::vector<boost::shared_ptr<Content> > ContentList;
-typedef std::vector<boost::shared_ptr<AudioContent> > AudioContentList;
 typedef std::vector<boost::shared_ptr<FFmpegContent> > FFmpegContentList;
 
 typedef int64_t Frame;
diff --git a/src/lib/video_content.cc b/src/lib/video_content.cc
index 561ebb62c..567ab3cf8 100644
--- a/src/lib/video_content.cc
+++ b/src/lib/video_content.cc
@@ -119,43 +119,42 @@ VideoContent::VideoContent (Content* parent, shared_ptr<const Film> film, vector
 	, _video_length (0)
 	, _yuv (false)
 {
-	shared_ptr<VideoContent> ref = dynamic_pointer_cast<VideoContent> (c[0]);
+	shared_ptr<VideoContent> ref = c[0]->video;
 	DCPOMATIC_ASSERT (ref);
 
-	for (size_t i = 0; i < c.size(); ++i) {
-		shared_ptr<VideoContent> vc = dynamic_pointer_cast<VideoContent> (c[i]);
+	for (size_t i = 1; i < c.size(); ++i) {
 
-		if (vc->video_size() != ref->video_size()) {
+		if (c[i]->video->video_size() != ref->video_size()) {
 			throw JoinError (_("Content to be joined must have the same picture size."));
 		}
 
-		if (vc->video_frame_rate() != ref->video_frame_rate()) {
+		if (c[i]->video->video_frame_rate() != ref->video_frame_rate()) {
 			throw JoinError (_("Content to be joined must have the same video frame rate."));
 		}
 
-		if (vc->video_frame_type() != ref->video_frame_type()) {
+		if (c[i]->video->video_frame_type() != ref->video_frame_type()) {
 			throw JoinError (_("Content to be joined must have the same video frame type."));
 		}
 
-		if (vc->crop() != ref->crop()) {
+		if (c[i]->video->crop() != ref->crop()) {
 			throw JoinError (_("Content to be joined must have the same crop."));
 		}
 
-		if (vc->scale() != ref->scale()) {
+		if (c[i]->video->scale() != ref->scale()) {
 			throw JoinError (_("Content to be joined must have the same scale setting."));
 		}
 
-		if (vc->colour_conversion() != ref->colour_conversion()) {
+		if (c[i]->video->colour_conversion() != ref->colour_conversion()) {
 			throw JoinError (_("Content to be joined must have the same colour conversion."));
 		}
 
-		if (vc->fade_in() != ref->fade_in() || vc->fade_out() != ref->fade_out()) {
+		if (c[i]->video->fade_in() != ref->fade_in() || c[i]->video->fade_out() != ref->fade_out()) {
 			throw JoinError (_("Content to be joined must have the same fades."));
 		}
 
-		_video_length += vc->video_length ();
+		_video_length += c[i]->video->video_length ();
 
-		if (vc->yuv ()) {
+		if (c[i]->video->yuv ()) {
 			_yuv = true;
 		}
 	}