*/
+#include <stdint.h>
#include "player.h"
#include "film.h"
#include "ffmpeg_decoder.h"
#include "ffmpeg_content.h"
-#include "imagemagick_decoder.h"
-#include "imagemagick_content.h"
+#include "still_image_decoder.h"
+#include "still_image_content.h"
#include "sndfile_decoder.h"
#include "sndfile_content.h"
+#include "subtitle_content.h"
#include "playlist.h"
#include "job.h"
+#include "image.h"
+#include "ratio.h"
+#include "log.h"
+#include "scaler.h"
using std::list;
using std::cout;
+using std::min;
+using std::max;
using std::vector;
+using std::pair;
+using std::map;
using boost::shared_ptr;
using boost::weak_ptr;
using boost::dynamic_pointer_cast;
+//#define DEBUG_PLAYER 1
+
+class Piece
+{
+public:
+ Piece (shared_ptr<Content> c)
+ : content (c)
+ , video_position (c->start ())
+ , audio_position (c->start ())
+ {}
+
+ Piece (shared_ptr<Content> c, shared_ptr<Decoder> d)
+ : content (c)
+ , decoder (d)
+ , video_position (c->start ())
+ , audio_position (c->start ())
+ {}
+
+ shared_ptr<Content> content;
+ shared_ptr<Decoder> decoder;
+ Time video_position;
+ Time audio_position;
+};
+
+#ifdef DEBUG_PLAYER
+std::ostream& operator<<(std::ostream& s, Piece const & p)
+{
+ if (dynamic_pointer_cast<FFmpegContent> (p.content)) {
+ s << "\tffmpeg ";
+ } else if (dynamic_pointer_cast<StillImageContent> (p.content)) {
+ s << "\tstill image";
+ } else if (dynamic_pointer_cast<SndfileContent> (p.content)) {
+ s << "\tsndfile ";
+ }
+
+ s << " at " << p.content->start() << " until " << p.content->end();
+
+ return s;
+}
+#endif
+
Player::Player (shared_ptr<const Film> f, shared_ptr<const Playlist> p)
: _film (f)
, _playlist (p)
, _video (true)
, _audio (true)
- , _subtitles (true)
- , _have_valid_decoders (false)
+ , _have_valid_pieces (false)
+ , _video_position (0)
+ , _audio_position (0)
+ , _audio_buffers (f->audio_channels(), 0)
{
_playlist->Changed.connect (bind (&Player::playlist_changed, this));
- _playlist->ContentChanged.connect (bind (&Player::content_changed, this, _1, _2));
+ _playlist->ContentChanged.connect (bind (&Player::content_changed, this, _1, _2, _3));
+ _film->Changed.connect (bind (&Player::film_changed, this, _1));
+ set_video_container_size (_film->container()->size (_film->full_frame ()));
}
void
_audio = false;
}
-void
-Player::disable_subtitles ()
-{
- _subtitles = false;
-}
-
bool
Player::pass ()
{
- if (!_have_valid_decoders) {
- setup_decoders ();
- _have_valid_decoders = true;
+ if (!_have_valid_pieces) {
+ setup_pieces ();
+ _have_valid_pieces = true;
}
-
- bool done = true;
-
- if (_video && _video_decoder < _video_decoders.size ()) {
- /* Run video decoder; this may also produce audio */
-
- if (_video_decoders[_video_decoder]->pass ()) {
- _video_decoder++;
- }
-
- if (_video_decoder < _video_decoders.size ()) {
- done = false;
- }
-
- }
+#ifdef DEBUG_PLAYER
+ cout << "= PASS\n";
+#endif
- if (!_video && _audio && _playlist->audio_from() == Playlist::AUDIO_FFMPEG && _sequential_audio_decoder < _audio_decoders.size ()) {
+ Time earliest_t = TIME_MAX;
+ shared_ptr<Piece> earliest;
+ enum {
+ VIDEO,
+ AUDIO
+ } type = VIDEO;
- /* We're not producing video, so we may need to run FFmpeg content to get the audio */
-
- if (_audio_decoders[_sequential_audio_decoder]->pass ()) {
- _sequential_audio_decoder++;
+ for (list<shared_ptr<Piece> >::iterator i = _pieces.begin(); i != _pieces.end(); ++i) {
+ if ((*i)->decoder->done ()) {
+ continue;
}
-
- if (_sequential_audio_decoder < _audio_decoders.size ()) {
- done = false;
+
+ if (_video && dynamic_pointer_cast<VideoDecoder> ((*i)->decoder)) {
+ if ((*i)->video_position < earliest_t) {
+ earliest_t = (*i)->video_position;
+ earliest = *i;
+ type = VIDEO;
+ }
}
-
- }
- if (_audio && _playlist->audio_from() == Playlist::AUDIO_SNDFILE) {
-
- /* We're getting audio from SndfileContent */
-
- for (vector<shared_ptr<AudioDecoder> >::iterator i = _audio_decoders.begin(); i != _audio_decoders.end(); ++i) {
- if (!(*i)->pass ()) {
- done = false;
+ if (_audio && dynamic_pointer_cast<AudioDecoder> ((*i)->decoder)) {
+ if ((*i)->audio_position < earliest_t) {
+ earliest_t = (*i)->audio_position;
+ earliest = *i;
+ type = AUDIO;
}
}
+ }
- Audio (_audio_buffers, _audio_time.get());
- _audio_buffers.reset ();
- _audio_time = boost::none;
+ if (!earliest) {
+#ifdef DEBUG_PLAYER
+ cout << "no earliest piece.\n";
+#endif
+
+ flush ();
+ return true;
}
- return done;
+ switch (type) {
+ case VIDEO:
+ if (earliest_t > _video_position) {
+#ifdef DEBUG_PLAYER
+ cout << "no video here; emitting black frame (earliest=" << earliest_t << ", video_position=" << _video_position << ").\n";
+#endif
+ emit_black ();
+ } else {
+#ifdef DEBUG_PLAYER
+ cout << "Pass " << *earliest << "\n";
+#endif
+ earliest->decoder->pass ();
+ }
+ break;
+
+ case AUDIO:
+ if (earliest_t > _audio_position) {
+#ifdef DEBUG_PLAYER
+ cout << "no audio here; emitting silence.\n";
+#endif
+ emit_silence (_film->time_to_audio_frames (earliest_t - _audio_position));
+ } else {
+#ifdef DEBUG_PLAYER
+ cout << "Pass " << *earliest << "\n";
+#endif
+ earliest->decoder->pass ();
+ }
+ break;
+ }
+
+#ifdef DEBUG_PLAYER
+ cout << "\tpost pass " << _video_position << " " << _audio_position << "\n";
+#endif
+
+ return false;
}
void
-Player::set_progress (shared_ptr<Job> job)
+Player::process_video (weak_ptr<Piece> weak_piece, shared_ptr<const Image> image, Eyes eyes, bool same, VideoContent::Frame frame)
{
- /* Assume progress can be divined from how far through the video we are */
+ shared_ptr<Piece> piece = weak_piece.lock ();
+ if (!piece) {
+ return;
+ }
+
+ shared_ptr<VideoContent> content = dynamic_pointer_cast<VideoContent> (piece->content);
+ assert (content);
- if (_video_decoder >= _video_decoders.size() || !_playlist->video_length()) {
+ FrameRateConversion frc (content->video_frame_rate(), _film->video_frame_rate());
+ if (frc.skip && (frame % 2) == 1) {
return;
}
- job->set_progress ((_video_start[_video_decoder] + _video_decoders[_video_decoder]->video_frame()) / _playlist->video_length ());
-}
+ shared_ptr<Image> work_image = image->crop (content->crop(), true);
-void
-Player::process_video (shared_ptr<const Image> i, bool same, shared_ptr<Subtitle> s, double t)
-{
- Video (i, same, s, _video_start[_video_decoder] + t);
-}
+ libdcp::Size const image_size = content->ratio()->size (_video_container_size);
+
+ work_image = work_image->scale_and_convert_to_rgb (image_size, _film->scaler(), true);
-void
-Player::process_audio (weak_ptr<const AudioContent> c, shared_ptr<const AudioBuffers> b, double t)
-{
- AudioMapping mapping = _film->audio_mapping ();
- if (!_audio_buffers) {
- _audio_buffers.reset (new AudioBuffers (mapping.dcp_channels(), b->frames ()));
- _audio_buffers->make_silent ();
- _audio_time = t;
- if (_playlist->audio_from() == Playlist::AUDIO_FFMPEG) {
- _audio_time = _audio_time.get() + _audio_start[_sequential_audio_decoder];
- }
+ Time time = content->start() + (frame * frc.factor() * TIME_HZ / _film->video_frame_rate());
+
+ if (_film->with_subtitles () && _out_subtitle.image && time >= _out_subtitle.from && time <= _out_subtitle.to) {
+ work_image->alpha_blend (_out_subtitle.image, _out_subtitle.position);
}
- for (int i = 0; i < b->channels(); ++i) {
- list<libdcp::Channel> dcp = mapping.content_to_dcp (AudioMapping::Channel (c, i));
- for (list<libdcp::Channel>::iterator j = dcp.begin(); j != dcp.end(); ++j) {
- _audio_buffers->accumulate (b, i, static_cast<int> (*j));
- }
+ if (image_size != _video_container_size) {
+ assert (image_size.width <= _video_container_size.width);
+ assert (image_size.height <= _video_container_size.height);
+ shared_ptr<Image> im (new Image (PIX_FMT_RGB24, _video_container_size, true));
+ im->make_black ();
+ im->copy (work_image, Position<int> ((_video_container_size.width - image_size.width) / 2, (_video_container_size.height - image_size.height) / 2));
+ work_image = im;
}
- if (_playlist->audio_from() == Playlist::AUDIO_FFMPEG) {
- /* We can just emit this audio now as it will all be here */
- Audio (_audio_buffers, t);
- _audio_buffers.reset ();
- _audio_time = boost::none;
+#ifdef DCPOMATIC_DEBUG
+ _last_video = piece->content;
+#endif
+
+ Video (work_image, eyes, same, time);
+ time += TIME_HZ / _film->video_frame_rate();
+
+ if (frc.repeat) {
+ Video (work_image, eyes, true, time);
+ time += TIME_HZ / _film->video_frame_rate();
}
+
+ _video_position = piece->video_position = time;
}
-/** @return true on error */
-bool
-Player::seek (double t)
+void
+Player::process_audio (weak_ptr<Piece> weak_piece, shared_ptr<const AudioBuffers> audio, AudioContent::Frame frame)
{
- if (!_have_valid_decoders) {
- setup_decoders ();
- _have_valid_decoders = true;
+ shared_ptr<Piece> piece = weak_piece.lock ();
+ if (!piece) {
+ return;
}
- if (_video_decoders.empty ()) {
- return true;
- }
+ shared_ptr<AudioContent> content = dynamic_pointer_cast<AudioContent> (piece->content);
+ assert (content);
- /* Find the decoder that contains this position */
- _video_decoder = 0;
- while (1) {
- ++_video_decoder;
- if (_video_decoder >= _video_decoders.size () || t < _video_start[_video_decoder]) {
- --_video_decoder;
- t -= _video_start[_video_decoder];
- break;
+ /* Remap channels */
+ shared_ptr<AudioBuffers> dcp_mapped (new AudioBuffers (_film->audio_channels(), audio->frames()));
+ dcp_mapped->make_silent ();
+ list<pair<int, libdcp::Channel> > map = content->audio_mapping().content_to_dcp ();
+ for (list<pair<int, libdcp::Channel> >::iterator i = map.begin(); i != map.end(); ++i) {
+ if (i->first < audio->channels() && i->second < dcp_mapped->channels()) {
+ dcp_mapped->accumulate_channel (audio.get(), i->first, i->second);
}
}
- if (_video_decoder < _video_decoders.size()) {
- _video_decoders[_video_decoder]->seek (t);
- } else {
- return true;
+ audio = dcp_mapped;
+
+ Time time = content->start()
+ + _film->audio_frames_to_time (frame)
+ + (content->audio_delay() * TIME_HZ / 1000);
+
+ /* We must cut off anything that comes before the start of all time */
+ if (time < 0) {
+ int const frames = - time * _film->audio_frame_rate() / TIME_HZ;
+ if (frames >= audio->frames ()) {
+ return;
+ }
+
+ shared_ptr<AudioBuffers> trimmed (new AudioBuffers (audio->channels(), audio->frames() - frames));
+ trimmed->copy_from (audio.get(), audio->frames() - frames, frames, 0);
+
+ audio = trimmed;
+ time = 0;
}
- /* XXX: don't seek audio because we don't need to... */
+ /* The time of this audio may indicate that some of our buffered audio is not going to
+ be added to any more, so it can be emitted.
+ */
+
+ if (time > _audio_position) {
+ /* We can emit some audio from our buffers; this is how many frames */
+ OutputAudioFrame const N = _film->time_to_audio_frames (time - _audio_position);
+ if (N > _audio_buffers.frames()) {
+ /* We need some extra silence before whatever is in the buffers */
+ _audio_buffers.ensure_size (N);
+ _audio_buffers.move (0, N - _audio_buffers.frames(), _audio_buffers.frames ());
+ _audio_buffers.make_silent (0, _audio_buffers.frames());
+ _audio_buffers.set_frames (N);
+ }
+ assert (N <= _audio_buffers.frames());
- return false;
-}
+ /* XXX: not convinced that a copy is necessary here */
+ shared_ptr<AudioBuffers> emit (new AudioBuffers (_audio_buffers.channels(), N));
+ emit->copy_from (&_audio_buffers, N, 0, 0);
+ Audio (emit, _audio_position);
+ _audio_position = piece->audio_position = _audio_position + _film->audio_frames_to_time (N);
+ /* And remove it from our buffers */
+ if (_audio_buffers.frames() > N) {
+ _audio_buffers.move (N, 0, _audio_buffers.frames() - N);
+ }
+ _audio_buffers.set_frames (_audio_buffers.frames() - N);
+ }
+
+ /* Now accumulate the new audio into our buffers */
+ _audio_buffers.ensure_size (_audio_buffers.frames() + audio->frames());
+ _audio_buffers.accumulate_frames (audio.get(), 0, 0, audio->frames ());
+ _audio_buffers.set_frames (_audio_buffers.frames() + audio->frames());
+}
void
-Player::seek_back ()
+Player::flush ()
{
- /* XXX */
+ if (_audio_buffers.frames() > 0) {
+ shared_ptr<AudioBuffers> emit (new AudioBuffers (_audio_buffers.channels(), _audio_buffers.frames()));
+ emit->copy_from (&_audio_buffers, _audio_buffers.frames(), 0, 0);
+ Audio (emit, _audio_position);
+ _audio_position += _film->audio_frames_to_time (_audio_buffers.frames ());
+ _audio_buffers.set_frames (0);
+ }
+
+ while (_video_position < _audio_position) {
+ emit_black ();
+ }
+
+ while (_audio_position < _video_position) {
+ emit_silence (_film->time_to_audio_frames (_video_position - _audio_position));
+ }
+
}
+/** Seek so that the next pass() will yield (approximately) the requested frame.
+ * Pass accurate = true to try harder to get close to the request.
+ * @return true on error
+ */
void
-Player::seek_forward ()
+Player::seek (Time t, bool accurate)
{
- /* XXX */
-}
+ if (!_have_valid_pieces) {
+ setup_pieces ();
+ _have_valid_pieces = true;
+ }
+
+ if (_pieces.empty ()) {
+ return;
+ }
+
+ for (list<shared_ptr<Piece> >::iterator i = _pieces.begin(); i != _pieces.end(); ++i) {
+ shared_ptr<VideoContent> vc = dynamic_pointer_cast<VideoContent> ((*i)->content);
+ if (!vc) {
+ continue;
+ }
+
+ Time s = t - vc->start ();
+ s = max (static_cast<Time> (0), s);
+ s = min (vc->length(), s);
+
+ (*i)->video_position = (*i)->audio_position = vc->start() + s;
+
+ FrameRateConversion frc (vc->video_frame_rate(), _film->video_frame_rate());
+ /* Here we are converting from time (in the DCP) to a frame number in the content.
+ Hence we need to use the DCP's frame rate and the double/skip correction, not
+ the source's rate.
+ */
+ VideoContent::Frame f = s * _film->video_frame_rate() / (frc.factor() * TIME_HZ);
+ dynamic_pointer_cast<VideoDecoder>((*i)->decoder)->seek (f, accurate);
+ }
+ _video_position = _audio_position = t;
+
+ /* XXX: don't seek audio because we don't need to... */
+}
void
-Player::setup_decoders ()
+Player::setup_pieces ()
{
- _video_decoders.clear ();
- _video_decoder = 0;
- _audio_decoders.clear ();
- _sequential_audio_decoder = 0;
+ list<shared_ptr<Piece> > old_pieces = _pieces;
- _video_start.clear();
- _audio_start.clear();
+ _pieces.clear ();
+
+ ContentList content = _playlist->content ();
+ sort (content.begin(), content.end(), ContentSorter ());
+
+ for (ContentList::iterator i = content.begin(); i != content.end(); ++i) {
+
+ shared_ptr<Piece> piece (new Piece (*i));
- double video_so_far = 0;
- double audio_so_far = 0;
-
- list<shared_ptr<const VideoContent> > vc = _playlist->video ();
- for (list<shared_ptr<const VideoContent> >::iterator i = vc.begin(); i != vc.end(); ++i) {
-
- shared_ptr<const VideoContent> video_content;
- shared_ptr<const AudioContent> audio_content;
- shared_ptr<VideoDecoder> video_decoder;
- shared_ptr<AudioDecoder> audio_decoder;
-
/* XXX: into content? */
-
+
shared_ptr<const FFmpegContent> fc = dynamic_pointer_cast<const FFmpegContent> (*i);
if (fc) {
- shared_ptr<FFmpegDecoder> fd (
- new FFmpegDecoder (
- _film, fc, _video,
- _audio && _playlist->audio_from() == Playlist::AUDIO_FFMPEG,
- _subtitles
- )
- );
+ shared_ptr<FFmpegDecoder> fd (new FFmpegDecoder (_film, fc, _video, _audio));
- video_content = fc;
- audio_content = fc;
- video_decoder = fd;
- audio_decoder = fd;
+ fd->Video.connect (bind (&Player::process_video, this, piece, _1, _2, _3, _4));
+ fd->Audio.connect (bind (&Player::process_audio, this, piece, _1, _2));
+ fd->Subtitle.connect (bind (&Player::process_subtitle, this, piece, _1, _2, _3, _4));
+
+ piece->decoder = fd;
}
- shared_ptr<const ImageMagickContent> ic = dynamic_pointer_cast<const ImageMagickContent> (*i);
+ shared_ptr<const StillImageContent> ic = dynamic_pointer_cast<const StillImageContent> (*i);
if (ic) {
- video_content = ic;
- video_decoder.reset (new ImageMagickDecoder (_film, ic));
- }
-
- video_decoder->connect_video (shared_from_this ());
- _video_decoders.push_back (video_decoder);
- _video_start.push_back (video_so_far);
- video_so_far += video_content->video_length() / video_content->video_frame_rate();
-
- if (audio_decoder && _playlist->audio_from() == Playlist::AUDIO_FFMPEG) {
- audio_decoder->Audio.connect (bind (&Player::process_audio, this, audio_content, _1, _2));
- _audio_decoders.push_back (audio_decoder);
- _audio_start.push_back (audio_so_far);
- audio_so_far += double(audio_content->audio_length()) / audio_content->audio_frame_rate();
+ shared_ptr<StillImageDecoder> id;
+
+ /* See if we can re-use an old StillImageDecoder */
+ for (list<shared_ptr<Piece> >::const_iterator j = old_pieces.begin(); j != old_pieces.end(); ++j) {
+ shared_ptr<StillImageDecoder> imd = dynamic_pointer_cast<StillImageDecoder> ((*j)->decoder);
+ if (imd && imd->content() == ic) {
+ id = imd;
+ }
+ }
+
+ if (!id) {
+ id.reset (new StillImageDecoder (_film, ic));
+ id->Video.connect (bind (&Player::process_video, this, piece, _1, _2, _3, _4));
+ }
+
+ piece->decoder = id;
}
- }
-
- _video_decoder = 0;
- _sequential_audio_decoder = 0;
- if (_playlist->audio_from() == Playlist::AUDIO_SNDFILE) {
-
- list<shared_ptr<const AudioContent> > ac = _playlist->audio ();
- for (list<shared_ptr<const AudioContent> >::iterator i = ac.begin(); i != ac.end(); ++i) {
-
- shared_ptr<const SndfileContent> sc = dynamic_pointer_cast<const SndfileContent> (*i);
- assert (sc);
-
- shared_ptr<AudioDecoder> d (new SndfileDecoder (_film, sc));
- d->Audio.connect (bind (&Player::process_audio, this, sc, _1, _2));
- _audio_decoders.push_back (d);
- _audio_start.push_back (audio_so_far);
+ shared_ptr<const SndfileContent> sc = dynamic_pointer_cast<const SndfileContent> (*i);
+ if (sc) {
+ shared_ptr<AudioDecoder> sd (new SndfileDecoder (_film, sc));
+ sd->Audio.connect (bind (&Player::process_audio, this, piece, _1, _2));
+
+ piece->decoder = sd;
}
+
+ _pieces.push_back (piece);
}
-}
-double
-Player::last_video_time () const
-{
- return _video_start[_video_decoder] + _video_decoders[_video_decoder]->last_content_time ();
+#ifdef DEBUG_PLAYER
+ cout << "=== Player setup:\n";
+ for (list<shared_ptr<Piece> >::iterator i = _pieces.begin(); i != _pieces.end(); ++i) {
+ cout << *(i->get()) << "\n";
+ }
+#endif
}
void
-Player::content_changed (weak_ptr<Content> w, int p)
+Player::content_changed (weak_ptr<Content> w, int property, bool frequent)
{
shared_ptr<Content> c = w.lock ();
if (!c) {
return;
}
- if (p == VideoContentProperty::VIDEO_LENGTH) {
- if (dynamic_pointer_cast<FFmpegContent> (c)) {
- /* FFmpeg content length changes are serious; we need new decoders */
- _have_valid_decoders = false;
- }
+ if (
+ property == ContentProperty::START || property == ContentProperty::LENGTH ||
+ property == VideoContentProperty::VIDEO_CROP || property == VideoContentProperty::VIDEO_RATIO
+ ) {
+
+ _have_valid_pieces = false;
+ Changed (frequent);
+
+ } else if (property == SubtitleContentProperty::SUBTITLE_OFFSET || property == SubtitleContentProperty::SUBTITLE_SCALE) {
+ update_subtitle ();
+ Changed (frequent);
+ } else if (property == VideoContentProperty::VIDEO_FRAME_TYPE) {
+ Changed (frequent);
}
}
void
Player::playlist_changed ()
{
- _have_valid_decoders = false;
+ _have_valid_pieces = false;
+ Changed (false);
+}
+
+void
+Player::set_video_container_size (libdcp::Size s)
+{
+ _video_container_size = s;
+ _black_frame.reset (new Image (PIX_FMT_RGB24, _video_container_size, true));
+ _black_frame->make_black ();
+}
+
+void
+Player::emit_black ()
+{
+#ifdef DCPOMATIC_DEBUG
+ _last_video.reset ();
+#endif
+
+ /* XXX: use same here */
+ Video (_black_frame, EYES_BOTH, false, _video_position);
+ _video_position += _film->video_frames_to_time (1);
+}
+
+void
+Player::emit_silence (OutputAudioFrame most)
+{
+ OutputAudioFrame N = min (most, _film->audio_frame_rate() / 2);
+ shared_ptr<AudioBuffers> silence (new AudioBuffers (_film->audio_channels(), N));
+ silence->make_silent ();
+ Audio (silence, _audio_position);
+ _audio_position += _film->audio_frames_to_time (N);
+}
+
+void
+Player::film_changed (Film::Property p)
+{
+ /* Here we should notice Film properties that affect our output, and
+ alert listeners that our output now would be different to how it was
+ last time we were run.
+ */
+
+ if (p == Film::SCALER || p == Film::WITH_SUBTITLES || p == Film::CONTAINER) {
+ Changed (false);
+ }
+}
+
+void
+Player::process_subtitle (weak_ptr<Piece> weak_piece, shared_ptr<Image> image, dcpomatic::Rect<double> rect, Time from, Time to)
+{
+ _in_subtitle.piece = weak_piece;
+ _in_subtitle.image = image;
+ _in_subtitle.rect = rect;
+ _in_subtitle.from = from;
+ _in_subtitle.to = to;
+
+ update_subtitle ();
+}
+
+void
+Player::update_subtitle ()
+{
+ shared_ptr<Piece> piece = _in_subtitle.piece.lock ();
+ if (!piece) {
+ return;
+ }
+
+ if (!_in_subtitle.image) {
+ _out_subtitle.image.reset ();
+ return;
+ }
+
+ shared_ptr<SubtitleContent> sc = dynamic_pointer_cast<SubtitleContent> (piece->content);
+ assert (sc);
+
+ dcpomatic::Rect<double> in_rect = _in_subtitle.rect;
+ libdcp::Size scaled_size;
+
+ in_rect.y += sc->subtitle_offset ();
+
+ /* We will scale the subtitle up to fit _video_container_size, and also by the additional subtitle_scale */
+ scaled_size.width = in_rect.width * _video_container_size.width * sc->subtitle_scale ();
+ scaled_size.height = in_rect.height * _video_container_size.height * sc->subtitle_scale ();
+
+ /* Then we need a corrective translation, consisting of two parts:
+ *
+ * 1. that which is the result of the scaling of the subtitle by _video_container_size; this will be
+ * rect.x * _video_container_size.width and rect.y * _video_container_size.height.
+ *
+ * 2. that to shift the origin of the scale by subtitle_scale to the centre of the subtitle; this will be
+ * (width_before_subtitle_scale * (1 - subtitle_scale) / 2) and
+ * (height_before_subtitle_scale * (1 - subtitle_scale) / 2).
+ *
+ * Combining these two translations gives these expressions.
+ */
+
+ _out_subtitle.position.x = rint (_video_container_size.width * (in_rect.x + (in_rect.width * (1 - sc->subtitle_scale ()) / 2)));
+ _out_subtitle.position.y = rint (_video_container_size.height * (in_rect.y + (in_rect.height * (1 - sc->subtitle_scale ()) / 2)));
+
+ _out_subtitle.image = _in_subtitle.image->scale (libdcp::Size (scaled_size.width, scaled_size.height), Scaler::from_id ("bicubic"), true);
+ _out_subtitle.from = _in_subtitle.from + piece->content->start ();
+ _out_subtitle.to = _in_subtitle.to + piece->content->start ();
}