Attempts to simplify black-filling logic in Player.
[dcpomatic.git] / src / lib / player.cc
index 1e0a6dcf03b6044fc1dda191217cdf72d85834a1..32c0026b610b4596dbde9ee57024ae4985a7d3e3 100644 (file)
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2013-2016 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2013-2017 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -47,6 +47,7 @@
 #include "content_subtitle.h"
 #include "dcp_decoder.h"
 #include "image_decoder.h"
+#include "compose.hpp"
 #include <dcp/reel.h>
 #include <dcp/reel_sound_asset.h>
 #include <dcp/reel_subtitle_asset.h>
@@ -76,24 +77,6 @@ using boost::dynamic_pointer_cast;
 using boost::optional;
 using boost::scoped_ptr;
 
-static bool
-has_video (Content* c)
-{
-       return static_cast<bool>(c->video);
-}
-
-static bool
-has_audio (Content* c)
-{
-       return static_cast<bool>(c->audio);
-}
-
-static bool
-has_subtitle (Content* c)
-{
-       return static_cast<bool>(c->subtitle);
-}
-
 Player::Player (shared_ptr<const Film> film, shared_ptr<const Playlist> playlist)
        : _film (film)
        , _playlist (playlist)
@@ -103,7 +86,7 @@ Player::Player (shared_ptr<const Film> film, shared_ptr<const Playlist> playlist
        , _always_burn_subtitles (false)
        , _fast (false)
        , _play_referenced (false)
-       , _audio_merger (_film->audio_channels(), _film->audio_frame_rate())
+       , _audio_merger (_film->audio_frame_rate())
 {
        _film_changed_connection = _film->Changed.connect (bind (&Player::film_changed, this, _1));
        _playlist_changed_connection = _playlist->Changed.connect (bind (&Player::playlist_changed, this));
@@ -111,6 +94,8 @@ Player::Player (shared_ptr<const Film> film, shared_ptr<const Playlist> playlist
        set_video_container_size (_film->frame_size ());
 
        film_changed (Film::AUDIO_PROCESSOR);
+
+       seek (DCPTime (), true);
 }
 
 void
@@ -140,10 +125,6 @@ Player::setup_pieces ()
                        decoder->audio->set_ignore ();
                }
 
-               if (decoder->audio && _fast) {
-                       decoder->audio->set_fast ();
-               }
-
                shared_ptr<DCPDecoder> dcp = dynamic_pointer_cast<DCPDecoder> (decoder);
                if (dcp && _play_referenced) {
                        dcp->set_decode_referenced ();
@@ -161,11 +142,36 @@ Player::setup_pieces ()
                }
 
                if (decoder->subtitle) {
-                       decoder->subtitle->ImageData.connect (bind (&Player::image_subtitle, this, weak_ptr<Piece> (piece), _1));
-                       decoder->subtitle->TextData.connect (bind (&Player::text_subtitle, this, weak_ptr<Piece> (piece), _1));
+                       decoder->subtitle->ImageStart.connect (bind (&Player::image_subtitle_start, this, weak_ptr<Piece> (piece), _1));
+                       decoder->subtitle->TextStart.connect (bind (&Player::text_subtitle_start, this, weak_ptr<Piece> (piece), _1));
+                       decoder->subtitle->Stop.connect (bind (&Player::subtitle_stop, this, weak_ptr<Piece> (piece), _1));
                }
        }
 
+       BOOST_FOREACH (shared_ptr<Piece> i, _pieces) {
+               if (i->content->audio) {
+                       BOOST_FOREACH (AudioStreamPtr j, i->content->audio->streams()) {
+                               _stream_states[j] = StreamState (i, i->content->position ());
+                       }
+               }
+       }
+
+       if (!_play_referenced) {
+               BOOST_FOREACH (shared_ptr<Piece> i, _pieces) {
+                       shared_ptr<DCPContent> dc = dynamic_pointer_cast<DCPContent> (i->content);
+                       if (dc) {
+                               if (dc->reference_video()) {
+                                       _no_video.push_back (DCPTimePeriod (dc->position(), dc->end()));
+                               }
+                               if (dc->reference_audio()) {
+                                       _no_audio.push_back (DCPTimePeriod (dc->position(), dc->end()));
+                               }
+                       }
+               }
+       }
+
+       _last_video_time = DCPTime ();
+       _last_audio_time = DCPTime ();
        _have_valid_pieces = true;
 }
 
@@ -222,10 +228,16 @@ Player::playlist_content_changed (weak_ptr<Content> w, int property, bool freque
 void
 Player::set_video_container_size (dcp::Size s)
 {
+       if (s == _video_container_size) {
+               return;
+       }
+
        _video_container_size = s;
 
        _black_image.reset (new Image (AV_PIX_FMT_RGB24, _video_container_size, true));
        _black_image->make_black ();
+
+       Changed (false);
 }
 
 void
@@ -304,12 +316,11 @@ Player::transform_image_subtitles (list<ImageSubtitle> subs) const
 }
 
 shared_ptr<PlayerVideo>
-Player::black_player_video_frame (DCPTime time) const
+Player::black_player_video_frame () const
 {
        return shared_ptr<PlayerVideo> (
                new PlayerVideo (
                        shared_ptr<const ImageProxy> (new RawImageProxy (_black_image)),
-                       time,
                        Crop (),
                        optional<double> (),
                        _video_container_size,
@@ -359,12 +370,12 @@ DCPTime
 Player::resampled_audio_to_dcp (shared_ptr<const Piece> piece, Frame f) const
 {
        /* See comment in dcp_to_content_video */
-       DCPTime const d = DCPTime::from_frames (f, _film->audio_frame_rate()) - DCPTime (piece->content->trim_start (), piece->frc);
+       DCPTime const d = DCPTime::from_frames (f, _film->audio_frame_rate()) - DCPTime (piece->content->trim_start(), piece->frc);
        return max (DCPTime (), d + piece->content->position ());
 }
 
 ContentTime
-Player::dcp_to_content_subtitle (shared_ptr<const Piece> piece, DCPTime t) const
+Player::dcp_to_content_time (shared_ptr<const Piece> piece, DCPTime t) const
 {
        DCPTime s = t - piece->content->position ();
        s = min (piece->content->length_after_trim(), s);
@@ -372,7 +383,7 @@ Player::dcp_to_content_subtitle (shared_ptr<const Piece> piece, DCPTime t) const
 }
 
 DCPTime
-Player::content_subtitle_to_dcp (shared_ptr<const Piece> piece, ContentTime t) const
+Player::content_time_to_dcp (shared_ptr<const Piece> piece, ContentTime t) const
 {
        return max (DCPTime (), DCPTime (t - piece->content->trim_start(), piece->frc) + piece->content->position());
 }
@@ -405,13 +416,6 @@ Player::set_ignore_video ()
        _ignore_video = true;
 }
 
-/** Set this player never to produce any audio data */
-void
-Player::set_ignore_audio ()
-{
-       _ignore_audio = true;
-}
-
 /** Set whether or not this player should always burn text subtitles into the image,
  *  regardless of the content settings.
  *  @param burn true to always burn subtitles, false to obey content settings.
@@ -502,43 +506,114 @@ Player::get_reel_assets ()
        return a;
 }
 
-list<shared_ptr<Piece> >
-Player::overlaps (DCPTime from, DCPTime to, boost::function<bool (Content *)> valid)
+bool
+Player::pass ()
 {
        if (!_have_valid_pieces) {
                setup_pieces ();
        }
 
-       list<shared_ptr<Piece> > overlaps;
+       bool filled = false;
+
+       if (_last_video_time && !_playlist->video_content_at(*_last_video_time) && *_last_video_time < _playlist->length()) {
+               /* _last_video_time is the time just after the last video we emitted, and there is no video content
+                  at this time so we need to emit some black.
+               */
+               emit_video (black_player_video_frame(), *_last_video_time);
+               filled = true;
+       } else if (_playlist->length() == DCPTime()) {
+               /* Special case of an empty Film; just give one black frame */
+               emit_video (black_player_video_frame(), DCPTime());
+               filled = true;
+       }
+
+       if (_last_audio_time && !_playlist->audio_content_at(*_last_audio_time) && *_last_audio_time < _playlist->length()) {
+               /* _last_audio_time is the time just after the last audio we emitted.  There is no audio here
+                  so we need to emit some silence.
+               */
+               shared_ptr<Content> next = _playlist->next_audio_content(*_last_audio_time);
+               DCPTimePeriod period (*_last_audio_time, next ? next->position() : _playlist->length());
+               if (period.duration() > one_video_frame()) {
+                       period = DCPTimePeriod (*_last_audio_time, *_last_audio_time + one_video_frame());
+               }
+               fill_audio (period);
+               filled = true;
+       }
+
+       /* Now pass() the decoder which is farthest behind where we are */
+
+       shared_ptr<Piece> earliest;
+       DCPTime earliest_content;
+
        BOOST_FOREACH (shared_ptr<Piece> i, _pieces) {
-               if (valid (i->content.get ()) && i->content->position() < to && i->content->end() > from) {
-                       overlaps.push_back (i);
+               if (!i->done) {
+                       DCPTime const t = content_time_to_dcp (i, i->decoder->position());
+                       if (!earliest || t < earliest_content) {
+                               earliest_content = t;
+                               earliest = i;
+                       }
                }
        }
 
-       return overlaps;
+       if (!filled && earliest) {
+               earliest->done = earliest->decoder->pass ();
+       }
+
+       /* Emit any audio that is ready */
+
+       DCPTime pull_to = _playlist->length ();
+       for (map<AudioStreamPtr, StreamState>::const_iterator i = _stream_states.begin(); i != _stream_states.end(); ++i) {
+               if (!i->second.piece->done && i->second.last_push_end < pull_to) {
+                       pull_to = i->second.last_push_end;
+               }
+       }
+
+       list<pair<shared_ptr<AudioBuffers>, DCPTime> > audio = _audio_merger.pull (pull_to);
+       for (list<pair<shared_ptr<AudioBuffers>, DCPTime> >::iterator i = audio.begin(); i != audio.end(); ++i) {
+               if (_last_audio_time && i->second < *_last_audio_time) {
+                       /* There has been an accurate seek and we have received some audio before the seek time;
+                          discard it.
+                       */
+                       pair<shared_ptr<AudioBuffers>, DCPTime> cut = discard_audio (i->first, i->second, *_last_audio_time);
+                       if (!cut.first) {
+                               continue;
+                       }
+                       *i = cut;
+               }
+
+               if (_last_audio_time) {
+                       fill_audio (DCPTimePeriod (*_last_audio_time, i->second));
+               }
+
+               emit_audio (i->first, i->second);
+       }
+
+       return !earliest && !filled;
 }
 
-bool
-Player::pass ()
+optional<PositionImage>
+Player::subtitles_for_frame (DCPTime time) const
 {
-       if (!_have_valid_pieces) {
-               setup_pieces ();
-       }
+       list<PositionImage> subtitles;
 
-       shared_ptr<Piece> earliest;
-       DCPTime earliest_position;
-       BOOST_FOREACH (shared_ptr<Piece> i, _pieces) {
-               DCPTime const t = i->content->position() + DCPTime (i->decoder->position(), i->frc);
-               if (t < earliest_position) {
-                       earliest_position = t;
-                       earliest = i;
+       BOOST_FOREACH (PlayerSubtitles i, _active_subtitles.get_burnt (time, _always_burn_subtitles)) {
+
+               /* Image subtitles */
+               list<PositionImage> c = transform_image_subtitles (i.image);
+               copy (c.begin(), c.end(), back_inserter (subtitles));
+
+               /* Text subtitles (rendered to an image) */
+               if (!i.text.empty ()) {
+                       list<PositionImage> s = render_subtitles (i.text, i.fonts, _video_container_size, time);
+                       copy (s.begin(), s.end(), back_inserter (subtitles));
                }
        }
 
-       earliest->decoder->pass ();
+       if (subtitles.empty ()) {
+               return optional<PositionImage> ();
+       }
 
-       /* XXX: collect audio and maybe emit some */
+       return merge (subtitles);
 }
 
 void
@@ -549,45 +624,98 @@ Player::video (weak_ptr<Piece> wp, ContentVideo video)
                return;
        }
 
-       /* XXX: get subs to burn in and burn them in */
+       FrameRateChange frc(piece->content->active_video_frame_rate(), _film->video_frame_rate());
+       if (frc.skip && (video.frame % 2) == 1) {
+               return;
+       }
 
+       /* Time and period of the frame we will emit */
+       DCPTime const time = content_video_to_dcp (piece, video.frame);
+       DCPTimePeriod const period (time, time + one_video_frame());
 
-       /* Fill gaps */
+       /* Fill gaps that we discover now that we have some video which needs to be emitted */
 
-       DCPTime const time = content_video_to_dcp (piece, video.frame.index());
+       optional<DCPTime> fill_to;
+       if (_last_video_time) {
+               fill_to = _last_video_time;
+       }
 
-       for (DCPTime i = _last_video_time; i < time; i += DCPTime::from_frames (1, _film->video_frame_rate())) {
-               if (_playlist->video_content_at(i) && _last_video) {
-                       Video (_last_video->clone (i));
-               } else {
-                       Video (black_player_video_frame (i));
+       if (fill_to) {
+               /* XXX: this may not work for 3D */
+               BOOST_FOREACH (DCPTimePeriod i, subtract(DCPTimePeriod (*fill_to, time), _no_video)) {
+                       for (DCPTime j = i.from; j < i.to; j += one_video_frame()) {
+                               LastVideoMap::const_iterator k = _last_video.find (wp);
+                               if (k != _last_video.end ()) {
+                                       emit_video (k->second, j);
+                               } else {
+                                       emit_video (black_player_video_frame(), j);
+                               }
+                       }
                }
        }
 
-       _last_video.reset (
+       /* Discard if it's outside the content's period or if it's before the last accurate seek */
+       if (
+               time < piece->content->position() ||
+               time >= piece->content->end() ||
+               (_last_video_time && time < *_last_video_time)) {
+               return;
+       }
+
+       _last_video[wp].reset (
                new PlayerVideo (
                        video.image,
-                       time,
                        piece->content->video->crop (),
-                       piece->content->video->fade (video.frame.index()),
+                       piece->content->video->fade (video.frame),
                        piece->content->video->scale().size (
                                piece->content->video, _video_container_size, _film->frame_size ()
                                ),
                        _video_container_size,
-                       video.frame.eyes(),
+                       video.eyes,
                        video.part,
                        piece->content->video->colour_conversion ()
                        )
                );
 
-       _last_video_time = time;
+       emit_video (_last_video[wp], time);
+}
+
+/** Do our common processing on some audio */
+void
+Player::audio_transform (shared_ptr<AudioContent> content, AudioStreamPtr stream, ContentAudio content_audio, DCPTime time)
+{
+       DCPOMATIC_ASSERT (content_audio.audio->frames() > 0);
+
+       /* Gain */
+
+       if (content->gain() != 0) {
+               shared_ptr<AudioBuffers> gain (new AudioBuffers (content_audio.audio));
+               gain->apply_gain (content->gain ());
+               content_audio.audio = gain;
+       }
+
+       /* Remap */
+
+       content_audio.audio = remap (content_audio.audio, _film->audio_channels(), stream->mapping());
 
-       Video (_last_video);
+       /* Process */
+
+       if (_audio_processor) {
+               content_audio.audio = _audio_processor->run (content_audio.audio, _film->audio_channels ());
+       }
+
+       /* Push */
+
+       _audio_merger.push (content_audio.audio, time);
+       DCPOMATIC_ASSERT (_stream_states.find (stream) != _stream_states.end ());
+       _stream_states[stream].last_push_end = time + DCPTime::from_frames (content_audio.audio->frames(), _film->audio_frame_rate());
 }
 
 void
 Player::audio (weak_ptr<Piece> wp, AudioStreamPtr stream, ContentAudio content_audio)
 {
+       DCPOMATIC_ASSERT (content_audio.audio->frames() > 0);
+
        shared_ptr<Piece> piece = wp.lock ();
        if (!piece) {
                return;
@@ -596,65 +724,223 @@ Player::audio (weak_ptr<Piece> wp, AudioStreamPtr stream, ContentAudio content_a
        shared_ptr<AudioContent> content = piece->content->audio;
        DCPOMATIC_ASSERT (content);
 
-       shared_ptr<AudioBuffers> audio = content_audio.audio;
+       /* Compute time in the DCP */
+       DCPTime time = resampled_audio_to_dcp (piece, content_audio.frame) + DCPTime::from_seconds (content->delay() / 1000.0);
+       /* And the end of this block in the DCP */
+       DCPTime end = time + DCPTime::from_frames(content_audio.audio->frames(), content->resampled_frame_rate());
+
+       /* Remove anything that comes before the start or after the end of the content */
+       if (time < piece->content->position()) {
+               pair<shared_ptr<AudioBuffers>, DCPTime> cut = discard_audio (content_audio.audio, time, piece->content->position());
+               if (!cut.first) {
+                       /* This audio is entirely discarded */
+                       return;
+               }
+               content_audio.audio = cut.first;
+               time = cut.second;
+       } else if (time > piece->content->end()) {
+               /* Discard it all */
+               return;
+       } else if (end > piece->content->end()) {
+               Frame const remaining_frames = DCPTime(piece->content->end() - time).frames_round(_film->audio_frame_rate());
+               if (remaining_frames == 0) {
+                       return;
+               }
+               shared_ptr<AudioBuffers> cut (new AudioBuffers (content_audio.audio->channels(), remaining_frames));
+               cut->copy_from (content_audio.audio.get(), remaining_frames, 0, 0);
+               content_audio.audio = cut;
+       }
+
+       audio_transform (content, stream, content_audio, time);
+}
 
-       /* Gain */
-       if (content->gain() != 0) {
-               shared_ptr<AudioBuffers> gain (new AudioBuffers (audio));
-               gain->apply_gain (content->gain ());
-               audio = gain;
+void
+Player::image_subtitle_start (weak_ptr<Piece> wp, ContentImageSubtitle subtitle)
+{
+       shared_ptr<Piece> piece = wp.lock ();
+       if (!piece) {
+               return;
        }
 
-       /* XXX: end-trimming used to be checked here */
+       /* Apply content's subtitle offsets */
+       subtitle.sub.rectangle.x += piece->content->subtitle->x_offset ();
+       subtitle.sub.rectangle.y += piece->content->subtitle->y_offset ();
 
-       /* Compute time in the DCP */
-       DCPTime const time = resampled_audio_to_dcp (piece, content_audio.frame) + DCPTime::from_seconds (content->delay() / 1000);
-
-       /* Remap channels */
-       shared_ptr<AudioBuffers> dcp_mapped (new AudioBuffers (_film->audio_channels(), audio->frames()));
-       dcp_mapped->make_silent ();
-
-       AudioMapping map = stream->mapping ();
-       for (int i = 0; i < map.input_channels(); ++i) {
-               for (int j = 0; j < dcp_mapped->channels(); ++j) {
-                       if (map.get (i, static_cast<dcp::Channel> (j)) > 0) {
-                               dcp_mapped->accumulate_channel (
-                                       audio.get(),
-                                       i,
-                                       static_cast<dcp::Channel> (j),
-                                       map.get (i, static_cast<dcp::Channel> (j))
-                                       );
-                       }
+       /* Apply content's subtitle scale */
+       subtitle.sub.rectangle.width *= piece->content->subtitle->x_scale ();
+       subtitle.sub.rectangle.height *= piece->content->subtitle->y_scale ();
+
+       /* Apply a corrective translation to keep the subtitle centred after that scale */
+       subtitle.sub.rectangle.x -= subtitle.sub.rectangle.width * (piece->content->subtitle->x_scale() - 1);
+       subtitle.sub.rectangle.y -= subtitle.sub.rectangle.height * (piece->content->subtitle->y_scale() - 1);
+
+       PlayerSubtitles ps;
+       ps.image.push_back (subtitle.sub);
+       DCPTime from (content_time_to_dcp (piece, subtitle.from()));
+
+       _active_subtitles.add_from (wp, ps, from);
+}
+
+void
+Player::text_subtitle_start (weak_ptr<Piece> wp, ContentTextSubtitle subtitle)
+{
+       shared_ptr<Piece> piece = wp.lock ();
+       if (!piece) {
+               return;
+       }
+
+       PlayerSubtitles ps;
+       DCPTime const from (content_time_to_dcp (piece, subtitle.from()));
+
+       BOOST_FOREACH (dcp::SubtitleString s, subtitle.subs) {
+               s.set_h_position (s.h_position() + piece->content->subtitle->x_offset ());
+               s.set_v_position (s.v_position() + piece->content->subtitle->y_offset ());
+               float const xs = piece->content->subtitle->x_scale();
+               float const ys = piece->content->subtitle->y_scale();
+               float size = s.size();
+
+               /* Adjust size to express the common part of the scaling;
+                  e.g. if xs = ys = 0.5 we scale size by 2.
+               */
+               if (xs > 1e-5 && ys > 1e-5) {
+                       size *= 1 / min (1 / xs, 1 / ys);
                }
+               s.set_size (size);
+
+               /* Then express aspect ratio changes */
+               if (fabs (1.0 - xs / ys) > dcp::ASPECT_ADJUST_EPSILON) {
+                       s.set_aspect_adjust (xs / ys);
+               }
+
+               s.set_in (dcp::Time(from.seconds(), 1000));
+               ps.text.push_back (SubtitleString (s, piece->content->subtitle->outline_width()));
+               ps.add_fonts (piece->content->subtitle->fonts ());
+       }
+
+       _active_subtitles.add_from (wp, ps, from);
+}
+
+void
+Player::subtitle_stop (weak_ptr<Piece> wp, ContentTime to)
+{
+       if (!_active_subtitles.have (wp)) {
+               return;
        }
 
-       audio = dcp_mapped;
+       shared_ptr<Piece> piece = wp.lock ();
+       if (!piece) {
+               return;
+       }
+
+       DCPTime const dcp_to = content_time_to_dcp (piece, to);
+
+       pair<PlayerSubtitles, DCPTime> from = _active_subtitles.add_to (wp, dcp_to);
 
+       if (piece->content->subtitle->use() && !_always_burn_subtitles && !piece->content->subtitle->burn()) {
+               Subtitle (from.first, DCPTimePeriod (from.second, dcp_to));
+       }
+}
+
+void
+Player::seek (DCPTime time, bool accurate)
+{
        if (_audio_processor) {
-               audio = _audio_processor->run (audio, _film->audio_channels ());
+               _audio_processor->flush ();
+       }
+
+       _audio_merger.clear ();
+       _active_subtitles.clear ();
+
+       BOOST_FOREACH (shared_ptr<Piece> i, _pieces) {
+               if (time < i->content->position()) {
+                       /* Before; seek to 0 */
+                       i->decoder->seek (ContentTime(), accurate);
+                       i->done = false;
+               } else if (i->content->position() <= time && time < i->content->end()) {
+                       /* During; seek to position */
+                       i->decoder->seek (dcp_to_content_time (i, time), accurate);
+                       i->done = false;
+               } else {
+                       /* After; this piece is done */
+                       i->done = true;
+               }
+       }
+
+       if (accurate) {
+               _last_video_time = time;
+               _last_audio_time = time;
+       } else {
+               _last_video_time = optional<DCPTime>();
+               _last_audio_time = optional<DCPTime>();
        }
 
-       _audio_merger.push (audio, time);
+       _last_video.clear ();
 }
 
 void
-Player::image_subtitle (weak_ptr<Piece> piece, ContentImageSubtitle subtitle)
+Player::emit_video (shared_ptr<PlayerVideo> pv, DCPTime time)
 {
-       /* XXX: Store for video to see */
+       optional<PositionImage> subtitles = subtitles_for_frame (time);
+       if (subtitles) {
+               pv->set_subtitle (subtitles.get ());
+       }
+
+       cout << "Player emit @ " << to_string(time) << "\n";
+       Video (pv, time);
+
+       if (pv->eyes() == EYES_BOTH || pv->eyes() == EYES_RIGHT) {
+               _last_video_time = time + one_video_frame();
+               _active_subtitles.clear_before (time);
+       }
 }
 
 void
-Player::text_subtitle (weak_ptr<Piece> piece, ContentTextSubtitle subtitle)
+Player::emit_audio (shared_ptr<AudioBuffers> data, DCPTime time)
 {
-       /* XXX: Store for video to see, or emit */
+       Audio (data, time);
+       _last_audio_time = time + DCPTime::from_frames (data->frames(), _film->audio_frame_rate());
 }
 
 void
-Player::seek (DCPTime time, bool accurate)
+Player::fill_audio (DCPTimePeriod period)
+{
+       if (period.from == period.to) {
+               return;
+       }
+
+       DCPOMATIC_ASSERT (period.from < period.to);
+
+       BOOST_FOREACH (DCPTimePeriod i, subtract(period, _no_audio)) {
+               DCPTime t = i.from;
+               while (t < i.to) {
+                       DCPTime block = min (DCPTime::from_seconds (0.5), i.to - t);
+                       Frame const samples = block.frames_round(_film->audio_frame_rate());
+                       if (samples) {
+                               shared_ptr<AudioBuffers> silence (new AudioBuffers (_film->audio_channels(), samples));
+                               silence->make_silent ();
+                               emit_audio (silence, t);
+                       }
+                       t += block;
+               }
+       }
+}
+
+DCPTime
+Player::one_video_frame () const
 {
-       /* XXX: seek decoders */
+       return DCPTime::from_frames (1, _film->video_frame_rate ());
+}
 
-       if (accurate) {
-               _last_video_time = time - DCPTime::from_frames (1, _film->video_frame_rate ());
+pair<shared_ptr<AudioBuffers>, DCPTime>
+Player::discard_audio (shared_ptr<const AudioBuffers> audio, DCPTime time, DCPTime discard_to) const
+{
+       DCPTime const discard_time = discard_to - time;
+       Frame const discard_frames = discard_time.frames_round(_film->audio_frame_rate());
+       Frame remaining_frames = audio->frames() - discard_frames;
+       if (remaining_frames <= 0) {
+               return make_pair(shared_ptr<AudioBuffers>(), DCPTime());
        }
+       shared_ptr<AudioBuffers> cut (new AudioBuffers (audio->channels(), remaining_frames));
+       cut->copy_from (audio.get(), remaining_frames, discard_frames, 0);
+       return make_pair(cut, time + discard_time);
 }