X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Flib%2Fffmpeg_decoder.cc;h=a67905daeedde17ebc590f6f130b9911508faa4c;hb=ef9801159e02595d906f669f5604789f1103dca0;hp=a1a6636fb6ed005a12577cffede608c369f94149;hpb=90933dc804de225df47897ddd3a19c5a60ec67e0;p=dcpomatic.git

diff --git a/src/lib/ffmpeg_decoder.cc b/src/lib/ffmpeg_decoder.cc
index a1a6636fb..a67905dae 100644
--- a/src/lib/ffmpeg_decoder.cc
+++ b/src/lib/ffmpeg_decoder.cc
@@ -1,5 +1,3 @@
-/* -*- c-basic-offset: 8; default-tab-width: 8; -*- */
-
 /*
     Copyright (C) 2012 Carl Hetherington <cth@carlh.net>
 
@@ -30,18 +28,12 @@
 #include <iostream>
 #include <stdint.h>
 #include <boost/lexical_cast.hpp>
+#include <sndfile.h>
 extern "C" {
-#include <tiffio.h>
 #include <libavcodec/avcodec.h>
 #include <libavformat/avformat.h>
-#include <libswscale/swscale.h>
-#include <libpostproc/postprocess.h>
 }
-#include <sndfile.h>
 #include "film.h"
-#include "format.h"
-#include "transcoder.h"
-#include "job.h"
 #include "filter.h"
 #include "exceptions.h"
 #include "image.h"
@@ -49,7 +41,6 @@ extern "C" {
 #include "log.h"
 #include "ffmpeg_decoder.h"
 #include "filter_graph.h"
-#include "subtitle.h"
 #include "audio_buffers.h"
 
 #include "i18n.h"
@@ -60,167 +51,76 @@ using std::vector;
 using std::stringstream;
 using std::list;
 using std::min;
+using std::pair;
 using boost::shared_ptr;
 using boost::optional;
 using boost::dynamic_pointer_cast;
 using libdcp::Size;
 
-boost::mutex FFmpegDecoder::_mutex;
-
-FFmpegDecoder::FFmpegDecoder (shared_ptr<const Film> f, shared_ptr<const FFmpegContent> c, bool video, bool audio, bool subtitles)
+FFmpegDecoder::FFmpegDecoder (shared_ptr<const Film> f, shared_ptr<const FFmpegContent> c, bool video, bool audio)
 	: Decoder (f)
-	, VideoDecoder (f, c)
-	, AudioDecoder (f, c)
-	, _ffmpeg_content (c)
-	, _format_context (0)
-	, _video_stream (-1)
-	, _frame (0)
-	, _video_codec_context (0)
-	, _video_codec (0)
-	, _audio_codec_context (0)
-	, _audio_codec (0)
+	, VideoDecoder (f)
+	, AudioDecoder (f)
+	, SubtitleDecoder (f)
+	, FFmpeg (c)
 	, _subtitle_codec_context (0)
 	, _subtitle_codec (0)
 	, _decode_video (video)
 	, _decode_audio (audio)
-	, _decode_subtitles (subtitles)
+	, _video_pts_offset (0)
+	, _audio_pts_offset (0)
+	, _just_sought (false)
 {
-	setup_general ();
-	setup_video ();
-	setup_audio ();
 	setup_subtitle ();
-}
 
-FFmpegDecoder::~FFmpegDecoder ()
-{
-	boost::mutex::scoped_lock lm (_mutex);
-	
-	if (_audio_codec_context) {
-		avcodec_close (_audio_codec_context);
-	}
+	/* Audio and video frame PTS values may not start with 0.  We want
+	   to fiddle them so that:
 
-	if (_video_codec_context) {
-		avcodec_close (_video_codec_context);
-	}
+	   1.  One of them starts at time 0.
+	   2.  The first video PTS value ends up on a frame boundary.
 
-	if (_subtitle_codec_context) {
-		avcodec_close (_subtitle_codec_context);
-	}
+	   Then we remove big initial gaps in PTS and we allow our
+	   insertion of black frames to work.
 
-	av_free (_frame);
-	
-	avformat_close_input (&_format_context);
-}	
+	   We will do:
+	     audio_pts_to_use = audio_pts_from_ffmpeg + audio_pts_offset;
+	     video_pts_to_use = video_pts_from_ffmpeg + video_pts_offset;
+	*/
 
-void
-FFmpegDecoder::setup_general ()
-{
-	av_register_all ();
+	bool const have_video = video && c->first_video();
+	bool const have_audio = audio && c->audio_stream() && c->audio_stream()->first_audio;
 
-	if (avformat_open_input (&_format_context, _ffmpeg_content->file().string().c_str(), 0, 0) < 0) {
-		throw OpenFileError (_ffmpeg_content->file().string ());
-	}
+	/* First, make one of them start at 0 */
 
-	if (avformat_find_stream_info (_format_context, 0) < 0) {
-		throw DecodeError (_("could not find stream information"));
+	if (have_audio && have_video) {
+		_video_pts_offset = _audio_pts_offset = - min (c->first_video().get(), c->audio_stream()->first_audio.get());
+	} else if (have_video) {
+		_video_pts_offset = - c->first_video().get();
 	}
 
-	/* Find video, audio and subtitle streams */
-
-	for (uint32_t i = 0; i < _format_context->nb_streams; ++i) {
-		AVStream* s = _format_context->streams[i];
-		if (s->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
-			_video_stream = i;
-		} else if (s->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
-
-			/* This is a hack; sometimes it seems that _audio_codec_context->channel_layout isn't set up,
-			   so bodge it here.  No idea why we should have to do this.
-			*/
-
-			if (s->codec->channel_layout == 0) {
-				s->codec->channel_layout = av_get_default_channel_layout (s->codec->channels);
-			}
-			
-			_audio_streams.push_back (
-				shared_ptr<FFmpegAudioStream> (
-					new FFmpegAudioStream (stream_name (s), i, s->codec->sample_rate, s->codec->channels)
-					)
-				);
-
-		} else if (s->codec->codec_type == AVMEDIA_TYPE_SUBTITLE) {
-			_subtitle_streams.push_back (shared_ptr<FFmpegSubtitleStream> (new FFmpegSubtitleStream (stream_name (s), i)));
+	/* Now adjust both so that the video pts starts on a frame */
+	if (have_video && have_audio) {
+		double first_video = c->first_video().get() + _video_pts_offset;
+		double const old_first_video = first_video;
+		
+		/* Round the first video up to a frame boundary */
+		if (fabs (rint (first_video * c->video_frame_rate()) - first_video * c->video_frame_rate()) > 1e-6) {
+			first_video = ceil (first_video * c->video_frame_rate()) / c->video_frame_rate ();
 		}
-	}
-
-	if (_video_stream < 0) {
-		throw DecodeError (N_("could not find video stream"));
-	}
-
-	_frame = avcodec_alloc_frame ();
-	if (_frame == 0) {
-		throw DecodeError (N_("could not allocate frame"));
-	}
-}
-
-void
-FFmpegDecoder::setup_video ()
-{
-	boost::mutex::scoped_lock lm (_mutex);
-	
-	_video_codec_context = _format_context->streams[_video_stream]->codec;
-	_video_codec = avcodec_find_decoder (_video_codec_context->codec_id);
-
-	if (_video_codec == 0) {
-		throw DecodeError (_("could not find video decoder"));
-	}
 
-	if (avcodec_open2 (_video_codec_context, _video_codec, 0) < 0) {
-		throw DecodeError (N_("could not open video decoder"));
+		_video_pts_offset += first_video - old_first_video;
+		_audio_pts_offset += first_video - old_first_video;
 	}
 }
 
-void
-FFmpegDecoder::setup_audio ()
-{
-	boost::mutex::scoped_lock lm (_mutex);
-	
-	if (!_ffmpeg_content->audio_stream ()) {
-		return;
-	}
-
-	_audio_codec_context = _format_context->streams[_ffmpeg_content->audio_stream()->id]->codec;
-	_audio_codec = avcodec_find_decoder (_audio_codec_context->codec_id);
-
-	if (_audio_codec == 0) {
-		throw DecodeError (_("could not find audio decoder"));
-	}
-
-	if (avcodec_open2 (_audio_codec_context, _audio_codec, 0) < 0) {
-		throw DecodeError (N_("could not open audio decoder"));
-	}
-}
-
-void
-FFmpegDecoder::setup_subtitle ()
+FFmpegDecoder::~FFmpegDecoder ()
 {
 	boost::mutex::scoped_lock lm (_mutex);
-	
-	if (!_ffmpeg_content->subtitle_stream() || _ffmpeg_content->subtitle_stream()->id >= int (_format_context->nb_streams)) {
-		return;
-	}
-
-	_subtitle_codec_context = _format_context->streams[_ffmpeg_content->subtitle_stream()->id]->codec;
-	_subtitle_codec = avcodec_find_decoder (_subtitle_codec_context->codec_id);
 
-	if (_subtitle_codec == 0) {
-		throw DecodeError (_("could not find subtitle decoder"));
-	}
-	
-	if (avcodec_open2 (_subtitle_codec_context, _subtitle_codec, 0) < 0) {
-		throw DecodeError (N_("could not open subtitle decoder"));
+	if (_subtitle_codec_context) {
+		avcodec_close (_subtitle_codec_context);
 	}
-}
-
+}	
 
 void
 FFmpegDecoder::pass ()
@@ -245,13 +145,16 @@ FFmpegDecoder::pass ()
 		/* XXX: should we reset _packet.data and size after each *_decode_* call? */
 		
 		if (_decode_video) {
-			while (decode_video_packet ());
+			while (decode_video_packet ()) {}
 		}
 
 		if (_ffmpeg_content->audio_stream() && _decode_audio) {
 			decode_audio_packet ();
 		}
-			
+
+		/* Stop us being asked for any more data */
+		_video_position = _ffmpeg_content->video_length ();
+		_audio_position = _ffmpeg_content->audio_length ();
 		return;
 	}
 
@@ -261,26 +164,8 @@ FFmpegDecoder::pass ()
 		decode_video_packet ();
 	} else if (_ffmpeg_content->audio_stream() && _packet.stream_index == _ffmpeg_content->audio_stream()->id && _decode_audio) {
 		decode_audio_packet ();
-	} else if (_ffmpeg_content->subtitle_stream() && _packet.stream_index == _ffmpeg_content->subtitle_stream()->id && _decode_subtitles) {
-
-		int got_subtitle;
-		AVSubtitle sub;
-		if (avcodec_decode_subtitle2 (_subtitle_codec_context, &sub, &got_subtitle, &_packet) && got_subtitle) {
-			/* Sometimes we get an empty AVSubtitle, which is used by some codecs to
-			   indicate that the previous subtitle should stop.
-			*/
-			if (sub.num_rects > 0) {
-				shared_ptr<TimedSubtitle> ts;
-				try {
-					subtitle (shared_ptr<TimedSubtitle> (new TimedSubtitle (sub)));
-				} catch (...) {
-					/* some problem with the subtitle; we probably didn't understand it */
-				}
-			} else {
-				subtitle (shared_ptr<TimedSubtitle> ());
-			}
-			avsubtitle_free (&sub);
-		}
+	} else if (_ffmpeg_content->subtitle_stream() && _packet.stream_index == _ffmpeg_content->subtitle_stream()->id) {
+		decode_subtitle_packet ();
 	}
 
 	av_free_packet (&_packet);
@@ -382,59 +267,14 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
 	return audio;
 }
 
-float
-FFmpegDecoder::video_frame_rate () const
-{
-	AVStream* s = _format_context->streams[_video_stream];
-
-	if (s->avg_frame_rate.num && s->avg_frame_rate.den) {
-		return av_q2d (s->avg_frame_rate);
-	}
-
-	return av_q2d (s->r_frame_rate);
-}
-
 AVSampleFormat
 FFmpegDecoder::audio_sample_format () const
 {
-	if (_audio_codec_context == 0) {
+	if (!_ffmpeg_content->audio_stream()) {
 		return (AVSampleFormat) 0;
 	}
 	
-	return _audio_codec_context->sample_fmt;
-}
-
-libdcp::Size
-FFmpegDecoder::video_size () const
-{
-	return libdcp::Size (_video_codec_context->width, _video_codec_context->height);
-}
-
-string
-FFmpegDecoder::stream_name (AVStream* s) const
-{
-	stringstream n;
-
-	if (s->metadata) {
-		AVDictionaryEntry const * lang = av_dict_get (s->metadata, N_("language"), 0, 0);
-		if (lang) {
-			n << lang->value;
-		}
-		
-		AVDictionaryEntry const * title = av_dict_get (s->metadata, N_("title"), 0, 0);
-		if (title) {
-			if (!n.str().empty()) {
-				n << N_(" ");
-			}
-			n << title->value;
-		}
-	}
-
-	if (n.str().empty()) {
-		n << N_("unknown");
-	}
-
-	return n.str ();
+	return audio_codec_context()->sample_fmt;
 }
 
 int
@@ -444,74 +284,69 @@ FFmpegDecoder::bytes_per_audio_sample () const
 }
 
 void
-FFmpegDecoder::seek (Time t)
+FFmpegDecoder::seek (VideoContent::Frame frame, bool accurate)
 {
-	do_seek (t, false, false);
-}
+	double const time_base = av_q2d (_format_context->streams[_video_stream]->time_base);
 
-void
-FFmpegDecoder::seek_back ()
-{
-	if (next() < (2.5 * TIME_HZ / video_frame_rate())) {
-		return;
+	/* If we are doing an accurate seek, our initial shot will be 5 frames (5 being
+	   a number plucked from the air) earlier than we want to end up.  The loop below
+	   will hopefully then step through to where we want to be.
+	*/
+	int initial = frame;
+
+	if (accurate) {
+		initial -= 5;
 	}
-	
-	do_seek (next() - 2.5 * TIME_HZ / video_frame_rate(), true, true);
-}
 
-void
-FFmpegDecoder::seek_forward ()
-{
-	if (next() >= (_ffmpeg_content->length() - 0.5 * TIME_HZ / video_frame_rate())) {
-		return;
+	if (initial < 0) {
+		initial = 0;
 	}
-	
-	do_seek (next() - 0.5 * TIME_HZ / video_frame_rate(), true, true);
-}
 
-void
-FFmpegDecoder::do_seek (Time t, bool backwards, bool accurate)
-{
-	int64_t const vt = t / (av_q2d (_format_context->streams[_video_stream]->time_base) * TIME_HZ);
-	av_seek_frame (_format_context, _video_stream, vt, backwards ? AVSEEK_FLAG_BACKWARD : 0);
+	/* Initial seek time in the stream's timebase */
+	int64_t const initial_vt = ((initial / _ffmpeg_content->video_frame_rate()) - _video_pts_offset) / time_base;
 
-	avcodec_flush_buffers (_video_codec_context);
+	av_seek_frame (_format_context, _video_stream, initial_vt, AVSEEK_FLAG_BACKWARD);
+
+	avcodec_flush_buffers (video_codec_context());
 	if (_subtitle_codec_context) {
 		avcodec_flush_buffers (_subtitle_codec_context);
 	}
 
-	if (accurate) {
-		while (1) {
-			int r = av_read_frame (_format_context, &_packet);
-			if (r < 0) {
-				return;
-			}
-			
-			avcodec_get_frame_defaults (_frame);
-			
-			if (_packet.stream_index == _video_stream) {
-				int finished = 0;
-				int const r = avcodec_decode_video2 (_video_codec_context, _frame, &finished, &_packet);
-				if (r >= 0 && finished) {
-					int64_t const bet = av_frame_get_best_effort_timestamp (_frame);
-					if (bet > vt) {
-						break;
-					}
-				}
-			}
-			
-			av_free_packet (&_packet);
-		}
+	_just_sought = true;
+	_video_position = frame;
+	
+	if (frame == 0 || !accurate) {
+		/* We're already there, or we're as close as we need to be */
+		return;
 	}
 
-	return;
-}
+	while (1) {
+		int r = av_read_frame (_format_context, &_packet);
+		if (r < 0) {
+			return;
+		}
 
-/** @return Length (in video frames) according to our content's header */
-ContentVideoFrame
-FFmpegDecoder::video_length () const
-{
-	return (double(_format_context->duration) / AV_TIME_BASE) * video_frame_rate();
+		if (_packet.stream_index != _video_stream) {
+			continue;
+		}
+		
+		avcodec_get_frame_defaults (_frame);
+		
+		int finished = 0;
+		r = avcodec_decode_video2 (video_codec_context(), _frame, &finished, &_packet);
+		if (r >= 0 && finished) {
+			_video_position = rint (
+				(av_frame_get_best_effort_timestamp (_frame) * time_base + _video_pts_offset) * _ffmpeg_content->video_frame_rate()
+				);
+
+			if (_video_position >= (frame - 1)) {
+				av_free_packet (&_packet);
+				break;
+			}
+		}
+		
+		av_free_packet (&_packet);
+	}
 }
 
 void
@@ -526,24 +361,38 @@ FFmpegDecoder::decode_audio_packet ()
 	while (copy_packet.size > 0) {
 
 		int frame_finished;
-		int const decode_result = avcodec_decode_audio4 (_audio_codec_context, _frame, &frame_finished, &copy_packet);
+		int const decode_result = avcodec_decode_audio4 (audio_codec_context(), _frame, &frame_finished, &copy_packet);
 		if (decode_result >= 0) {
 			if (frame_finished) {
-			
-				/* Where we are in the source, in seconds */
-				double const source_pts_seconds = av_q2d (_format_context->streams[copy_packet.stream_index]->time_base)
-					* av_frame_get_best_effort_timestamp(_frame);
-				
+
+				if (_audio_position == 0) {
+					/* Where we are in the source, in seconds */
+					double const pts = av_q2d (_format_context->streams[copy_packet.stream_index]->time_base)
+						* av_frame_get_best_effort_timestamp(_frame) + _audio_pts_offset;
+
+					if (pts > 0) {
+						/* Emit some silence */
+						shared_ptr<AudioBuffers> silence (
+							new AudioBuffers (
+								_ffmpeg_content->audio_channels(),
+								pts * _ffmpeg_content->content_audio_frame_rate()
+								)
+							);
+						
+						silence->make_silent ();
+						audio (silence, _audio_position);
+					}
+				}
+
 				int const data_size = av_samples_get_buffer_size (
-					0, _audio_codec_context->channels, _frame->nb_samples, audio_sample_format (), 1
+					0, audio_codec_context()->channels, _frame->nb_samples, audio_sample_format (), 1
 					);
+
+				audio (deinterleave_audio (_frame->data, data_size), _audio_position);
 				
-				assert (_audio_codec_context->channels == _ffmpeg_content->audio_channels());
-				audio (deinterleave_audio (_frame->data, data_size), source_pts_seconds);
+				copy_packet.data += decode_result;
+				copy_packet.size -= decode_result;
 			}
-			
-			copy_packet.data += decode_result;
-			copy_packet.size -= decode_result;
 		}
 	}
 }
@@ -552,10 +401,10 @@ bool
 FFmpegDecoder::decode_video_packet ()
 {
 	int frame_finished;
-	if (avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet) < 0 || !frame_finished) {
+	if (avcodec_decode_video2 (video_codec_context(), _frame, &frame_finished, &_packet) < 0 || !frame_finished) {
 		return false;
 	}
-		
+
 	boost::mutex::scoped_lock lm (_filter_graphs_mutex);
 
 	shared_ptr<FilterGraph> graph;
@@ -577,24 +426,57 @@ FFmpegDecoder::decode_video_packet ()
 		graph = *i;
 	}
 
-	list<shared_ptr<Image> > images = graph->process (_frame);
+	list<pair<shared_ptr<Image>, int64_t> > images = graph->process (_frame);
 
 	string post_process = Filter::ffmpeg_strings (_ffmpeg_content->filters()).second;
 	
-	for (list<shared_ptr<Image> >::iterator i = images.begin(); i != images.end(); ++i) {
+	for (list<pair<shared_ptr<Image>, int64_t> >::iterator i = images.begin(); i != images.end(); ++i) {
 
-		shared_ptr<Image> image = *i;
+		shared_ptr<Image> image = i->first;
 		if (!post_process.empty ()) {
 			image = image->post_process (post_process, true);
 		}
 		
-		int64_t const bet = av_frame_get_best_effort_timestamp (_frame);
-		if (bet != AV_NOPTS_VALUE) {
-			/* XXX: may need to insert extra frames / remove frames here ...
-			   (as per old Matcher)
-			*/
-			Time const t = bet * av_q2d (_format_context->streams[_video_stream]->time_base) * TIME_HZ;
-			video (image, false, t);
+		if (i->second != AV_NOPTS_VALUE) {
+
+			double const pts = i->second * av_q2d (_format_context->streams[_video_stream]->time_base) + _video_pts_offset;
+
+			if (_just_sought) {
+				/* We just did a seek, so disable any attempts to correct for where we
+				   are / should be.
+				*/
+				_video_position = rint (pts * _ffmpeg_content->video_frame_rate ());
+				_just_sought = false;
+			}
+
+			double const next = _video_position / _ffmpeg_content->video_frame_rate();
+			double const one_frame = 1 / _ffmpeg_content->video_frame_rate ();
+			double delta = pts - next;
+
+			while (delta > one_frame) {
+				/* This PTS is more than one frame forward in time of where we think we should be; emit
+				   a black frame.
+				*/
+
+				/* XXX: I think this should be a copy of the last frame... */
+				boost::shared_ptr<Image> black (
+					new Image (
+						static_cast<AVPixelFormat> (_frame->format),
+						libdcp::Size (video_codec_context()->width, video_codec_context()->height),
+						true
+						)
+					);
+				
+				black->make_black ();
+				video (image, false, _video_position);
+				delta -= one_frame;
+			}
+
+			if (delta > -one_frame) {
+				/* This PTS is within a frame of being right; emit this (otherwise it will be dropped) */
+				video (image, false, _video_position);
+			}
+				
 		} else {
 			shared_ptr<const Film> film = _film.lock ();
 			assert (film);
@@ -605,16 +487,103 @@ FFmpegDecoder::decode_video_packet ()
 	return true;
 }
 
-Time
-FFmpegDecoder::next () const
+	
+void
+FFmpegDecoder::setup_subtitle ()
+{
+	boost::mutex::scoped_lock lm (_mutex);
+	
+	if (!_ffmpeg_content->subtitle_stream() || _ffmpeg_content->subtitle_stream()->id >= int (_format_context->nb_streams)) {
+		return;
+	}
+
+	_subtitle_codec_context = _format_context->streams[_ffmpeg_content->subtitle_stream()->id]->codec;
+	_subtitle_codec = avcodec_find_decoder (_subtitle_codec_context->codec_id);
+
+	if (_subtitle_codec == 0) {
+		throw DecodeError (_("could not find subtitle decoder"));
+	}
+	
+	if (avcodec_open2 (_subtitle_codec_context, _subtitle_codec, 0) < 0) {
+		throw DecodeError (N_("could not open subtitle decoder"));
+	}
+}
+
+bool
+FFmpegDecoder::done () const
+{
+	bool const vd = !_decode_video || (_video_position >= _ffmpeg_content->video_length());
+	bool const ad = !_decode_audio || !_ffmpeg_content->audio_stream() || (_audio_position >= _ffmpeg_content->audio_length());
+	return vd && ad;
+}
+	
+void
+FFmpegDecoder::decode_subtitle_packet ()
 {
-	if (_decode_video && _decode_audio && _audio_codec_context) {
-		return min (_next_video, _next_audio);
+	int got_subtitle;
+	AVSubtitle sub;
+	if (avcodec_decode_subtitle2 (_subtitle_codec_context, &sub, &got_subtitle, &_packet) < 0 || !got_subtitle) {
+		return;
 	}
 
-	if (_decode_audio && _audio_codec_context) {
-		return _next_audio;
+	/* Sometimes we get an empty AVSubtitle, which is used by some codecs to
+	   indicate that the previous subtitle should stop.
+	*/
+	if (sub.num_rects <= 0) {
+		subtitle (shared_ptr<Image> (), dcpomatic::Rect<double> (), 0, 0);
+		return;
+	} else if (sub.num_rects > 1) {
+		throw DecodeError (_("multi-part subtitles not yet supported"));
 	}
+		
+	/* Subtitle PTS in seconds (within the source, not taking into account any of the
+	   source that we may have chopped off for the DCP)
+	*/
+	double const packet_time = static_cast<double> (sub.pts) / AV_TIME_BASE;
+	
+	/* hence start time for this sub */
+	Time const from = (packet_time + (double (sub.start_display_time) / 1e3)) * TIME_HZ;
+	Time const to = (packet_time + (double (sub.end_display_time) / 1e3)) * TIME_HZ;
 
-	return _next_video;
+	AVSubtitleRect const * rect = sub.rects[0];
+
+	if (rect->type != SUBTITLE_BITMAP) {
+		throw DecodeError (_("non-bitmap subtitles not yet supported"));
+	}
+	
+	shared_ptr<Image> image (new Image (PIX_FMT_RGBA, libdcp::Size (rect->w, rect->h), true));
+
+	/* Start of the first line in the subtitle */
+	uint8_t* sub_p = rect->pict.data[0];
+	/* sub_p looks up into a RGB palette which is here */
+	uint32_t const * palette = (uint32_t *) rect->pict.data[1];
+	/* Start of the output data */
+	uint32_t* out_p = (uint32_t *) image->data()[0];
+	
+	for (int y = 0; y < rect->h; ++y) {
+		uint8_t* sub_line_p = sub_p;
+		uint32_t* out_line_p = out_p;
+		for (int x = 0; x < rect->w; ++x) {
+			*out_line_p++ = palette[*sub_line_p++];
+		}
+		sub_p += rect->pict.linesize[0];
+		out_p += image->stride()[0] / sizeof (uint32_t);
+	}
+
+	libdcp::Size const vs = _ffmpeg_content->video_size ();
+
+	subtitle (
+		image,
+		dcpomatic::Rect<double> (
+			static_cast<double> (rect->x) / vs.width,
+			static_cast<double> (rect->y) / vs.height,
+			static_cast<double> (rect->w) / vs.width,
+			static_cast<double> (rect->h) / vs.height
+			),
+		from,
+		to
+		);
+			  
+	
+	avsubtitle_free (&sub);
 }