Merge master and multifarious hackery.
[dcpomatic.git] / src / lib / ffmpeg_decoder.cc
index 982139515b0af588eeb9c8180e5accd74cef444f..119e82851ec5de9433d119e2409b1b951067104f 100644 (file)
@@ -1,3 +1,5 @@
+/* -*- c-basic-offset: 8; default-tab-width: 8; -*- */
+
 /*
     Copyright (C) 2012 Carl Hetherington <cth@carlh.net>
 
@@ -41,7 +43,6 @@ extern "C" {
 #include "transcoder.h"
 #include "job.h"
 #include "filter.h"
-#include "options.h"
 #include "exceptions.h"
 #include "image.h"
 #include "util.h"
@@ -49,6 +50,7 @@ extern "C" {
 #include "ffmpeg_decoder.h"
 #include "filter_graph.h"
 #include "subtitle.h"
+#include "audio_buffers.h"
 
 #include "i18n.h"
 
@@ -57,15 +59,19 @@ using std::string;
 using std::vector;
 using std::stringstream;
 using std::list;
+using std::min;
 using boost::shared_ptr;
 using boost::optional;
 using boost::dynamic_pointer_cast;
 using libdcp::Size;
 
-FFmpegDecoder::FFmpegDecoder (shared_ptr<Film> f, DecodeOptions o)
-       : Decoder (f, o)
-       , VideoDecoder (f, o)
-       , AudioDecoder (f, o)
+boost::mutex FFmpegDecoder::_mutex;
+
+FFmpegDecoder::FFmpegDecoder (shared_ptr<const Film> f, shared_ptr<const FFmpegContent> c, bool video, bool audio, bool subtitles)
+       : Decoder (f)
+       , VideoDecoder (f, c)
+       , AudioDecoder (f, c)
+       , _ffmpeg_content (c)
        , _format_context (0)
        , _video_stream (-1)
        , _frame (0)
@@ -75,6 +81,9 @@ FFmpegDecoder::FFmpegDecoder (shared_ptr<Film> f, DecodeOptions o)
        , _audio_codec (0)
        , _subtitle_codec_context (0)
        , _subtitle_codec (0)
+       , _decode_video (video)
+       , _decode_audio (audio)
+       , _decode_subtitles (subtitles)
 {
        setup_general ();
        setup_video ();
@@ -84,10 +93,12 @@ FFmpegDecoder::FFmpegDecoder (shared_ptr<Film> f, DecodeOptions o)
 
 FFmpegDecoder::~FFmpegDecoder ()
 {
+       boost::mutex::scoped_lock lm (_mutex);
+       
        if (_audio_codec_context) {
                avcodec_close (_audio_codec_context);
        }
-       
+
        if (_video_codec_context) {
                avcodec_close (_video_codec_context);
        }
@@ -106,15 +117,15 @@ FFmpegDecoder::setup_general ()
 {
        av_register_all ();
 
-       if (avformat_open_input (&_format_context, _film->content_path().c_str(), 0, 0) < 0) {
-               throw OpenFileError (_film->content_path ());
+       if (avformat_open_input (&_format_context, _ffmpeg_content->file().string().c_str(), 0, 0) < 0) {
+               throw OpenFileError (_ffmpeg_content->file().string ());
        }
 
        if (avformat_find_stream_info (_format_context, 0) < 0) {
                throw DecodeError (_("could not find stream information"));
        }
 
-       /* Find video, audio and subtitle streams and choose the first of each */
+       /* Find video, audio and subtitle streams */
 
        for (uint32_t i = 0; i < _format_context->nb_streams; ++i) {
                AVStream* s = _format_context->streams[i];
@@ -131,17 +142,13 @@ FFmpegDecoder::setup_general ()
                        }
                        
                        _audio_streams.push_back (
-                               shared_ptr<AudioStream> (
-                                       new FFmpegAudioStream (stream_name (s), i, s->codec->sample_rate, s->codec->channel_layout)
+                               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<SubtitleStream> (
-                                       new SubtitleStream (stream_name (s), i)
-                                       )
-                               );
+                       _subtitle_streams.push_back (shared_ptr<FFmpegSubtitleStream> (new FFmpegSubtitleStream (stream_name (s), i)));
                }
        }
 
@@ -158,6 +165,8 @@ FFmpegDecoder::setup_general ()
 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);
 
@@ -173,14 +182,13 @@ FFmpegDecoder::setup_video ()
 void
 FFmpegDecoder::setup_audio ()
 {
-       if (!_audio_stream) {
+       boost::mutex::scoped_lock lm (_mutex);
+       
+       if (!_ffmpeg_content->audio_stream ()) {
                return;
        }
 
-       shared_ptr<FFmpegAudioStream> ffa = dynamic_pointer_cast<FFmpegAudioStream> (_audio_stream);
-       assert (ffa);
-       
-       _audio_codec_context = _format_context->streams[ffa->id()]->codec;
+       _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) {
@@ -195,11 +203,13 @@ FFmpegDecoder::setup_audio ()
 void
 FFmpegDecoder::setup_subtitle ()
 {
-       if (!_subtitle_stream || _subtitle_stream->id() >= int (_format_context->nb_streams)) {
+       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[_subtitle_stream->id()]->codec;
+       _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) {
@@ -212,17 +222,19 @@ FFmpegDecoder::setup_subtitle ()
 }
 
 
-bool
+void
 FFmpegDecoder::pass ()
 {
        int r = av_read_frame (_format_context, &_packet);
-       
+
        if (r < 0) {
                if (r != AVERROR_EOF) {
                        /* Maybe we should fail here, but for now we'll just finish off instead */
                        char buf[256];
                        av_strerror (r, buf, sizeof(buf));
-                       _film->log()->log (String::compose (N_("error on av_read_frame (%1) (%2)"), buf, r));
+                       shared_ptr<const Film> film = _film.lock ();
+                       assert (film);
+                       film->log()->log (String::compose (N_("error on av_read_frame (%1) (%2)"), buf, r));
                }
 
                /* Get any remaining frames */
@@ -232,41 +244,24 @@ FFmpegDecoder::pass ()
                
                /* XXX: should we reset _packet.data and size after each *_decode_* call? */
                
-               int frame_finished;
-               
-               if (_opt.decode_video) {
-                       while (avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet) >= 0 && frame_finished) {
-                               filter_and_emit_video ();
-                       }
+               if (_decode_video) {
+                       while (decode_video_packet ());
                }
-               
-               if (_audio_stream && _opt.decode_audio) {
+
+               if (_ffmpeg_content->audio_stream() && _decode_audio) {
                        decode_audio_packet ();
                }
                        
-               return true;
+               return;
        }
 
        avcodec_get_frame_defaults (_frame);
 
-       shared_ptr<FFmpegAudioStream> ffa = dynamic_pointer_cast<FFmpegAudioStream> (_audio_stream);
-
-       if (_packet.stream_index == _video_stream && _opt.decode_video) {
-
-               int frame_finished;
-               int const r = avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet);
-               if (r >= 0 && frame_finished) {
-
-                       if (r != _packet.size) {
-                               _film->log()->log (String::compose (N_("Used only %1 bytes of %2 in packet"), r, _packet.size));
-                       }
-
-                       filter_and_emit_video ();
-               }
-
-       } else if (ffa && _packet.stream_index == ffa->id() && _opt.decode_audio) {
+       if (_packet.stream_index == _video_stream && _decode_video) {
+               decode_video_packet ();
+       } else if (_ffmpeg_content->audio_stream() && _packet.stream_index == _ffmpeg_content->audio_stream()->id && _decode_audio) {
                decode_audio_packet ();
-       } else if (_subtitle_stream && _packet.stream_index == _subtitle_stream->id() && _opt.decode_subtitles) {
+       } else if (_ffmpeg_content->subtitle_stream() && _packet.stream_index == _ffmpeg_content->subtitle_stream()->id && _decode_subtitles) {
 
                int got_subtitle;
                AVSubtitle sub;
@@ -277,19 +272,18 @@ FFmpegDecoder::pass ()
                        if (sub.num_rects > 0) {
                                shared_ptr<TimedSubtitle> ts;
                                try {
-                                       emit_subtitle (shared_ptr<TimedSubtitle> (new TimedSubtitle (sub)));
+                                       subtitle (shared_ptr<TimedSubtitle> (new TimedSubtitle (sub)));
                                } catch (...) {
                                        /* some problem with the subtitle; we probably didn't understand it */
                                }
                        } else {
-                               emit_subtitle (shared_ptr<TimedSubtitle> ());
+                               subtitle (shared_ptr<TimedSubtitle> ());
                        }
                        avsubtitle_free (&sub);
                }
        }
-       
+
        av_free_packet (&_packet);
-       return false;
 }
 
 /** @param data pointer to array of pointers to buffers.
@@ -298,19 +292,16 @@ FFmpegDecoder::pass ()
 shared_ptr<AudioBuffers>
 FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
 {
-       assert (_film->audio_channels());
+       assert (_ffmpeg_content->audio_channels());
        assert (bytes_per_audio_sample());
 
-       shared_ptr<FFmpegAudioStream> ffa = dynamic_pointer_cast<FFmpegAudioStream> (_audio_stream);
-       assert (ffa);
-       
        /* Deinterleave and convert to float */
 
-       assert ((size % (bytes_per_audio_sample() * ffa->channels())) == 0);
+       assert ((size % (bytes_per_audio_sample() * _ffmpeg_content->audio_channels())) == 0);
 
        int const total_samples = size / bytes_per_audio_sample();
-       int const frames = total_samples / _film->audio_channels();
-       shared_ptr<AudioBuffers> audio (new AudioBuffers (ffa->channels(), frames));
+       int const frames = total_samples / _ffmpeg_content->audio_channels();
+       shared_ptr<AudioBuffers> audio (new AudioBuffers (_ffmpeg_content->audio_channels(), frames));
 
        switch (audio_sample_format()) {
        case AV_SAMPLE_FMT_S16:
@@ -322,7 +313,7 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
                        audio->data(channel)[sample] = float(*p++) / (1 << 15);
 
                        ++channel;
-                       if (channel == _film->audio_channels()) {
+                       if (channel == _ffmpeg_content->audio_channels()) {
                                channel = 0;
                                ++sample;
                        }
@@ -333,7 +324,7 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
        case AV_SAMPLE_FMT_S16P:
        {
                int16_t** p = reinterpret_cast<int16_t **> (data);
-               for (int i = 0; i < _film->audio_channels(); ++i) {
+               for (int i = 0; i < _ffmpeg_content->audio_channels(); ++i) {
                        for (int j = 0; j < frames; ++j) {
                                audio->data(i)[j] = static_cast<float>(p[i][j]) / (1 << 15);
                        }
@@ -350,7 +341,7 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
                        audio->data(channel)[sample] = static_cast<float>(*p++) / (1 << 31);
 
                        ++channel;
-                       if (channel == _film->audio_channels()) {
+                       if (channel == _ffmpeg_content->audio_channels()) {
                                channel = 0;
                                ++sample;
                        }
@@ -367,7 +358,7 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
                        audio->data(channel)[sample] = *p++;
 
                        ++channel;
-                       if (channel == _film->audio_channels()) {
+                       if (channel == _ffmpeg_content->audio_channels()) {
                                channel = 0;
                                ++sample;
                        }
@@ -378,7 +369,7 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
        case AV_SAMPLE_FMT_FLTP:
        {
                float** p = reinterpret_cast<float**> (data);
-               for (int i = 0; i < _film->audio_channels(); ++i) {
+               for (int i = 0; i < _ffmpeg_content->audio_channels(); ++i) {
                        memcpy (audio->data(i), p[i], frames * sizeof(float));
                }
        }
@@ -392,7 +383,7 @@ FFmpegDecoder::deinterleave_audio (uint8_t** data, int size)
 }
 
 float
-FFmpegDecoder::frames_per_second () const
+FFmpegDecoder::video_frame_rate () const
 {
        AVStream* s = _format_context->streams[_video_stream];
 
@@ -414,41 +405,11 @@ FFmpegDecoder::audio_sample_format () const
 }
 
 libdcp::Size
-FFmpegDecoder::native_size () const
+FFmpegDecoder::video_size () const
 {
        return libdcp::Size (_video_codec_context->width, _video_codec_context->height);
 }
 
-PixelFormat
-FFmpegDecoder::pixel_format () const
-{
-       return _video_codec_context->pix_fmt;
-}
-
-int
-FFmpegDecoder::time_base_numerator () const
-{
-       return _video_codec_context->time_base.num;
-}
-
-int
-FFmpegDecoder::time_base_denominator () const
-{
-       return _video_codec_context->time_base.den;
-}
-
-int
-FFmpegDecoder::sample_aspect_ratio_numerator () const
-{
-       return _video_codec_context->sample_aspect_ratio.num;
-}
-
-int
-FFmpegDecoder::sample_aspect_ratio_denominator () const
-{
-       return _video_codec_context->sample_aspect_ratio.den;
-}
-
 string
 FFmpegDecoder::stream_name (AVStream* s) const
 {
@@ -483,89 +444,36 @@ FFmpegDecoder::bytes_per_audio_sample () const
 }
 
 void
-FFmpegDecoder::set_audio_stream (shared_ptr<AudioStream> s)
-{
-       AudioDecoder::set_audio_stream (s);
-       setup_audio ();
-}
-
-void
-FFmpegDecoder::set_subtitle_stream (shared_ptr<SubtitleStream> s)
+FFmpegDecoder::seek (Time t)
 {
-       VideoDecoder::set_subtitle_stream (s);
-       setup_subtitle ();
-       OutputChanged ();
+       do_seek (t, false, false);
 }
 
 void
-FFmpegDecoder::filter_and_emit_video ()
+FFmpegDecoder::seek_back ()
 {
-       int64_t const bet = av_frame_get_best_effort_timestamp (_frame);
-       if (bet == AV_NOPTS_VALUE) {
-               _film->log()->log ("Dropping frame without PTS");
+       if (next() < (2.5 * TIME_HZ / video_frame_rate())) {
                return;
        }
        
-       shared_ptr<FilterGraph> graph;
-
-       {
-               boost::mutex::scoped_lock lm (_filter_graphs_mutex);
-               
-               list<shared_ptr<FilterGraph> >::iterator i = _filter_graphs.begin();
-               while (i != _filter_graphs.end() && !(*i)->can_process (libdcp::Size (_frame->width, _frame->height), (AVPixelFormat) _frame->format)) {
-                       ++i;
-               }
-               
-               if (i == _filter_graphs.end ()) {
-                       graph = filter_graph_factory (_film, this, libdcp::Size (_frame->width, _frame->height), (AVPixelFormat) _frame->format);
-                       _filter_graphs.push_back (graph);
-                       _film->log()->log (String::compose (N_("New graph for %1x%2, pixel format %3"), _frame->width, _frame->height, _frame->format));
-               } else {
-                       graph = *i;
-               }
-       }
-
-       list<shared_ptr<Image> > images = graph->process (_frame);
-
-       for (list<shared_ptr<Image> >::iterator i = images.begin(); i != images.end(); ++i) {
-               emit_video (*i, false, bet * av_q2d (_format_context->streams[_video_stream]->time_base));
-       }
-}
-
-bool
-FFmpegDecoder::seek (double p)
-{
-       return do_seek (p, false, false);
-}
-
-bool
-FFmpegDecoder::seek_to_last ()
-{
-       /* This AVSEEK_FLAG_BACKWARD in do_seek is a bit of a hack; without it, if we ask for a seek to the same place as last time
-          (used when we change decoder parameters and want to re-fetch the frame) we end up going forwards rather than
-          staying in the same place.
-       */
-       return do_seek (last_source_time(), true, false);
-}
-
-void
-FFmpegDecoder::seek_back ()
-{
-       do_seek (last_source_time() - 2.5 / frames_per_second (), true, true);
+       do_seek (next() - 2.5 * TIME_HZ / video_frame_rate(), true, true);
 }
 
 void
 FFmpegDecoder::seek_forward ()
 {
-       do_seek (last_source_time() - 0.5 / frames_per_second(), true, true);
+       if (next() >= (_ffmpeg_content->length() - 0.5 * TIME_HZ / video_frame_rate())) {
+               return;
+       }
+       
+       do_seek (next() - 0.5 * TIME_HZ / video_frame_rate(), true, true);
 }
 
-bool
-FFmpegDecoder::do_seek (double p, bool backwards, bool accurate)
+void
+FFmpegDecoder::do_seek (Time t, bool backwards, bool accurate)
 {
-       int64_t const vt = p / av_q2d (_format_context->streams[_video_stream]->time_base);
-
-       int const r = av_seek_frame (_format_context, _video_stream, vt, backwards ? AVSEEK_FLAG_BACKWARD : 0);
+       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);
 
        avcodec_flush_buffers (_video_codec_context);
        if (_subtitle_codec_context) {
@@ -576,7 +484,7 @@ FFmpegDecoder::do_seek (double p, bool backwards, bool accurate)
                while (1) {
                        int r = av_read_frame (_format_context, &_packet);
                        if (r < 0) {
-                               return true;
+                               return;
                        }
                        
                        avcodec_get_frame_defaults (_frame);
@@ -595,93 +503,20 @@ FFmpegDecoder::do_seek (double p, bool backwards, bool accurate)
                        av_free_packet (&_packet);
                }
        }
-               
-       return r < 0;
-}
-
-shared_ptr<FFmpegAudioStream>
-FFmpegAudioStream::create (string t, optional<int> v)
-{
-       if (!v) {
-               /* version < 1; no type in the string, and there's only FFmpeg streams anyway */
-               return shared_ptr<FFmpegAudioStream> (new FFmpegAudioStream (t, v));
-       }
-
-       stringstream s (t);
-       string type;
-       s >> type;
-       if (type != N_("ffmpeg")) {
-               return shared_ptr<FFmpegAudioStream> ();
-       }
-
-       return shared_ptr<FFmpegAudioStream> (new FFmpegAudioStream (t, v));
-}
-
-FFmpegAudioStream::FFmpegAudioStream (string t, optional<int> version)
-{
-       stringstream n (t);
-       
-       int name_index = 4;
-       if (!version) {
-               name_index = 2;
-               int channels;
-               n >> _id >> channels;
-               _channel_layout = av_get_default_channel_layout (channels);
-               _sample_rate = 0;
-       } else {
-               string type;
-               /* Current (marked version 1) */
-               n >> type >> _id >> _sample_rate >> _channel_layout;
-               assert (type == N_("ffmpeg"));
-       }
-
-       for (int i = 0; i < name_index; ++i) {
-               size_t const s = t.find (' ');
-               if (s != string::npos) {
-                       t = t.substr (s + 1);
-               }
-       }
-
-       _name = t;
-}
-
-string
-FFmpegAudioStream::to_string () const
-{
-       return String::compose (N_("ffmpeg %1 %2 %3 %4"), _id, _sample_rate, _channel_layout, _name);
-}
-
-void
-FFmpegDecoder::film_changed (Film::Property p)
-{
-       switch (p) {
-       case Film::CROP:
-       case Film::FILTERS:
-       {
-               boost::mutex::scoped_lock lm (_filter_graphs_mutex);
-               _filter_graphs.clear ();
-       }
-       OutputChanged ();
-       break;
 
-       default:
-               break;
-       }
+       return;
 }
 
 /** @return Length (in video frames) according to our content's header */
-SourceFrame
-FFmpegDecoder::length () const
+ContentVideoFrame
+FFmpegDecoder::video_length () const
 {
-       return (double(_format_context->duration) / AV_TIME_BASE) * frames_per_second();
+       return (double(_format_context->duration) / AV_TIME_BASE) * video_frame_rate();
 }
 
 void
 FFmpegDecoder::decode_audio_packet ()
 {
-       shared_ptr<FFmpegAudioStream> ffa = dynamic_pointer_cast<FFmpegAudioStream> (_audio_stream);
-       assert (ffa);
-
        /* Audio packets can contain multiple frames, so we may have to call avcodec_decode_audio4
           several times.
        */
@@ -703,7 +538,7 @@ FFmpegDecoder::decode_audio_packet ()
                                        0, _audio_codec_context->channels, _frame->nb_samples, audio_sample_format (), 1
                                        );
                                
-                               assert (_audio_codec_context->channels == _film->audio_channels());
+                               assert (_audio_codec_context->channels == _ffmpeg_content->audio_channels());
                                Audio (deinterleave_audio (_frame->data, data_size), source_pts_seconds);
                        }
                        
@@ -712,3 +547,74 @@ FFmpegDecoder::decode_audio_packet ()
                }
        }
 }
+
+bool
+FFmpegDecoder::decode_video_packet ()
+{
+       int 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;
+       
+       list<shared_ptr<FilterGraph> >::iterator i = _filter_graphs.begin();
+       while (i != _filter_graphs.end() && !(*i)->can_process (libdcp::Size (_frame->width, _frame->height), (AVPixelFormat) _frame->format)) {
+               ++i;
+       }
+
+       if (i == _filter_graphs.end ()) {
+               shared_ptr<const Film> film = _film.lock ();
+               assert (film);
+
+               graph.reset (new FilterGraph (_ffmpeg_content, libdcp::Size (_frame->width, _frame->height), (AVPixelFormat) _frame->format));
+               _filter_graphs.push_back (graph);
+
+               film->log()->log (String::compose (N_("New graph for %1x%2, pixel format %3"), _frame->width, _frame->height, _frame->format));
+       } else {
+               graph = *i;
+       }
+
+       list<shared_ptr<Image> > 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) {
+
+               shared_ptr<Image> image = *i;
+               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);
+               } else {
+                       shared_ptr<const Film> film = _film.lock ();
+                       assert (film);
+                       film->log()->log ("Dropping frame without PTS");
+               }
+       }
+
+       return true;
+}
+
+Time
+FFmpegDecoder::next () const
+{
+       if (_decode_video && _decode_audio) {
+               return min (_next_video, _next_audio);
+       }
+
+       if (_decode_audio) {
+               return _next_audio;
+       }
+
+       return _next_video;
+}