Merge branch 'master' into speed-up
[dcpomatic.git] / src / lib / ffmpeg_decoder.cc
index 8dbec87fd364bd50f96acd612f8753157ddedbd4..acaf149f43ade599dff78d95c109d36c86133097 100644 (file)
@@ -27,6 +27,7 @@
 #include <iomanip>
 #include <iostream>
 #include <stdint.h>
+#include <boost/lexical_cast.hpp>
 extern "C" {
 #include <tiffio.h>
 #include <libavcodec/avcodec.h>
@@ -40,23 +41,30 @@ extern "C" {
 #include "transcoder.h"
 #include "job.h"
 #include "filter.h"
-#include "film_state.h"
 #include "options.h"
 #include "exceptions.h"
 #include "image.h"
 #include "util.h"
 #include "log.h"
 #include "ffmpeg_decoder.h"
-
-using namespace std;
-using namespace boost;
-
-FFmpegDecoder::FFmpegDecoder (boost::shared_ptr<const FilmState> s, boost::shared_ptr<const Options> o, Job* j, Log* l, bool minimal, bool ignore_length)
-       : Decoder (s, o, j, l, minimal, ignore_length)
+#include "filter_graph.h"
+#include "subtitle.h"
+
+using std::cout;
+using std::string;
+using std::vector;
+using std::stringstream;
+using std::list;
+using boost::shared_ptr;
+using boost::optional;
+using boost::dynamic_pointer_cast;
+
+FFmpegDecoder::FFmpegDecoder (shared_ptr<Film> f, shared_ptr<const Options> o, Job* j)
+       : Decoder (f, o, j)
+       , VideoDecoder (f, o, j)
+       , AudioDecoder (f, o, j)
        , _format_context (0)
        , _video_stream (-1)
-       , _audio_stream (-1)
-       , _subtitle_stream (-1)
        , _frame (0)
        , _video_codec_context (0)
        , _video_codec (0)
@@ -64,7 +72,6 @@ FFmpegDecoder::FFmpegDecoder (boost::shared_ptr<const FilmState> s, boost::share
        , _audio_codec (0)
        , _subtitle_codec_context (0)
        , _subtitle_codec (0)
-       , _have_subtitle (false)
 {
        setup_general ();
        setup_video ();
@@ -82,15 +89,12 @@ FFmpegDecoder::~FFmpegDecoder ()
                avcodec_close (_video_codec_context);
        }
 
-       if (_have_subtitle) {
-               avsubtitle_free (&_subtitle);
-       }
-
        if (_subtitle_codec_context) {
                avcodec_close (_subtitle_codec_context);
        }
-       
+
        av_free (_frame);
+       
        avformat_close_input (&_format_context);
 }      
 
@@ -101,21 +105,42 @@ FFmpegDecoder::setup_general ()
        
        av_register_all ();
 
-       if ((r = avformat_open_input (&_format_context, _fs->content_path().c_str(), 0, 0)) != 0) {
-               throw OpenFileError (_fs->content_path ());
+       if ((r = avformat_open_input (&_format_context, _film->content_path().c_str(), 0, 0)) != 0) {
+               throw OpenFileError (_film->content_path ());
        }
 
        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 */
+
        for (uint32_t i = 0; i < _format_context->nb_streams; ++i) {
-               if (_format_context->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
+               AVStream* s = _format_context->streams[i];
+               if (s->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
                        _video_stream = i;
-               } else if (_format_context->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
-                       _audio_stream = i;
-               } else if (_format_context->streams[i]->codec->codec_type == AVMEDIA_TYPE_SUBTITLE) {
-                       _subtitle_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<AudioStream> (
+                                       new FFmpegAudioStream (stream_name (s), i, s->codec->sample_rate, s->codec->channel_layout)
+                                       )
+                               );
+                       
+               } else if (s->codec->codec_type == AVMEDIA_TYPE_SUBTITLE) {
+                       _subtitle_streams.push_back (
+                               shared_ptr<SubtitleStream> (
+                                       new SubtitleStream (stream_name (s), i)
+                                       )
+                               );
                }
        }
 
@@ -138,7 +163,7 @@ FFmpegDecoder::setup_video ()
        if (_video_codec == 0) {
                throw DecodeError ("could not find video decoder");
        }
-       
+
        if (avcodec_open2 (_video_codec_context, _video_codec, 0) < 0) {
                throw DecodeError ("could not open video decoder");
        }
@@ -147,11 +172,14 @@ FFmpegDecoder::setup_video ()
 void
 FFmpegDecoder::setup_audio ()
 {
-       if (_audio_stream < 0) {
+       if (!_audio_stream) {
                return;
        }
+
+       shared_ptr<FFmpegAudioStream> ffa = dynamic_pointer_cast<FFmpegAudioStream> (_audio_stream);
+       assert (ffa);
        
-       _audio_codec_context = _format_context->streams[_audio_stream]->codec;
+       _audio_codec_context = _format_context->streams[ffa->id()]->codec;
        _audio_codec = avcodec_find_decoder (_audio_codec_context->codec_id);
 
        if (_audio_codec == 0) {
@@ -161,24 +189,16 @@ FFmpegDecoder::setup_audio ()
        if (avcodec_open2 (_audio_codec_context, _audio_codec, 0) < 0) {
                throw DecodeError ("could not open audio decoder");
        }
-
-       /* 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 (_audio_codec_context->channel_layout == 0) {
-               _audio_codec_context->channel_layout = av_get_default_channel_layout (audio_channels ());
-       }
 }
 
 void
 FFmpegDecoder::setup_subtitle ()
 {
-       if (_subtitle_stream < 0) {
+       if (!_subtitle_stream) {
                return;
        }
 
-       _subtitle_codec_context = _format_context->streams[_subtitle_stream]->codec;
+       _subtitle_codec_context = _format_context->streams[_subtitle_stream->id()]->codec;
        _subtitle_codec = avcodec_find_decoder (_subtitle_codec_context->codec_id);
 
        if (_subtitle_codec == 0) {
@@ -192,12 +212,16 @@ FFmpegDecoder::setup_subtitle ()
 
 
 bool
-FFmpegDecoder::do_pass ()
+FFmpegDecoder::pass ()
 {
        int r = av_read_frame (_format_context, &_packet);
+       
        if (r < 0) {
                if (r != AVERROR_EOF) {
-                       throw DecodeError ("error on av_read_frame");
+                       /* 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 ("error on av_read_frame (%1) (%2)", buf, r));
                }
                
                /* Get any remaining frames */
@@ -205,135 +229,153 @@ FFmpegDecoder::do_pass ()
                _packet.data = 0;
                _packet.size = 0;
 
-               int frame_finished;
+               /* XXX: should we reset _packet.data and size after each *_decode_* call? */
 
-               if (_opt->decode_video) {
-                       while (avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet) >= 0 && frame_finished) {
+               int frame_finished;
 
-                               process_video (_frame);
-                       }
+               while (avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet) >= 0 && frame_finished) {
+                       filter_and_emit_video (_frame);
                }
 
-               if (_audio_stream >= 0 && _opt->decode_audio) {
+               if (_audio_stream && _opt->decode_audio) {
                        while (avcodec_decode_audio4 (_audio_codec_context, _frame, &frame_finished, &_packet) >= 0 && frame_finished) {
                                int const data_size = av_samples_get_buffer_size (
                                        0, _audio_codec_context->channels, _frame->nb_samples, audio_sample_format (), 1
                                        );
-                               
-                               assert (_audio_codec_context->channels == _fs->audio_channels);
-                               process_audio (_frame->data[0], data_size);
+
+                               assert (_audio_codec_context->channels == _film->audio_channels());
+                               Audio (deinterleave_audio (_frame->data[0], data_size));
                        }
                }
 
                return true;
        }
 
-       if (_packet.stream_index == _video_stream && _opt->decode_video) {
+       avcodec_get_frame_defaults (_frame);
+
+       shared_ptr<FFmpegAudioStream> ffa = dynamic_pointer_cast<FFmpegAudioStream> (_audio_stream);
+       
+       if (_packet.stream_index == _video_stream) {
 
                int frame_finished;
-               if (avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet) >= 0 && frame_finished) {
-                       
-                       if (_have_subtitle) {
-                               for (unsigned int i = 0; i < _subtitle.num_rects; ++i) {
-                                       AVSubtitleRect* rect = _subtitle.rects[i];
-                                       if (rect->type != SUBTITLE_BITMAP) {
-                                               throw DecodeError ("non-bitmap subtitles not yet supported");
-                                       }
+               int const r = avcodec_decode_video2 (_video_codec_context, _frame, &frame_finished, &_packet);
+               if (r >= 0 && frame_finished) {
 
-                                       /* XXX: all this assumes YUV420 in _frame */
-                                       
-                                       assert (rect->nb_colors == 4);
-                                       assert (rect->pict.data[0]);
+                       if (r != _packet.size) {
+                               _film->log()->log (String::compose ("Used only %1 bytes of %2 in packet", r, _packet.size));
+                       }
 
-                                       /* Start of the first line in the target frame */
-                                       uint8_t* frame_y_p = _frame->data[0] + rect->y * _frame->linesize[0];
-                                       uint8_t* frame_u_p = _frame->data[1] + (rect->y / 2) * _frame->linesize[1];
-                                       uint8_t* frame_v_p = _frame->data[2] + (rect->y / 2) * _frame->linesize[2];
-                                       
-                                       /* 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];
-                                       
-                                       for (int sub_y = 0; sub_y < rect->h; ++sub_y) {
-                                               /* Pointers to the start of this line */
-                                               uint8_t* sub_line_p = sub_p;
-                                               uint8_t* frame_line_y_p = frame_y_p + rect->x;
-                                               uint8_t* frame_line_u_p = frame_u_p + (rect->x / 2);
-                                               uint8_t* frame_line_v_p = frame_v_p + (rect->x / 2);
-
-                                               /* U and V are subsampled */
-                                               uint8_t current_u = 0;
-                                               uint8_t current_v = 0;
-                                               int subsample_step = 0;
-                                               
-                                               for (int sub_x = 0; sub_x < rect->w; ++sub_x) {
-
-                                                       /* RGB value for this subtitle pixel */
-                                                       uint32_t const val = palette[*sub_line_p++];
-                                                       
-                                                       int const     red =  (val &       0xff);
-                                                       int const   green =  (val &     0xff00) >> 8;
-                                                       int const    blue =  (val &   0xff0000) >> 16;
-                                                       float const alpha = ((val & 0xff000000) >> 24) / 255.0;
-
-                                                       /* Alpha-blend Y */
-                                                       int const cy = *frame_line_y_p;
-                                                       *frame_line_y_p++ = int (cy * (1 - alpha)) + int (RGB_TO_Y_CCIR (red, green, blue) * alpha);
-
-                                                       /* Store up U and V */
-                                                       current_u |= ((RGB_TO_U_CCIR (red, green, blue, 0) & 0xf0) >> 4) << (4 * subsample_step);
-                                                       current_v |= ((RGB_TO_V_CCIR (red, green, blue, 0) & 0xf0) >> 4) << (4 * subsample_step);
-
-                                                       if (subsample_step == 1 && (sub_y % 2) == 0) {
-                                                               /* We have complete U and V bytes, so alpha-blend them into the frame */
-                                                               int const cu = *frame_line_u_p;
-                                                               int const cv = *frame_line_v_p;
-                                                               *frame_line_u_p++ = int (cu * (1 - alpha)) + int (current_u * alpha);
-                                                               *frame_line_v_p++ = int (cv * (1 - alpha)) + int (current_v * alpha);
-                                                               current_u = current_v = 0;
-                                                       }
-
-                                                       subsample_step = (subsample_step + 1) % 2;
-                                               }
-
-                                               sub_p += rect->pict.linesize[0];
-                                               frame_y_p += _frame->linesize[0];
-                                               if ((sub_y % 2) == 0) {
-                                                       frame_u_p += _frame->linesize[1];
-                                                       frame_v_p += _frame->linesize[2];
-                                               }
-                                       }
+                       /* Where we are in the output, in seconds */
+                       double const out_pts_seconds = video_frame() / frames_per_second();
+
+                       /* Where we are in the source, in seconds */
+                       double const source_pts_seconds = av_q2d (_format_context->streams[_packet.stream_index]->time_base)
+                               * av_frame_get_best_effort_timestamp(_frame);
+
+                       _film->log()->log (
+                               String::compose ("Source video frame ready; source at %1, output at %2", source_pts_seconds, out_pts_seconds),
+                               Log::VERBOSE
+                               );
+
+                       if (!_first_video) {
+                               _first_video = source_pts_seconds;
+                       }
+
+                       /* Difference between where we are and where we should be */
+                       double const delta = source_pts_seconds - _first_video.get() - out_pts_seconds;
+                       double const one_frame = 1 / frames_per_second();
+
+                       /* Insert frames if required to get out_pts_seconds up to pts_seconds */
+                       if (delta > one_frame) {
+                               int const extra = rint (delta / one_frame);
+                               for (int i = 0; i < extra; ++i) {
+                                       repeat_last_video ();
+                                       _film->log()->log (
+                                               String::compose (
+                                                       "Extra video frame inserted at %1s; source frame %2, source PTS %3 (at %4 fps)",
+                                                       out_pts_seconds, video_frame(), source_pts_seconds, frames_per_second()
+                                                       )
+                                               );
                                }
                        }
-                       
-                       process_video (_frame);
+
+                       if (delta > -one_frame) {
+                               /* Process this frame */
+                               filter_and_emit_video (_frame);
+                       } else {
+                               /* Otherwise we are omitting a frame to keep things right */
+                               _film->log()->log (String::compose ("Frame removed at %1s", out_pts_seconds));
+                       }
                }
 
-       } else if (_audio_stream >= 0 && _packet.stream_index == _audio_stream && _opt->decode_audio) {
-               
-               avcodec_get_frame_defaults (_frame);
-               
+       } else if (ffa && _packet.stream_index == ffa->id() && _opt->decode_audio) {
+
                int frame_finished;
                if (avcodec_decode_audio4 (_audio_codec_context, _frame, &frame_finished, &_packet) >= 0 && frame_finished) {
-                       int const data_size = av_samples_get_buffer_size (
-                               0, _audio_codec_context->channels, _frame->nb_samples, audio_sample_format (), 1
-                               );
 
-                       assert (_audio_codec_context->channels == _fs->audio_channels);
-                       process_audio (_frame->data[0], data_size);
-               }
+                       /* Where we are in the source, in seconds */
+                       double const source_pts_seconds = av_q2d (_format_context->streams[_packet.stream_index]->time_base)
+                               * av_frame_get_best_effort_timestamp(_frame);
+
+                       /* We only decode audio if we've had our first video packet through, and if it
+                          was before this packet.  Until then audio is thrown away.
+                       */
+                               
+                       if (_first_video && _first_video.get() <= source_pts_seconds) {
 
-       } else if (_subtitle_stream >= 0 && _packet.stream_index == _subtitle_stream) {
+                               if (!_first_audio) {
+                                       _first_audio = source_pts_seconds;
+                                       
+                                       /* This is our first audio frame, and if we've arrived here we must have had our
+                                          first video frame.  Push some silence to make up any gap between our first
+                                          video frame and our first audio.
+                                       */
+                       
+                                       /* frames of silence that we must push */
+                                       int const s = rint ((_first_audio.get() - _first_video.get()) * ffa->sample_rate ());
+                                       
+                                       _film->log()->log (
+                                               String::compose (
+                                                       "First video at %1, first audio at %2, pushing %3 audio frames of silence for %4 channels (%5 bytes per sample)",
+                                                       _first_video.get(), _first_audio.get(), s, ffa->channels(), bytes_per_audio_sample()
+                                                       )
+                                               );
+                                       
+                                       if (s) {
+                                               shared_ptr<AudioBuffers> audio (new AudioBuffers (ffa->channels(), s));
+                                               audio->make_silent ();
+                                               Audio (audio);
+                                       }
+                               }
 
-               if (_have_subtitle) {
-                       avsubtitle_free (&_subtitle);
-                       _have_subtitle = false;
+                               int const data_size = av_samples_get_buffer_size (
+                                       0, _audio_codec_context->channels, _frame->nb_samples, audio_sample_format (), 1
+                                       );
+                               
+                               assert (_audio_codec_context->channels == _film->audio_channels());
+                               Audio (deinterleave_audio (_frame->data[0], data_size));
+                       }
                }
+                       
+       } else if (_subtitle_stream && _packet.stream_index == _subtitle_stream->id() && _opt->decode_subtitles && _first_video) {
 
                int got_subtitle;
-               if (avcodec_decode_subtitle2 (_subtitle_codec_context, &_subtitle, &got_subtitle, &_packet) && got_subtitle) {
-                       _have_subtitle = true;
+               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 {
+                                       emit_subtitle (shared_ptr<TimedSubtitle> (new TimedSubtitle (sub, _first_video.get())));
+                               } catch (...) {
+                                       /* some problem with the subtitle; we probably didn't understand it */
+                               }
+                       } else {
+                               emit_subtitle (shared_ptr<TimedSubtitle> ());
+                       }
+                       avsubtitle_free (&sub);
                }
        }
        
@@ -341,36 +383,84 @@ FFmpegDecoder::do_pass ()
        return false;
 }
 
-int
-FFmpegDecoder::length_in_frames () const
+shared_ptr<AudioBuffers>
+FFmpegDecoder::deinterleave_audio (uint8_t* data, int size)
 {
-       return (_format_context->duration / AV_TIME_BASE) * frames_per_second ();
-}
+       assert (_film->audio_channels());
+       assert (bytes_per_audio_sample());
 
-float
-FFmpegDecoder::frames_per_second () const
-{
-       return av_q2d (_format_context->streams[_video_stream]->avg_frame_rate);
-}
+       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);
+
+       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));
+
+       switch (audio_sample_format()) {
+       case AV_SAMPLE_FMT_S16:
+       {
+               int16_t* p = (int16_t *) data;
+               int sample = 0;
+               int channel = 0;
+               for (int i = 0; i < total_samples; ++i) {
+                       audio->data(channel)[sample] = float(*p++) / (1 << 15);
+
+                       ++channel;
+                       if (channel == _film->audio_channels()) {
+                               channel = 0;
+                               ++sample;
+                       }
+               }
+       }
+       break;
+
+       case AV_SAMPLE_FMT_S32:
+       {
+               int32_t* p = (int32_t *) data;
+               int sample = 0;
+               int channel = 0;
+               for (int i = 0; i < total_samples; ++i) {
+                       audio->data(channel)[sample] = float(*p++) / (1 << 31);
+
+                       ++channel;
+                       if (channel == _film->audio_channels()) {
+                               channel = 0;
+                               ++sample;
+                       }
+               }
+       }
 
-int
-FFmpegDecoder::audio_channels () const
-{
-       if (_audio_codec_context == 0) {
-               return 0;
+       case AV_SAMPLE_FMT_FLTP:
+       {
+               float* p = reinterpret_cast<float*> (data);
+               for (int i = 0; i < _film->audio_channels(); ++i) {
+                       memcpy (audio->data(i), p, frames * sizeof(float));
+                       p += frames;
+               }
        }
+       break;
 
-       return _audio_codec_context->channels;
+       default:
+               assert (false);
+       }
+
+       return audio;
 }
 
-int
-FFmpegDecoder::audio_sample_rate () const
+float
+FFmpegDecoder::frames_per_second () const
 {
-       if (_audio_codec_context == 0) {
-               return 0;
+       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 _audio_codec_context->sample_rate;
+
+       return av_q2d (s->r_frame_rate);
 }
 
 AVSampleFormat
@@ -383,16 +473,6 @@ FFmpegDecoder::audio_sample_format () const
        return _audio_codec_context->sample_fmt;
 }
 
-int64_t
-FFmpegDecoder::audio_channel_layout () const
-{
-       if (_audio_codec_context == 0) {
-               return 0;
-       }
-       
-       return _audio_codec_context->channel_layout;
-}
-
 Size
 FFmpegDecoder::native_size () const
 {
@@ -429,3 +509,131 @@ FFmpegDecoder::sample_aspect_ratio_denominator () const
        return _video_codec_context->sample_aspect_ratio.den;
 }
 
+string
+FFmpegDecoder::stream_name (AVStream* s) const
+{
+       stringstream n;
+       
+       AVDictionaryEntry const * lang = av_dict_get (s->metadata, "language", 0, 0);
+       if (lang) {
+               n << lang->value;
+       }
+       
+       AVDictionaryEntry const * title = av_dict_get (s->metadata, "title", 0, 0);
+       if (title) {
+               if (!n.str().empty()) {
+                       n << " ";
+               }
+               n << title->value;
+       }
+
+       if (n.str().empty()) {
+               n << "unknown";
+       }
+
+       return n.str ();
+}
+
+int
+FFmpegDecoder::bytes_per_audio_sample () const
+{
+       return av_get_bytes_per_sample (audio_sample_format ());
+}
+
+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)
+{
+       VideoDecoder::set_subtitle_stream (s);
+       setup_subtitle ();
+}
+
+void
+FFmpegDecoder::filter_and_emit_video (AVFrame* frame)
+{
+       shared_ptr<FilterGraph> graph;
+
+       list<shared_ptr<FilterGraph> >::iterator i = _filter_graphs.begin();
+       while (i != _filter_graphs.end() && !(*i)->can_process (Size (frame->width, frame->height), (AVPixelFormat) frame->format)) {
+               ++i;
+       }
+
+       if (i == _filter_graphs.end ()) {
+               graph.reset (new FilterGraph (_film, this, _opt->apply_crop, Size (frame->width, frame->height), (AVPixelFormat) frame->format));
+               _filter_graphs.push_back (graph);
+               _film->log()->log (String::compose ("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);
+       }
+}
+
+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 != "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 == "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 ("ffmpeg %1 %2 %3 %4", _id, _sample_rate, _channel_layout, _name);
+}
+
+/** @return Length (in video frames) according to our content's header */
+SourceFrame
+FFmpegDecoder::length () const
+{
+       return (double(_format_context->duration) / AV_TIME_BASE) * frames_per_second();
+}