gstreamer/gst/matroska/matroska-demux.c

/* GStreamer Matroska muxer/demuxer
 * (c) 2003 Ronald Bultje <rbultje@ronald.bitfreak.net>
 *
 * matroska-demux.c: matroska file/stream demuxer
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <math.h>
#include <string.h>

/* For AVI compatibility mode... Who did that? */
#include <gst/riff/riff-ids.h>
#include <gst/riff/riff-media.h>

#include "matroska-demux.h"
#include "matroska-ids.h"

GST_DEBUG_CATEGORY (matroskademux_debug);
#define GST_CAT_DEFAULT matroskademux_debug

enum
{
  /* FILL ME */
  LAST_SIGNAL
};

enum
{
  ARG_0,
  ARG_METADATA,
  ARG_STREAMINFO
      /* FILL ME */
};

static GstStaticPadTemplate sink_templ = GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/x-matroska")
    );

/* gobject magic foo */
static void gst_matroska_demux_base_init (GstMatroskaDemuxClass * klass);
static void gst_matroska_demux_class_init (GstMatroskaDemuxClass * klass);
static void gst_matroska_demux_init (GstMatroskaDemux * demux);

/* element functions */
static void gst_matroska_demux_loop (GstElement * element);
static gboolean gst_matroska_demux_send_event (GstElement * element,
    GstEvent * event);

/* pad functions */
static const GstEventMask *gst_matroska_demux_get_event_mask (GstPad * pad);
static gboolean gst_matroska_demux_handle_src_event (GstPad * pad,
    GstEvent * event);
static const GstFormat *gst_matroska_demux_get_src_formats (GstPad * pad);
static const GstQueryType *gst_matroska_demux_get_src_query_types (GstPad *
    pad);
static gboolean gst_matroska_demux_handle_src_query (GstPad * pad,
    GstQueryType type, GstFormat * format, gint64 * value);

/* gst internal change state handler */
static GstElementStateReturn
gst_matroska_demux_change_state (GstElement * element);
static void gst_matroska_demux_set_clock (GstElement * element,
    GstClock * clock);

/* caps functions */
static GstCaps *gst_matroska_demux_video_caps (GstMatroskaTrackVideoContext
    * videocontext,
    const gchar * codec_id,
    gpointer data, guint size, GstMatroskaDemux * demux);
static GstCaps *gst_matroska_demux_audio_caps (GstMatroskaTrackAudioContext
    * audiocontext,
    const gchar * codec_id,
    gpointer data, guint size, GstMatroskaDemux * demux);
static GstCaps *gst_matroska_demux_complex_caps (GstMatroskaTrackComplexContext
    * complexcontext, const gchar * codec_id, gpointer data, guint size);
static GstCaps
    * gst_matroska_demux_subtitle_caps (GstMatroskaTrackSubtitleContext *
    subtitlecontext, const gchar * codec_id, gpointer data, guint size);

/* stream methods */
static void gst_matroska_demux_reset (GstElement * element);

static GstEbmlReadClass *parent_class = NULL;
static GstPadTemplate *videosrctempl, *audiosrctempl, *subtitlesrctempl;

/*static guint gst_matroska_demux_signals[LAST_SIGNAL] = { 0 };*/

GType
gst_matroska_demux_get_type (void)
{
  static GType gst_matroska_demux_type = 0;

  if (!gst_matroska_demux_type) {
    static const GTypeInfo gst_matroska_demux_info = {
      sizeof (GstMatroskaDemuxClass),
      (GBaseInitFunc) gst_matroska_demux_base_init,
      NULL,
      (GClassInitFunc) gst_matroska_demux_class_init,
      NULL,
      NULL,
      sizeof (GstMatroskaDemux),
      0,
      (GInstanceInitFunc) gst_matroska_demux_init,
    };

    gst_matroska_demux_type =
        g_type_register_static (GST_TYPE_EBML_READ,
        "GstMatroskaDemux", &gst_matroska_demux_info, 0);
  }

  return gst_matroska_demux_type;
}

static void
gst_matroska_demux_base_init (GstMatroskaDemuxClass * klass)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
  static GstElementDetails gst_matroska_demux_details = {
    "Matroska demuxer",
    "Codec/Demuxer",
    "Demuxes a Matroska Stream into video/audio/subtitles",
    "Ronald Bultje <rbultje@ronald.bitfreak.net>"
  };

  gst_element_class_add_pad_template (element_class, videosrctempl);
  gst_element_class_add_pad_template (element_class, audiosrctempl);
  gst_element_class_add_pad_template (element_class, subtitlesrctempl);
  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&sink_templ));
  gst_element_class_set_details (element_class, &gst_matroska_demux_details);
}

static void
gst_matroska_demux_class_init (GstMatroskaDemuxClass * klass)
{
  GstElementClass *gstelement_class;

  gstelement_class = (GstElementClass *) klass;

  parent_class = g_type_class_ref (GST_TYPE_EBML_READ);

  gstelement_class->change_state = gst_matroska_demux_change_state;
  gstelement_class->send_event = gst_matroska_demux_send_event;
  gstelement_class->set_clock = gst_matroska_demux_set_clock;

  GST_DEBUG_CATEGORY_INIT (matroskademux_debug, "matroskademux", 0,
      "Matroska demuxer");
}

static void
gst_matroska_demux_init (GstMatroskaDemux * demux)
{
  GstElementClass *klass = GST_ELEMENT_GET_CLASS (demux);
  gint i;

  GST_FLAG_SET (GST_OBJECT (demux), GST_ELEMENT_EVENT_AWARE);

  demux->sinkpad =
      gst_pad_new_from_template (gst_element_class_get_pad_template (klass,
          "sink"), "sink");
  gst_element_add_pad (GST_ELEMENT (demux), demux->sinkpad);
  GST_EBML_READ (demux)->sinkpad = demux->sinkpad;

  gst_element_set_loop_function (GST_ELEMENT (demux), gst_matroska_demux_loop);

  /* initial stream no. */
  for (i = 0; i < GST_MATROSKA_DEMUX_MAX_STREAMS; i++) {
    demux->src[i] = NULL;
  }
  demux->writing_app = demux->muxing_app = NULL;
  demux->index = NULL;

  /* finish off */
  gst_matroska_demux_reset (GST_ELEMENT (demux));
}

static void
gst_matroska_demux_reset (GstElement * element)
{
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (element);
  guint i;

  /* reset input */
  demux->state = GST_MATROSKA_DEMUX_STATE_START;

  /* clean up existing streams */
  for (i = 0; i < GST_MATROSKA_DEMUX_MAX_STREAMS; i++) {
    if (demux->src[i] != NULL) {
      if (demux->src[i]->pad != NULL) {
        gst_element_remove_pad (GST_ELEMENT (demux), demux->src[i]->pad);
      }
      g_free (demux->src[i]->codec_id);
      g_free (demux->src[i]->codec_name);
      g_free (demux->src[i]->name);
      g_free (demux->src[i]->language);
      g_free (demux->src[i]->codec_priv);
      g_free (demux->src[i]);
      demux->src[i] = NULL;
    }
  }
  demux->num_streams = 0;
  demux->num_a_streams = 0;
  demux->num_t_streams = 0;
  demux->num_v_streams = 0;

  /* reset media info */
  g_free (demux->writing_app);
  demux->writing_app = NULL;
  g_free (demux->muxing_app);
  demux->muxing_app = NULL;

  /* reset indexes */
  demux->num_indexes = 0;
  g_free (demux->index);
  demux->index = NULL;

  /* reset timers */
  demux->clock = NULL;
  demux->time_scale = 1000000;
  demux->duration = 0;
  demux->pos = 0;
  demux->created = G_MININT64;
  demux->seek_pending = GST_CLOCK_TIME_NONE;

  demux->metadata_parsed = FALSE;
  demux->index_parsed = FALSE;
}

static void
gst_matroska_demux_set_clock (GstElement * element, GstClock * clock)
{
  GST_MATROSKA_DEMUX (element)->clock = clock;
}

static gint
gst_matroska_demux_stream_from_num (GstMatroskaDemux * demux, guint track_num)
{
  guint n;

  for (n = 0; n < demux->num_streams; n++) {
    if (demux->src[n] != NULL && demux->src[n]->num == track_num) {
      return n;
    }
  }

  if (n == demux->num_streams) {
    GST_WARNING ("Failed to find corresponding pad for tracknum %d", track_num);
  }

  return -1;
}

static GstCaps *
gst_matroska_demux_src_getcaps (GstPad * pad)
{
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (gst_pad_get_parent (pad));
  guint n;

  for (n = 0; n < demux->num_streams; n++) {
    if (demux->src[n] != NULL && demux->src[n]->pad == pad) {
      break;
    }
  }

  if (n == demux->num_streams)
    return gst_caps_new_empty ();

  return gst_caps_copy (demux->src[n]->caps);
}

static gboolean
gst_matroska_demux_add_stream (GstMatroskaDemux * demux)
{
  GstElementClass *klass = GST_ELEMENT_GET_CLASS (demux);
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  GstMatroskaTrackContext *context;
  GstPadTemplate *templ = NULL;
  GstCaps *caps = NULL;
  gchar *padname = NULL;
  gboolean res = TRUE;
  guint32 id;

  if (demux->num_streams >= GST_MATROSKA_DEMUX_MAX_STREAMS) {
    GST_WARNING ("Maximum number of streams (%d) exceeded, skipping",
        GST_MATROSKA_DEMUX_MAX_STREAMS);
    return gst_ebml_read_skip (ebml);   /* skip-and-continue */
  }

  /* allocate generic... if we know the type, we'll g_renew()
   * with the precise type */
  context = g_new0 (GstMatroskaTrackContext, 1);
  demux->src[demux->num_streams] = context;
  context->index = demux->num_streams;
  context->type = 0;            /* no type yet */
  demux->num_streams++;

  /* start with the master */
  if (!gst_ebml_read_master (ebml, &id))
    return FALSE;

  /* try reading the trackentry headers */
  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up > 0) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* track number (unique stream ID) */
      case GST_MATROSKA_ID_TRACKNUMBER:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        context->num = num;
        break;
      }

        /* track UID (unique identifier) */
      case GST_MATROSKA_ID_TRACKUID:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        context->uid = num;
        break;
      }

        /* track type (video, audio, combined, subtitle, etc.) */
      case GST_MATROSKA_ID_TRACKTYPE:{
        guint64 num;

        if (context->type != 0) {
          GST_WARNING
              ("More than one tracktype defined in a trackentry - skipping");
          break;
        }
        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        context->type = num;

        /* ok, so we're actually going to reallocate this thing */
        switch (context->type) {
          case GST_MATROSKA_TRACK_TYPE_VIDEO:
            context = (GstMatroskaTrackContext *)
                g_renew (GstMatroskaTrackVideoContext, context, 1);
            break;
          case GST_MATROSKA_TRACK_TYPE_AUDIO:
            context = (GstMatroskaTrackContext *)
                g_renew (GstMatroskaTrackAudioContext, context, 1);
            /* defaults */
            ((GstMatroskaTrackAudioContext *) context)->channels = 1;
            ((GstMatroskaTrackAudioContext *) context)->samplerate = 8000;
            break;
          case GST_MATROSKA_TRACK_TYPE_COMPLEX:
            context = (GstMatroskaTrackContext *)
                g_renew (GstMatroskaTrackComplexContext, context, 1);
            break;
          case GST_MATROSKA_TRACK_TYPE_SUBTITLE:
            context = (GstMatroskaTrackContext *)
                g_renew (GstMatroskaTrackSubtitleContext, context, 1);
            break;
          case GST_MATROSKA_TRACK_TYPE_LOGO:
          case GST_MATROSKA_TRACK_TYPE_CONTROL:
          default:
            GST_WARNING ("Unknown or unsupported track type 0x%x",
                context->type);
            context->type = 0;
            break;
        }
        demux->src[demux->num_streams - 1] = context;
        break;
      }

        /* tracktype specific stuff for video */
      case GST_MATROSKA_ID_TRACKVIDEO:{
        GstMatroskaTrackVideoContext *videocontext;

        if (context->type != GST_MATROSKA_TRACK_TYPE_VIDEO) {
          GST_WARNING
              ("trackvideo EBML entry in non-video track - ignoring track");
          res = FALSE;
          break;
        } else if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        videocontext = (GstMatroskaTrackVideoContext *) context;

        while (res) {
          if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
            res = FALSE;
            break;
          } else if (demux->level_up > 0) {
            demux->level_up--;
            break;
          }

          switch (id) {
              /* fixme, this should be one-up, but I get it here (?) */
            case GST_MATROSKA_ID_TRACKDEFAULTDURATION:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              context->default_duration = num;
              break;
            }

              /* video framerate */
            case GST_MATROSKA_ID_VIDEOFRAMERATE:{
              gdouble num;

              if (!gst_ebml_read_float (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              context->default_duration = GST_SECOND * (1. / num);
              break;
            }

              /* width of the size to display the video at */
            case GST_MATROSKA_ID_VIDEODISPLAYWIDTH:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              videocontext->display_width = num;
              GST_DEBUG ("display_width %" G_GUINT64_FORMAT, num);
              break;
            }

              /* height of the size to display the video at */
            case GST_MATROSKA_ID_VIDEODISPLAYHEIGHT:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              videocontext->display_height = num;
              GST_DEBUG ("display_height %" G_GUINT64_FORMAT, num);
              break;
            }

              /* width of the video in the file */
            case GST_MATROSKA_ID_VIDEOPIXELWIDTH:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              videocontext->pixel_width = num;
              GST_DEBUG ("pixel_width %" G_GUINT64_FORMAT, num);
              break;
            }

              /* height of the video in the file */
            case GST_MATROSKA_ID_VIDEOPIXELHEIGHT:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              videocontext->pixel_height = num;
              GST_DEBUG ("pixel_height %" G_GUINT64_FORMAT, num);
              break;
            }

              /* whether the video is interlaced */
            case GST_MATROSKA_ID_VIDEOFLAGINTERLACED:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              if (num)
                context->flags |= GST_MATROSKA_VIDEOTRACK_INTERLACED;
              else
                context->flags &= ~GST_MATROSKA_VIDEOTRACK_INTERLACED;
              break;
            }

              /* stereo mode (whether the video has two streams, where
               * one is for the left eye and the other for the right eye,
               * which creates a 3D-like effect) */
            case GST_MATROSKA_ID_VIDEOSTEREOMODE:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              if (num != GST_MATROSKA_EYE_MODE_MONO &&
                  num != GST_MATROSKA_EYE_MODE_LEFT &&
                  num != GST_MATROSKA_EYE_MODE_RIGHT &&
                  num != GST_MATROSKA_EYE_MODE_BOTH) {
                GST_WARNING ("Unknown eye mode 0x%x - ignoring", (guint) num);
                break;
              }
              videocontext->eye_mode = num;
              break;
            }

              /* aspect ratio behaviour */
            case GST_MATROSKA_ID_VIDEOASPECTRATIO:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              if (num != GST_MATROSKA_ASPECT_RATIO_MODE_FREE &&
                  num != GST_MATROSKA_ASPECT_RATIO_MODE_KEEP &&
                  num != GST_MATROSKA_ASPECT_RATIO_MODE_FIXED) {
                GST_WARNING ("Unknown aspect ratio mode 0x%x - ignoring",
                    (guint) num);
                break;
              }
              videocontext->asr_mode = num;
              break;
            }

              /* colourspace (only matters for raw video) fourcc */
            case GST_MATROSKA_ID_VIDEOCOLOURSPACE:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              videocontext->fourcc = num;
              break;
            }

            default:
              GST_WARNING ("Unknown video track header entry 0x%x - ignoring",
                  id);
              /* pass-through */

            case GST_EBML_ID_VOID:
              if (!gst_ebml_read_skip (ebml))
                res = FALSE;
              break;
          }

          if (demux->level_up) {
            demux->level_up--;
            break;
          }
        }
        break;
      }

        /* tracktype specific stuff for audio */
      case GST_MATROSKA_ID_TRACKAUDIO:{
        GstMatroskaTrackAudioContext *audiocontext;

        if (context->type != GST_MATROSKA_TRACK_TYPE_AUDIO) {
          GST_WARNING
              ("trackaudio EBML entry in non-audio track - ignoring track");
          res = FALSE;
          break;
        } else if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        audiocontext = (GstMatroskaTrackAudioContext *) context;

        while (res) {
          if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
            res = FALSE;
            break;
          } else if (demux->level_up > 0) {
            demux->level_up--;
            break;
          }

          switch (id) {
              /* samplerate */
            case GST_MATROSKA_ID_AUDIOSAMPLINGFREQ:{
              gdouble num;

              if (!gst_ebml_read_float (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              audiocontext->samplerate = num;
              break;
            }

              /* bitdepth */
            case GST_MATROSKA_ID_AUDIOBITDEPTH:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              audiocontext->bitdepth = num;
              break;
            }

              /* channels */
            case GST_MATROSKA_ID_AUDIOCHANNELS:{
              guint64 num;

              if (!gst_ebml_read_uint (ebml, &id, &num)) {
                res = FALSE;
                break;
              }
              audiocontext->channels = num;
              break;
            }

            default:
              GST_WARNING ("Unknown audio track header entry 0x%x - ignoring",
                  id);
              /* pass-through */

            case GST_EBML_ID_VOID:
              if (!gst_ebml_read_skip (ebml))
                res = FALSE;
              break;
          }

          if (demux->level_up) {
            demux->level_up--;
            break;
          }
        }
        break;
      }

        /* codec identifier */
      case GST_MATROSKA_ID_CODECID:{
        gchar *text;

        if (!gst_ebml_read_ascii (ebml, &id, &text)) {
          res = FALSE;
          break;
        }
        context->codec_id = text;
        break;
      }

        /* codec private data */
      case GST_MATROSKA_ID_CODECPRIVATE:{
        guint8 *data;
        guint64 size;

        if (!gst_ebml_read_binary (ebml, &id, &data, &size)) {
          res = FALSE;
          break;
        }
        context->codec_priv = data;
        context->codec_priv_size = size;
        break;
      }

        /* name of the codec */
      case GST_MATROSKA_ID_CODECNAME:{
        gchar *text;

        if (!gst_ebml_read_utf8 (ebml, &id, &text)) {
          res = FALSE;
          break;
        }
        context->codec_name = text;
        break;
      }

        /* name of this track */
      case GST_MATROSKA_ID_TRACKNAME:{
        gchar *text;

        if (!gst_ebml_read_utf8 (ebml, &id, &text)) {
          res = FALSE;
          break;
        }
        context->name = text;
        break;
      }

        /* language (matters for audio/subtitles, mostly) */
      case GST_MATROSKA_ID_TRACKLANGUAGE:{
        gchar *text;

        if (!gst_ebml_read_utf8 (ebml, &id, &text)) {
          res = FALSE;
          break;
        }
        context->language = text;
        break;
      }

        /* whether this is actually used */
      case GST_MATROSKA_ID_TRACKFLAGENABLED:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        if (num)
          context->flags |= GST_MATROSKA_TRACK_ENABLED;
        else
          context->flags &= ~GST_MATROSKA_TRACK_ENABLED;
        break;
      }

        /* whether it's the default for this track type */
      case GST_MATROSKA_ID_TRACKFLAGDEFAULT:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        if (num)
          context->flags |= GST_MATROSKA_TRACK_DEFAULT;
        else
          context->flags &= ~GST_MATROSKA_TRACK_DEFAULT;
        break;
      }

        /* lacing (like MPEG, where blocks don't end/start on frame
         * boundaries) */
      case GST_MATROSKA_ID_TRACKFLAGLACING:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        if (num)
          context->flags |= GST_MATROSKA_TRACK_LACING;
        else
          context->flags &= ~GST_MATROSKA_TRACK_LACING;
        break;
      }

        /* default length (in time) of one data block in this track */
      case GST_MATROSKA_ID_TRACKDEFAULTDURATION:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        context->default_duration = num;
        break;
      }

      default:
        GST_WARNING ("Unknown track header entry 0x%x - ignoring", id);
        /* pass-through */

        /* we ignore these because they're nothing useful (i.e. crap). */
      case GST_MATROSKA_ID_CODECINFOURL:
      case GST_MATROSKA_ID_CODECDOWNLOADURL:
      case GST_MATROSKA_ID_TRACKMINCACHE:
      case GST_MATROSKA_ID_TRACKMAXCACHE:
      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  if (context->type == 0 || context->codec_id == NULL || !res) {
    if (res)
      GST_WARNING ("Unknown stream/codec in track entry header");

    demux->num_streams--;
    demux->src[demux->num_streams] = NULL;
    if (context) {
      g_free (context->codec_id);
      g_free (context->codec_name);
      g_free (context->name);
      g_free (context->language);
      g_free (context->codec_priv);
      g_free (context);
    }

    return res;
  }

  /* now create the GStreamer connectivity */
  switch (context->type) {
    case GST_MATROSKA_TRACK_TYPE_VIDEO:{
      GstMatroskaTrackVideoContext *videocontext =
          (GstMatroskaTrackVideoContext *) context;
      padname = g_strdup_printf ("video_%02d", demux->num_v_streams++);
      templ = gst_element_class_get_pad_template (klass, "video_%02d");
      caps = gst_matroska_demux_video_caps (videocontext,
          context->codec_id,
          context->codec_priv, context->codec_priv_size, demux);
      break;
    }

    case GST_MATROSKA_TRACK_TYPE_AUDIO:{
      GstMatroskaTrackAudioContext *audiocontext =
          (GstMatroskaTrackAudioContext *) context;
      padname = g_strdup_printf ("audio_%02d", demux->num_a_streams++);
      templ = gst_element_class_get_pad_template (klass, "audio_%02d");
      caps = gst_matroska_demux_audio_caps (audiocontext,
          context->codec_id,
          context->codec_priv, context->codec_priv_size, demux);
      break;
    }

    case GST_MATROSKA_TRACK_TYPE_COMPLEX:{
      GstMatroskaTrackComplexContext *complexcontext =
          (GstMatroskaTrackComplexContext *) context;
      padname = g_strdup_printf ("video_%02d", demux->num_v_streams++);
      templ = gst_element_class_get_pad_template (klass, "video_%02d");
      caps = gst_matroska_demux_complex_caps (complexcontext,
          context->codec_id, context->codec_priv, context->codec_priv_size);
      break;
    }

    case GST_MATROSKA_TRACK_TYPE_SUBTITLE:{
      GstMatroskaTrackSubtitleContext *subtitlecontext =
          (GstMatroskaTrackSubtitleContext *) context;
      padname = g_strdup_printf ("subtitle_%02d", demux->num_t_streams++);
      templ = gst_element_class_get_pad_template (klass, "subtitle_%02d");
      caps = gst_matroska_demux_subtitle_caps (subtitlecontext,
          context->codec_id, context->codec_priv, context->codec_priv_size);
      break;
    }

    case GST_MATROSKA_TRACK_TYPE_LOGO:
    case GST_MATROSKA_TRACK_TYPE_CONTROL:
    default:
      /* we should already have quit by now */
      g_assert (0);
  }

  /* the pad in here */
  context->pad = gst_pad_new_from_template (templ, padname);
  context->caps = caps ? caps : gst_caps_new_empty ();

  g_free (padname);

  /* set some functions */
  gst_pad_set_formats_function (context->pad,
      gst_matroska_demux_get_src_formats);
  gst_pad_set_event_mask_function (context->pad,
      gst_matroska_demux_get_event_mask);
  gst_pad_set_event_function (context->pad,
      gst_matroska_demux_handle_src_event);
  gst_pad_set_query_type_function (context->pad,
      gst_matroska_demux_get_src_query_types);
  gst_pad_set_query_function (context->pad,
      gst_matroska_demux_handle_src_query);
  gst_pad_set_getcaps_function (context->pad, gst_matroska_demux_src_getcaps);

  gst_element_add_pad (GST_ELEMENT (demux), context->pad);

  /* tadaah! */
  return TRUE;
}

static const GstFormat *
gst_matroska_demux_get_src_formats (GstPad * pad)
{
  /*GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (gst_pad_get_parent (pad)); */

  /* we could try to look for units (i.e. samples) in audio streams
   * or video streams, but both samplerate and framerate are not
   * always constant, and since we only have a time indication, we
   * cannot guarantee anything here based purely on index. So, we
   * only support time for now. */
  static const GstFormat src_formats[] = {
    GST_FORMAT_TIME,
    (GstFormat) 0
  };

  return src_formats;
}

static const GstQueryType *
gst_matroska_demux_get_src_query_types (GstPad * pad)
{
  static const GstQueryType src_types[] = {
    GST_QUERY_TOTAL,
    GST_QUERY_POSITION,
    (GstQueryType) 0
  };

  return src_types;
}

static gboolean
gst_matroska_demux_handle_src_query (GstPad * pad,
    GstQueryType type, GstFormat * format, gint64 * value)
{
  gboolean res = TRUE;
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (gst_pad_get_parent (pad));

  switch (type) {
    case GST_QUERY_TOTAL:
      switch (*format) {
        case GST_FORMAT_DEFAULT:
          *format = GST_FORMAT_TIME;
          /* fall through */
        case GST_FORMAT_TIME:
          *value = demux->duration;
          break;
        default:
          res = FALSE;
          break;
      }
      break;

    case GST_QUERY_POSITION:
      switch (*format) {
        case GST_FORMAT_DEFAULT:
          *format = GST_FORMAT_TIME;
          /* fall through */
        case GST_FORMAT_TIME:
          *value = demux->pos;
          break;
        default:
          res = FALSE;
          break;
      }
      break;

    default:
      res = FALSE;
      break;
  }

  return res;
}

static GstMatroskaIndex *
gst_matroskademux_seek (GstMatroskaDemux * demux)
{
  guint entry = (guint) - 1;
  guint64 offset = demux->seek_pending;
  guint n;

  /* make sure we don't seek twice */
  demux->seek_pending = GST_CLOCK_TIME_NONE;

  for (n = 0; n < demux->num_indexes; n++) {
    if (entry == (guint) - 1) {
      entry = n;
    } else {
      gfloat diff_old = fabs (1. * (demux->index[entry].time - offset)),
          diff_new = fabs (1. * (demux->index[n].time - offset));

      if (diff_new < diff_old) {
        entry = n;
      }
    }
  }

  if (entry != (guint) - 1) {
    return &demux->index[entry];
  }

  return NULL;
}

static gboolean
gst_matroska_demux_send_event (GstElement * element, GstEvent * event)
{
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (element);
  gboolean res = TRUE;

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEEK:
      switch (GST_EVENT_SEEK_FORMAT (event)) {
        case GST_FORMAT_TIME:
          demux->seek_pending = GST_EVENT_SEEK_OFFSET (event);
          break;

        default:
          GST_WARNING ("Only time seek is supported");
          res = FALSE;
          break;
      }
      break;

    default:
      GST_WARNING ("Unhandled event of type %d", GST_EVENT_TYPE (event));
      res = FALSE;
      break;
  }

  gst_event_unref (event);

  return res;
}

static const GstEventMask *
gst_matroska_demux_get_event_mask (GstPad * pad)
{
  static const GstEventMask masks[] = {
    {GST_EVENT_SEEK, (GstEventFlag) ((gint) GST_SEEK_METHOD_SET |
              (gint) GST_SEEK_FLAG_KEY_UNIT)},
    {GST_EVENT_SEEK_SEGMENT, (GstEventFlag) ((gint) GST_SEEK_METHOD_SET |
              (gint) GST_SEEK_FLAG_KEY_UNIT)},
    {(GstEventType) 0, (GstEventFlag) 0}
  };

  return masks;
}

static gboolean
gst_matroska_demux_handle_src_event (GstPad * pad, GstEvent * event)
{
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (gst_pad_get_parent (pad));
  gboolean res = TRUE;

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEEK_SEGMENT:
    case GST_EVENT_SEEK:
      return gst_matroska_demux_send_event (GST_ELEMENT (demux), event);

      /* events we don't need to handle */
    case GST_EVENT_NAVIGATION:
      break;

    default:
      GST_WARNING ("Unhandled event of type %d", GST_EVENT_TYPE (event));
      res = FALSE;
      break;
  }

  gst_event_unref (event);

  return res;
}

static gboolean
gst_matroska_demux_handle_seek_event (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  GstMatroskaIndex *entry = gst_matroskademux_seek (demux);
  GstEvent *event;
  guint i;

  if (!entry)
    return FALSE;

  /* seek (relative to segment) */
  if (!(event = gst_ebml_read_seek (ebml, entry->pos + demux->segment_start)))
    return FALSE;
  gst_event_unref (event);      /* byte - we want time */
  event =
      gst_event_new_discontinuous (FALSE, GST_FORMAT_TIME, entry->time,
      GST_FORMAT_UNDEFINED);

  /* forward to all src pads */
  for (i = 0; i < demux->num_streams; i++) {
    if (GST_PAD_IS_USABLE (demux->src[i]->pad)) {
      gst_event_ref (event);
      gst_pad_push (demux->src[i]->pad, GST_DATA (event));
    }
  }

  gst_event_unref (event);

  return TRUE;
}

static gboolean
gst_matroska_demux_init_stream (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  guint32 id;
  gchar *doctype;
  guint version;

  if (!gst_ebml_read_header (ebml, &doctype, &version))
    return FALSE;

  if (!doctype || strcmp (doctype, "matroska") != 0) {
    GST_ELEMENT_ERROR (demux, STREAM, WRONG_TYPE, (NULL),
        ("Input is not a matroska stream (doctype=%s)",
            doctype ? doctype : "none"));
    g_free (doctype);
    return FALSE;
  }
  g_free (doctype);
  if (version > 1) {
    GST_ELEMENT_ERROR (demux, STREAM, DEMUX, (NULL),
        ("Demuxer version (1) is too old to read stream version %d", version));
    return FALSE;
  }

  /* find segment, must be the next element */
  while (1) {
    guint last_level;

    if (!(id = gst_ebml_peek_id (ebml, &last_level)))
      return FALSE;

    if (id == GST_MATROSKA_ID_SEGMENT)
      break;

    /* oi! */
    GST_WARNING ("Expected a Segment ID (0x%x), but received 0x%x!",
        GST_MATROSKA_ID_SEGMENT, id);
    if (!gst_ebml_read_skip (ebml))
      return FALSE;
  }

  /* we now have a EBML segment */
  if (!gst_ebml_read_master (ebml, &id))
    return FALSE;
  /* seeks are from the beginning of the segment,
   * after the segment ID/length */
  demux->segment_start = gst_bytestream_tell (ebml->bs);

  return TRUE;
}

static gboolean
gst_matroska_demux_parse_tracks (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;

  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* one track within the "all-tracks" header */
      case GST_MATROSKA_ID_TRACKENTRY:
        if (!gst_matroska_demux_add_stream (demux))
          res = FALSE;
        break;

      default:
        GST_WARNING ("Unknown entry 0x%x in track header", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static gboolean
gst_matroska_demux_parse_index (GstMatroskaDemux * demux, gboolean prevent_eos)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;
  GstMatroskaIndex idx;
  guint64 length = 0;

  if (prevent_eos) {
    length = gst_bytestream_length (ebml->bs);
  }

  while (res) {
    /* We're an element that can be seeked to. If we are, then
     * we want to prevent EOS, since that'll kill us. So we cache
     * file size and seek until there, and don't call EOS upon os. */
    if (prevent_eos && length == gst_bytestream_tell (ebml->bs)) {
      res = FALSE;
      break;
    } else if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* one single index entry ('point') */
      case GST_MATROSKA_ID_POINTENTRY:
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }

        /* in the end, we hope to fill one entry with a
         * timestamp, a file position and a tracknum */
        idx.pos = (guint64) - 1;
        idx.time = (guint64) - 1;
        idx.track = (guint16) - 1;

        while (res) {
          if (prevent_eos && length == gst_bytestream_tell (ebml->bs)) {
            res = FALSE;
            break;
          } else if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
            res = FALSE;
            break;
          } else if (demux->level_up) {
            demux->level_up--;
            break;
          }

          switch (id) {
              /* one single index entry ('point') */
            case GST_MATROSKA_ID_CUETIME:{
              gint64 time;

              if (!gst_ebml_read_uint (ebml, &id, &time)) {
                res = FALSE;
                break;
              }
              idx.time = time * demux->time_scale;
              break;
            }

              /* position in the file + track to which it belongs */
            case GST_MATROSKA_ID_CUETRACKPOSITION:
              if (!gst_ebml_read_master (ebml, &id)) {
                res = FALSE;
                break;
              }

              while (res) {
                if (prevent_eos && length == gst_bytestream_tell (ebml->bs)) {
                  res = FALSE;
                  break;
                } else if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
                  res = FALSE;
                  break;
                } else if (demux->level_up) {
                  demux->level_up--;
                  break;
                }

                switch (id) {
                    /* track number */
                  case GST_MATROSKA_ID_CUETRACK:{
                    guint64 num;

                    if (!gst_ebml_read_uint (ebml, &id, &num)) {
                      res = FALSE;
                      break;
                    }
                    idx.track = num;
                    break;
                  }

                    /* position in file */
                  case GST_MATROSKA_ID_CUECLUSTERPOSITION:{
                    guint64 num;

                    if (!gst_ebml_read_uint (ebml, &id, &num)) {
                      res = FALSE;
                      break;
                    }
                    idx.pos = num;
                    break;
                  }

                  default:
                    GST_WARNING ("Unknown entry 0x%x in CuesTrackPositions",
                        id);
                    /* fall-through */

                  case GST_EBML_ID_VOID:
                    if (!gst_ebml_read_skip (ebml))
                      res = FALSE;
                    break;
                }

                if (demux->level_up) {
                  demux->level_up--;
                  break;
                }
              }

              break;

            default:
              GST_WARNING ("Unknown entry 0x%x in cuespoint index", id);
              /* fall-through */

            case GST_EBML_ID_VOID:
              if (!gst_ebml_read_skip (ebml))
                res = FALSE;
              break;
          }

          if (demux->level_up) {
            demux->level_up--;
            break;
          }
        }

        /* so let's see if we got what we wanted */
        if (idx.pos != (guint64) - 1 &&
            idx.time != (guint64) - 1 && idx.track != (guint16) - 1) {
          if (demux->num_indexes % 32 == 0) {
            /* re-allocate bigger index */
            demux->index = g_renew (GstMatroskaIndex, demux->index,
                demux->num_indexes + 32);
          }
          demux->index[demux->num_indexes].pos = idx.pos;
          demux->index[demux->num_indexes].time = idx.time;
          demux->index[demux->num_indexes].track = idx.track;
          demux->num_indexes++;
        }

        break;

      default:
        GST_WARNING ("Unknown entry 0x%x in cues header", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static gboolean
gst_matroska_demux_parse_info (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;

  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* cluster timecode */
      case GST_MATROSKA_ID_TIMECODESCALE:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        demux->time_scale = num;
        break;
      }

      case GST_MATROSKA_ID_DURATION:{
        gdouble num;

        if (!gst_ebml_read_float (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        demux->duration = num * demux->time_scale;
        break;
      }

      case GST_MATROSKA_ID_WRITINGAPP:{
        gchar *text;

        if (!gst_ebml_read_utf8 (ebml, &id, &text)) {
          res = FALSE;
          break;
        }
        demux->writing_app = text;
        break;
      }

      case GST_MATROSKA_ID_MUXINGAPP:{
        gchar *text;

        if (!gst_ebml_read_utf8 (ebml, &id, &text)) {
          res = FALSE;
          break;
        }
        demux->muxing_app = text;
        break;
      }

      case GST_MATROSKA_ID_DATEUTC:{
        gint64 time;

        if (!gst_ebml_read_date (ebml, &id, &time)) {
          res = FALSE;
          break;
        }
        demux->created = time;
        break;
      }

      default:
        GST_WARNING ("Unknown entry 0x%x in info header", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static gboolean
gst_matroska_demux_parse_metadata (GstMatroskaDemux * demux,
    gboolean prevent_eos)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;
  guint64 length = 0;
  struct
  {
    gchar *matroska_tagname;
    gchar *gstreamer_tagname;
  }
  tag_conv[] =
  {
    {
    GST_MATROSKA_TAG_ID_TITLE, GST_TAG_TITLE}
    , {
    GST_MATROSKA_TAG_ID_AUTHOR, GST_TAG_ARTIST}
    , {
    GST_MATROSKA_TAG_ID_ALBUM, GST_TAG_ALBUM}
    , {
    GST_MATROSKA_TAG_ID_COMMENTS, GST_TAG_COMMENT}
    , {
    GST_MATROSKA_TAG_ID_BITSPS, GST_TAG_BITRATE}
    , {
    GST_MATROSKA_TAG_ID_ENCODER, GST_TAG_ENCODER}
    , {
    GST_MATROSKA_TAG_ID_DATE, GST_TAG_DATE}
    , {
    GST_MATROSKA_TAG_ID_ISRC, GST_TAG_ISRC}
    , {
    GST_MATROSKA_TAG_ID_COPYRIGHT, GST_TAG_COPYRIGHT}
    , {
    NULL, NULL}
  };
  gint i;
  gboolean have_tags = FALSE;
  GstTagList *taglist = gst_tag_list_new ();

  if (prevent_eos) {
    length = gst_bytestream_length (ebml->bs);
  }

  while (res) {
    /* We're an element that can be seeked to. If we are, then
     * we want to prevent EOS, since that'll kill us. So we cache
     * file size and seek until there, and don't call EOS upon os. */
    if (prevent_eos && length == gst_bytestream_tell (ebml->bs)) {
      res = FALSE;
      break;
    } else if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
      case GST_MATROSKA_ID_TAG:
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }

        while (res) {
          /* read all sub-entries */
          if (prevent_eos && length == gst_bytestream_tell (ebml->bs)) {
            res = FALSE;
            break;
          } else if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
            res = FALSE;
            break;
          } else if (demux->level_up) {
            demux->level_up--;
            break;
          }

          switch (id) {
            case GST_MATROSKA_ID_SIMPLETAG:{
              gchar *tag = NULL, *value = NULL;

              if (!gst_ebml_read_master (ebml, &id)) {
                res = FALSE;
                break;
              }

              while (res) {
                /* read all sub-entries */
                if (prevent_eos && length == gst_bytestream_tell (ebml->bs)) {
                  res = FALSE;
                  break;
                } else if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
                  res = FALSE;
                  break;
                } else if (demux->level_up) {
                  demux->level_up--;
                  break;
                }

                switch (id) {
                  case GST_MATROSKA_ID_TAGNAME:
                    g_free (tag);
                    res = gst_ebml_read_ascii (ebml, &id, &tag);
                    break;

                  case GST_MATROSKA_ID_TAGSTRING:
                    g_free (value);
                    res = gst_ebml_read_utf8 (ebml, &id, &value);
                    break;

                  default:
                    GST_WARNING ("Unknown entry 0x%x in metadata collection",
                        id);
                    /* fall-through */

                  case GST_EBML_ID_VOID:
                    if (!gst_ebml_read_skip (ebml))
                      res = FALSE;
                    break;
                }

                if (demux->level_up) {
                  demux->level_up--;
                  break;
                }
              }

              if (tag && value) {
                for (i = 0; tag_conv[i].matroska_tagname != NULL; i++) {
                  if (!strcmp (tag_conv[i].matroska_tagname, tag)) {
                    GValue src = { 0 }
                    , dest =
                    {
                    0};
                    const gchar *type = tag_conv[i].gstreamer_tagname;
                    GType dest_type = gst_tag_get_type (type);

                    g_value_init (&src, G_TYPE_STRING);
                    g_value_set_string (&src, value);
                    g_value_init (&dest, dest_type);
                    g_value_transform (&src, &dest);
                    g_value_unset (&src);
                    gst_tag_list_add_values (taglist, GST_TAG_MERGE_APPEND,
                        type, &dest, NULL);
                    g_value_unset (&dest);
                    have_tags = TRUE;
                    break;
                  }
                }
              }
              g_free (tag);
              g_free (value);
              break;
            }

            default:
              GST_WARNING ("Unknown entry 0x%x in metadata collection", id);
              /* fall-through */

            case GST_EBML_ID_VOID:
              if (!gst_ebml_read_skip (ebml))
                res = FALSE;
              break;
          }

          if (demux->level_up) {
            demux->level_up--;
            break;
          }
        }
        break;

      default:
        GST_WARNING ("Unknown entry 0x%x in metadata header", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  if (have_tags) {
    const GList *padlist;

    /* let the world know about this wonderful thing */
    for (padlist = gst_element_get_pad_list (GST_ELEMENT (ebml));
        padlist != NULL; padlist = padlist->next) {
      if (GST_PAD_IS_SRC (padlist->data) && GST_PAD_IS_USABLE (padlist->data)) {
        gst_pad_push (GST_PAD (padlist->data),
            GST_DATA (gst_event_new_tag (taglist)));
      }
    }
    gst_element_found_tags (GST_ELEMENT (ebml), taglist);
  } else {
    gst_tag_list_free (taglist);
  }

  return res;
}

/*
 * Read signed/unsigned "EBML" numbers.
 * Return: number of bytes processed.
 */

static gint
gst_matroska_ebmlnum_uint (guint8 * data, guint size, guint64 * num)
{
  gint len_mask = 0x80, read = 1, n = 1, num_ffs = 0;
  guint64 total;

  if (size <= 0) {
    return -1;
  }

  total = data[0];
  while (read <= 8 && !(total & len_mask)) {
    read++;
    len_mask >>= 1;
  }
  if (read > 8)
    return -1;

  if ((total &= (len_mask - 1)) == len_mask - 1)
    num_ffs++;
  if (size < read)
    return -1;
  while (n < read) {
    if (data[n] == 0xff)
      num_ffs++;
    total = (total << 8) | data[n];
    n++;
  }

  if (!total)
    return -1;

  if (read == num_ffs)
    *num = G_MAXUINT64;
  else
    *num = total;

  return read;
}

static gint
gst_matroska_ebmlnum_sint (guint8 * data, guint size, gint64 * num)
{
  guint64 unum;
  gint res;

  /* read as unsigned number first */
  if ((res = gst_matroska_ebmlnum_uint (data, size, &unum)) < 0)
    return -1;

  /* make signed */
  if (unum == G_MAXUINT64)
    *num = G_MAXINT64;
  else
    *num = unum - ((1 << ((7 * res) - 1)) - 1);

  return res;
}

static gboolean
gst_matroska_demux_parse_blockgroup (GstMatroskaDemux * demux,
    guint64 cluster_time)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;

  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* one block inside the group. Note, block parsing is one
         * of the harder things, so this code is a bit complicated.
         * See http://www.matroska.org/ for documentation. */
      case GST_MATROSKA_ID_BLOCK:{
        GstBuffer *buf;
        guint8 *data;
        gint64 time;
        guint size, *lace_size = NULL;
        gint n, stream, flags, laces = 0;
        guint64 num;

        if (!gst_ebml_read_buffer (ebml, &id, &buf)) {
          res = FALSE;
          break;
        }
        data = GST_BUFFER_DATA (buf);
        size = GST_BUFFER_SIZE (buf);

        /* first byte(s): blocknum */
        if ((n = gst_matroska_ebmlnum_uint (data, size, &num)) < 0) {
          GST_ELEMENT_ERROR (demux, STREAM, DEMUX, (NULL), ("Data error"));
          gst_buffer_unref (buf);
          res = FALSE;
          break;
        }
        data += n;
        size -= n;

        /* fetch stream from num */
        stream = gst_matroska_demux_stream_from_num (demux, num);
        if (size <= 3 || stream < 0 || stream >= demux->num_streams) {
          gst_buffer_unref (buf);
          GST_WARNING ("Invalid stream %d or size %u", stream, size);
          break;
        }
        if (!GST_PAD_IS_USABLE (demux->src[stream]->pad)) {
          gst_buffer_unref (buf);
          break;
        }

        /* time (relative to cluster time) */
        time = (GINT16_FROM_BE (*(gint16 *) data)) * demux->time_scale;
        data += 2;
        size -= 2;
        flags = *(guint8 *) data;
        data += 1;
        size -= 1;
        switch ((flags & 0x06) >> 1) {
          case 0x0:            /* no lacing */
            laces = 1;
            lace_size = g_new (gint, 1);
            lace_size[0] = size;
            break;

          case 0x1:            /* xiph lacing */
          case 0x2:            /* fixed-size lacing */
          case 0x3:            /* EBML lacing */
            if (size == 0) {
              res = FALSE;
              break;
            }
            laces = (*(guint8 *) data) + 1;
            data += 1;
            size -= 1;
            lace_size = g_new0 (gint, laces);

            switch ((flags & 0x06) >> 1) {
              case 0x1:        /* xiph lacing */  {
                guint temp, total = 0;

                for (n = 0; res && n < laces - 1; n++) {
                  while (1) {
                    if (size == 0) {
                      res = FALSE;
                      break;
                    }
                    temp = *(guint8 *) data;
                    lace_size[n] += temp;
                    data += 1;
                    size -= 1;
                    if (temp != 0xff)
                      break;
                  }
                  total += lace_size[n];
                }
                lace_size[n] = size - total;
                break;
              }

              case 0x2:        /* fixed-size lacing */
                for (n = 0; n < laces; n++)
                  lace_size[n] = size / laces;
                break;

              case 0x3:        /* EBML lacing */  {
                guint total;

                if ((n = gst_matroska_ebmlnum_uint (data, size, &num)) < 0) {
                  GST_ELEMENT_ERROR (demux, STREAM, DEMUX, (NULL),
                      ("Data error"));
                  res = FALSE;
                  break;
                }
                data += n;
                size -= n;
                total = lace_size[0] = num;
                for (n = 1; res && n < laces - 1; n++) {
                  gint64 snum;
                  gint r;

                  if ((r = gst_matroska_ebmlnum_sint (data, size, &snum)) < 0) {
                    GST_ELEMENT_ERROR (demux, STREAM, DEMUX, (NULL),
                        ("Data error"));
                    res = FALSE;
                    break;
                  }
                  data += r;
                  size -= r;
                  lace_size[n] = lace_size[n - 1] + snum;
                  total += lace_size[n];
                }
                lace_size[n] = size - total;
                break;
              }
            }
            break;
        }

        if (res) {
          for (n = 0; n < laces; n++) {
            GstBuffer *sub = gst_buffer_create_sub (buf,
                GST_BUFFER_SIZE (buf) - size,
                lace_size[n]);

            if (cluster_time != GST_CLOCK_TIME_NONE) {
              if (time < 0 && (-time) > cluster_time)
                GST_BUFFER_TIMESTAMP (sub) = cluster_time;
              else
                GST_BUFFER_TIMESTAMP (sub) = cluster_time + time;
            }
            /* FIXME: duration */

            gst_pad_push (demux->src[stream]->pad, GST_DATA (sub));

            size -= lace_size[n];
          }
        }

        g_free (lace_size);
        gst_buffer_unref (buf);
        break;
      }

      case GST_MATROSKA_ID_BLOCKDURATION:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        GST_WARNING ("FIXME: implement support for BlockDuration");
        break;
      }
      case GST_MATROSKA_ID_REFERENCEBLOCK:{
        /* FIXME: this segfaults
           gint64 num;
           if (!gst_ebml_read_sint (ebml, &id, &num)) {
           res = FALSE;
           break;
           }
           GST_WARNING ("FIXME: implement support for ReferenceBlock");
         */
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
      }


      default:
        GST_WARNING ("Unknown entry 0x%x in blockgroup data", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static gboolean
gst_matroska_demux_parse_cluster (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;
  guint64 cluster_time = GST_CLOCK_TIME_NONE;

  /* We seek after index/header parsing before doing a new
   * buffer. So here. */
  if (demux->seek_pending != GST_CLOCK_TIME_NONE) {
    if (!gst_matroska_demux_handle_seek_event (demux))
      return FALSE;
    demux->seek_pending = GST_CLOCK_TIME_NONE;
  }

  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* cluster timecode */
      case GST_MATROSKA_ID_CLUSTERTIMECODE:{
        guint64 num;

        if (!gst_ebml_read_uint (ebml, &id, &num)) {
          res = FALSE;
          break;
        }
        cluster_time = num * demux->time_scale;
        break;
      }

        /* a group of blocks inside a cluster */
      case GST_MATROSKA_ID_BLOCKGROUP:
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        res = gst_matroska_demux_parse_blockgroup (demux, cluster_time);
        break;

      default:
        GST_WARNING ("Unknown entry 0x%x in cluster data", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static gboolean
gst_matroska_demux_parse_contents (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;

  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
      case GST_MATROSKA_ID_SEEKENTRY:{
        guint32 seek_id = 0;
        guint64 seek_pos = (guint64) - 1, t;

        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }

        while (res) {
          if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
            res = FALSE;
            break;
          } else if (demux->level_up) {
            demux->level_up--;
            break;
          }

          switch (id) {
            case GST_MATROSKA_ID_SEEKID:
              if (!gst_ebml_read_uint (ebml, &id, &t))
                res = FALSE;
              seek_id = t;
              break;

            case GST_MATROSKA_ID_SEEKPOSITION:
              if (!gst_ebml_read_uint (ebml, &id, &seek_pos))
                res = FALSE;
              break;

            default:
              GST_WARNING ("Unknown seekhead ID 0x%x", id);
              /* fall-through */

            case GST_EBML_ID_VOID:
              if (!gst_ebml_read_skip (ebml))
                res = FALSE;
              break;
          }

          if (demux->level_up) {
            demux->level_up--;
            break;
          }
        }

        if (!seek_id || seek_pos == (guint64) - 1) {
          GST_WARNING ("Incomplete seekhead entry (0x%x/%"
              G_GUINT64_FORMAT ")", seek_id, seek_pos);
          break;
        }

        switch (seek_id) {
          case GST_MATROSKA_ID_CUES:
          case GST_MATROSKA_ID_TAGS:{
            guint level_up = demux->level_up;
            guint64 before_pos, length;
            GstEbmlLevel *level;
            GstEvent *event;

            /* remember */
            length = gst_bytestream_length (ebml->bs);
            before_pos = gst_bytestream_tell (ebml->bs);

            /* check for validity */
            if (seek_pos + demux->segment_start + 12 >= length) {
              g_warning ("Seekhead reference lies outside file!");
              break;
            }

            /* seek */
            if (!(event = gst_ebml_read_seek (ebml,
                        seek_pos + demux->segment_start)))
              return FALSE;
            gst_event_unref (event);

            /* we don't want to lose our seekhead level, so we add
             * a dummy. This is a crude hack. */
            level = g_new (GstEbmlLevel, 1);
            level->start = 0;
            level->length = G_MAXUINT64;
            ebml->level = g_list_append (ebml->level, level);

            /* check ID */
            if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
              res = FALSE;
              break;
            }
            if (id != seek_id) {
              g_warning ("We looked for ID=0x%x but got ID=0x%x (pos=%llu)",
                  seek_id, id, seek_pos + demux->segment_start);
              goto finish;
            }

            /* read master + parse */
            switch (id) {
              case GST_MATROSKA_ID_CUES:
                if (!gst_ebml_read_master (ebml, &id))
                  res = FALSE;
                else if (!gst_matroska_demux_parse_index (demux, TRUE) &&
                    gst_bytestream_length (ebml->bs) !=
                    gst_bytestream_tell (ebml->bs))
                  res = FALSE;
                else
                  demux->index_parsed = TRUE;
                break;
              case GST_MATROSKA_ID_TAGS:
                if (!gst_ebml_read_master (ebml, &id))
                  res = FALSE;
                else if (!gst_matroska_demux_parse_metadata (demux, TRUE) &&
                    gst_bytestream_length (ebml->bs) !=
                    gst_bytestream_tell (ebml->bs))
                  res = FALSE;
                else
                  demux->metadata_parsed = TRUE;
                break;
            }
            if (!res)
              break;

          finish:
            /* remove dummy level */
            while (ebml->level) {
              guint64 length;

              level = g_list_last (ebml->level)->data;
              ebml->level = g_list_remove (ebml->level, level);
              length = level->length;
              g_free (level);
              if (length == G_MAXUINT64)
                break;
            }

            /* seek back */
            if (!(event = gst_ebml_read_seek (ebml, before_pos)))
              return FALSE;
            gst_event_unref (event);
            demux->level_up = level_up;
            break;
          }

          default:
            GST_INFO ("Ignoring seekhead entry for ID=0x%x", seek_id);
            break;
        }

        break;
      }

      default:
        GST_WARNING ("Unknown seekhead ID 0x%x", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static gboolean
gst_matroska_demux_loop_stream (GstMatroskaDemux * demux)
{
  GstEbmlRead *ebml = GST_EBML_READ (demux);
  gboolean res = TRUE;
  guint32 id;

  /* we've found our segment, start reading the different contents in here */
  while (res) {
    if (!(id = gst_ebml_peek_id (ebml, &demux->level_up))) {
      res = FALSE;
      break;
    } else if (demux->level_up) {
      demux->level_up--;
      break;
    }

    switch (id) {
        /* stream info */
      case GST_MATROSKA_ID_INFO:{
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        res = gst_matroska_demux_parse_info (demux);
        break;
      }

        /* track info headers */
      case GST_MATROSKA_ID_TRACKS:{
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        res = gst_matroska_demux_parse_tracks (demux);
        break;
      }

        /* stream index */
      case GST_MATROSKA_ID_CUES:{
        if (!demux->index_parsed) {
          if (!gst_ebml_read_master (ebml, &id)) {
            res = FALSE;
            break;
          }
          res = gst_matroska_demux_parse_index (demux, FALSE);
        } else
          res = gst_ebml_read_skip (ebml);
        break;
      }

        /* metadata */
      case GST_MATROSKA_ID_TAGS:{
        if (!demux->index_parsed) {
          if (!gst_ebml_read_master (ebml, &id)) {
            res = FALSE;
            break;
          }
          res = gst_matroska_demux_parse_metadata (demux, FALSE);
        } else
          res = gst_ebml_read_skip (ebml);
        break;
      }

        /* file index (if seekable, seek to Cues/Tags to parse it) */
      case GST_MATROSKA_ID_SEEKHEAD:{
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        res = gst_matroska_demux_parse_contents (demux);
        break;
      }

      case GST_MATROSKA_ID_CLUSTER:{
        if (!gst_ebml_read_master (ebml, &id)) {
          res = FALSE;
          break;
        }
        /* The idea is that we parse one cluster per loop and
         * then break out of the loop here. In the next call
         * of the loopfunc, we will get back here with the
         * next cluster. If an error occurs, we didn't
         * actually push a buffer, but we still want to break
         * out of the loop to handle a possible error. We'll
         * get back here if it's recoverable. */
        gst_matroska_demux_parse_cluster (demux);
        demux->state = GST_MATROSKA_DEMUX_STATE_DATA;
        res = FALSE;
        break;
      }

      default:
        GST_WARNING ("Unknown matroska file header ID 0x%x", id);
        /* fall-through */

      case GST_EBML_ID_VOID:
        if (!gst_ebml_read_skip (ebml))
          res = FALSE;
        break;
    }

    if (demux->level_up) {
      demux->level_up--;
      break;
    }
  }

  return res;
}

static void
gst_matroska_demux_loop (GstElement * element)
{
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (element);

  /* first, if we're to start, let's actually get starting */
  if (demux->state == GST_MATROSKA_DEMUX_STATE_START) {
    if (!gst_matroska_demux_init_stream (demux)) {
      return;
    }
    demux->state = GST_MATROSKA_DEMUX_STATE_HEADER;
  }

  gst_matroska_demux_loop_stream (demux);
}

static GstCaps *
gst_matroska_demux_video_caps (GstMatroskaTrackVideoContext * videocontext,
    const gchar * codec_id, gpointer data, guint size, GstMatroskaDemux * demux)
{
  GstMatroskaTrackContext *context = (GstMatroskaTrackContext *) videocontext;
  GstCaps *caps = NULL;

  if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_VFW_FOURCC)) {
    gst_riff_strf_vids *vids = NULL;

    if (data) {
      char *codec_name = NULL;
      GstTagList *list = gst_tag_list_new ();

      vids = (gst_riff_strf_vids *) data;

      /* assure size is big enough */
      if (size < 24) {
        GST_WARNING ("Too small BITMAPINFOHEADER (%d bytes)", size);
        return NULL;
      }
      if (size < sizeof (gst_riff_strf_vids)) {
        vids =
            (gst_riff_strf_vids *) g_realloc (vids,
            sizeof (gst_riff_strf_vids));
      }

      /* little-endian -> byte-order */
      vids->size = GUINT32_FROM_LE (vids->size);
      vids->width = GUINT32_FROM_LE (vids->width);
      vids->height = GUINT32_FROM_LE (vids->height);
      vids->planes = GUINT16_FROM_LE (vids->planes);
      vids->bit_cnt = GUINT16_FROM_LE (vids->bit_cnt);
      vids->compression = GUINT32_FROM_LE (vids->compression);
      vids->image_size = GUINT32_FROM_LE (vids->image_size);
      vids->xpels_meter = GUINT32_FROM_LE (vids->xpels_meter);
      vids->ypels_meter = GUINT32_FROM_LE (vids->ypels_meter);
      vids->num_colors = GUINT32_FROM_LE (vids->num_colors);
      vids->imp_colors = GUINT32_FROM_LE (vids->imp_colors);

      caps = gst_riff_create_video_caps (vids->compression, NULL, vids,
          &codec_name);
      gst_tag_list_add (list, GST_TAG_MERGE_APPEND, GST_TAG_VIDEO_CODEC,
          codec_name, NULL);
      if (GST_IS_ELEMENT (demux))
        gst_element_found_tags (GST_ELEMENT (demux), list);
      gst_tag_list_free (list);
      if (codec_name)
        g_free (codec_name);
    } else {
      caps = gst_riff_create_video_template_caps ();
    }
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_UNCOMPRESSED)) {
    /* how nice, this is undocumented... */
    if (videocontext != NULL) {
      guint32 fourcc = 0;

      switch (videocontext->fourcc) {
        case GST_MAKE_FOURCC ('I', '4', '2', '0'):
        case GST_MAKE_FOURCC ('Y', 'U', 'Y', '2'):
          fourcc = videocontext->fourcc;
          break;

        default:
          GST_DEBUG ("Unknown fourcc " GST_FOURCC_FORMAT,
              GST_FOURCC_ARGS (videocontext->fourcc));
          return NULL;
      }

      caps = gst_caps_new_simple ("video/x-raw-yuv",
          "format", GST_TYPE_FOURCC, fourcc, NULL);
    } else {
      caps = gst_caps_from_string ("video/x-raw-yuv, "
          "format = (fourcc) { I420, YUY2, YV12 }");
    }
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG4_SP)) {
    caps = gst_caps_new_simple ("video/x-divx",
        "divxversion", G_TYPE_INT, 4, NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG4_ASP) ||
      !strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG4_AP)) {
    caps = gst_caps_new_full (gst_structure_new ("video/x-divx",
            "divxversion", G_TYPE_INT, 5, NULL),
        gst_structure_new ("video/x-xvid", NULL),
        gst_structure_new ("video/mpeg",
            "mpegversion", G_TYPE_INT, 4,
            "systemstream", G_TYPE_BOOLEAN, FALSE, NULL), NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MSMPEG4V3)) {
    caps = gst_caps_new_full (gst_structure_new ("video/x-divx",
            "divxversion", G_TYPE_INT, 3, NULL),
        gst_structure_new ("video/x-msmpeg",
            "msmpegversion", G_TYPE_INT, 43, NULL), NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG1) ||
      !strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG2)) {
    gint mpegversion = -1;

    if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG1))
      mpegversion = 1;
    else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MPEG2))
      mpegversion = 2;
    else
      g_assert (0);

    caps = gst_caps_new_simple ("video/mpeg",
        "systemstream", G_TYPE_BOOLEAN, FALSE,
        "mpegversion", G_TYPE_INT, mpegversion, NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_VIDEO_MJPEG)) {
    caps = gst_caps_new_simple ("video/x-jpeg", NULL);
  } else {
    GST_WARNING ("Unknown codec '%s', cannot build Caps", codec_id);
    return NULL;
  }

  if (caps != NULL) {
    int i;
    GstStructure *structure;

    for (i = 0; i < gst_caps_get_size (caps); i++) {
      structure = gst_caps_get_structure (caps, i);
      if (videocontext != NULL) {
        GST_DEBUG ("video size %dx%d, target display size %dx%d (any unit)",
            videocontext->pixel_width,
            videocontext->pixel_height,
            videocontext->display_width, videocontext->display_height);
        /* pixel width and height are the w and h of the video in pixels */
        if (videocontext->pixel_width > 0 && videocontext->pixel_height > 0) {
          gint w = videocontext->pixel_width;
          gint h = videocontext->pixel_height;

          gst_structure_set (structure,
              "width", G_TYPE_INT, w, "height", G_TYPE_INT, h, NULL);
        } else {
          gst_structure_set (structure,
              "width", GST_TYPE_INT_RANGE, 16, 4096,
              "height", GST_TYPE_INT_RANGE, 16, 4096, NULL);
        }

        if (videocontext->display_width > 0 && videocontext->display_height > 0) {
          int n, d;

          /* calculate the pixel aspect ratio using the display and pixel w/h */
          n = videocontext->display_width * videocontext->pixel_height;
          d = videocontext->display_height * videocontext->pixel_width;
          GST_DEBUG ("setting PAR to %d/%d", n, d);
          gst_structure_set (structure, "pixel-aspect-ratio", GST_TYPE_FRACTION,
              videocontext->display_width * videocontext->pixel_height,
              videocontext->display_height * videocontext->pixel_width, NULL);
        }

        if (context->default_duration > 0) {
          gfloat framerate = 1. * GST_SECOND / context->default_duration;

          gst_structure_set (structure,
              "framerate", G_TYPE_DOUBLE, framerate, NULL);
        } else {
          /* sort of a hack to get most codecs to support,
           * even if the default_duration is missing */
          gst_structure_set (structure, "framerate", G_TYPE_DOUBLE, 25.0, NULL);
        }
      } else {
        gst_structure_set (structure,
            "width", GST_TYPE_INT_RANGE, 16, 4096,
            "height", GST_TYPE_INT_RANGE, 16, 4096,
            "framerate", GST_TYPE_DOUBLE_RANGE, 0.0, G_MAXDOUBLE, NULL);
      }
    }
  }

  return caps;
}

static GstCaps *
gst_matroska_demux_audio_caps (GstMatroskaTrackAudioContext * audiocontext,
    const gchar * codec_id, gpointer data, guint size, GstMatroskaDemux * demux)
{
  GstMatroskaTrackContext *context = (GstMatroskaTrackContext *) audiocontext;
  GstCaps *caps = NULL;

  if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L1) ||
      !strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L2) ||
      !strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L3)) {
    gint layer = -1;

    if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L1))
      layer = 1;
    else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L2))
      layer = 2;
    else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L3))
      layer = 3;
    else
      g_assert (0);

    caps = gst_caps_new_simple ("audio/mpeg",
        "mpegversion", G_TYPE_INT, 1, "layer", G_TYPE_INT, layer, NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_PCM_INT_BE) ||
      !strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_PCM_INT_LE)) {
    gint endianness = -1;

    if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_PCM_INT_BE))
      endianness = G_BIG_ENDIAN;
    else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_PCM_INT_LE))
      endianness = G_LITTLE_ENDIAN;
    else
      g_assert (0);

    if (context != NULL) {
      caps = gst_caps_new_simple ("audio/x-raw-int",
          "width", G_TYPE_INT, audiocontext->bitdepth,
          "depth", G_TYPE_INT, audiocontext->bitdepth,
          "signed", G_TYPE_BOOLEAN, audiocontext->bitdepth == 8, NULL);
    } else {
      caps = gst_caps_from_string ("audio/x-raw-int, "
          "signed = (boolean) { TRUE, FALSE }, "
          "depth = (int) { 8, 16 }, " "width = (int) { 8, 16 }");
    }
    gst_caps_set_simple (caps, "endianness", G_TYPE_INT, endianness, NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_PCM_FLOAT)) {
    caps = gst_caps_new_simple ("audio/x-raw-float",
        "endianness", G_TYPE_INT, G_BYTE_ORDER,
        "buffer-frames", GST_TYPE_INT_RANGE, 1, G_MAXINT, NULL);
    if (audiocontext != NULL) {
      gst_caps_set_simple (caps,
          "width", G_TYPE_INT, audiocontext->bitdepth, NULL);
    } else {
      gst_caps_set_simple (caps, "width", GST_TYPE_INT_RANGE, 32, 64, NULL);
    }
  } else if (!strncmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_AC3,
          strlen (GST_MATROSKA_CODEC_ID_AUDIO_AC3)) ||
      !strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_DTS)) {
    caps = gst_caps_new_simple ("audio/x-ac3", NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_VORBIS)) {
    caps = gst_caps_new_simple ("audio/x-vorbis", NULL);
  } else if (!strcmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_ACM)) {
    gst_riff_strf_auds *auds = NULL;

    if (data) {
      char *codec_name = NULL;
      GstTagList *list = gst_tag_list_new ();

      auds = (gst_riff_strf_auds *) data;

      /* little-endian -> byte-order */
      auds->format = GUINT16_FROM_LE (auds->format);
      auds->channels = GUINT16_FROM_LE (auds->channels);
      auds->rate = GUINT32_FROM_LE (auds->rate);
      auds->av_bps = GUINT32_FROM_LE (auds->av_bps);
      auds->blockalign = GUINT16_FROM_LE (auds->blockalign);
      auds->size = GUINT16_FROM_LE (auds->size);

      caps = gst_riff_create_audio_caps (auds->format, NULL, auds, &codec_name);
      gst_tag_list_add (list, GST_TAG_MERGE_APPEND, GST_TAG_AUDIO_CODEC,
          codec_name, NULL);
      if (GST_IS_ELEMENT (demux))
        gst_element_found_tags (GST_ELEMENT (demux), list);
      gst_tag_list_free (list);
      if (codec_name)
        g_free (codec_name);
    } else {
      caps = gst_riff_create_audio_template_caps ();
    }
  } else if (!strncmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG2,
          strlen (GST_MATROSKA_CODEC_ID_AUDIO_MPEG2)) ||
      !strncmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG4,
          strlen (GST_MATROSKA_CODEC_ID_AUDIO_MPEG4))) {
    gint mpegversion = -1;

    if (!strncmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG2,
            strlen (GST_MATROSKA_CODEC_ID_AUDIO_MPEG2)))
      mpegversion = 2;
    else if (!strncmp (codec_id, GST_MATROSKA_CODEC_ID_AUDIO_MPEG4,
            strlen (GST_MATROSKA_CODEC_ID_AUDIO_MPEG4)))
      mpegversion = 4;
    else
      g_assert (0);

    caps = gst_caps_new_simple ("audio/mpeg",
        "mpegversion", G_TYPE_INT, mpegversion, NULL);
  } else {
    GST_WARNING ("Unknown codec '%s', cannot build Caps", codec_id);
    g_print ("Codec=%s\n", codec_id);
    return NULL;
  }

  if (caps != NULL) {
    GstStructure *structure;
    int i;

    for (i = 0; i < gst_caps_get_size (caps); i++) {
      structure = gst_caps_get_structure (caps, i);
      if (audiocontext != NULL) {
        if (audiocontext->samplerate > 0 && audiocontext->channels > 0) {
          gst_structure_set (structure,
              "channels", G_TYPE_INT, audiocontext->channels,
              "rate", G_TYPE_INT, audiocontext->samplerate, NULL);
        }
      } else {
        gst_structure_set (structure,
            "channels", GST_TYPE_INT_RANGE, 1, 6,
            "rate", GST_TYPE_INT_RANGE, 4000, 96000, NULL);
      }
    }
  }

  return caps;
}

static GstCaps *
gst_matroska_demux_complex_caps (GstMatroskaTrackComplexContext *
    complexcontext, const gchar * codec_id, gpointer data, guint size)
{
  GstCaps *caps = NULL;

  //..

  return caps;
}

static GstCaps *
gst_matroska_demux_subtitle_caps (GstMatroskaTrackSubtitleContext *
    subtitlecontext, const gchar * codec_id, gpointer data, guint size)
{
  GstCaps *caps = NULL;

  //..

  return caps;
}

static GstElementStateReturn
gst_matroska_demux_change_state (GstElement * element)
{
  GstMatroskaDemux *demux = GST_MATROSKA_DEMUX (element);

  switch (GST_STATE_TRANSITION (element)) {
    case GST_STATE_PAUSED_TO_READY:
      gst_matroska_demux_reset (GST_ELEMENT (demux));
      break;
    default:
      break;
  }

  if (((GstElementClass *) parent_class)->change_state)
    return ((GstElementClass *) parent_class)->change_state (element);

  return GST_STATE_SUCCESS;
}

gboolean
gst_matroska_demux_plugin_init (GstPlugin * plugin)
{
  gint i;
  GstCaps *videosrccaps, *audiosrccaps, *subtitlesrccaps, *temp;
  const gchar *video_id[] = {
    GST_MATROSKA_CODEC_ID_VIDEO_VFW_FOURCC,
    GST_MATROSKA_CODEC_ID_VIDEO_UNCOMPRESSED,
    GST_MATROSKA_CODEC_ID_VIDEO_MPEG4_SP,
    GST_MATROSKA_CODEC_ID_VIDEO_MPEG4_ASP,
    GST_MATROSKA_CODEC_ID_VIDEO_MSMPEG4V3,
    GST_MATROSKA_CODEC_ID_VIDEO_MPEG1,
    GST_MATROSKA_CODEC_ID_VIDEO_MPEG2,
    GST_MATROSKA_CODEC_ID_VIDEO_MJPEG,
    /* TODO: Real/Quicktime */
    /* FILLME */
    NULL,
  }, *audio_id[] =
  {
    GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L1,
        GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L2,
        GST_MATROSKA_CODEC_ID_AUDIO_MPEG1_L3,
        GST_MATROSKA_CODEC_ID_AUDIO_PCM_INT_BE,
        GST_MATROSKA_CODEC_ID_AUDIO_PCM_INT_LE,
        GST_MATROSKA_CODEC_ID_AUDIO_PCM_FLOAT,
        GST_MATROSKA_CODEC_ID_AUDIO_AC3,
        GST_MATROSKA_CODEC_ID_AUDIO_ACM,
        GST_MATROSKA_CODEC_ID_AUDIO_VORBIS,
        GST_MATROSKA_CODEC_ID_AUDIO_MPEG2, GST_MATROSKA_CODEC_ID_AUDIO_MPEG4,
        /* TODO: AC3-9/10, Real, Musepack, Quicktime */
        /* FILLME */
  NULL,}
  , *complex_id[] = {
    /* FILLME */
  NULL,}
  , *subtitle_id[] = {
    /* FILLME */
  NULL,};

  /* this filter needs the riff parser */
  if (!gst_library_load ("gstbytestream") || !gst_library_load ("riff"))        /* for fourcc stuff */
    return FALSE;

  /* video src template */
  videosrccaps = gst_caps_new_empty ();
  for (i = 0; video_id[i] != NULL; i++) {
    temp = gst_matroska_demux_video_caps (NULL, video_id[i], NULL, 0, NULL);
    gst_caps_append (videosrccaps, temp);
  }
  for (i = 0; complex_id[i] != NULL; i++) {
    temp = gst_matroska_demux_complex_caps (NULL, video_id[i], NULL, 0);
    gst_caps_append (videosrccaps, temp);
  }
  videosrctempl = gst_pad_template_new ("video_%02d",
      GST_PAD_SRC, GST_PAD_SOMETIMES, videosrccaps);

  audiosrccaps = gst_caps_new_empty ();
  /* audio src template */
  for (i = 0; audio_id[i] != NULL; i++) {
    temp = gst_matroska_demux_audio_caps (NULL, audio_id[i], NULL, 0, NULL);
    gst_caps_append (audiosrccaps, temp);
  }
  audiosrctempl = gst_pad_template_new ("audio_%02d",
      GST_PAD_SRC, GST_PAD_SOMETIMES, audiosrccaps);

  subtitlesrccaps = gst_caps_new_empty ();
  /* subtitle src template */
  for (i = 0; subtitle_id[i] != NULL; i++) {
    temp = gst_matroska_demux_subtitle_caps (NULL, subtitle_id[i], NULL, 0);
    gst_caps_append (subtitlesrccaps, temp);
  }
  subtitlesrctempl = gst_pad_template_new ("subtitle_%02d",
      GST_PAD_SRC, GST_PAD_SOMETIMES, subtitlesrccaps);

  /* create an elementfactory for the matroska_demux element */
  if (!gst_element_register (plugin, "matroskademux",
          GST_RANK_PRIMARY, GST_TYPE_MATROSKA_DEMUX))
    return FALSE;

  return TRUE;
}