gstreamer/ext/ogg/gstoggdemux.c

/* GStreamer
 * Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
 *
 * gstoggdemux.c: ogg 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 <gst/gst.h>
#include <ogg/ogg.h>
/* memcpy - if someone knows a way to get rid of it, please speak up 
 * note: the ogg docs even say you ned this... */
#include <string.h> 

GST_DEBUG_CATEGORY_STATIC (gst_ogg_demux_debug);
#define GST_CAT_DEFAULT gst_ogg_demux_debug

#define GST_TYPE_OGG_DEMUX (gst_ogg_demux_get_type()) 
#define GST_OGG_DEMUX(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_OGG_DEMUX, GstOggDemux))
#define GST_OGG_DEMUX_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_OGG_DEMUX, GstOggDemux))
#define GST_IS_OGG_DEMUX(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_OGG_DEMUX))
#define GST_IS_OGG_DEMUX_CLASS(obj) (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_OGG_DEMUX))

typedef struct _GstOggDemux GstOggDemux;
typedef struct _GstOggDemuxClass GstOggDemuxClass;

typedef enum {
  /* just because you shouldn't make a valid enum value 0 */
  GST_OGG_STATE_INAVLID,
  /* just started, we need to decide if we should do setup */
  GST_OGG_STATE_START,
  /* setup is analyzing the stream, getting lengths and so on */
  GST_OGG_STATE_SETUP,
  /* after a seek, during resyncing */
  GST_OGG_STATE_SEEK,
  /* normal playback */
  GST_OGG_STATE_PLAY
} GstOggState;

/* all information needed for one ogg stream */
typedef struct {
  GstPad *		pad; /* reference for this pad is held by element we belong to */

  gint			serial;
  ogg_stream_state	stream;
  guint64		offset; /* end offset of last buffer */
  guint64		known_offset; /* last known offset */
  gint64		packetno; /* number of next expected packet */
  
  guint64		length;	/* length of stream or 0 */
  glong			pages; /* number of pages in stream or 0 */

  guint			flags;
} GstOggPad;

typedef enum {
  GST_OGG_PAD_NEEDS_DISCONT	= (1 << 0),
  GST_OGG_PAD_NEEDS_FLUSH	= (1 << 1)
}
GstOggPadFlags;

/* all information needed for one ogg chain (relevant for chained bitstreams) */
typedef struct {
  GSList *		pads; /* list of GstOggPad */
} GstOggChain;
#define CURRENT_CHAIN(ogg) (&g_array_index ((ogg)->chains, GstOggChain, (ogg)->current_chain))
#define FOR_PAD_IN_CURRENT_CHAIN(ogg, _pad, ...) G_STMT_START{			\
  GSList *_walk;							      	\
  for (_walk = CURRENT_CHAIN (ogg)->pads; _walk; _walk = g_slist_next (_walk)) { \
    GstOggPad *_pad = (GstOggPad *) _walk->data;				\
    __VA_ARGS__									\
  }										\
}G_STMT_END

typedef enum {
  GST_OGG_FLAG_BOS = GST_ELEMENT_FLAG_LAST,
  GST_OGG_FLAG_EOS,
  GST_OGG_FLAG_WAIT_FOR_DISCONT
} GstOggFlag;

struct _GstOggDemux {
  GstElement		element;

  /* pad */
  GstPad *		sinkpad;
  
  /* state */
  GstOggState		state;
  GArray *		chains;
  gint			current_chain;
  guint			flags;
  
  /* ogg stuff */
  ogg_sync_state	sync;
 
  /* seeking */
  GstOggPad *		seek_pad;
  guint64		seek_to;
};

struct _GstOggDemuxClass {
  GstElementClass parent_class;
};

/* elementfactory information */
static GstElementDetails gst_ogg_demux_details = GST_ELEMENT_DETAILS (
  "ogg demuxer",
  "Codec/Demuxer",
  "demux ogg streams (info about ogg: http://xiph.org)",
  "Benjamin Otte <in7y118@public.uni-hamburg.de>"
);


/* signals and args */
enum {
  /* FILL ME */
  LAST_SIGNAL
};

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

static GstStaticPadTemplate ogg_demux_src_template_factory =
GST_STATIC_PAD_TEMPLATE (
  "src",
  GST_PAD_SRC,
  GST_PAD_SOMETIMES,
  GST_STATIC_CAPS_ANY
);

static GstStaticPadTemplate ogg_demux_sink_template_factory =
GST_STATIC_PAD_TEMPLATE (
  "sink",
  GST_PAD_SINK,
  GST_PAD_ALWAYS,
  GST_STATIC_CAPS ("application/ogg")
);


static void		gst_ogg_demux_finalize		(GObject *		object);

static gboolean		gst_ogg_demux_src_event		(GstPad *		pad, 
							 GstEvent *		event);
static const GstEventMask* gst_ogg_demux_get_event_masks (GstPad *		pad);
static const GstQueryType* gst_ogg_demux_get_query_types (GstPad *		pad);

static gboolean		gst_ogg_demux_src_query		(GstPad *		pad,
							 GstQueryType		type,
							 GstFormat *		format, 
							 gint64 *		value);

static void		gst_ogg_demux_chain		(GstPad *		pad,
							 GstData *		buffer);

static GstElementStateReturn gst_ogg_demux_change_state	(GstElement *		element);

static GstOggPad *	gst_ogg_pad_new			(GstOggDemux *		ogg,
							 int			serial_no);
static void		gst_ogg_pad_remove		(GstOggDemux *		ogg,
							 GstOggPad *		ogg_pad);
static void		gst_ogg_pad_reset		(GstOggDemux *		ogg,
							 GstOggPad *		pad);
static void		gst_ogg_demux_push		(GstOggDemux *		ogg,
							 ogg_page *		page);
static void		gst_ogg_pad_push		(GstOggDemux *		ogg,
							 GstOggPad *		ogg_pad);

static GstCaps *	gst_ogg_type_find		(ogg_packet *		packet);
  
static void		gst_ogg_print			(GstOggDemux *		demux);

#define GST_OGG_SET_STATE(ogg, new_state) G_STMT_START{				\
  GST_DEBUG_OBJECT (ogg, "setting state to %s", G_STRINGIFY (new_state));	\
  ogg->state = new_state;							\
}G_STMT_END
	
GST_BOILERPLATE (GstOggDemux, gst_ogg_demux, GstElement, GST_TYPE_ELEMENT)

static void
gst_ogg_demux_base_init (gpointer g_class)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
  
  gst_element_class_set_details (element_class, &gst_ogg_demux_details);

  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&ogg_demux_sink_template_factory));
  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&ogg_demux_src_template_factory));
}
static void
gst_ogg_demux_class_init (GstOggDemuxClass *klass)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  
  gstelement_class->change_state = gst_ogg_demux_change_state;

  gobject_class->finalize = gst_ogg_demux_finalize;
}
static void
gst_ogg_demux_init (GstOggDemux *ogg)
{
  /* create the sink pad */
  ogg->sinkpad = gst_pad_new_from_template(
      gst_static_pad_template_get (&ogg_demux_sink_template_factory), "sink");
  gst_element_add_pad (GST_ELEMENT (ogg), ogg->sinkpad);
  gst_pad_set_chain_function (ogg->sinkpad, GST_DEBUG_FUNCPTR (gst_ogg_demux_chain));

  /* initalize variables */
  GST_OGG_SET_STATE (ogg, GST_OGG_STATE_START);
  ogg->chains = g_array_new (TRUE, TRUE, sizeof (GstOggChain));
  ogg->current_chain = -1;
  
  GST_FLAG_SET (ogg, GST_ELEMENT_EVENT_AWARE);
}
static void
gst_ogg_demux_finalize (GObject *object)
{
  GstOggDemux *ogg;

  ogg = GST_OGG_DEMUX (object);

  /* chains are removed when going to READY */
  g_assert (ogg->current_chain == -1);
  g_assert (ogg->chains->len == 0);
  g_array_free (ogg->chains, TRUE);
}

static const GstEventMask*
gst_ogg_demux_get_event_masks (GstPad *pad)
{
  static const GstEventMask gst_ogg_demux_src_event_masks[] = {
    { GST_EVENT_SEEK, GST_SEEK_METHOD_SET |
                      GST_SEEK_FLAG_FLUSH },
    { 0, }
  };
  return gst_ogg_demux_src_event_masks;
}
static const GstQueryType*
gst_ogg_demux_get_query_types (GstPad *pad)
{
  static const GstQueryType gst_ogg_demux_src_query_types[] = {
    GST_QUERY_TOTAL,
    GST_QUERY_POSITION,
    0
  };
  return gst_ogg_demux_src_query_types;
}

static GstOggPad *
gst_ogg_get_pad_by_pad (GstOggDemux *ogg, GstPad *pad)
{
  GSList *walk;
  GstOggPad *cur;
  
  for (walk = CURRENT_CHAIN (ogg)->pads; walk; walk = g_slist_next (walk)) {
    cur = (GstOggPad *) walk->data;
    if (cur->pad == pad)
      return cur;
  }
  return NULL;
}

static gboolean
gst_ogg_demux_src_query (GstPad *pad, GstQueryType type,
		       GstFormat *format, gint64 *value)
{
  gboolean res = FALSE;
  GstOggDemux *ogg = GST_OGG_DEMUX (gst_pad_get_parent (pad));
  GstOggPad *cur = gst_ogg_get_pad_by_pad (ogg, pad);

  switch (type) {
    case GST_QUERY_TOTAL: {
      if (*format == GST_FORMAT_DEFAULT) {
	*value = cur->length;
	res = TRUE;
      }
      break;
    }
    case GST_QUERY_POSITION:
      if (*format == GST_FORMAT_DEFAULT && cur->length != 0) {
	*value = cur->known_offset;
	res = TRUE;
      }
      break;
    default:
      break;
  }
  return res;
}

/* The current seeking implementation is the most simple I could come up with:
 * - when seeking forwards, just discard data until desired position is reached
 * - when seeking backwards, seek to beginning and seek forward from there
 * Anyone is free to improve this algorithm as it is quite stupid and probably
 * really slow.
 */
static gboolean
gst_ogg_demux_src_event (GstPad *pad, GstEvent *event)
{
  GstOggDemux *ogg;
  GstOggPad *cur;

  ogg = GST_OGG_DEMUX (gst_pad_get_parent (pad));
  cur = gst_ogg_get_pad_by_pad (ogg, pad);
  /* FIXME: optimize this so events from inactive chains work? 
   * in theory there shouldn't be an exisiting pad for inactive chains */
  if (cur == NULL) goto error;
  
  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEEK:
    {
      gint64 offset;
      if (GST_EVENT_SEEK_FORMAT (event) != GST_FORMAT_DEFAULT)
	goto error;
      offset = GST_EVENT_SEEK_OFFSET (event);
      switch (GST_EVENT_SEEK_METHOD (event)) {
	case GST_SEEK_METHOD_END:
	  if (cur->length == 0 || offset > 0)
	    goto error;
	  offset = cur->length + offset;
	  break;
	case GST_SEEK_METHOD_CUR:
	  offset += cur->known_offset;
	  break;
	case GST_SEEK_METHOD_SET:
	  break;
	default:
	  g_warning ("invalid seek method in seek event");
	  goto error;
      }
      if (offset < cur->known_offset) {
	GstEvent *restart = gst_event_new_seek (GST_FORMAT_BYTES | GST_SEEK_METHOD_SET | GST_EVENT_SEEK_FLAGS (event), 0);
	if (!gst_pad_send_event (GST_PAD_PEER (ogg->sinkpad), restart))
	  goto error;
      } else {
	FOR_PAD_IN_CURRENT_CHAIN (ogg, pad,
	  if (GST_PAD_IS_USABLE (pad->pad))
	    gst_pad_push (pad->pad, GST_DATA (gst_event_new (GST_EVENT_FLUSH)));
	);
      }

      GST_OGG_SET_STATE (ogg, GST_OGG_STATE_SEEK);
      FOR_PAD_IN_CURRENT_CHAIN (ogg, pad,
	pad->flags |= GST_OGG_PAD_NEEDS_DISCONT;
      );
      GST_DEBUG_OBJECT (ogg, "initiating seeking to offset %"G_GUINT64_FORMAT, offset);
      ogg->seek_pad = cur; 
      ogg->seek_to = offset;
      gst_event_unref (event);
      return TRUE;
    }
    default:
      return gst_pad_event_default (pad, event);
  }

  g_assert_not_reached ();
  
error:
  gst_event_unref (event);
  return FALSE;
}

static void
gst_ogg_start_playing (GstOggDemux *ogg)
{
  GST_DEBUG_OBJECT (ogg, "got EOS in setup, changing to playback now");
  if (!gst_pad_send_event (GST_PAD_PEER (ogg->sinkpad),
      gst_event_new_seek (GST_FORMAT_BYTES | GST_SEEK_METHOD_SET, 0))) {
    GST_ELEMENT_ERROR (ogg, CORE, SEEK, (NULL), 
	("cannot seek to start after EOS"));
  }
  ogg->current_chain = 0;
  GST_FLAG_UNSET (ogg, GST_OGG_FLAG_EOS);
  GST_FLAG_SET (ogg, GST_OGG_FLAG_WAIT_FOR_DISCONT);
  GST_OGG_SET_STATE (ogg, GST_OGG_STATE_PLAY);
  gst_ogg_print (ogg);
}

static void
gst_ogg_demux_handle_event (GstPad *pad, GstEvent *event)
{
  GstOggDemux *ogg = GST_OGG_DEMUX (gst_pad_get_parent (pad));
  
  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_DISCONTINUOUS:
      GST_DEBUG_OBJECT (ogg, "got a discont event");
      ogg_sync_reset (&ogg->sync);
      gst_event_unref (event);
      GST_FLAG_UNSET (ogg, GST_OGG_FLAG_WAIT_FOR_DISCONT);
      FOR_PAD_IN_CURRENT_CHAIN (ogg, pad,
	pad->flags |= GST_OGG_PAD_NEEDS_DISCONT;
      );
      break;
    case GST_EVENT_EOS:
      if (ogg->state == GST_OGG_STATE_SETUP) {
	gst_ogg_start_playing (ogg);
      } else {
	guint i;
	GSList *walk;
	GST_DEBUG_OBJECT (ogg, "got EOS");
	ogg->current_chain = -1;
	for (i = 0; i < ogg->chains->len; i++) {
	  GstOggChain *chain = &g_array_index (ogg->chains, GstOggChain, i);
	  for (walk = chain->pads; walk; walk = g_slist_next (walk)) {
	    GstOggPad *pad = (GstOggPad *) walk->data;
	    if (pad->pad && GST_PAD_IS_USABLE (pad->pad)) {
              gst_data_ref (GST_DATA (event));
	      gst_pad_push (pad->pad, GST_DATA (event));
            }
	  }
	}
	gst_element_set_eos (GST_ELEMENT (ogg));
      }
      gst_event_unref (event);
      break;
    default:
      gst_pad_event_default (pad, event);
      break;
  }
  return;
}

/* get the pad with the given serial in the current stream or NULL if none */
static GstOggPad *
gst_ogg_pad_get_in_current_chain (GstOggDemux *ogg, int serial)
{
  GSList *walk;
  
  if (ogg->current_chain == -1) return NULL;
  g_return_val_if_fail (ogg->current_chain < ogg->chains->len, NULL);

  for (walk = CURRENT_CHAIN (ogg)->pads; walk; walk = g_slist_next (walk)) {
    GstOggPad *pad = (GstOggPad *) walk->data;
    if (pad->serial == serial)
      return pad;
  }
  return NULL;
}

static void
gst_ogg_add_chain (GstOggDemux *ogg)
{
  GST_LOG_OBJECT (ogg, "adding chain %u", ogg->chains->len);
  ogg->current_chain = ogg->chains->len;
  g_array_set_size (ogg->chains, ogg->chains->len + 1);
}

static void
gst_ogg_demux_chain (GstPad *pad, GstData *buffer)
{
  GstOggDemux *ogg;
  guint8 *data;
  int pageout_ret = 1;
  guint64 offset_end;

  /* handle events */
  if (GST_IS_EVENT (buffer)) {
    gst_ogg_demux_handle_event (pad, GST_EVENT (buffer));
    return;
  }

  ogg = GST_OGG_DEMUX (gst_pad_get_parent (pad));

  if (GST_FLAG_IS_SET (ogg, GST_OGG_FLAG_WAIT_FOR_DISCONT)) {
    GST_LOG_OBJECT (ogg, "waiting for discont event, discarding buffer");
    gst_data_unref (buffer);
    return; 
  }

  GST_LOG_OBJECT (ogg, "queueing buffer %p with offset %llu", buffer, GST_BUFFER_OFFSET (buffer));
  data = (guint8 *) ogg_sync_buffer(&ogg->sync, GST_BUFFER_SIZE (buffer));
  memcpy (data, GST_BUFFER_DATA (buffer), GST_BUFFER_SIZE (buffer));
  if (ogg_sync_wrote (&ogg->sync, GST_BUFFER_SIZE (buffer)) != 0) {
    gst_data_unref (buffer);
    GST_ELEMENT_ERROR (ogg, LIBRARY, TOO_LAZY, (NULL), ("ogg_sync_wrote failed"));
    return;
  }
  offset_end = GST_BUFFER_OFFSET_IS_VALID (buffer) ?
      GST_BUFFER_OFFSET (buffer) + GST_BUFFER_SIZE (buffer) :
      (guint64) -1;
  gst_data_unref (buffer);
  while (pageout_ret != 0) {
    ogg_page page;
    
    pageout_ret = ogg_sync_pageout (&ogg->sync, &page);
    switch (pageout_ret) {
      case -1:
	/* FIXME: need some kind of discont here, we don't know any values to send though,
	 * we only have the END_OFFSET */
	break;
      case 0:
	if (ogg->state == GST_OGG_STATE_SETUP) {
	  guint64 length;
	  GstFormat format = GST_FORMAT_BYTES;
	  if (!gst_pad_query (GST_PAD_PEER (ogg->sinkpad), GST_QUERY_TOTAL, &format, &length))
	    length = 0;
	  if (length <= offset_end) {
	    gst_ogg_start_playing (ogg);
	    goto out;
	  }
	}
	break;
      case 1:
	GST_LOG_OBJECT (ogg, "processing ogg page (serial %d, packet %ld, granule pos %llu",
	    ogg_page_serialno (&page), ogg_page_pageno (&page), ogg_page_granulepos (&page));
	switch (ogg->state) {
	  case GST_OGG_STATE_SETUP:
	    if (ogg_page_eos (&page)) {
	      GstOggPad *cur = gst_ogg_pad_get_in_current_chain (ogg, ogg_page_serialno (&page));
	      GST_FLAG_SET (ogg, GST_OGG_FLAG_EOS);
	      if (!cur) {
		GST_ERROR_OBJECT (ogg, "unknown serial %d", ogg_page_serialno (&page));
	      } else {
		cur->pages = ogg_page_pageno (&page);
		cur->length = ogg_page_granulepos (&page);
	      }
	    } else {
	      if (GST_FLAG_IS_SET (ogg, GST_OGG_FLAG_EOS) && ogg_page_bos (&page)) {
		gst_ogg_add_chain (ogg);
	      }
	      GST_FLAG_UNSET (ogg, GST_OGG_FLAG_EOS);
	    }
	    if (ogg_page_bos (&page)) {
	      if (gst_ogg_pad_get_in_current_chain (ogg, ogg_page_serialno (&page))) {
		GST_ERROR_OBJECT (ogg, "multiple BOS page for serial %d (page %ld)",
		    ogg_page_serialno (&page), ogg_page_pageno (&page));
	      } else {
		GstOggPad *pad = gst_ogg_pad_new (ogg, ogg_page_serialno (&page));
		CURRENT_CHAIN (ogg)->pads = g_slist_prepend (CURRENT_CHAIN (ogg)->pads, pad);
	      }
	      GST_FLAG_SET (ogg, GST_OGG_FLAG_BOS);
	    } else {
	      GST_FLAG_UNSET (ogg, GST_OGG_FLAG_BOS);
	    }
	    break;
	  case GST_OGG_STATE_START:
	    if (gst_pad_send_event (GST_PAD_PEER (ogg->sinkpad),
		gst_event_new_seek (GST_FORMAT_BYTES | GST_SEEK_METHOD_END, 0))) {
	      GST_OGG_SET_STATE (ogg, GST_OGG_STATE_SETUP);
	      GST_DEBUG_OBJECT (ogg, "stream can seek, try setup now");
	      if (!gst_pad_send_event (GST_PAD_PEER (ogg->sinkpad),
		  gst_event_new_seek (GST_FORMAT_BYTES | GST_SEEK_METHOD_SET, 0))) {
		GST_ELEMENT_ERROR (ogg, CORE, SEEK, (NULL), 
		    ("stream can seek to end, but not to start. Can't handle that."));
	      }
	      gst_ogg_add_chain (ogg);
	      GST_FLAG_SET (ogg, GST_OGG_FLAG_WAIT_FOR_DISCONT);
	      goto out;
	    }
	    gst_ogg_add_chain (ogg);
	    GST_OGG_SET_STATE (ogg, GST_OGG_STATE_PLAY);
	    /* fall through */
	  case GST_OGG_STATE_SEEK:
	  case GST_OGG_STATE_PLAY:
	    gst_ogg_demux_push (ogg, &page);
	    break;
	  default:
	    g_assert_not_reached ();
	    break;
	}
	break;
      default:
	GST_WARNING_OBJECT (ogg, "unknown return value %d from ogg_sync_pageout", pageout_ret);
	pageout_ret = 0;
	break;
    }
  }
out:
  return;
}
static GstOggPad *
gst_ogg_pad_new (GstOggDemux *ogg, int serial)
{
  GstOggPad *ret = g_new0 (GstOggPad, 1);

  ret->serial = serial;
  if (ogg_stream_init (&ret->stream, serial) != 0) {
    GST_ERROR_OBJECT (ogg, "Could not initialize ogg_stream struct for serial %d.", serial);
    g_free (ret);
    return NULL;
  }
  GST_LOG_OBJECT (ogg, "created new ogg src %p for stream with serial %d", ret, serial);

  return ret;
}
static void
gst_ogg_pad_remove (GstOggDemux *ogg, GstOggPad *pad)
{
  if (pad->pad) {
    /* FIXME:
     * we do it in the EOS signal already - EOS handling needs to be better thought out.
     * Correct way would be pushing EOS on eos page, but scheduler doesn't like that
    if (GST_PAD_IS_USEABLE (pad->pad))
      gst_pad_push (pad->pad, GST_DATA (gst_event_new (GST_EVENT_EOS)));
    */
    gst_element_remove_pad (GST_ELEMENT (ogg), pad->pad);
  }
  if (ogg_stream_clear (&pad->stream) != 0)
    GST_ERROR_OBJECT (ogg, "ogg_stream_clear (serial %d) did not return 0, ignoring this error", pad->serial);
  GST_LOG_OBJECT (ogg, "free ogg src %p for stream with serial %d", pad, pad->serial);
  g_free (pad);
}
static void
gst_ogg_demux_push (GstOggDemux *ogg, ogg_page* page)
{
  GSList *walk;
  GstOggPad *cur;

  /* find the stream */
  for (walk = CURRENT_CHAIN (ogg)->pads; walk; walk = g_slist_next (walk)) {
    cur = (GstOggPad *) walk->data;
    if (cur->serial == ogg_page_serialno (page)) {
      goto br;
    }
  }
  cur = NULL;
br:
  /* now we either have a stream (cur) or not */
  if (ogg_page_bos (page)) {
    if (cur) {
      GST_DEBUG_OBJECT (ogg, "ogg page declared as BOS while stream %d already existed."
	  "Possibly a seek happened.", cur->serial);
    } else if (cur) {
      GST_DEBUG_OBJECT (ogg, "reactivating deactivated stream %d.", cur->serial); 
    } else {
      /* FIXME: monitor if we are still in creation stage? */
      cur = gst_ogg_pad_new (ogg, ogg_page_serialno (page));
      if (!cur) {
	GST_ELEMENT_ERROR (ogg, LIBRARY, TOO_LAZY, (NULL), ("Creating ogg_stream struct failed."));
	return;
      }
      if (ogg->current_chain == -1) {
	/* add new one at the end */
	gst_ogg_add_chain (ogg);
      }
      CURRENT_CHAIN (ogg)->pads = g_slist_prepend (CURRENT_CHAIN (ogg)->pads, cur);
    }
  }
  if (cur == NULL) {
    GST_ELEMENT_ERROR (ogg, STREAM, DECODE, (NULL), ("invalid ogg stream serial no"));
    return;
  }
  if (ogg_stream_pagein (&cur->stream, page) != 0) {
    GST_WARNING_OBJECT (ogg, "ogg stream choked on page (serial %d), resetting stream", cur->serial);
    gst_ogg_pad_reset (ogg, cur);
    return;
  }
  switch (ogg->state) {
    case GST_OGG_STATE_SEEK:
      GST_LOG_OBJECT (ogg, "in seek - offset now: %"G_GUINT64_FORMAT" (pad %d) - desired offset %"
	  G_GUINT64_FORMAT" (pad %d)", cur->known_offset, cur->serial, 
	  ogg->seek_to, ogg->seek_pad->serial);
      if (cur == ogg->seek_pad) {
	if (ogg_page_granulepos (page) > ogg->seek_to) {
	  GST_OGG_SET_STATE (ogg, GST_OGG_STATE_PLAY);
          GST_DEBUG_OBJECT (ogg, "ended seek at offset %"G_GUINT64_FORMAT" (requested  %"G_GUINT64_FORMAT, cur->known_offset, ogg->seek_to);
	  ogg->seek_pad = NULL;
	  ogg->seek_to = 0;
	}
      }
      /* fallthrough */
    case GST_OGG_STATE_PLAY:
      cur->known_offset = ogg_page_granulepos (page);
      gst_ogg_pad_push (ogg, cur);
      break;
    default:
      g_assert_not_reached ();
      break;
  }
  if (ogg_page_eos (page)) {
    GST_DEBUG_OBJECT (ogg, "got EOS for stream with serial %d, sending EOS now",
	cur->serial);
#if 0
  /* Removing pads while PLAYING doesn't work with current schedulers */
  /* remove from list, as this will never be called again */
    gst_ogg_pad_remove (ogg, cur);
  /* this is also not possible because sending EOS this way confuses the scheduler */
    gst_pad_push (cur->pad, GST_DATA (gst_event_new (GST_EVENT_EOS)));
#else
#endif
  }
}
static void
gst_ogg_pad_push (GstOggDemux *ogg, GstOggPad *pad)
{
  ogg_packet packet;
  int ret;
  GstBuffer *buf;

  while (TRUE) {
    ret = ogg_stream_packetout (&pad->stream, &packet);
    switch (ret) {
      case 0:
	return;
      case -1:
	gst_ogg_pad_reset (ogg, pad);
	break;
      case 1: {
	/* only push data when playing, not during seek or similar */
	if (ogg->state != GST_OGG_STATE_PLAY)
	  continue;
	if (!pad->pad) {
	  GstCaps *caps = gst_ogg_type_find (&packet);
	  gchar *name = g_strdup_printf ("serial_%d", pad->serial);
	  
	  if (caps == NULL) {
	    GST_WARNING_OBJECT (ogg, "couldn't find caps for stream with serial %d", pad->serial);
	    caps = gst_caps_new_simple ("application/octet-stream", NULL);
	  }
	  pad->pad = gst_pad_new_from_template (
	      gst_static_pad_template_get (&ogg_demux_src_template_factory),
	      name);
	  g_free (name);
	  gst_pad_set_event_function (pad->pad, GST_DEBUG_FUNCPTR (gst_ogg_demux_src_event));
	  gst_pad_set_event_mask_function (pad->pad, GST_DEBUG_FUNCPTR (gst_ogg_demux_get_event_masks));
	  gst_pad_set_query_function (pad->pad, GST_DEBUG_FUNCPTR (gst_ogg_demux_src_query));
	  gst_pad_set_query_type_function (pad->pad, GST_DEBUG_FUNCPTR (gst_ogg_demux_get_query_types));
	  gst_pad_use_explicit_caps (pad->pad);
	  gst_pad_set_explicit_caps (pad->pad, caps);
	  gst_pad_set_active (pad->pad, TRUE);
	  gst_element_add_pad (GST_ELEMENT (ogg), pad->pad);
	}
	/* check for discont */
	if (packet.packetno != pad->packetno++) {
	  pad->flags |= GST_OGG_PAD_NEEDS_DISCONT;
	  pad->packetno = packet.packetno + 1;
	}
	/* send discont if needed */
	if ((pad->flags & GST_OGG_PAD_NEEDS_DISCONT) && GST_PAD_IS_USABLE (pad->pad)) {
	  GstEvent *event = gst_event_new_discontinuous (FALSE, 
	    GST_FORMAT_DEFAULT, pad->known_offset); /* FIXME: this might be wrong because we can only use the last known offset */
	  gst_pad_push (pad->pad, GST_DATA (event));
	  pad->flags &= (~GST_OGG_PAD_NEEDS_DISCONT);
	};
	/* optimization: use a bufferpool containing the ogg packet? */
	buf = gst_pad_alloc_buffer (pad->pad, GST_BUFFER_OFFSET_NONE, packet.bytes);
	memcpy (buf->data, packet.packet, packet.bytes);
	if (pad->offset != -1)
	  GST_BUFFER_OFFSET (buf) = pad->offset;
	if (packet.granulepos != -1)
	  GST_BUFFER_OFFSET_END (buf) = packet.granulepos;
	pad->offset = packet.granulepos;
	if (GST_PAD_IS_USABLE (pad->pad))
	  gst_pad_push (pad->pad, GST_DATA (buf));
	break;
      }
      default:
	GST_ERROR_OBJECT (ogg, "invalid return value %d for ogg_stream_packetout, resetting stream", ret);
	gst_ogg_pad_reset (ogg, pad);
	break;
    }
  }
}
static void
gst_ogg_pad_reset (GstOggDemux *ogg, GstOggPad *pad)
{
  ogg_stream_reset (&pad->stream);
  pad->offset = GST_BUFFER_OFFSET_NONE;
  /* FIXME: need a discont here */
}

static void
gst_ogg_chains_clear (GstOggDemux *ogg)
{
  gint i;
  GSList *walk;
  
  for (i = ogg->chains->len - 1; i >= 0; i--) {
    GstOggChain *cur = &g_array_index (ogg->chains, GstOggChain, i);
    for (walk = cur->pads; walk; walk = g_slist_next (walk)) {
      gst_ogg_pad_remove (ogg, (GstOggPad *) walk->data);
    }
    g_slist_free (cur->pads);
    g_array_remove_index (ogg->chains, i);
  }
  ogg->current_chain = -1;
}

static GstElementStateReturn
gst_ogg_demux_change_state (GstElement *element)
{
  GstOggDemux *ogg;

  ogg = GST_OGG_DEMUX (element);

  switch (GST_STATE_TRANSITION (element)) {
    case GST_STATE_NULL_TO_READY:
      ogg_sync_init (&ogg->sync);
      break;
    case GST_STATE_READY_TO_PAUSED:
      ogg_sync_reset (&ogg->sync);
      break;
    case GST_STATE_PAUSED_TO_PLAYING:
      break;
    case GST_STATE_PLAYING_TO_PAUSED:
      break;
    case GST_STATE_PAUSED_TO_READY:
      gst_ogg_chains_clear (ogg);
      GST_OGG_SET_STATE (ogg, GST_OGG_STATE_START);
      ogg->seek_pad = NULL;
      ogg->seek_to = 0;
      break;
    case GST_STATE_READY_TO_NULL:
      ogg_sync_clear (&ogg->sync);
      break;
    default:
      g_assert_not_reached ();
      break;
  }

  return parent_class->change_state (element);
}

/*** typefinding **************************************************************/
/* ogg supports its own typefinding because the ogg spec defines that the first
 * packet of an ogg stream must identify the stream. Therefore ogg can use a
 * simplified approach at typefinding.
 */
typedef struct {
  ogg_packet *	packet;
  guint		best_probability;
  GstCaps *	caps;
} OggTypeFind;
static guint8 *
ogg_find_peek (gpointer data, gint64 offset, guint size)
{
  OggTypeFind *find = (OggTypeFind *) data;
  
  if (offset + size <= find->packet->bytes) {
    return ((guint8 *) find->packet->packet) + offset;
  } else {
    return NULL;
  }
}
static void
ogg_find_suggest (gpointer data, guint probability, const GstCaps *caps)
{
  OggTypeFind *find = (OggTypeFind *) data;
  
  if (probability > find->best_probability) {
    gst_caps_replace (&find->caps, gst_caps_copy (caps));
    find->best_probability = probability;
  }
}
static GstCaps *
gst_ogg_type_find (ogg_packet *packet)
{
  GstTypeFind gst_find;
  OggTypeFind find;
  GList *walk, *type_list = NULL;
  
  walk = type_list = gst_type_find_factory_get_list ();
  
  find.packet = packet;
  find.best_probability = 0;
  find.caps = NULL;
  gst_find.data = &find;
  gst_find.peek = ogg_find_peek;
  gst_find.suggest = ogg_find_suggest;
  
  while (walk) {
    GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (walk->data);
    
    gst_type_find_factory_call_function (factory, &gst_find);
    if (find.best_probability >= GST_TYPE_FIND_MAXIMUM)
      break;
    walk = g_list_next (walk);
  }
  
  if (find.best_probability > 0)
    return find.caps;

  return NULL;
}

static gboolean
plugin_init (GstPlugin *plugin)
{
  GST_DEBUG_CATEGORY_INIT (gst_ogg_demux_debug, "oggdemux", 0, "ogg demuxer");

  return gst_element_register (plugin, "oggdemux", GST_RANK_PRIMARY, GST_TYPE_OGG_DEMUX);
}
GST_PLUGIN_DEFINE (
  GST_VERSION_MAJOR,
  GST_VERSION_MINOR,
  "ogg",
  "ogg stream manipulation (info about ogg: http://xiph.org)",
  plugin_init,
  VERSION,
  GST_LICENSE,
  GST_PACKAGE,
  GST_ORIGIN
)

/* prints all info about the element */
static void
gst_ogg_print (GstOggDemux *ogg)
{
  guint i;
  GSList *walk;
  
  for (i = 0; i < ogg->chains->len; i++) {
    GstOggChain *chain = &g_array_index (ogg->chains, GstOggChain, i);
    GST_INFO_OBJECT (ogg, "chain %d (%u streams):", i, g_slist_length (chain->pads));
    for (walk = chain->pads; walk; walk = g_slist_next (walk)) {
      GstOggPad *pad = (GstOggPad *) walk->data;
      GST_INFO_OBJECT (ogg, "  stream %d:", pad->serial);
      GST_INFO_OBJECT (ogg, "    length %"G_GUINT64_FORMAT, pad->length);
      GST_INFO_OBJECT (ogg, "    pages %ld", pad->pages);
    }
  }
}