gstoggmux.c

/* OGG muxer plugin for GStreamer
 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
 * Copyright (C) 2006 Thomas Vander Stichele <thomas at apestaart dot org>
 *
 * 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 <gst/base/gstcollectpads.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 need this... */
#include <string.h>
#include <time.h>
#include <stdlib.h>             /* rand, srand, atoi */

GST_DEBUG_CATEGORY_STATIC (gst_ogg_mux_debug);
#define GST_CAT_DEFAULT gst_ogg_mux_debug

#define GST_TYPE_OGG_MUX (gst_ogg_mux_get_type())
#define GST_OGG_MUX(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_OGG_MUX, GstOggMux))
#define GST_OGG_MUX_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_OGG_MUX, GstOggMux))
#define GST_IS_OGG_MUX(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_OGG_MUX))
#define GST_IS_OGG_MUX_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_OGG_MUX))

/* This isn't generally what you'd want with an end-time macro, because
   technically the end time of a buffer with invalid duration is invalid. But
   for sorting ogg pages this is what we want. */
#define GST_BUFFER_END_TIME(buf) \
    (GST_BUFFER_DURATION_IS_VALID (buf) \
    ? GST_BUFFER_TIMESTAMP (buf) + GST_BUFFER_DURATION (buf) \
    : GST_BUFFER_TIMESTAMP (buf))

#define GST_GP_FORMAT "[gp %8" G_GINT64_FORMAT "]"

typedef struct _GstOggMux GstOggMux;
typedef struct _GstOggMuxClass GstOggMuxClass;

typedef enum
{
  GST_OGG_PAD_STATE_CONTROL = 0,
  GST_OGG_PAD_STATE_DATA = 1
}
GstOggPadState;

/* all information needed for one ogg stream */
typedef struct
{
  GstCollectData collect;       /* we extend the CollectData */

  GstBuffer *buffer;            /* the queued buffer for this pad */

  gint serial;
  ogg_stream_state stream;
  gint64 packetno;              /* number of next packet */
  gint64 pageno;                /* number of next page */
  guint64 duration;             /* duration of current page */
  gboolean eos;
  gint64 offset;
  GstClockTime timestamp;       /* timestamp of the first packet on the next
                                 * page to be dequeued */
  GstClockTime timestamp_end;   /* end timestamp of last complete packet on
                                   the next page to be dequeued */
  GstClockTime gp_time;         /* time corresponding to the gp value of the
                                   last complete packet on the next page to be
                                   dequeued */

  GstOggPadState state;         /* state of the pad */

  GList *headers;

  GQueue *pagebuffers;          /* List of pages in buffers ready for pushing */

  gboolean new_page;            /* starting a new page */
  gboolean first_delta;         /* was the first packet in the page a delta */
  gboolean prev_delta;          /* was the previous buffer a delta frame */
}
GstOggPad;

struct _GstOggMux
{
  GstElement element;

  /* source pad */
  GstPad *srcpad;

  /* sinkpads */
  GstCollectPads *collect;

  /* the pad we are currently using to fill a page */
  GstOggPad *pulling;

  /* next timestamp for the page */
  GstClockTime next_ts;

  /* Last timestamp actually output on src pad */
  GstClockTime last_ts;

  /* offset in stream */
  guint64 offset;

  /* need_headers */
  gboolean need_headers;

  guint64 max_delay;
  guint64 max_page_delay;

  GstOggPad *delta_pad;         /* when a delta frame is detected on a stream, we mark
                                   pages as delta frames up to the page that has the
                                   keyframe */

};

typedef enum
{
  GST_OGG_FLAG_BOS = GST_ELEMENT_FLAG_LAST,
  GST_OGG_FLAG_EOS
}
GstOggFlag;

struct _GstOggMuxClass
{
  GstElementClass parent_class;
};

/* elementfactory information */
static const GstElementDetails gst_ogg_mux_details =
GST_ELEMENT_DETAILS ("Ogg muxer",
    "Codec/Muxer",
    "mux ogg streams (info about ogg: http://xiph.org)",
    "Wim Taymans <wim@fluendo.com>");

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

/* set to 0.5 seconds by default */
#define DEFAULT_MAX_DELAY       G_GINT64_CONSTANT(500000000)
#define DEFAULT_MAX_PAGE_DELAY  G_GINT64_CONSTANT(500000000)
enum
{
  ARG_0,
  ARG_MAX_DELAY,
  ARG_MAX_PAGE_DELAY,
};

static GstStaticPadTemplate src_factory = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("application/ogg")
    );

static GstStaticPadTemplate sink_factory = GST_STATIC_PAD_TEMPLATE ("sink_%d",
    GST_PAD_SINK,
    GST_PAD_REQUEST,
    GST_STATIC_CAPS ("video/x-theora; "
        "audio/x-vorbis; audio/x-flac; audio/x-speex; "
        "application/x-ogm-video; application/x-ogm-audio; video/x-dirac; "
        "video/x-smoke; text/x-cmml, encoded = (boolean) TRUE")
    );

static void gst_ogg_mux_base_init (gpointer g_class);
static void gst_ogg_mux_class_init (GstOggMuxClass * klass);
static void gst_ogg_mux_init (GstOggMux * ogg_mux);
static void gst_ogg_mux_finalize (GObject * object);

static GstFlowReturn
gst_ogg_mux_collected (GstCollectPads * pads, GstOggMux * ogg_mux);
static gboolean gst_ogg_mux_handle_src_event (GstPad * pad, GstEvent * event);
static GstPad *gst_ogg_mux_request_new_pad (GstElement * element,
    GstPadTemplate * templ, const gchar * name);
static void gst_ogg_mux_release_pad (GstElement * element, GstPad * pad);

static void gst_ogg_mux_set_property (GObject * object,
    guint prop_id, const GValue * value, GParamSpec * pspec);
static void gst_ogg_mux_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec);
static GstStateChangeReturn gst_ogg_mux_change_state (GstElement * element,
    GstStateChange transition);

static GstElementClass *parent_class = NULL;

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

GType
gst_ogg_mux_get_type (void)
{
  static GType ogg_mux_type = 0;

  if (G_UNLIKELY (ogg_mux_type == 0)) {
    static const GTypeInfo ogg_mux_info = {
      sizeof (GstOggMuxClass),
      gst_ogg_mux_base_init,
      NULL,
      (GClassInitFunc) gst_ogg_mux_class_init,
      NULL,
      NULL,
      sizeof (GstOggMux),
      0,
      (GInstanceInitFunc) gst_ogg_mux_init,
    };

    ogg_mux_type =
        g_type_register_static (GST_TYPE_ELEMENT, "GstOggMux", &ogg_mux_info,
        0);
  }
  return ogg_mux_type;
}

static void
gst_ogg_mux_base_init (gpointer g_class)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);

  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&src_factory));
  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&sink_factory));

  gst_element_class_set_details (element_class, &gst_ogg_mux_details);
}

static void
gst_ogg_mux_class_init (GstOggMuxClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;

  gobject_class = (GObjectClass *) klass;
  gstelement_class = (GstElementClass *) klass;

  parent_class = g_type_class_peek_parent (klass);

  gobject_class->finalize = gst_ogg_mux_finalize;
  gobject_class->get_property = gst_ogg_mux_get_property;
  gobject_class->set_property = gst_ogg_mux_set_property;

  gstelement_class->request_new_pad = gst_ogg_mux_request_new_pad;
  gstelement_class->release_pad = gst_ogg_mux_release_pad;

  g_object_class_install_property (gobject_class, ARG_MAX_DELAY,
      g_param_spec_uint64 ("max-delay", "Max delay",
          "Maximum delay in multiplexing streams", 0, G_MAXUINT64,
          DEFAULT_MAX_DELAY, (GParamFlags) G_PARAM_READWRITE));
  g_object_class_install_property (gobject_class, ARG_MAX_PAGE_DELAY,
      g_param_spec_uint64 ("max-page-delay", "Max page delay",
          "Maximum delay for sending out a page", 0, G_MAXUINT64,
          DEFAULT_MAX_PAGE_DELAY, (GParamFlags) G_PARAM_READWRITE));

  gstelement_class->change_state = gst_ogg_mux_change_state;

}

#if 0
static const GstEventMask *
gst_ogg_mux_get_sink_event_masks (GstPad * pad)
{
  static const GstEventMask gst_ogg_mux_sink_event_masks[] = {
    {GST_EVENT_EOS, 0},
    {GST_EVENT_DISCONTINUOUS, 0},
    {0,}
  };

  return gst_ogg_mux_sink_event_masks;
}
#endif

static void
gst_ogg_mux_clear (GstOggMux * ogg_mux)
{
  ogg_mux->pulling = NULL;
  ogg_mux->need_headers = TRUE;
  ogg_mux->max_delay = DEFAULT_MAX_DELAY;
  ogg_mux->max_page_delay = DEFAULT_MAX_PAGE_DELAY;
  ogg_mux->delta_pad = NULL;
  ogg_mux->offset = 0;
  ogg_mux->next_ts = 0;
  ogg_mux->last_ts = GST_CLOCK_TIME_NONE;
}

static void
gst_ogg_mux_init (GstOggMux * ogg_mux)
{
  GstElementClass *klass = GST_ELEMENT_GET_CLASS (ogg_mux);

  ogg_mux->srcpad =
      gst_pad_new_from_template (gst_element_class_get_pad_template (klass,
          "src"), "src");
  gst_pad_set_event_function (ogg_mux->srcpad, gst_ogg_mux_handle_src_event);
  gst_element_add_pad (GST_ELEMENT (ogg_mux), ogg_mux->srcpad);

  GST_OBJECT_FLAG_SET (GST_ELEMENT (ogg_mux), GST_OGG_FLAG_BOS);

  /* seed random number generator for creation of serial numbers */
  srand (time (NULL));

  ogg_mux->collect = gst_collect_pads_new ();
  gst_collect_pads_set_function (ogg_mux->collect,
      (GstCollectPadsFunction) GST_DEBUG_FUNCPTR (gst_ogg_mux_collected),
      ogg_mux);

  gst_ogg_mux_clear (ogg_mux);
}

static void
gst_ogg_mux_finalize (GObject * object)
{
  GstOggMux *ogg_mux;

  ogg_mux = GST_OGG_MUX (object);

  if (ogg_mux->collect) {
    gst_object_unref (ogg_mux->collect);
    ogg_mux->collect = NULL;
  }

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static GstPadLinkReturn
gst_ogg_mux_sinkconnect (GstPad * pad, GstPad * peer)
{
  GstOggMux *ogg_mux;

  ogg_mux = GST_OGG_MUX (gst_pad_get_parent (pad));

  GST_DEBUG_OBJECT (ogg_mux, "sinkconnect triggered on %s", GST_PAD_NAME (pad));

  gst_object_unref (ogg_mux);

  return GST_PAD_LINK_OK;
}

static GstPad *
gst_ogg_mux_request_new_pad (GstElement * element,
    GstPadTemplate * templ, const gchar * req_name)
{
  GstOggMux *ogg_mux;
  GstPad *newpad;
  GstElementClass *klass;

  g_return_val_if_fail (templ != NULL, NULL);

  if (templ->direction != GST_PAD_SINK)
    goto wrong_direction;

  g_return_val_if_fail (GST_IS_OGG_MUX (element), NULL);
  ogg_mux = GST_OGG_MUX (element);

  klass = GST_ELEMENT_GET_CLASS (element);

  if (templ != gst_element_class_get_pad_template (klass, "sink_%d"))
    goto wrong_template;

  {
    gint serial;
    gchar *name;

    if (req_name == NULL || strlen (req_name) < 6) {
      /* no name given when requesting the pad, use random serial number */
      serial = rand ();
    } else {
      /* parse serial number from requested padname */
      serial = atoi (&req_name[5]);
    }
    /* create new pad with the name */
    name = g_strdup_printf ("sink_%d", serial);
    newpad = gst_pad_new_from_template (templ, name);
    g_free (name);

    /* construct our own wrapper data structure for the pad to
     * keep track of its status */
    {
      GstOggPad *oggpad;

      oggpad = (GstOggPad *)
          gst_collect_pads_add_pad (ogg_mux->collect, newpad,
          sizeof (GstOggPad));

      oggpad->serial = serial;
      ogg_stream_init (&oggpad->stream, serial);
      oggpad->packetno = 0;
      oggpad->pageno = 0;
      oggpad->eos = FALSE;
      /* we assume there will be some control data first for this pad */
      oggpad->state = GST_OGG_PAD_STATE_CONTROL;
      oggpad->new_page = TRUE;
      oggpad->first_delta = FALSE;
      oggpad->prev_delta = FALSE;
      oggpad->pagebuffers = g_queue_new ();
    }
  }

  /* setup some pad functions */
  gst_pad_set_link_function (newpad, gst_ogg_mux_sinkconnect);
  /* dd the pad to the element */
  gst_element_add_pad (element, newpad);

  return newpad;

  /* ERRORS */
wrong_direction:
  {
    g_warning ("ogg_mux: request pad that is not a SINK pad\n");
    return NULL;
  }
wrong_template:
  {
    g_warning ("ogg_mux: this is not our template!\n");
    return NULL;
  }
}

static void
gst_ogg_mux_release_pad (GstElement * element, GstPad * pad)
{
  GstOggMux *ogg_mux;
  GSList *walk;

  ogg_mux = GST_OGG_MUX (gst_pad_get_parent (pad));

  /* FIXME: When a request pad is released while paused or playing, 
   * we probably need to do something to finalise its stream in the
   * ogg data we're producing, but I'm not sure what */

  /* Find out GstOggPad in the collect pads info and clean it up */

  GST_OBJECT_LOCK (ogg_mux->collect);
  for (walk = ogg_mux->collect->data; walk; walk = g_slist_next (walk)) {
    GstOggPad *oggpad = (GstOggPad *) walk->data;
    GstCollectData *cdata = (GstCollectData *) walk->data;
    GstBuffer *buf;

    if (cdata->pad == pad) {
      ogg_stream_clear (&oggpad->stream);

      while ((buf = g_queue_pop_head (oggpad->pagebuffers)) != NULL) {
        gst_buffer_unref (buf);
      }

      g_queue_free (oggpad->pagebuffers);
      oggpad->pagebuffers = NULL;
    }
  }
  GST_OBJECT_UNLOCK (ogg_mux->collect);

  gst_collect_pads_remove_pad (ogg_mux->collect, pad);
}

/* handle events */
static gboolean
gst_ogg_mux_handle_src_event (GstPad * pad, GstEvent * event)
{
  GstEventType type;

  type = event ? GST_EVENT_TYPE (event) : GST_EVENT_UNKNOWN;

  switch (type) {
    case GST_EVENT_SEEK:
      /* disable seeking for now */
      return FALSE;
    default:
      break;
  }

  return gst_pad_event_default (pad, event);
}

static GstBuffer *
gst_ogg_mux_buffer_from_page (GstOggMux * mux, ogg_page * page, gboolean delta)
{
  GstBuffer *buffer;

  /* allocate space for header and body */
  buffer = gst_buffer_new_and_alloc (page->header_len + page->body_len);
  memcpy (GST_BUFFER_DATA (buffer), page->header, page->header_len);
  memcpy (GST_BUFFER_DATA (buffer) + page->header_len,
      page->body, page->body_len);

  /* Here we set granulepos as our OFFSET_END to give easy direct access to
   * this value later. Before we push it, we reset this to OFFSET + SIZE
   * (see gst_ogg_mux_push_buffer). */
  GST_BUFFER_OFFSET_END (buffer) = ogg_page_granulepos (page);
  if (delta)
    GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT);

  GST_LOG_OBJECT (mux, GST_GP_FORMAT
      " created buffer %p from ogg page", ogg_page_granulepos (page), buffer);

  return buffer;
}

static GstFlowReturn
gst_ogg_mux_push_buffer (GstOggMux * mux, GstBuffer * buffer)
{
  GstCaps *caps;

  /* fix up OFFSET and OFFSET_END again */
  GST_BUFFER_OFFSET (buffer) = mux->offset;
  mux->offset += GST_BUFFER_SIZE (buffer);
  GST_BUFFER_OFFSET_END (buffer) = mux->offset;

  /* Ensure we have monotonically increasing timestamps in the output. */
  if (GST_BUFFER_TIMESTAMP_IS_VALID (buffer)) {
    if (GST_BUFFER_TIMESTAMP (buffer) < mux->last_ts)
      GST_BUFFER_TIMESTAMP (buffer) = mux->last_ts;
    else
      mux->last_ts = GST_BUFFER_TIMESTAMP (buffer);
  }

  caps = gst_pad_get_negotiated_caps (mux->srcpad);
  gst_buffer_set_caps (buffer, caps);
  gst_caps_unref (caps);

  return gst_pad_push (mux->srcpad, buffer);
}

/* if all queues have at least one page, dequeue the page with the lowest
 * timestamp */
static gboolean
gst_ogg_mux_dequeue_page (GstOggMux * mux, GstFlowReturn * flowret)
{
  GSList *walk;
  GstOggPad *opad = NULL;       /* "oldest" pad */
  GstClockTime oldest = GST_CLOCK_TIME_NONE;
  GstBuffer *buf = NULL;
  gboolean ret = FALSE;

  *flowret = GST_FLOW_OK;

  walk = mux->collect->data;
  while (walk) {
    GstOggPad *pad = (GstOggPad *) walk->data;

    /* We need each queue to either be at EOS, or have one or more pages
     * available with a set granulepos (i.e. not -1), otherwise we don't have
     * enough data yet to determine which stream needs to go next for correct
     * time ordering. */
    if (pad->pagebuffers->length == 0) {
      if (pad->eos) {
        GST_LOG_OBJECT (pad->collect.pad,
            "pad is EOS, skipping for dequeue decision");
      } else {
        GST_LOG_OBJECT (pad->collect.pad,
            "no pages in this queue, can't dequeue");
        return FALSE;
      }
    } else {
      /* We then need to check for a non-negative granulepos */
      int i;
      gboolean valid = FALSE;

      for (i = 0; i < pad->pagebuffers->length; i++) {
        buf = g_queue_peek_nth (pad->pagebuffers, i);
        /* Here we check the OFFSET_END, which is actually temporarily the
         * granulepos value for this buffer */
        if (GST_BUFFER_OFFSET_END (buf) != -1) {
          valid = TRUE;
          break;
        }
      }
      if (!valid) {
        GST_LOG_OBJECT (pad->collect.pad,
            "No page timestamps in queue, can't dequeue");
        return FALSE;
      }
    }

    walk = g_slist_next (walk);
  }

  walk = mux->collect->data;
  while (walk) {
    GstOggPad *pad = (GstOggPad *) walk->data;

    /* any page with a granulepos of -1 can be pushed immediately.
     * TODO: it CAN be, but it seems silly to do so? */
    buf = g_queue_peek_head (pad->pagebuffers);
    while (buf && GST_BUFFER_OFFSET_END (buf) == -1) {
      GST_LOG_OBJECT (pad->collect.pad, "[gp        -1] pushing page");
      g_queue_pop_head (pad->pagebuffers);
      *flowret = gst_ogg_mux_push_buffer (mux, buf);
      buf = g_queue_peek_head (pad->pagebuffers);
      ret = TRUE;
    }

    if (buf) {
      /* if no oldest buffer yet, take this one */
      if (oldest == GST_CLOCK_TIME_NONE) {
        GST_LOG_OBJECT (mux, "no oldest yet, taking buffer %p from pad %"
            GST_PTR_FORMAT " with gp time %" GST_TIME_FORMAT,
            buf, pad->collect.pad, GST_TIME_ARGS (GST_BUFFER_OFFSET (buf)));
        oldest = GST_BUFFER_OFFSET (buf);
        opad = pad;
      } else {
        /* if we have an oldest, compare with this one */
        if (GST_BUFFER_OFFSET (buf) < oldest) {
          GST_LOG_OBJECT (mux, "older buffer %p, taking from pad %"
              GST_PTR_FORMAT " with gp time %" GST_TIME_FORMAT,
              buf, pad->collect.pad, GST_TIME_ARGS (GST_BUFFER_OFFSET (buf)));
          oldest = GST_BUFFER_OFFSET (buf);
          opad = pad;
        }
      }
    }
    walk = g_slist_next (walk);
  }

  if (oldest != GST_CLOCK_TIME_NONE) {
    g_assert (opad);
    buf = g_queue_pop_head (opad->pagebuffers);
    GST_LOG_OBJECT (opad->collect.pad,
        GST_GP_FORMAT " pushing oldest page buffer %p (granulepos time %"
        GST_TIME_FORMAT ")", GST_BUFFER_OFFSET_END (buf), buf,
        GST_TIME_ARGS (GST_BUFFER_OFFSET (buf)));
    *flowret = gst_ogg_mux_push_buffer (mux, buf);
    ret = TRUE;
  }

  return ret;
}

/* put the given ogg page on a per-pad queue, timestamping it correctly.
 * after that, dequeue and push as many pages as possible.
 * Caller should make sure:
 * pad->timestamp     was set with the timestamp of the first packet put
 *                    on the page
 * pad->timestamp_end was set with the timestamp + duration of the last packet
 *                    put on the page
 * pad->gp_time       was set with the time matching the gp of the last
 *                    packet put on the page
 *
 * will also reset timestamp and timestamp_end, so caller func can restart
 * counting.
 */
static GstFlowReturn
gst_ogg_mux_pad_queue_page (GstOggMux * mux, GstOggPad * pad, ogg_page * page,
    gboolean delta)
{
  GstFlowReturn ret;
  GstBuffer *buffer = gst_ogg_mux_buffer_from_page (mux, page, delta);

  /* take the timestamp of the first packet on this page */
  GST_BUFFER_TIMESTAMP (buffer) = pad->timestamp;
  GST_BUFFER_DURATION (buffer) = pad->timestamp_end - pad->timestamp;
  /* take the gp time of the last completed packet on this page */
  GST_BUFFER_OFFSET (buffer) = pad->gp_time;

  /* the next page will start where the current page's end time leaves off */
  pad->timestamp = pad->timestamp_end;

  g_queue_push_tail (pad->pagebuffers, buffer);
  GST_LOG_OBJECT (pad->collect.pad, GST_GP_FORMAT
      " queued buffer page %p (gp time %"
      GST_TIME_FORMAT ", timestamp %" GST_TIME_FORMAT
      "), %d page buffers queued", ogg_page_granulepos (page),
      buffer, GST_TIME_ARGS (GST_BUFFER_OFFSET (buffer)),
      GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buffer)),
      g_queue_get_length (pad->pagebuffers));

  while (gst_ogg_mux_dequeue_page (mux, &ret)) {
    if (ret != GST_FLOW_OK)
      break;
  }

  return ret;
}

/*
 * Given two pads, compare the buffers queued on it.
 * Returns:
 *  0 if they have an equal priority
 * -1 if the first is better
 *  1 if the second is better
 * Priority decided by: a) validity, b) older timestamp, c) smaller number
 * of muxed pages
 */
static gint
gst_ogg_mux_compare_pads (GstOggMux * ogg_mux, GstOggPad * first,
    GstOggPad * second)
{
  guint64 firsttime, secondtime;

  /* if the first pad doesn't contain anything or is even NULL, return
   * the second pad as best candidate and vice versa */
  if (first == NULL || first->buffer == NULL)
    return 1;
  if (second == NULL || second->buffer == NULL)
    return -1;

  /* no timestamp on first buffer, it must go first */
  firsttime = GST_BUFFER_TIMESTAMP (first->buffer);
  if (firsttime == GST_CLOCK_TIME_NONE)
    return -1;

  /* no timestamp on second buffer, it must go first */
  secondtime = GST_BUFFER_TIMESTAMP (second->buffer);
  if (secondtime == GST_CLOCK_TIME_NONE)
    return 1;

  /* first buffer has higher timestamp, second one should go first */
  if (secondtime < firsttime)
    return 1;
  /* second buffer has higher timestamp, first one should go first */
  else if (secondtime > firsttime)
    return -1;
  else {
    /* buffers with equal timestamps, prefer the pad that has the
     * least number of pages muxed */
    if (second->pageno < first->pageno)
      return 1;
    else if (second->pageno > first->pageno)
      return -1;
  }

  /* same priority if all of the above failed */
  return 0;
}

/* make sure a buffer is queued on all pads, returns a pointer to an oggpad
 * that holds the best buffer or NULL when no pad was usable.
 * "best" means the buffer marked with the lowest timestamp */
static GstOggPad *
gst_ogg_mux_queue_pads (GstOggMux * ogg_mux)
{
  GstOggPad *bestpad = NULL, *still_hungry = NULL;
  GSList *walk;

  /* try to make sure we have a buffer from each usable pad first */
  walk = ogg_mux->collect->data;
  while (walk) {
    GstOggPad *pad;
    GstCollectData *data;

    data = (GstCollectData *) walk->data;
    pad = (GstOggPad *) data;

    walk = g_slist_next (walk);

    GST_LOG_OBJECT (data->pad, "looking at pad for buffer");

    /* try to get a new buffer for this pad if needed and possible */
    if (pad->buffer == NULL) {
      GstBuffer *buf;
      gboolean incaps;

      buf = gst_collect_pads_pop (ogg_mux->collect, data);
      GST_LOG_OBJECT (data->pad, "popped buffer %" GST_PTR_FORMAT, buf);

      /* On EOS we get a NULL buffer */
      if (buf != NULL) {
        incaps = GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_IN_CAPS);
        /* if we need headers */
        if (pad->state == GST_OGG_PAD_STATE_CONTROL) {
          /* and we have one */
          if (incaps) {
            GST_DEBUG_OBJECT (ogg_mux,
                "got incaps buffer in control state, ignoring");
            /* just ignore */
            gst_buffer_unref (buf);
            buf = NULL;
          } else {
            GST_DEBUG_OBJECT (ogg_mux,
                "got data buffer in control state, switching " "to data mode");
            /* this is a data buffer so switch to data state */
            pad->state = GST_OGG_PAD_STATE_DATA;
          }
        }
      } else {
        GST_DEBUG_OBJECT (data->pad, "EOS on pad");
        if (!pad->eos) {
          ogg_page page;
          GstFlowReturn ret;

          /* Just gone to EOS. Flush existing page(s) */
          pad->eos = TRUE;

          while (ogg_stream_flush (&pad->stream, &page)) {
            /* Place page into the per-pad queue */
            ret = gst_ogg_mux_pad_queue_page (ogg_mux, pad, &page,
                pad->first_delta);
            /* increment the page number counter */
            pad->pageno++;
            /* mark other pages as delta */
            pad->first_delta = TRUE;
          }
        }
      }

      pad->buffer = buf;
    }

    /* we should have a buffer now, see if it is the best pad to
     * pull on */
    if (pad->buffer) {
      if (gst_ogg_mux_compare_pads (ogg_mux, bestpad, pad) > 0) {
        GST_LOG_OBJECT (data->pad, "new best pad");

        bestpad = pad;
      }
    } else if (!pad->eos) {
      GST_LOG_OBJECT (data->pad, "hungry pad");
      still_hungry = pad;
    }
  }

  if (still_hungry)
    /* drop back into collectpads... */
    return still_hungry;
  else
    return bestpad;
}

static GList *
gst_ogg_mux_get_headers (GstOggPad * pad)
{
  GList *res = NULL;
  GstOggMux *ogg_mux;
  GstStructure *structure;
  GstCaps *caps;
  GstPad *thepad;

  thepad = pad->collect.pad;

  ogg_mux = GST_OGG_MUX (GST_PAD_PARENT (thepad));

  GST_LOG_OBJECT (thepad, "getting headers");

  caps = gst_pad_get_negotiated_caps (thepad);
  if (caps != NULL) {
    const GValue *streamheader;

    structure = gst_caps_get_structure (caps, 0);
    streamheader = gst_structure_get_value (structure, "streamheader");
    if (streamheader != NULL) {
      GST_LOG_OBJECT (thepad, "got header");
      if (G_VALUE_TYPE (streamheader) == GST_TYPE_ARRAY) {
        GArray *bufarr = g_value_peek_pointer (streamheader);
        gint i;

        GST_LOG_OBJECT (thepad, "got fixed list");

        for (i = 0; i < bufarr->len; i++) {
          GValue *bufval = &g_array_index (bufarr, GValue, i);

          GST_LOG_OBJECT (thepad, "item %d", i);
          if (G_VALUE_TYPE (bufval) == GST_TYPE_BUFFER) {
            GstBuffer *buf = g_value_peek_pointer (bufval);

            GST_LOG_OBJECT (thepad, "adding item %d to header list", i);

            gst_buffer_ref (buf);
            res = g_list_append (res, buf);
          }
        }
      } else {
        GST_LOG_OBJECT (thepad, "streamheader is not fixed list");
      }
    } else {
      GST_LOG_OBJECT (thepad, "caps done have streamheader");
    }
    gst_caps_unref (caps);
  } else {
    GST_LOG_OBJECT (thepad, "got empty caps as negotiated format");
  }
  return res;
}

static GstCaps *
gst_ogg_mux_set_header_on_caps (GstCaps * caps, GList * buffers)
{
  GstStructure *structure;
  GValue array = { 0 };
  GList *walk = buffers;

  caps = gst_caps_make_writable (caps);

  structure = gst_caps_get_structure (caps, 0);

  /* put buffers in a fixed list */
  g_value_init (&array, GST_TYPE_ARRAY);

  while (walk) {
    GstBuffer *buf = GST_BUFFER (walk->data);
    GstBuffer *copy;
    GValue value = { 0 };

    walk = walk->next;

    /* mark buffer */
    GST_LOG ("Setting IN_CAPS on buffer of length %d", GST_BUFFER_SIZE (buf));
    GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_IN_CAPS);

    g_value_init (&value, GST_TYPE_BUFFER);
    copy = gst_buffer_copy (buf);
    gst_value_set_buffer (&value, copy);
    gst_buffer_unref (copy);
    gst_value_array_append_value (&array, &value);
    g_value_unset (&value);
  }
  gst_structure_set_value (structure, "streamheader", &array);
  g_value_unset (&array);

  return caps;
}

/*
 * For each pad we need to write out one (small) header in one
 * page that allows decoders to identify the type of the stream.
 * After that we need to write out all extra info for the decoders.
 * In the case of a codec that also needs data as configuration, we can
 * find that info in the streamcaps. 
 * After writing the headers we must start a new page for the data.
 */
static GstFlowReturn
gst_ogg_mux_send_headers (GstOggMux * mux)
{
  GSList *walk;
  GList *hbufs, *hwalk;
  GstCaps *caps;
  GstFlowReturn ret;

  hbufs = NULL;
  ret = GST_FLOW_OK;

  GST_LOG_OBJECT (mux, "collecting headers");

  walk = mux->collect->data;
  while (walk) {
    GstOggPad *pad;
    GstPad *thepad;

    pad = (GstOggPad *) walk->data;
    thepad = pad->collect.pad;

    walk = g_slist_next (walk);

    GST_LOG_OBJECT (mux, "looking at pad %s:%s", GST_DEBUG_PAD_NAME (thepad));

    /* if the pad has no buffer, we don't care */
    if (pad->buffer == NULL)
      continue;

    /* now figure out the headers */
    pad->headers = gst_ogg_mux_get_headers (pad);
  }

  GST_LOG_OBJECT (mux, "creating BOS pages");
  walk = mux->collect->data;
  while (walk) {
    GstOggPad *pad;
    GstBuffer *buf;
    ogg_packet packet;
    ogg_page page;
    GstPad *thepad;
    GstCaps *caps;
    GstStructure *structure;
    GstBuffer *hbuf;

    pad = (GstOggPad *) walk->data;
    thepad = pad->collect.pad;
    caps = gst_pad_get_negotiated_caps (thepad);
    structure = gst_caps_get_structure (caps, 0);

    walk = walk->next;

    pad->packetno = 0;

    GST_LOG_OBJECT (thepad, "looping over headers");

    if (pad->headers) {
      buf = GST_BUFFER (pad->headers->data);
      pad->headers = g_list_remove (pad->headers, buf);
    } else if (pad->buffer) {
      buf = pad->buffer;
      gst_buffer_ref (buf);
    } else {
      /* fixme -- should be caught in the previous list traversal. */
      GST_OBJECT_LOCK (pad);