libs/gst/base/gstbasesrc.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *               2000,2005 Wim Taymans <wim@fluendo.com>
 *
 * gstbasesrc.c:
 *
 * 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.
 */

/**
 * SECTION:gstbasesrc
 * @short_description: Base class for getrange based source elements
 * @see_also: #GstPushSrc, #GstBaseTransform, #GstBaseSink
 *
 * This is a generice base class for source elements. The following
 * types of sources are supported:
 * <itemizedlist>
 *   <listitem><para>random access sources like files</para></listitem>
 *   <listitem><para>seekable sources</para></listitem>
 *   <listitem><para>live sources</para></listitem>
 * </itemizedlist>
 *
 * The source can be configured to operate in a any #GstFormat with the
 * gst_base_src_set_format(). This format determines the format of the
 * internal #GstSegment and the #GST_EVENT_NEW_SEGMENT. The default format for
 * #GstBaseSrc is GST_FORMAT_BYTES.
 *
 * #GstBaseSrc always supports the push mode scheduling. If the following
 * conditions are met, it also supports pull mode scheduling:
 * <itemizedlist>
 *   <listitem><para>the format is set to GST_FORMAT_BYTES (default).</para></listitem>
 *   <listitem><para>#GstBaseSrc::is_seekable returns TRUE.</para></listitem>
 * </itemizedlist>
 *
 * If all the conditions are met for operating in pull mode, #GstBaseSrc is
 * automatically seekable in push mode as well. The following conditions must be
 * met to make the element seekable in push mode when the format is not
 * GST_FORMAT_BYTES:
 * <itemizedlist>
 *   <listitem><para>
 *     #GstBaseSrc::is_seekable returns TRUE.
 *   </para></listitem>
 *   <listitem><para>
 *     #GstBaseSrc::query can convert all supported seek formats to the
 *     internal format as set with gst_base_src_set_format().
 *   </para></listitem>
 *   <listitem><para>
 *     #GstBaseSrc::do_seek is implemented, performs the seek and returns TRUE.
 *   </para></listitem>
 * </itemizedlist>
 *
 * When the default format is not GST_FORMAT_BYTES, the element should ignore the
 * offset and length in the #GstBaseSrc::create method. It is recommended to subclass
 * #GstPushSrc instead in this situation.
 *
 * #GstBaseSrc has support for live sources. Live sources are sources that produce
 * data at a fixed rate, such as audio or video capture. A typical live source also
 * provides a clock to export the rate at which they produce data.
 * Use gst_base_src_set_live() to activate the live source mode.
 *
 * A live source does not produce data in the PAUSED state, this means that the 
 * #GstBaseSrc::create method will not be called in PAUSED but only in PLAYING.
 * To signal the pipeline that the element will not produce data, its return
 * value from the READY to PAUSED state will be GST_STATE_CHANGE_NO_PREROLL.
 * 
 * A typical live source will timestamp the buffers they create with the current
 * stream time of the pipeline. This is why they can only produce data in PLAYING,
 * when the clock is actually distributed and running.
 *
 * The #GstBaseSrc::get_times method can be used to implement pseudo-live sources.
 * The base source will wait for the specified stream time returned in 
 * #GstBaseSrc::get_times before pushing out the buffer. It only makes sense to implement
 * the ::get_times function if the source is a live source.
 *
 * There is only support in GstBaseSrc for one source pad, which should be named
 * "src". A source implementation (subclass of GstBaseSrc) should install a pad
 * template in its base_init function, like so:
 *
 * <programlisting>
 * static void
 * my_element_base_init (gpointer g_class)
 * {
 *   GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class);
 *   // srctemplate should be a #GstStaticPadTemplate with direction
 *   // #GST_PAD_SRC and name "src"
 *   gst_element_class_add_pad_template (gstelement_class,
 *       gst_static_pad_template_get (&amp;srctemplate));
 *   // see #GstElementDetails
 *   gst_element_class_set_details (gstelement_class, &amp;details);
 * }
 * </programlisting>
 *
 * Last reviewed on 2005-12-18 (0.10.0)
 */

#include <stdlib.h>
#include <string.h>

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

#include "gstbasesrc.h"
#include "gsttypefindhelper.h"
#include <gst/gstmarshal.h>
#include <gst/gst-i18n-lib.h>

GST_DEBUG_CATEGORY_STATIC (gst_base_src_debug);
#define GST_CAT_DEFAULT gst_base_src_debug

#define GST_LIVE_GET_LOCK(elem)               (GST_BASE_SRC_CAST(elem)->live_lock)
#define GST_LIVE_LOCK(elem)                   g_mutex_lock(GST_LIVE_GET_LOCK(elem))
#define GST_LIVE_TRYLOCK(elem)                g_mutex_trylock(GST_LIVE_GET_LOCK(elem))
#define GST_LIVE_UNLOCK(elem)                 g_mutex_unlock(GST_LIVE_GET_LOCK(elem))
#define GST_LIVE_GET_COND(elem)               (GST_BASE_SRC_CAST(elem)->live_cond)
#define GST_LIVE_WAIT(elem)                   g_cond_wait (GST_LIVE_GET_COND (elem), GST_LIVE_GET_LOCK (elem))
#define GST_LIVE_TIMED_WAIT(elem, timeval)    g_cond_timed_wait (GST_LIVE_GET_COND (elem), GST_LIVE_GET_LOCK (elem),\
                                                                                timeval)
#define GST_LIVE_SIGNAL(elem)                 g_cond_signal (GST_LIVE_GET_COND (elem));
#define GST_LIVE_BROADCAST(elem)              g_cond_broadcast (GST_LIVE_GET_COND (elem));

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

#define DEFAULT_BLOCKSIZE       4096
#define DEFAULT_NUM_BUFFERS     -1
#define DEFAULT_TYPEFIND	FALSE

enum
{
  PROP_0,
  PROP_BLOCKSIZE,
  PROP_NUM_BUFFERS,
  PROP_TYPEFIND,
};

static GstElementClass *parent_class = NULL;

static void gst_base_src_base_init (gpointer g_class);
static void gst_base_src_class_init (GstBaseSrcClass * klass);
static void gst_base_src_init (GstBaseSrc * src, gpointer g_class);
static void gst_base_src_finalize (GObject * object);


GType
gst_base_src_get_type (void)
{
  static GType base_src_type = 0;

  if (!base_src_type) {
    static const GTypeInfo base_src_info = {
      sizeof (GstBaseSrcClass),
      (GBaseInitFunc) gst_base_src_base_init,
      NULL,
      (GClassInitFunc) gst_base_src_class_init,
      NULL,
      NULL,
      sizeof (GstBaseSrc),
      0,
      (GInstanceInitFunc) gst_base_src_init,
    };

    base_src_type = g_type_register_static (GST_TYPE_ELEMENT,
        "GstBaseSrc", &base_src_info, G_TYPE_FLAG_ABSTRACT);
  }
  return base_src_type;
}
static GstCaps *gst_base_src_getcaps (GstPad * pad);
static gboolean gst_base_src_setcaps (GstPad * pad, GstCaps * caps);

static gboolean gst_base_src_activate_push (GstPad * pad, gboolean active);
static gboolean gst_base_src_activate_pull (GstPad * pad, gboolean active);
static void gst_base_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_base_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);
static gboolean gst_base_src_event_handler (GstPad * pad, GstEvent * event);
static gboolean gst_base_src_send_event (GstElement * elem, GstEvent * event);
static gboolean gst_base_src_default_event (GstBaseSrc * src, GstEvent * event);

static gboolean gst_base_src_query (GstPad * pad, GstQuery * query);

static gboolean gst_base_src_default_negotiate (GstBaseSrc * basesrc);
static gboolean gst_base_src_default_do_seek (GstBaseSrc * src,
    GstSegment * segment);
static gboolean gst_base_src_default_query (GstBaseSrc * src, GstQuery * query);

static gboolean gst_base_src_unlock (GstBaseSrc * basesrc);
static gboolean gst_base_src_start (GstBaseSrc * basesrc);
static gboolean gst_base_src_stop (GstBaseSrc * basesrc);

static GstStateChangeReturn gst_base_src_change_state (GstElement * element,
    GstStateChange transition);

static void gst_base_src_loop (GstPad * pad);
static gboolean gst_base_src_check_get_range (GstPad * pad);
static GstFlowReturn gst_base_src_pad_get_range (GstPad * pad, guint64 offset,
    guint length, GstBuffer ** buf);
static GstFlowReturn gst_base_src_get_range (GstBaseSrc * src, guint64 offset,
    guint length, GstBuffer ** buf);

static void
gst_base_src_base_init (gpointer g_class)
{
  GST_DEBUG_CATEGORY_INIT (gst_base_src_debug, "basesrc", 0, "basesrc element");
}

static void
gst_base_src_class_init (GstBaseSrcClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;

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

  parent_class = g_type_class_ref (GST_TYPE_ELEMENT);

  gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_base_src_finalize);
  gobject_class->set_property = GST_DEBUG_FUNCPTR (gst_base_src_set_property);
  gobject_class->get_property = GST_DEBUG_FUNCPTR (gst_base_src_get_property);

  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_BLOCKSIZE,
      g_param_spec_ulong ("blocksize", "Block size",
          "Size in bytes to read per buffer", 1, G_MAXULONG, DEFAULT_BLOCKSIZE,
          G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_NUM_BUFFERS,
      g_param_spec_int ("num-buffers", "num-buffers",
          "Number of buffers to output before sending EOS", -1, G_MAXINT,
          DEFAULT_NUM_BUFFERS, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_TYPEFIND,
      g_param_spec_boolean ("typefind", "Typefind",
          "Run typefind before negotiating", DEFAULT_TYPEFIND,
          G_PARAM_READWRITE));

  gstelement_class->change_state =
      GST_DEBUG_FUNCPTR (gst_base_src_change_state);
  gstelement_class->send_event = GST_DEBUG_FUNCPTR (gst_base_src_send_event);

  klass->negotiate = GST_DEBUG_FUNCPTR (gst_base_src_default_negotiate);
  klass->event = GST_DEBUG_FUNCPTR (gst_base_src_default_event);
  klass->do_seek = GST_DEBUG_FUNCPTR (gst_base_src_default_do_seek);
  klass->query = GST_DEBUG_FUNCPTR (gst_base_src_default_query);
}

static void
gst_base_src_init (GstBaseSrc * basesrc, gpointer g_class)
{
  GstPad *pad;
  GstPadTemplate *pad_template;

  basesrc->is_live = FALSE;
  basesrc->live_lock = g_mutex_new ();
  basesrc->live_cond = g_cond_new ();
  basesrc->num_buffers = DEFAULT_NUM_BUFFERS;
  basesrc->num_buffers_left = -1;

  basesrc->can_activate_push = TRUE;
  basesrc->pad_mode = GST_ACTIVATE_NONE;

  pad_template =
      gst_element_class_get_pad_template (GST_ELEMENT_CLASS (g_class), "src");
  g_return_if_fail (pad_template != NULL);

  GST_DEBUG_OBJECT (basesrc, "creating src pad");
  pad = gst_pad_new_from_template (pad_template, "src");

  GST_DEBUG_OBJECT (basesrc, "setting functions on src pad");
  gst_pad_set_activatepush_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_src_activate_push));
  gst_pad_set_activatepull_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_src_activate_pull));
  gst_pad_set_event_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_src_event_handler));
  gst_pad_set_query_function (pad, GST_DEBUG_FUNCPTR (gst_base_src_query));
  gst_pad_set_checkgetrange_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_src_check_get_range));
  gst_pad_set_getrange_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_src_pad_get_range));
  gst_pad_set_getcaps_function (pad, GST_DEBUG_FUNCPTR (gst_base_src_getcaps));
  gst_pad_set_setcaps_function (pad, GST_DEBUG_FUNCPTR (gst_base_src_setcaps));

  /* hold pointer to pad */
  basesrc->srcpad = pad;
  GST_DEBUG_OBJECT (basesrc, "adding src pad");
  gst_element_add_pad (GST_ELEMENT (basesrc), pad);

  basesrc->blocksize = DEFAULT_BLOCKSIZE;
  basesrc->clock_id = NULL;
  /* we operate in BYTES by default */
  gst_base_src_set_format (basesrc, GST_FORMAT_BYTES);
  basesrc->ABI.typefind = DEFAULT_TYPEFIND;

  GST_OBJECT_FLAG_UNSET (basesrc, GST_BASE_SRC_STARTED);

  GST_DEBUG_OBJECT (basesrc, "init done");
}

static void
gst_base_src_finalize (GObject * object)
{
  GstBaseSrc *basesrc;

  basesrc = GST_BASE_SRC (object);

  g_mutex_free (basesrc->live_lock);
  g_cond_free (basesrc->live_cond);

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

/**
 * gst_base_src_set_live:
 * @src: base source instance
 * @live: new live-mode
 *
 * If the element listens to a live source, the @livemode should
 * be set to %TRUE. This declares that this source can't seek.
 */
void
gst_base_src_set_live (GstBaseSrc * src, gboolean live)
{
  GST_LIVE_LOCK (src);
  src->is_live = live;
  GST_LIVE_UNLOCK (src);
}

/**
 * gst_base_src_is_live:
 * @src: base source instance
 *
 * Check if an element is in live mode.
 *
 * Returns: %TRUE if element is in live mode.
 */
gboolean
gst_base_src_is_live (GstBaseSrc * src)
{
  gboolean result;

  GST_LIVE_LOCK (src);
  result = src->is_live;
  GST_LIVE_UNLOCK (src);

  return result;
}

/**
 * gst_base_src_set_format:
 * @src: base source instance
 * @format: the format to use
 *
 * Sets the default format of the source. This will be the format used
 * for sending NEW_SEGMENT events and for performing seeks.
 *
 * If a format of GST_FORMAT_BYTES is set, the element will be able to
 * operate in pull mode if the #GstBaseSrc::is_seekable returns TRUE.
 *
 * @Since: 0.10.1
 */
void
gst_base_src_set_format (GstBaseSrc * src, GstFormat format)
{
  gst_segment_init (&src->segment, format);
}

static gboolean
gst_base_src_setcaps (GstPad * pad, GstCaps * caps)
{
  GstBaseSrcClass *bclass;
  GstBaseSrc *bsrc;
  gboolean res = TRUE;

  bsrc = GST_BASE_SRC (GST_PAD_PARENT (pad));
  bclass = GST_BASE_SRC_GET_CLASS (bsrc);

  if (bclass->set_caps)
    res = bclass->set_caps (bsrc, caps);

  return res;
}

static GstCaps *
gst_base_src_getcaps (GstPad * pad)
{
  GstBaseSrcClass *bclass;
  GstBaseSrc *bsrc;
  GstCaps *caps = NULL;

  bsrc = GST_BASE_SRC (GST_PAD_PARENT (pad));
  bclass = GST_BASE_SRC_GET_CLASS (bsrc);
  if (bclass->get_caps)
    caps = bclass->get_caps (bsrc);

  if (caps == NULL) {
    GstPadTemplate *pad_template;

    pad_template =
        gst_element_class_get_pad_template (GST_ELEMENT_CLASS (bclass), "src");
    if (pad_template != NULL) {
      caps = gst_caps_ref (gst_pad_template_get_caps (pad_template));
    }
  }
  return caps;
}

static gboolean
gst_base_src_default_query (GstBaseSrc * src, GstQuery * query)
{
  gboolean res;

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_POSITION:
    {
      GstFormat format;

      gst_query_parse_position (query, &format, NULL);
      switch (format) {
        case GST_FORMAT_PERCENT:
        {
          gint64 percent;
          gint64 position;
          gint64 duration;

          position = src->segment.last_stop;
          duration = src->segment.duration;

          if (position != -1 && duration != -1) {
            if (position < duration)
              percent = gst_util_uint64_scale (GST_FORMAT_PERCENT_MAX, position,
                  duration);
            else
              percent = GST_FORMAT_PERCENT_MAX;
          } else
            percent = -1;

          gst_query_set_position (query, GST_FORMAT_PERCENT, percent);
          res = TRUE;
          break;
        }
        default:
        {
          gint64 position;

          position = src->segment.last_stop;

          if (position != -1) {
            /* convert to requested format */
            res =
                gst_pad_query_convert (src->srcpad, src->segment.format,
                position, &format, &position);
          } else
            res = TRUE;

          gst_query_set_position (query, format, position);
          break;
        }
      }
      break;
    }
    case GST_QUERY_DURATION:
    {
      GstFormat format;

      gst_query_parse_duration (query, &format, NULL);
      switch (format) {
        case GST_FORMAT_PERCENT:
          gst_query_set_duration (query, GST_FORMAT_PERCENT,
              GST_FORMAT_PERCENT_MAX);
          res = TRUE;
          break;
        default:
        {
          gint64 duration;

          duration = src->segment.duration;

          if (duration != -1) {
            /* convert to requested format */
            res =
                gst_pad_query_convert (src->srcpad, src->segment.format,
                duration, &format, &duration);
          } else {
            res = TRUE;
          }
          gst_query_set_duration (query, format, duration);
          break;
        }
      }
      break;
    }

    case GST_QUERY_SEEKING:
    {
      gst_query_set_seeking (query, src->segment.format,
          src->seekable, 0, src->segment.duration);
      res = TRUE;
      break;
    }
    case GST_QUERY_SEGMENT:
    {
      gint64 start, stop;

      /* no end segment configured, current duration then */
      if ((stop = src->segment.stop) == -1)
        stop = src->segment.duration;
      start = src->segment.start;

      /* adjust to stream time */
      if (src->segment.time != -1) {
        start -= src->segment.time;
        if (stop != -1)
          stop -= src->segment.time;
      }
      gst_query_set_segment (query, src->segment.rate, src->segment.format,
          start, stop);
      res = TRUE;
      break;
    }

    case GST_QUERY_FORMATS:
    {
      gst_query_set_formats (query, 3, GST_FORMAT_DEFAULT,
          GST_FORMAT_BYTES, GST_FORMAT_PERCENT);
      res = TRUE;
      break;
    }
    case GST_QUERY_LATENCY:
    case GST_QUERY_JITTER:
    case GST_QUERY_RATE:
    case GST_QUERY_CONVERT:
    {
      GstFormat src_fmt, dest_fmt;
      gint64 src_val, dest_val;

      gst_query_parse_convert (query, &src_fmt, &src_val, &dest_fmt, &dest_val);

      /* we can only convert between equal formats... */
      if (src_fmt == dest_fmt) {
        dest_val = src_val;
        res = TRUE;
      } else
        res = FALSE;

      gst_query_set_convert (query, src_fmt, src_val, dest_fmt, dest_val);
      break;
    }
    default:
      res = FALSE;
      break;
  }
  return res;
}

static gboolean
gst_base_src_query (GstPad * pad, GstQuery * query)
{
  GstBaseSrc *src;
  GstBaseSrcClass *bclass;
  gboolean result = FALSE;

  src = GST_BASE_SRC (gst_pad_get_parent (pad));

  bclass = GST_BASE_SRC_GET_CLASS (src);

  if (bclass->query)
    result = bclass->query (src, query);
  else
    result = gst_pad_query_default (pad, query);

  gst_object_unref (src);

  return result;
}

static gboolean
gst_base_src_default_do_seek (GstBaseSrc * src, GstSegment * segment)
{
  gboolean res = TRUE;

  /* update our offset if the start/stop position was updated */
  if (segment->format == GST_FORMAT_BYTES) {
    segment->last_stop = segment->start;
    segment->time = segment->start;
  } else if (segment->start == 0) {
    /* seek to start, we can implement a default for this. */
    segment->last_stop = 0;
    segment->time = 0;
    res = TRUE;
  } else
    res = FALSE;

  return res;
}

static gboolean
gst_base_src_do_seek (GstBaseSrc * src, GstSegment * segment)
{
  GstBaseSrcClass *bclass;
  gboolean result = FALSE;

  bclass = GST_BASE_SRC_GET_CLASS (src);

  if (bclass->do_seek)
    result = bclass->do_seek (src, segment);

  return result;
}

/* this code implements the seeking. It is a good example
 * handling all cases.
 *
 * A seek updates the currently configured segment.start
 * and segment.stop values based on the SEEK_TYPE. If the
 * segment.start value is updated, a seek to this new position
 * should be performed.
 *
 * The seek can only be executed when we are not currently
 * streaming any data, to make sure that this is the case, we
 * acquire the STREAM_LOCK which is taken when we are in the
 * _loop() function or when a getrange() is called. Normally
 * we will not receive a seek if we are operating in pull mode
 * though.
 *
 * When we are in the loop() function, we might be in the middle
 * of pushing a buffer, which might block in a sink. To make sure
 * that the push gets unblocked we push out a FLUSH_START event.
 * Our loop function will get a WRONG_STATE return value from
 * the push and will pause, effectively releasing the STREAM_LOCK.
 *
 * For a non-flushing seek, we pause the task, which might eventually
 * release the STREAM_LOCK. We say eventually because when the sink
 * blocks on the sample we might wait a very long time until the sink
 * unblocks the sample. In any case we acquire the STREAM_LOCK and
 * can continue the seek. A non-flushing seek is normally done in a 
 * running pipeline to perform seamless playback.
 * In the case of a non-flushing seek we need to make sure that the
 * data we output after the seek is continuous with the previous data,
 * this is because a non-flushing seek does not reset the stream-time
 * to 0. We do this by closing the currently running segment, ie. sending
 * a new_segment event with the stop position set to the last processed 
 * position.
 *
 * After updating the segment.start/stop values, we prepare for
 * streaming again. We push out a FLUSH_STOP to make the peer pad
 * accept data again and we start our task again.
 *
 * A segment seek posts a message on the bus saying that the playback
 * of the segment started. We store the segment flag internally because
 * when we reach the segment.stop we have to post a segment.done
 * instead of EOS when doing a segment seek.
 */
/* FIXME, we have the unlock gboolean here because most current implementations
 * (fdsrc, -base/gst/tcp/, ...) not only unlock when there is something to
 * unlock
 */
static gboolean
gst_base_src_perform_seek (GstBaseSrc * src, GstEvent * event, gboolean unlock)
{
  gboolean res;
  gdouble rate;
  GstFormat format;
  GstSeekFlags flags;
  GstSeekType cur_type, stop_type;
  gint64 cur, stop;
  gboolean flush;
  gboolean update;
  GstSegment seeksegment;

  GST_DEBUG_OBJECT (src, "doing seek");

  if (event) {
    gst_event_parse_seek (event, &rate, &format, &flags,
        &cur_type, &cur, &stop_type, &stop);

    /* we have to have a format as the segment format. Try to convert
     * if not. */
    if (src->segment.format != format) {
      GstFormat fmt;

      fmt = src->segment.format;
      res = TRUE;
      if (cur_type != GST_SEEK_TYPE_NONE)
        res = gst_pad_query_convert (src->srcpad, format, cur, &fmt, &cur);
      if (res && stop_type != GST_SEEK_TYPE_NONE)
        res = gst_pad_query_convert (src->srcpad, format, stop, &fmt, &stop);
      if (!res)
        goto no_format;

      format = fmt;
    }
  } else {
    flags = 0;
  }

  flush = flags & GST_SEEK_FLAG_FLUSH;

  /* send flush start */
  if (flush)
    gst_pad_push_event (src->srcpad, gst_event_new_flush_start ());
  else
    gst_pad_pause_task (src->srcpad);

  /* unblock streaming thread */
  if (unlock)
    gst_base_src_unlock (src);

  /* grab streaming lock, this should eventually be possible, either
   * because the task is paused or out streaming thread stopped 
   * because our peer is flushing. */
  GST_PAD_STREAM_LOCK (src->srcpad);

  /* make copy into temp structure, we can only update the main one
   * when the subclass actually could to the seek. */
  memcpy (&seeksegment, &src->segment, sizeof (GstSegment));

  /* now configure the seek segment */
  if (event) {
    gst_segment_set_seek (&seeksegment, rate, format, flags,
        cur_type, cur, stop_type, stop, &update);
  }

  GST_DEBUG_OBJECT (src, "segment configured from %" G_GINT64_FORMAT
      " to %" G_GINT64_FORMAT ", position %" G_GINT64_FORMAT,
      seeksegment.start, seeksegment.stop, seeksegment.last_stop);

  /* do the seek, segment.last_stop contains new position. */
  res = gst_base_src_do_seek (src, &seeksegment);

  /* and prepare to continue streaming */
  if (flush) {
    /* send flush stop, peer will accept data and events again. We
     * are not yet providing data as we still have the STREAM_LOCK. */
    gst_pad_push_event (src->srcpad, gst_event_new_flush_stop ());
  } else if (res && src->ABI.running) {
    /* we are running the current segment and doing a non-flushing seek, 
     * close the segment first based on the last_stop. */
    GST_DEBUG_OBJECT (src, "closing running segment %" G_GINT64_FORMAT
        " to %" G_GINT64_FORMAT, src->segment.start, src->segment.last_stop);

    gst_pad_push_event (src->srcpad,
        gst_event_new_new_segment (TRUE,
            src->segment.rate, src->segment.format,
            src->segment.start, src->segment.last_stop, src->segment.time));
  }

  /* if successfull seek, we update our real segment and push
   * out the new segment. */
  if (res) {
    memcpy (&src->segment, &seeksegment, sizeof (GstSegment));

    if (src->segment.flags & GST_SEEK_FLAG_SEGMENT) {
      gst_element_post_message (GST_ELEMENT (src),
          gst_message_new_segment_start (GST_OBJECT (src),
              src->segment.format, src->segment.last_stop));
    }

    if ((stop = src->segment.stop) == -1)
      stop = src->segment.duration;

    /* now send the newsegment */
    GST_DEBUG_OBJECT (src, "Sending newsegment from %" G_GINT64_FORMAT
        " to %" G_GINT64_FORMAT, src->segment.start, stop);

    gst_pad_push_event (src->srcpad,
        gst_event_new_new_segment (FALSE,
            src->segment.rate, src->segment.format,
            src->segment.last_stop, stop, src->segment.time));
  }

  src->ABI.running = TRUE;
  /* and restart the task in case it got paused explicitely or by
   * the FLUSH_START event we pushed out. */
  gst_pad_start_task (src->srcpad, (GstTaskFunction) gst_base_src_loop,
      src->srcpad);

  /* and release the lock again so we can continue streaming */
  GST_PAD_STREAM_UNLOCK (src->srcpad);

  return res;

  /* ERROR */
no_format:
  {
    GST_DEBUG_OBJECT (src, "undefined format given, seek aborted.");
    return FALSE;
  }
}

/* all events send to this element directly
 */
static gboolean
gst_base_src_send_event (GstElement * element, GstEvent * event)
{
  GstBaseSrc *src;
  gboolean result;

  src = GST_BASE_SRC (element);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEEK:
    {
      GST_OBJECT_LOCK (src);
      /* gst_event_replace? */
      if (src->ABI.pending_seek)
        gst_event_unref (src->ABI.pending_seek);
      gst_event_ref (event);
      src->ABI.pending_seek = event;
      GST_OBJECT_UNLOCK (src);
      result = TRUE;
      break;
    }
    default:
      result = FALSE;
      break;
  }
  gst_event_unref (event);

  return result;
}

static gboolean
gst_base_src_default_event (GstBaseSrc * src, GstEvent * event)
{
  gboolean result;

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEEK:
      /* is normally called when in push mode */
      if (!src->seekable)
        goto not_seekable;

      result = gst_base_src_perform_seek (src, event, TRUE);
      break;
    case GST_EVENT_FLUSH_START:
      /* cancel any blocking getrange, is normally called
       * when in pull mode. */
      result = gst_base_src_unlock (src);
      break;
    case GST_EVENT_FLUSH_STOP:
    default:
      result = TRUE;
      break;
  }
  return result;

  /* ERRORS */
not_seekable:
  {
    GST_DEBUG_OBJECT (src, "is not seekable");
    return FALSE;
  }
}

static gboolean
gst_base_src_event_handler (GstPad * pad, GstEvent * event)
{
  GstBaseSrc *src;
  GstBaseSrcClass *bclass;
  gboolean result = FALSE;

  src = GST_BASE_SRC (gst_pad_get_parent (pad));
  bclass = GST_BASE_SRC_GET_CLASS (src);

  if (bclass->event) {
    if (!(result = bclass->event (src, event)))
      goto subclass_failed;
  }

done:
  gst_event_unref (event);
  gst_object_unref (src);

  return result;

  /* ERRORS */
subclass_failed:
  {
    GST_DEBUG_OBJECT (src, "subclass refused event");
    goto done;
  }
}

static void
gst_base_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstBaseSrc *src;

  src = GST_BASE_SRC (object);

  switch (prop_id) {
    case PROP_BLOCKSIZE:
      src->blocksize = g_value_get_ulong (value);
      break;
    case PROP_NUM_BUFFERS:
      src->num_buffers = g_value_get_int (value);
      break;
    case PROP_TYPEFIND:
      src->ABI.typefind = g_value_get_boolean (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_base_src_get_property (GObject * object, guint prop_id, GValue * value,
    GParamSpec * pspec)
{
  GstBaseSrc *src;

  src = GST_BASE_SRC (object);

  switch (prop_id) {
    case PROP_BLOCKSIZE:
      g_value_set_ulong (value, src->blocksize);
      break;
    case PROP_NUM_BUFFERS:
      g_value_set_int (value, src->num_buffers);
      break;
    case PROP_TYPEFIND:
      g_value_set_boolean (value, src->ABI.typefind);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

/* with STREAM_LOCK and LOCK*/
static GstClockReturn
gst_base_src_wait (GstBaseSrc * basesrc, GstClockTime time)
{
  GstClockReturn ret;
  GstClockID id;
  GstClock *clock;

  /* get clock, if no clock, we don't sync */
  if ((clock = GST_ELEMENT_CLOCK (basesrc)) == NULL)
    return GST_CLOCK_OK;

  /* clock_id should be NULL outside of this function */
  g_assert (basesrc->clock_id == NULL);
  g_assert (GST_CLOCK_TIME_IS_VALID (time));

  id = gst_clock_new_single_shot_id (clock, time);

  basesrc->clock_id = id;
  /* release the object lock while waiting */
  GST_OBJECT_UNLOCK (basesrc);

  ret = gst_clock_id_wait (id, NULL);

  GST_OBJECT_LOCK (basesrc);
  gst_clock_id_unref (id);
  basesrc->clock_id = NULL;

  return ret;
}

/* perform synchronisation on a buffer. 
 * with STREAM_LOCK.
 */
static GstClockReturn
gst_base_src_do_sync (GstBaseSrc * basesrc, GstBuffer * buffer)
{
  GstClockReturn result;
  GstClockTime start, end;
  GstBaseSrcClass *bclass;
  GstClockTime base_time;

  bclass = GST_BASE_SRC_GET_CLASS (basesrc);

  start = end = -1;
  if (bclass->get_times)
    bclass->get_times (basesrc, buffer, &start, &end);

  /* if we don't have a timestamp, we don't sync */
  if (!GST_CLOCK_TIME_IS_VALID (start))
    goto invalid_start;

  /* now do clocking */
  GST_OBJECT_LOCK (basesrc);
  base_time = GST_ELEMENT_CAST (basesrc)->base_time;

  GST_LOG_OBJECT (basesrc,
      "waiting for clock, base time %" GST_TIME_FORMAT
      ", stream_start %" GST_TIME_FORMAT,
      GST_TIME_ARGS (base_time), GST_TIME_ARGS (start));

  result = gst_base_src_wait (basesrc, start + base_time);
  GST_OBJECT_UNLOCK (basesrc);

  GST_LOG_OBJECT (basesrc, "clock entry done: %d", result);

  return result;

  /* special cases */
invalid_start:
  {
    GST_DEBUG_OBJECT (basesrc, "get_times returned invalid start");
    return GST_CLOCK_OK;
  }
}

static gboolean
gst_base_src_update_length (GstBaseSrc * src, guint64 offset, guint * length)
{
  guint64 size, maxsize;
  GstBaseSrcClass *bclass;

  bclass = GST_BASE_SRC_GET_CLASS (src);

  /* only operate if we are working with bytes */
  if (src->segment.format != GST_FORMAT_BYTES)
    return TRUE;

  size = (guint64) src->segment.duration;

  /* the max amount of bytes to read is the total size or
   * up to the segment.stop if present. */
  if (src->segment.stop != -1)
    maxsize = MIN (size, src->segment.stop);
  else
    maxsize = size;

  GST_DEBUG_OBJECT (src,
      "reading offset %" G_GUINT64_FORMAT ", length %u, size %" G_GINT64_FORMAT
      ", segment.stop %" G_GINT64_FORMAT ", maxsize %" G_GINT64_FORMAT, offset,
      *length, size, src->segment.stop, maxsize);

  /* check size */
  if (maxsize != -1) {
    if (offset > maxsize)
      goto unexpected_length;

    if (offset + *length > maxsize) {
      /* see if length of the file changed */
      if (bclass->get_size)
        bclass->get_size (src, &size);

      if (src->segment.stop != -1)
        maxsize = MIN (size, src->segment.stop);
      else
        maxsize = size;

      if (offset + *length > maxsize) {
        *length = maxsize - offset;
      }
    }
  }
  if (*length == 0)
    goto unexpected_length;

  return TRUE;

  /* ERRORS */
unexpected_length:
  {
    return FALSE;
  }
}

static GstFlowReturn
gst_base_src_get_range (GstBaseSrc * src, guint64 offset, guint length,
    GstBuffer ** buf)
{
  GstFlowReturn ret;
  GstBaseSrcClass *bclass;
  GstClockReturn status;

  bclass = GST_BASE_SRC_GET_CLASS (src);

  GST_LIVE_LOCK (src);
  if (src->is_live) {
    while (!src->live_running) {
      GST_DEBUG ("live source signal waiting");
      GST_LIVE_SIGNAL (src);
      GST_DEBUG ("live source waiting for running state");
      GST_LIVE_WAIT (src);
      GST_DEBUG ("live source unlocked");
    }
    /* FIXME, use another variable to signal stopping */
    GST_OBJECT_LOCK (src->srcpad);
    if (GST_PAD_IS_FLUSHING (src->srcpad))
      goto flushing;
    GST_OBJECT_UNLOCK (src->srcpad);
  }
  GST_LIVE_UNLOCK (src);

  if (!GST_OBJECT_FLAG_IS_SET (src, GST_BASE_SRC_STARTED))
    goto not_started;

  if (G_UNLIKELY (!bclass->create))
    goto no_function;

  if (!gst_base_src_update_length (src, offset, &length))
    goto unexpected_length;

  if (src->num_buffers_left == 0) {
    goto reached_num_buffers;
  } else {
    if (src->num_buffers_left > 0)
      src->num_buffers_left--;
  }

  ret = bclass->create (src, offset, length, buf);
  if (ret != GST_FLOW_OK)
    goto done;

  /* no timestamp set and we are at offset 0 */
  if (offset == 0 && src->segment.time == 0
      && GST_BUFFER_TIMESTAMP (*buf) == -1)
    GST_BUFFER_TIMESTAMP (*buf) = 0;

  /* now sync before pushing the buffer */
  status = gst_base_src_do_sync (src, *buf);
  switch (status) {
    case GST_CLOCK_EARLY:
      GST_DEBUG_OBJECT (src, "buffer too late!, returning anyway");
      break;
    case GST_CLOCK_OK:
      GST_DEBUG_OBJECT (src, "buffer ok");
      break;
    default:
      GST_DEBUG_OBJECT (src, "clock returned %d, not returning", status);
      gst_buffer_unref (*buf);
      *buf = NULL;
      ret = GST_FLOW_WRONG_STATE;
      break;
  }
done:
  return ret;

  /* ERROR */
flushing:
  {
    GST_DEBUG_OBJECT (src, "pad is flushing");
    GST_OBJECT_UNLOCK (src->srcpad);
    GST_LIVE_UNLOCK (src);
    return GST_FLOW_WRONG_STATE;
  }
not_started:
  {
    GST_DEBUG_OBJECT (src, "getrange but not started");
    return GST_FLOW_WRONG_STATE;
  }
no_function:
  {
    GST_DEBUG_OBJECT (src, "no create function");
    return GST_FLOW_ERROR;
  }
unexpected_length:
  {
    GST_DEBUG_OBJECT (src, "unexpected length %u (offset=%" G_GUINT64_FORMAT
        ", size=%" G_GINT64_FORMAT ")", length, offset, src->segment.duration);
    return GST_FLOW_UNEXPECTED;
  }
reached_num_buffers:
  {
    GST_DEBUG_OBJECT (src, "sent all buffers");
    return GST_FLOW_UNEXPECTED;
  }
}

static GstFlowReturn
gst_base_src_pad_get_range (GstPad * pad, guint64 offset, guint length,
    GstBuffer ** buf)
{
  GstBaseSrc *src;
  GstFlowReturn res;

  src = GST_BASE_SRC (gst_pad_get_parent (pad));

  res = gst_base_src_get_range (src, offset, length, buf);

  gst_object_unref (src);

  return res;
}

static gboolean
gst_base_src_check_get_range (GstPad * pad)
{
  GstBaseSrc *src;
  gboolean res;

  src = GST_BASE_SRC (gst_pad_get_parent (pad));

  if (!GST_OBJECT_FLAG_IS_SET (src, GST_BASE_SRC_STARTED)) {
    gst_base_src_start (src);
    gst_base_src_stop (src);
  }

  /* we can operate in getrange mode if the native format is bytes
   * and we are seekable, this condition is set in the random_access
   * flag and is set in the _start() method. */
  res = src->random_access;

  gst_object_unref (src);

  return res;
}

static void
gst_base_src_loop (GstPad * pad)
{
  GstBaseSrc *src;
  GstBuffer *buf = NULL;
  GstFlowReturn ret;
  gint64 position;

  src = GST_BASE_SRC (gst_pad_get_parent (pad));

  /* if we operate in bytes, we can calculate an offset */
  if (src->segment.format == GST_FORMAT_BYTES)
    position = src->segment.last_stop;
  else
    position = -1;

  ret = gst_base_src_get_range (src, position, src->blocksize, &buf);
  if (G_UNLIKELY (ret != GST_FLOW_OK)) {
    if (ret == GST_FLOW_UNEXPECTED)
      goto eos;
    else
      goto pause;
  }
  if (G_UNLIKELY (buf == NULL))
    goto error;

  /* figure out the new position */
  switch (src->segment.format) {
    case GST_FORMAT_BYTES:
      position += GST_BUFFER_SIZE (buf);
      break;
    case GST_FORMAT_TIME:
    {
      GstClockTime start, duration;

      start = GST_BUFFER_TIMESTAMP (buf);
      duration = GST_BUFFER_DURATION (buf);

      if (GST_CLOCK_TIME_IS_VALID (start))
        position = start;
      else
        position = src->segment.last_stop;

      if (GST_CLOCK_TIME_IS_VALID (duration))
        position += duration;
      break;
    }
    case GST_FORMAT_DEFAULT:
      position = GST_BUFFER_OFFSET_END (buf);
      break;
    default:
      position = -1;
      break;
  }
  if (position != -1)
    gst_segment_set_last_stop (&src->segment, src->segment.format, position);

  ret = gst_pad_push (pad, buf);
  if (G_UNLIKELY (ret != GST_FLOW_OK))
    goto pause;

done:
  gst_object_unref (src);
  return;

  /* special cases */
eos:
  {
    GST_DEBUG_OBJECT (src, "going to EOS, getrange returned UNEXPECTED");
    /* we finished the segment */
    src->ABI.running = FALSE;
    gst_pad_pause_task (pad);
    if (src->segment.flags & GST_SEEK_FLAG_SEGMENT) {
      gst_element_post_message (GST_ELEMENT (src),
          gst_message_new_segment_done (GST_OBJECT (src),
              src->segment.format, src->segment.last_stop));
    } else {
      gst_pad_push_event (pad, gst_event_new_eos ());
    }
    goto done;
  }
pause:
  {
    const gchar *reason = gst_flow_get_name (ret);

    GST_DEBUG_OBJECT (src, "pausing task, reason %s", reason);
    gst_pad_pause_task (pad);
    if (GST_FLOW_IS_FATAL (ret) || ret == GST_FLOW_NOT_LINKED) {
      /* for fatal errors we post an error message */
      GST_ELEMENT_ERROR (src, STREAM, FAILED,
          (_("Internal data flow error.")),
          ("streaming task paused, reason %s", reason));
      gst_pad_push_event (pad, gst_event_new_eos ());
    }
    goto done;
  }
error:
  {
    GST_ELEMENT_ERROR (src, STREAM, FAILED,
        (_("Internal data flow error.")), ("element returned NULL buffer"));
    /* we finished the segment on error */
    src->ABI.running = FALSE;
    gst_pad_pause_task (pad);
    gst_pad_push_event (pad, gst_event_new_eos ());
    goto done;
  }
}

/* this will always be called between start() and stop(). So you can rely on
 * resources allocated by start() and freed from stop(). This needs to be added
 * to the docs at some point. */
static gboolean
gst_base_src_unlock (GstBaseSrc * basesrc)
{
  GstBaseSrcClass *bclass;
  gboolean result = TRUE;

  GST_DEBUG ("unlock");
  /* unblock whatever the subclass is doing */
  bclass = GST_BASE_SRC_GET_CLASS (basesrc);
  if (bclass->unlock)
    result = bclass->unlock (basesrc);

  GST_DEBUG ("unschedule clock");
  /* and unblock the clock as well, if any */
  GST_OBJECT_LOCK (basesrc);
  if (basesrc->clock_id) {
    gst_clock_id_unschedule (basesrc->clock_id);
  }
  GST_OBJECT_UNLOCK (basesrc);

  GST_DEBUG ("unlock done");

  return result;
}

/* default negotiation code. 
 *
 * Take intersection between src and sink pads, take first
 * caps and fixate. 
 */
static gboolean
gst_base_src_default_negotiate (GstBaseSrc * basesrc)
{
  GstCaps *thiscaps;
  GstCaps *caps = NULL;
  GstCaps *peercaps = NULL;
  gboolean result = FALSE;

  /* first see what is possible on our source pad */
  thiscaps = gst_pad_get_caps (GST_BASE_SRC_PAD (basesrc));
  GST_DEBUG_OBJECT (basesrc, "caps of src: %" GST_PTR_FORMAT, thiscaps);
  /* nothing or anything is allowed, we're done */
  if (thiscaps == NULL || gst_caps_is_any (thiscaps))
    goto no_nego_needed;

  /* get the peer caps */
  peercaps = gst_pad_peer_get_caps (GST_BASE_SRC_PAD (basesrc));
  GST_DEBUG_OBJECT (basesrc, "caps of peer: %" GST_PTR_FORMAT, peercaps);
  if (peercaps) {
    GstCaps *icaps;

    /* get intersection */
    icaps = gst_caps_intersect (thiscaps, peercaps);
    GST_DEBUG_OBJECT (basesrc, "intersect: %" GST_PTR_FORMAT, icaps);
    gst_caps_unref (thiscaps);
    gst_caps_unref (peercaps);
    if (icaps) {
      /* take first (and best, since they are sorted) possibility */
      caps = gst_caps_copy_nth (icaps, 0);
      gst_caps_unref (icaps);
    }
  } else {
    /* no peer, work with our own caps then */
    caps = thiscaps;
  }
  if (caps) {
    caps = gst_caps_make_writable (caps);
    gst_caps_truncate (caps);

    /* now fixate */
    if (!gst_caps_is_empty (caps)) {
      gst_pad_fixate_caps (GST_BASE_SRC_PAD (basesrc), caps);
      GST_DEBUG_OBJECT (basesrc, "fixated to: %" GST_PTR_FORMAT, caps);

      if (gst_caps_is_any (caps)) {
        /* hmm, still anything, so element can do anything and
         * nego is not needed */
        result = TRUE;
      } else if (gst_caps_is_fixed (caps)) {
        /* yay, fixed caps, use those then */
        gst_pad_set_caps (GST_BASE_SRC_PAD (basesrc), caps);
        result = TRUE;
      }
    }
    gst_caps_unref (caps);
  }
  return result;

no_nego_needed:
  {
    GST_DEBUG_OBJECT (basesrc, "no negotiation needed");
    if (thiscaps)
      gst_caps_unref (thiscaps);
    return TRUE;
  }
}

static gboolean
gst_base_src_negotiate (GstBaseSrc * basesrc)
{
  GstBaseSrcClass *bclass;
  gboolean result = TRUE;

  bclass = GST_BASE_SRC_GET_CLASS (basesrc);

  if (bclass->negotiate)
    result = bclass->negotiate (basesrc);

  return result;
}

static gboolean
gst_base_src_start (GstBaseSrc * basesrc)
{
  GstBaseSrcClass *bclass;
  gboolean result;
  guint64 size;

  if (GST_OBJECT_FLAG_IS_SET (basesrc, GST_BASE_SRC_STARTED))
    return TRUE;

  GST_DEBUG_OBJECT (basesrc, "starting source");

  basesrc->num_buffers_left = basesrc->num_buffers;

  gst_segment_init (&basesrc->segment, basesrc->segment.format);
  basesrc->ABI.running = FALSE;

  bclass = GST_BASE_SRC_GET_CLASS (basesrc);
  if (bclass->start)
    result = bclass->start (basesrc);
  else
    result = TRUE;

  if (!result)
    goto could_not_start;

  GST_OBJECT_FLAG_SET (basesrc, GST_BASE_SRC_STARTED);

  /* figure out the size */
  if (basesrc->segment.format == GST_FORMAT_BYTES) {
    if (bclass->get_size) {
      if (!(result = bclass->get_size (basesrc, &size)))
        size = -1;
    } else {
      result = FALSE;
      size = -1;
    }
    /* only update the size when operating in bytes, subclass is supposed
     * to set duration in the start method for other formats */
    gst_segment_set_duration (&basesrc->segment, GST_FORMAT_BYTES, size);
  }

  GST_DEBUG_OBJECT (basesrc,
      "format: %d, have size: %d, size: %" G_GUINT64_FORMAT ", duration: %"
      G_GINT64_FORMAT, basesrc->segment.format, result, size,
      basesrc->segment.duration);

  /* check if we can seek */
  if (bclass->is_seekable)
    basesrc->seekable = bclass->is_seekable (basesrc);
  else
    basesrc->seekable = FALSE;

  GST_DEBUG_OBJECT (basesrc, "is seekable: %d", basesrc->seekable);

  /* update for random access flag */
  basesrc->random_access = basesrc->seekable &&
      basesrc->segment.format == GST_FORMAT_BYTES;

  GST_DEBUG_OBJECT (basesrc, "is random_access: %d", basesrc->random_access);

  /* run typefind if we are random_access and the typefinding is enabled. */
  if (basesrc->random_access && basesrc->ABI.typefind && size != -1) {
    GstCaps *caps;

    caps = gst_type_find_helper (basesrc->srcpad, size);
    gst_pad_set_caps (basesrc->srcpad, caps);
    gst_caps_unref (caps);
  } else {
    /* use class or default negotiate function */
    if (!gst_base_src_negotiate (basesrc))
      goto could_not_negotiate;
  }

  return TRUE;

  /* ERROR */
could_not_start:
  {
    GST_DEBUG_OBJECT (basesrc, "could not start");
    return FALSE;
  }
could_not_negotiate:
  {
    GST_DEBUG_OBJECT (basesrc, "could not negotiate, stopping");
    GST_ELEMENT_ERROR (basesrc, STREAM, FORMAT,
        ("Could not negotiate format"), ("Check your filtered caps, if any"));
    gst_base_src_stop (basesrc);
    return FALSE;
  }
}

static gboolean
gst_base_src_stop (GstBaseSrc * basesrc)
{
  GstBaseSrcClass *bclass;
  gboolean result = TRUE;

  if (!GST_OBJECT_FLAG_IS_SET (basesrc, GST_BASE_SRC_STARTED))
    return TRUE;

  GST_DEBUG_OBJECT (basesrc, "stopping source");

  bclass = GST_BASE_SRC_GET_CLASS (basesrc);
  if (bclass->stop)
    result = bclass->stop (basesrc);

  if (result)
    GST_OBJECT_FLAG_UNSET (basesrc, GST_BASE_SRC_STARTED);

  return result;
}

static gboolean
gst_base_src_deactivate (GstBaseSrc * basesrc, GstPad * pad)
{
  gboolean result;

  GST_LIVE_LOCK (basesrc);
  basesrc->live_running = TRUE;
  GST_LIVE_SIGNAL (basesrc);
  GST_LIVE_UNLOCK (basesrc);

  /* step 1, unblock clock sync (if any) */
  result = gst_base_src_unlock (basesrc);

  /* step 2, make sure streaming finishes */
  result &= gst_pad_stop_task (pad);

  return result;
}

static gboolean
gst_base_src_activate_push (GstPad * pad, gboolean active)
{
  GstBaseSrc *basesrc;
  gboolean res;

  basesrc = GST_BASE_SRC (GST_OBJECT_PARENT (pad));

  /* prepare subclass first */
  if (active) {
    GstEvent *event;

    GST_DEBUG_OBJECT (basesrc, "Activating in push mode");

    if (!basesrc->can_activate_push)
      goto no_push_activation;

    if (!gst_base_src_start (basesrc))
      goto error_start;

    /* do initial seek, which will start the task */
    GST_OBJECT_LOCK (basesrc);
    event = basesrc->ABI.pending_seek;
    basesrc->ABI.pending_seek = NULL;
    GST_OBJECT_UNLOCK (basesrc);

    /* no need to unlock anything, the task is certainly
     * not running here. */
    res = gst_base_src_perform_seek (basesrc, event, FALSE);

    if (event)
      gst_event_unref (event);
  } else {
    GST_DEBUG_OBJECT (basesrc, "Deactivating in push mode");
    res = gst_base_src_deactivate (basesrc, pad);
  }
  return res;

  /* ERRORS */
no_push_activation:
  {
    GST_DEBUG_OBJECT (basesrc, "Subclass disabled push-mode activation");
    return FALSE;
  }
error_start:
  {
    gst_base_src_stop (basesrc);
    GST_DEBUG_OBJECT (basesrc, "Failed to start in push mode");
    return FALSE;
  }
}

static gboolean
gst_base_src_activate_pull (GstPad * pad, gboolean active)
{
  GstBaseSrc *basesrc;

  basesrc = GST_BASE_SRC (GST_OBJECT_PARENT (pad));

  /* prepare subclass first */
  if (active) {
    GST_DEBUG_OBJECT (basesrc, "Activating in pull mode");
    if (!gst_base_src_start (basesrc))
      goto error_start;

    /* if not random_access, we cannot operate in pull mode for now */
    if (!basesrc->random_access) {
      gst_base_src_stop (basesrc);
      return FALSE;
    }
    return TRUE;
  } else {
    GST_DEBUG_OBJECT (basesrc, "Deactivating in pull mode");

    if (!gst_base_src_stop (basesrc))
      goto error_stop;

    return gst_base_src_deactivate (basesrc, pad);
  }

error_start:
  {
    gst_base_src_stop (basesrc);
    GST_DEBUG_OBJECT (basesrc, "Failed to start in pull mode");
    return FALSE;
  }
error_stop:
  {
    GST_DEBUG_OBJECT (basesrc, "Failed to stop in pull mode");
    return FALSE;
  }
}

static GstStateChangeReturn
gst_base_src_change_state (GstElement * element, GstStateChange transition)
{
  GstBaseSrc *basesrc;
  GstStateChangeReturn result;
  gboolean no_preroll = FALSE;

  basesrc = GST_BASE_SRC (element);

  switch (transition) {
    case GST_STATE_CHANGE_NULL_TO_READY:
      break;
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      GST_LIVE_LOCK (element);
      if (basesrc->is_live) {
        no_preroll = TRUE;
        basesrc->live_running = FALSE;
      }
      GST_LIVE_UNLOCK (element);
      break;
    case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
      GST_LIVE_LOCK (element);
      if (basesrc->is_live) {
        basesrc->live_running = TRUE;
        GST_LIVE_SIGNAL (element);
      }
      GST_LIVE_UNLOCK (element);
      break;
    default:
      break;
  }

  if ((result =
          GST_ELEMENT_CLASS (parent_class)->change_state (element,
              transition)) == GST_STATE_CHANGE_FAILURE)
    goto failure;

  switch (transition) {
    case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
      GST_LIVE_LOCK (element);
      if (basesrc->is_live) {
        no_preroll = TRUE;
        basesrc->live_running = FALSE;
      }
      GST_LIVE_UNLOCK (element);
      break;
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      if (!gst_base_src_stop (basesrc))
        goto error_stop;
      break;
    case GST_STATE_CHANGE_READY_TO_NULL:
      break;
    default:
      break;
  }

  if (no_preroll && result == GST_STATE_CHANGE_SUCCESS)
    result = GST_STATE_CHANGE_NO_PREROLL;

  return result;

  /* ERRORS */
failure:
  {
    GST_DEBUG_OBJECT (basesrc, "parent failed state change");
    gst_base_src_stop (basesrc);
    return result;
  }
error_stop:
  {
    GST_DEBUG_OBJECT (basesrc, "Failed to stop");
    return GST_STATE_CHANGE_FAILURE;
  }
}