text: /* GStreamer
   * Copyright (c) 2005 Edward Hervey <bilboed@bilboed.com>
   * Copyright (C) 2010 Sebastian Dröge <sebastian.droege@collabora.co.uk>
   *
   * 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., 51 Franklin St, Fifth Floor,
   * Boston, MA 02110-1301, USA.
   */
  
  /**
   * SECTION:element-imagefreeze
   *
   * The imagefreeze element generates a still frame video stream from
   * the input. It duplicates the first frame with the framerate requested
   * by downstream, allows seeking and answers queries.
   *
   * <refsect2>
   * <title>Example launch line</title>
   * |[
   * gst-launch-1.0 -v filesrc location=some.png ! decodebin ! imagefreeze ! autovideosink
   * ]| This pipeline shows a still frame stream of a PNG file.
   * </refsect2>
   */
  
  /* This is based on the imagefreeze element from PiTiVi:
   * http://git.gnome.org/browse/pitivi/tree/pitivi/elements/imagefreeze.py
   */
  
  #ifdef HAVE_CONFIG_H
  #include "config.h"
  #endif
  
  #include <gst/glib-compat-private.h>
  
  #include "gstimagefreeze.h"
  
  #define DEFAULT_NUM_BUFFERS     -1
  
  enum
  {
    PROP_0,
    PROP_NUM_BUFFERS
  };
  
  static void gst_image_freeze_finalize (GObject * object);
  
  static void gst_image_freeze_reset (GstImageFreeze * self);
  
  static GstStateChangeReturn gst_image_freeze_change_state (GstElement * element,
      GstStateChange transition);
  
  static void gst_image_freeze_set_property (GObject * object, guint prop_id,
      const GValue * value, GParamSpec * pspec);
  static void gst_image_freeze_get_property (GObject * object, guint prop_id,
      GValue * value, GParamSpec * pspec);
  static GstFlowReturn gst_image_freeze_sink_chain (GstPad * pad,
      GstObject * parent, GstBuffer * buffer);
  static gboolean gst_image_freeze_sink_event (GstPad * pad, GstObject * parent,
      GstEvent * event);
  static gboolean gst_image_freeze_sink_setcaps (GstImageFreeze * self,
      GstCaps * caps);
  static GstCaps *gst_image_freeze_sink_getcaps (GstImageFreeze * self,
      GstCaps * filter);
  static gboolean gst_image_freeze_sink_query (GstPad * pad, GstObject * parent,
      GstQuery * query);
  static void gst_image_freeze_src_loop (GstPad * pad);
  static gboolean gst_image_freeze_src_event (GstPad * pad, GstObject * parent,
      GstEvent * event);
  static gboolean gst_image_freeze_src_query (GstPad * pad, GstObject * parent,
      GstQuery * query);
  
  static GstStaticPadTemplate sink_pad_template = GST_STATIC_PAD_TEMPLATE ("sink",
      GST_PAD_SINK,
      GST_PAD_ALWAYS,
      GST_STATIC_CAPS ("video/x-raw(ANY)"));
  
  static GstStaticPadTemplate src_pad_template =
  GST_STATIC_PAD_TEMPLATE ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
      GST_STATIC_CAPS ("video/x-raw(ANY)"));
  
  GST_DEBUG_CATEGORY_STATIC (gst_image_freeze_debug);
  #define GST_CAT_DEFAULT gst_image_freeze_debug
  
  #define gst_image_freeze_parent_class parent_class
  G_DEFINE_TYPE (GstImageFreeze, gst_image_freeze, GST_TYPE_ELEMENT);
  
  
  static void
  gst_image_freeze_class_init (GstImageFreezeClass * klass)
  {
    GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
    GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
  
    gobject_class->finalize = gst_image_freeze_finalize;
    gobject_class->set_property = gst_image_freeze_set_property;
    gobject_class->get_property = gst_image_freeze_get_property;
  
    g_object_class_install_property (gobject_class, PROP_NUM_BUFFERS,
        g_param_spec_int ("num-buffers", "num-buffers",
            "Number of buffers to output before sending EOS (-1 = unlimited)",
            -1, G_MAXINT, DEFAULT_NUM_BUFFERS, G_PARAM_READWRITE |
            G_PARAM_STATIC_STRINGS));
  
    gstelement_class->change_state =
        GST_DEBUG_FUNCPTR (gst_image_freeze_change_state);
  
    gst_element_class_set_static_metadata (gstelement_class,
        "Still frame stream generator",
        "Filter/Video",
        "Generates a still frame stream from an image",
        "Sebastian Dröge <sebastian.droege@collabora.co.uk>");
  
    gst_element_class_add_static_pad_template (gstelement_class,
        &sink_pad_template);
    gst_element_class_add_static_pad_template (gstelement_class,
        &src_pad_template);
  }
  
  static void
  gst_image_freeze_init (GstImageFreeze * self)
  {
    self->sinkpad = gst_pad_new_from_static_template (&sink_pad_template, "sink");
    gst_pad_set_chain_function (self->sinkpad,
        GST_DEBUG_FUNCPTR (gst_image_freeze_sink_chain));
    gst_pad_set_event_function (self->sinkpad,
        GST_DEBUG_FUNCPTR (gst_image_freeze_sink_event));
    gst_pad_set_query_function (self->sinkpad,
        GST_DEBUG_FUNCPTR (gst_image_freeze_sink_query));
    GST_PAD_SET_PROXY_ALLOCATION (self->sinkpad);
    gst_element_add_pad (GST_ELEMENT (self), self->sinkpad);
  
    self->srcpad = gst_pad_new_from_static_template (&src_pad_template, "src");
    gst_pad_set_event_function (self->srcpad,
        GST_DEBUG_FUNCPTR (gst_image_freeze_src_event));
    gst_pad_set_query_function (self->srcpad,
        GST_DEBUG_FUNCPTR (gst_image_freeze_src_query));
    gst_pad_use_fixed_caps (self->srcpad);
    gst_element_add_pad (GST_ELEMENT (self), self->srcpad);
  
    g_mutex_init (&self->lock);
  
    self->num_buffers = DEFAULT_NUM_BUFFERS;
  
    gst_image_freeze_reset (self);
  }
  
  static void
  gst_image_freeze_finalize (GObject * object)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (object);
  
    self->num_buffers = DEFAULT_NUM_BUFFERS;
  
    gst_image_freeze_reset (self);
  
    g_mutex_clear (&self->lock);
  
    G_OBJECT_CLASS (parent_class)->finalize (object);
  }
  
  static void
  gst_image_freeze_reset (GstImageFreeze * self)
  {
    GST_DEBUG_OBJECT (self, "Resetting internal state");
  
    g_mutex_lock (&self->lock);
    gst_buffer_replace (&self->buffer, NULL);
    self->num_buffers_left = self->num_buffers;
  
    gst_segment_init (&self->segment, GST_FORMAT_TIME);
    self->need_segment = TRUE;
  
    self->fps_n = self->fps_d = 0;
    self->offset = 0;
    self->seqnum = 0;
    g_mutex_unlock (&self->lock);
  
    g_atomic_int_set (&self->seeking, 0);
  }
  
  static gboolean
  gst_image_freeze_sink_setcaps (GstImageFreeze * self, GstCaps * caps)
  {
    gboolean ret = FALSE;
    GstStructure *s;
    gint fps_n, fps_d;
    GstCaps *othercaps, *intersection;
    guint i, n;
    GstPad *pad;
  
    pad = self->sinkpad;
    caps = gst_caps_copy (caps);
  
    GST_DEBUG_OBJECT (pad, "Setting caps: %" GST_PTR_FORMAT, caps);
  
    s = gst_caps_get_structure (caps, 0);
  
    /* 1. Remove framerate */
    gst_structure_remove_field (s, "framerate");
    gst_structure_set (s, "framerate", GST_TYPE_FRACTION_RANGE, 0, 1, G_MAXINT, 1,
        NULL);
  
    /* 2. Intersect with template caps */
    othercaps = (GstCaps *) gst_pad_get_pad_template_caps (pad);
    intersection = gst_caps_intersect (caps, othercaps);
    GST_DEBUG_OBJECT (pad, "Intersecting: %" GST_PTR_FORMAT, caps);
    GST_DEBUG_OBJECT (pad, "with: %" GST_PTR_FORMAT, othercaps);
    GST_DEBUG_OBJECT (pad, "gave: %" GST_PTR_FORMAT, intersection);
    gst_caps_unref (caps);
    gst_caps_unref (othercaps);
    caps = intersection;
    intersection = othercaps = NULL;
  
    /* 3. Intersect with downstream peer caps */
    othercaps = gst_pad_peer_query_caps (self->srcpad, caps);
    GST_DEBUG_OBJECT (pad, "Peer query resulted: %" GST_PTR_FORMAT, othercaps);
    gst_caps_unref (caps);
    caps = othercaps;
    othercaps = NULL;
  
    /* 4. For every candidate try to use it downstream with framerate as
     * near as possible to 25/1 */
    n = gst_caps_get_size (caps);
    for (i = 0; i < n; i++) {
      GstCaps *candidate = gst_caps_new_empty ();
      GstStructure *s = gst_structure_copy (gst_caps_get_structure (caps, i));
  
      gst_caps_append_structure (candidate, s);
      if (gst_structure_has_field_typed (s, "framerate", GST_TYPE_FRACTION) ||
          gst_structure_fixate_field_nearest_fraction (s, "framerate", 25, 1)) {
        gst_structure_get_fraction (s, "framerate", &fps_n, &fps_d);
        if (fps_d != 0) {
          if (gst_pad_set_caps (self->srcpad, candidate)) {
            g_mutex_lock (&self->lock);
            self->fps_n = fps_n;
            self->fps_d = fps_d;
            g_mutex_unlock (&self->lock);
            GST_DEBUG_OBJECT (pad, "Setting caps %" GST_PTR_FORMAT, candidate);
            ret = TRUE;
            gst_caps_unref (candidate);
            break;
          }
        } else {
          GST_WARNING_OBJECT (pad, "Invalid caps with framerate %d/%d", fps_n,
              fps_d);
        }
      }
      gst_caps_unref (candidate);
    }
  
    if (!ret)
      GST_ERROR_OBJECT (pad, "No usable caps found");
  
    gst_caps_unref (caps);
  
    return ret;
  }
  
  /* remove framerate in writable @caps */
  static void
  gst_image_freeze_remove_fps (GstImageFreeze * self, GstCaps * caps)
  {
    gint i, n;
  
    n = gst_caps_get_size (caps);
    for (i = 0; i < n; i++) {
      GstStructure *s = gst_caps_get_structure (caps, i);
  
      gst_structure_remove_field (s, "framerate");
      gst_structure_set (s, "framerate", GST_TYPE_FRACTION_RANGE, 0, 1, G_MAXINT,
          1, NULL);
    }
  }
  
  static GstCaps *
  gst_image_freeze_sink_getcaps (GstImageFreeze * self, GstCaps * filter)
  {
    GstCaps *ret, *tmp, *templ;
    GstPad *pad;
  
    pad = self->sinkpad;
  
    if (filter) {
      filter = gst_caps_copy (filter);
      gst_image_freeze_remove_fps (self, filter);
    }
    templ = gst_pad_get_pad_template_caps (pad);
    tmp = gst_pad_peer_query_caps (self->srcpad, filter);
    if (tmp) {
      GST_LOG_OBJECT (self, "peer caps %" GST_PTR_FORMAT, tmp);
      ret = gst_caps_intersect (tmp, templ);
      gst_caps_unref (tmp);
    } else {
      GST_LOG_OBJECT (self, "going to copy");
      ret = gst_caps_copy (templ);
    }
    if (templ)
      gst_caps_unref (templ);
    if (filter)
      gst_caps_unref (filter);
  
    ret = gst_caps_make_writable (ret);
    gst_image_freeze_remove_fps (self, ret);
  
    GST_LOG_OBJECT (pad, "Returning caps: %" GST_PTR_FORMAT, ret);
  
    return ret;
  }
  
  static gboolean
  gst_image_freeze_sink_query (GstPad * pad, GstObject * parent, GstQuery * query)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (parent);
    gboolean ret;
  
    GST_LOG_OBJECT (pad, "Handling query of type '%s'",
        gst_query_type_get_name (GST_QUERY_TYPE (query)));
  
    switch (GST_QUERY_TYPE (query)) {
      case GST_QUERY_CAPS:
      {
        GstCaps *caps;
  
        gst_query_parse_caps (query, &caps);
        caps = gst_image_freeze_sink_getcaps (self, caps);
        gst_query_set_caps_result (query, caps);
        gst_caps_unref (caps);
        ret = TRUE;
        break;
      }
      default:
        ret = gst_pad_query_default (pad, parent, query);
    }
  
    return ret;
  }
  
  static gboolean
  gst_image_freeze_convert (GstImageFreeze * self,
      GstFormat src_format, gint64 src_value,
      GstFormat * dest_format, gint64 * dest_value)
  {
    gboolean ret = FALSE;
  
    if (src_format == *dest_format) {
      *dest_value = src_value;
      return TRUE;
    }
  
    if (src_value == -1) {
      *dest_value = -1;
      return TRUE;
    }
  
    switch (src_format) {
      case GST_FORMAT_DEFAULT:{
        switch (*dest_format) {
          case GST_FORMAT_TIME:
            g_mutex_lock (&self->lock);
            if (self->fps_n == 0)
              *dest_value = -1;
            else
              *dest_value =
                  gst_util_uint64_scale (src_value, GST_SECOND * self->fps_d,
                  self->fps_n);
            g_mutex_unlock (&self->lock);
            ret = TRUE;
            break;
          default:
            break;
        }
        break;
      }
      case GST_FORMAT_TIME:{
        switch (*dest_format) {
          case GST_FORMAT_DEFAULT:
            g_mutex_lock (&self->lock);
            *dest_value =
                gst_util_uint64_scale (src_value, self->fps_n,
                self->fps_d * GST_SECOND);
            g_mutex_unlock (&self->lock);
            ret = TRUE;
            break;
          default:
            break;
        }
        break;
      }
      default:
        break;
    }
  
    return ret;
  }
  
  static gboolean
  gst_image_freeze_src_query (GstPad * pad, GstObject * parent, GstQuery * query)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (parent);
    gboolean ret = FALSE;
  
    GST_LOG_OBJECT (pad, "Handling query of type '%s'",
        gst_query_type_get_name (GST_QUERY_TYPE (query)));
  
    switch (GST_QUERY_TYPE (query)) {
      case GST_QUERY_CONVERT:{
        GstFormat src_format, dest_format;
        gint64 src_value, dest_value;
  
        gst_query_parse_convert (query, &src_format, &src_value, &dest_format,
            &dest_value);
        ret =
            gst_image_freeze_convert (self, src_format, src_value, &dest_format,
            &dest_value);
        if (ret)
          gst_query_set_convert (query, src_format, src_value, dest_format,
              dest_value);
        break;
      }
      case GST_QUERY_POSITION:{
        GstFormat format;
        gint64 position;
  
        gst_query_parse_position (query, &format, NULL);
        switch (format) {
          case GST_FORMAT_DEFAULT:{
            g_mutex_lock (&self->lock);
            position = self->offset;
            g_mutex_unlock (&self->lock);
            ret = TRUE;
            break;
          }
          case GST_FORMAT_TIME:{
            g_mutex_lock (&self->lock);
            position = self->segment.position;
            g_mutex_unlock (&self->lock);
            ret = TRUE;
            break;
          }
          default:
            break;
        }
  
        if (ret) {
          gst_query_set_position (query, format, position);
          GST_DEBUG_OBJECT (pad,
              "Returning position %" G_GINT64_FORMAT " in format %s", position,
              gst_format_get_name (format));
        } else {
          GST_DEBUG_OBJECT (pad, "Position query failed");
        }
        break;
      }
      case GST_QUERY_DURATION:{
        GstFormat format;
        gint64 duration;
  
        gst_query_parse_duration (query, &format, NULL);
        switch (format) {
          case GST_FORMAT_TIME:{
            g_mutex_lock (&self->lock);
            duration = self->segment.stop;
            g_mutex_unlock (&self->lock);
            ret = TRUE;
            break;
          }
          case GST_FORMAT_DEFAULT:{
            g_mutex_lock (&self->lock);
            duration = self->segment.stop;
            if (duration != -1)
              duration =
                  gst_util_uint64_scale (duration, self->fps_n,
                  GST_SECOND * self->fps_d);
            g_mutex_unlock (&self->lock);
            ret = TRUE;
            break;
          }
          default:
            break;
        }
  
        if (ret) {
          gst_query_set_duration (query, format, duration);
          GST_DEBUG_OBJECT (pad,
              "Returning duration %" G_GINT64_FORMAT " in format %s", duration,
              gst_format_get_name (format));
        } else {
          GST_DEBUG_OBJECT (pad, "Duration query failed");
        }
        break;
      }
      case GST_QUERY_SEEKING:{
        GstFormat format;
        gboolean seekable;
  
        gst_query_parse_seeking (query, &format, NULL, NULL, NULL);
        seekable = (format == GST_FORMAT_TIME || format == GST_FORMAT_DEFAULT);
  
        gst_query_set_seeking (query, format, seekable, (seekable ? 0 : -1), -1);
        ret = TRUE;
        break;
      }
      case GST_QUERY_LATENCY:
        /* This will only return an accurate latency for the first buffer since
         * all further buffers outputted by us are just copies of that one, and
         * the latency is 0 in that case. However, latency changes are not
         * straightforward, so let's do the conservative fix for now. */
        ret = gst_pad_query_default (pad, parent, query);
        break;
      default:
        ret = FALSE;
        break;
    }
  
    return ret;
  }
  
  
  static gboolean
  gst_image_freeze_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (parent);
    gboolean ret;
  
    GST_LOG_OBJECT (pad, "Got %s event", GST_EVENT_TYPE_NAME (event));
  
    switch (GST_EVENT_TYPE (event)) {
      case GST_EVENT_CAPS:
      {
        GstCaps *caps;
  
        gst_event_parse_caps (event, &caps);
        gst_image_freeze_sink_setcaps (self, caps);
        gst_event_unref (event);
        ret = TRUE;
        break;
      }
      case GST_EVENT_EOS:
        if (!self->buffer) {
          /* if we receive EOS before a buffer arrives, then let it pass */
          GST_DEBUG_OBJECT (self, "EOS without input buffer, passing on");
          ret = gst_pad_push_event (self->srcpad, event);
          break;
        }
        /* fall-through */
      case GST_EVENT_SEGMENT:
        GST_DEBUG_OBJECT (pad, "Dropping event");
        gst_event_unref (event);
        ret = TRUE;
        break;
      case GST_EVENT_FLUSH_START:
        gst_image_freeze_reset (self);
        /* fall through */
      default:
        ret = gst_pad_push_event (self->srcpad, event);
        break;
    }
  
    return ret;
  }
  
  static gboolean
  gst_image_freeze_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (parent);
    gboolean ret;
  
    GST_LOG_OBJECT (pad, "Got %s event", GST_EVENT_TYPE_NAME (event));
  
    switch (GST_EVENT_TYPE (event)) {
      case GST_EVENT_NAVIGATION:
      case GST_EVENT_QOS:
      case GST_EVENT_LATENCY:
      case GST_EVENT_STEP:
        GST_DEBUG_OBJECT (pad, "Dropping event");
        gst_event_unref (event);
        ret = TRUE;
        break;
      case GST_EVENT_SEEK:{
        gdouble rate;
        GstFormat format;
        GstSeekFlags flags;
        GstSeekType start_type, stop_type;
        gint64 start, stop;
        gint64 last_stop;
        gboolean start_task;
        gboolean flush;
        guint32 seqnum;
  
        seqnum = gst_event_get_seqnum (event);
        gst_event_parse_seek (event, &rate, &format, &flags, &start_type, &start,
            &stop_type, &stop);
        gst_event_unref (event);
  
        flush = ! !(flags & GST_SEEK_FLAG_FLUSH);
  
        if (format != GST_FORMAT_TIME && format != GST_FORMAT_DEFAULT) {
          GST_ERROR_OBJECT (pad, "Seek in invalid format: %s",
              gst_format_get_name (format));
          ret = FALSE;
          break;
        }
  
        if (format == GST_FORMAT_DEFAULT) {
          format = GST_FORMAT_TIME;
          if (!gst_image_freeze_convert (self, GST_FORMAT_DEFAULT, start, &format,
                  &start)
              || !gst_image_freeze_convert (self, GST_FORMAT_DEFAULT, stop,
                  &format, &stop)
              || start == -1 || stop == -1) {
            GST_ERROR_OBJECT (pad,
                "Failed to convert seek from DEFAULT format into TIME format");
            ret = FALSE;
            break;
          }
        }
  
        if (flush) {
          GstEvent *e;
  
          g_atomic_int_set (&self->seeking, 1);
          e = gst_event_new_flush_start ();
          gst_event_set_seqnum (e, seqnum);
          gst_pad_push_event (self->srcpad, e);
        } else {
          gst_pad_pause_task (self->srcpad);
        }
  
        GST_PAD_STREAM_LOCK (self->srcpad);
  
        g_mutex_lock (&self->lock);
  
        gst_segment_do_seek (&self->segment, rate, format, flags, start_type,
            start, stop_type, stop, NULL);
        self->need_segment = TRUE;
        last_stop = self->segment.position;
  
        start_task = self->buffer != NULL;
        g_mutex_unlock (&self->lock);
  
        if (flush) {
          GstEvent *e;
  
          e = gst_event_new_flush_stop (TRUE);
          gst_event_set_seqnum (e, seqnum);
          gst_pad_push_event (self->srcpad, e);
          g_atomic_int_set (&self->seeking, 0);
        }
  
        if (flags & GST_SEEK_FLAG_SEGMENT) {
          GstMessage *m;
  
          m = gst_message_new_segment_start (GST_OBJECT (self),
              format, last_stop);
          gst_element_post_message (GST_ELEMENT (self), m);
        }
  
        self->seqnum = seqnum;
        GST_PAD_STREAM_UNLOCK (self->srcpad);
  
        GST_DEBUG_OBJECT (pad, "Seek successful");
  
        if (start_task) {
          g_mutex_lock (&self->lock);
  
          if (self->buffer != NULL)
            gst_pad_start_task (self->srcpad,
                (GstTaskFunction) gst_image_freeze_src_loop, self->srcpad, NULL);
  
          g_mutex_unlock (&self->lock);
        }
  
        ret = TRUE;
        break;
      }
      case GST_EVENT_FLUSH_START:
        gst_image_freeze_reset (self);
        /* fall through */
      default:
        ret = gst_pad_push_event (self->sinkpad, event);
        break;
    }
  
    return ret;
  }
  
  static void
  gst_image_freeze_set_property (GObject * object, guint prop_id,
      const GValue * value, GParamSpec * pspec)
  {
    GstImageFreeze *self;
  
    self = GST_IMAGE_FREEZE (object);
  
    switch (prop_id) {
      case PROP_NUM_BUFFERS:
        self->num_buffers = g_value_get_int (value);
        break;
      default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
        break;
    }
  }
  
  static void
  gst_image_freeze_get_property (GObject * object, guint prop_id, GValue * value,
      GParamSpec * pspec)
  {
    GstImageFreeze *self;
  
    self = GST_IMAGE_FREEZE (object);
  
    switch (prop_id) {
      case PROP_NUM_BUFFERS:
        g_value_set_int (value, self->num_buffers);
        break;
      default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
        break;
    }
  }
  
  static GstFlowReturn
  gst_image_freeze_sink_chain (GstPad * pad, GstObject * parent,
      GstBuffer * buffer)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (parent);
  
    g_mutex_lock (&self->lock);
    if (self->buffer) {
      GST_DEBUG_OBJECT (pad, "Already have a buffer, dropping");
      gst_buffer_unref (buffer);
      g_mutex_unlock (&self->lock);
      return GST_FLOW_EOS;
    }
  
    self->buffer = buffer;
  
    gst_pad_start_task (self->srcpad, (GstTaskFunction) gst_image_freeze_src_loop,
        self->srcpad, NULL);
    g_mutex_unlock (&self->lock);
    return GST_FLOW_EOS;
  }
  
  static void
  gst_image_freeze_src_loop (GstPad * pad)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (GST_PAD_PARENT (pad));
    GstBuffer *buffer;
    guint64 offset;
    GstClockTime timestamp, timestamp_end;
    guint64 cstart, cstop;
    gboolean in_seg, eos;
    GstFlowReturn flow_ret = GST_FLOW_OK;
  
    g_mutex_lock (&self->lock);
    if (!gst_pad_has_current_caps (self->srcpad)) {
      GST_ERROR_OBJECT (pad, "Not negotiated yet");
      flow_ret = GST_FLOW_NOT_NEGOTIATED;
      g_mutex_unlock (&self->lock);
      goto pause_task;
    }
  
    if (!self->buffer) {
      GST_ERROR_OBJECT (pad, "Have no buffer yet");
      flow_ret = GST_FLOW_ERROR;
      g_mutex_unlock (&self->lock);
      goto pause_task;
    }
  
    /* normally we don't count buffers */
    if (G_UNLIKELY (self->num_buffers_left >= 0)) {
      GST_DEBUG_OBJECT (pad, "Buffers left %d", self->num_buffers_left);
      if (self->num_buffers_left == 0) {
        flow_ret = GST_FLOW_EOS;
        g_mutex_unlock (&self->lock);
        goto pause_task;
      } else {
        self->num_buffers_left--;
      }
    }
    buffer = gst_buffer_copy (self->buffer);
  
    g_mutex_unlock (&self->lock);
  
    if (self->need_segment) {
      GstEvent *e;
  
      GST_DEBUG_OBJECT (pad, "Pushing SEGMENT event: %" GST_SEGMENT_FORMAT,
          &self->segment);
      e = gst_event_new_segment (&self->segment);
  
      if (self->seqnum)
        gst_event_set_seqnum (e, self->seqnum);
  
      g_mutex_lock (&self->lock);
      if (self->segment.rate >= 0) {
        self->offset =
            gst_util_uint64_scale (self->segment.start, self->fps_n,
            self->fps_d * GST_SECOND);
      } else {
        self->offset =
            gst_util_uint64_scale (self->segment.stop, self->fps_n,
            self->fps_d * GST_SECOND);
      }
      g_mutex_unlock (&self->lock);
  
      self->need_segment = FALSE;
  
      gst_pad_push_event (self->srcpad, e);
    }
  
    g_mutex_lock (&self->lock);
    offset = self->offset;
  
    if (self->fps_n != 0) {
      timestamp =
          gst_util_uint64_scale (offset, self->fps_d * GST_SECOND, self->fps_n);
      timestamp_end =
          gst_util_uint64_scale (offset + 1, self->fps_d * GST_SECOND,
          self->fps_n);
    } else {
      timestamp = self->segment.start;
      timestamp_end = GST_CLOCK_TIME_NONE;
    }
  
    eos = (self->fps_n == 0 && offset > 0) ||
        (self->segment.rate >= 0 && self->segment.stop != -1
        && timestamp > self->segment.stop) || (self->segment.rate < 0
        && offset == 0) || (self->segment.rate < 0
        && self->segment.start != -1 && timestamp_end < self->segment.start);
  
    if (self->fps_n == 0 && offset > 0)
      in_seg = FALSE;
    else
      in_seg =
          gst_segment_clip (&self->segment, GST_FORMAT_TIME, timestamp,
          timestamp_end, &cstart, &cstop);
  
    if (in_seg) {
      self->segment.position = cstart;
      if (self->segment.rate >= 0)
        self->segment.position = cstop;
    }
  
    if (self->segment.rate >= 0)
      self->offset++;
    else
      self->offset--;
    g_mutex_unlock (&self->lock);
  
    GST_DEBUG_OBJECT (pad, "Handling buffer with timestamp %" GST_TIME_FORMAT,
        GST_TIME_ARGS (timestamp));
  
    if (in_seg) {
      GST_BUFFER_DTS (buffer) = GST_CLOCK_TIME_NONE;
      GST_BUFFER_PTS (buffer) = cstart;
      GST_BUFFER_DURATION (buffer) = cstop - cstart;
      GST_BUFFER_OFFSET (buffer) = offset;
      GST_BUFFER_OFFSET_END (buffer) = offset + 1;
      flow_ret = gst_pad_push (self->srcpad, buffer);
      GST_DEBUG_OBJECT (pad, "Pushing buffer resulted in %s",
          gst_flow_get_name (flow_ret));
      if (flow_ret != GST_FLOW_OK)
        goto pause_task;
    } else {
      gst_buffer_unref (buffer);
    }
  
    if (eos) {
      flow_ret = GST_FLOW_EOS;
      goto pause_task;
    }
  
    return;
  
  pause_task:
    {
      const gchar *reason = gst_flow_get_name (flow_ret);
  
      GST_LOG_OBJECT (self, "pausing task, reason %s", reason);
      gst_pad_pause_task (pad);
  
      if (flow_ret == GST_FLOW_EOS) {
        if ((self->segment.flags & GST_SEEK_FLAG_SEGMENT)) {
          GstMessage *m;
          GstEvent *e;
  
          GST_DEBUG_OBJECT (pad, "Sending segment done at end of segment");
          if (self->segment.rate >= 0) {
            m = gst_message_new_segment_done (GST_OBJECT_CAST (self),
                GST_FORMAT_TIME, self->segment.stop);
            e = gst_event_new_segment_done (GST_FORMAT_TIME, self->segment.stop);
          } else {
            m = gst_message_new_segment_done (GST_OBJECT_CAST (self),
                GST_FORMAT_TIME, self->segment.start);
            e = gst_event_new_segment_done (GST_FORMAT_TIME, self->segment.start);
          }
          gst_element_post_message (GST_ELEMENT_CAST (self), m);
          gst_pad_push_event (self->srcpad, e);
        } else {
          GstEvent *e = gst_event_new_eos ();
  
          GST_DEBUG_OBJECT (pad, "Sending EOS at end of segment");
  
          if (self->seqnum)
            gst_event_set_seqnum (e, self->seqnum);
          gst_pad_push_event (self->srcpad, e);
        }
      } else if (flow_ret == GST_FLOW_NOT_LINKED || flow_ret < GST_FLOW_EOS) {
        GstEvent *e = gst_event_new_eos ();
  
        GST_ELEMENT_FLOW_ERROR (self, flow_ret);
  
        if (self->seqnum)
          gst_event_set_seqnum (e, self->seqnum);
  
        gst_pad_push_event (self->srcpad, e);
      }
      return;
    }
  }
  
  static GstStateChangeReturn
  gst_image_freeze_change_state (GstElement * element, GstStateChange transition)
  {
    GstImageFreeze *self = GST_IMAGE_FREEZE (element);
    GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
  
    switch (transition) {
      case GST_STATE_CHANGE_READY_TO_PAUSED:
        gst_image_freeze_reset (self);
        break;
      case GST_STATE_CHANGE_PAUSED_TO_READY:
        gst_pad_stop_task (self->srcpad);
        gst_image_freeze_reset (self);
        break;
      default:
        break;
    }
  
    if (GST_ELEMENT_CLASS (parent_class)->change_state)
      ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
  
    switch (transition) {
      default:
        break;
    }
  
    return ret;
  }
  
  static gboolean
  plugin_init (GstPlugin * plugin)
  {
    GST_DEBUG_CATEGORY_INIT (gst_image_freeze_debug, "imagefreeze", 0,
        "imagefreeze element");
  
    if (!gst_element_register (plugin, "imagefreeze", GST_RANK_NONE,
            GST_TYPE_IMAGE_FREEZE))
      return FALSE;
  
    return TRUE;
  }
  
  GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
      GST_VERSION_MINOR,
      imagefreeze,
      "Still frame stream generator",
      plugin_init, VERSION, "LGPL", GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN)
  