imagefreeze: Add still frame stream generator element

configure.ac

@@ -275,6 +275,7 @@ AG_GST_CHECK_PLUGIN(h264parse)
 AG_GST_CHECK_PLUGIN(hdvparse)
 AG_GST_CHECK_PLUGIN(id3tag)
 AG_GST_CHECK_PLUGIN(invtelecine)
+AG_GST_CHECK_PLUGIN(imagefreeze)
 AG_GST_CHECK_PLUGIN(jpegformat)
 AG_GST_CHECK_PLUGIN(librfb)
 AG_GST_CHECK_PLUGIN(liveadder)
@@ -1639,7 +1640,11 @@ gst/frei0r/Makefile
 gst/h264parse/Makefile
 gst/hdvparse/Makefile
 gst/id3tag/Makefile
+<<<<<<< HEAD
 gst/invtelecine/Makefile
+=======
+gst/imagefreeze/Makefile
+>>>>>>> imagefreeze: Add still frame stream generator element
 gst/jpegformat/Makefile
 gst/legacyresample/Makefile
 gst/librfb/Makefile

gst/imagefreeze/Makefile.am

@@ -0,0 +1,11 @@
+plugin_LTLIBRARIES = libgstimagefreeze.la
+
+libgstimagefreeze_la_SOURCES = gstimagefreeze.c
+
+libgstimagefreeze_la_CFLAGS = $(GST_CFLAGS)
+libgstimagefreeze_la_LIBADD = $(GST_LIBS)
+libgstimagefreeze_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS)
+libgstimagefreeze_la_LIBTOOLFLAGS = --tag=disable-static
+
+noinst_HEADERS = gstimagefreeze.h
+

gst/imagefreeze/gstimagefreeze.c

@@ -0,0 +1,794 @@
+/* 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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, 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 -v filesrc location=some.png ! decodebin2 ! 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 "gstimagefreeze.h"
+
+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 GstFlowReturn gst_image_freeze_sink_chain (GstPad * pad,
+    GstBuffer * buffer);
+static gboolean gst_image_freeze_sink_event (GstPad * pad, GstEvent * event);
+static gboolean gst_image_freeze_sink_setcaps (GstPad * pad, GstCaps * caps);
+static GstCaps *gst_image_freeze_sink_getcaps (GstPad * pad);
+static gboolean gst_image_freeze_sink_query (GstPad * pad, GstQuery * query);
+static void gst_image_freeze_src_loop (GstPad * pad);
+static gboolean gst_image_freeze_src_event (GstPad * pad, GstEvent * event);
+static gboolean gst_image_freeze_src_query (GstPad * pad, GstQuery * query);
+static const GstQueryType *gst_image_freeze_src_query_type (GstPad * pad);
+
+static GstStaticPadTemplate sink_pad_template = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("video/x-raw-yuv; video/x-raw-rgb; video/x-raw-gray"));
+
+static GstStaticPadTemplate src_pad_template =
+    GST_STATIC_PAD_TEMPLATE ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("video/x-raw-yuv; video/x-raw-rgb; video/x-raw-gray"));
+
+GST_DEBUG_CATEGORY_STATIC (gst_image_freeze_debug);
+#define GST_CAT_DEFAULT gst_image_freeze_debug
+
+GST_BOILERPLATE (GstImageFreeze, gst_image_freeze, GstElement,
+    GST_TYPE_ELEMENT);
+
+static void
+gst_image_freeze_base_init (gpointer g_class)
+{
+  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class);
+
+  gst_element_class_set_details_simple (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_pad_template (gstelement_class,
+      gst_static_pad_template_get (&sink_pad_template));
+  gst_element_class_add_pad_template (gstelement_class,
+      gst_static_pad_template_get (&src_pad_template));
+}
+
+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;
+
+  gstelement_class->change_state =
+      GST_DEBUG_FUNCPTR (gst_image_freeze_change_state);
+}
+
+static void
+gst_image_freeze_init (GstImageFreeze * self, GstImageFreezeClass * g_class)
+{
+  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_setcaps_function (self->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_image_freeze_sink_setcaps));
+  gst_pad_set_getcaps_function (self->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_image_freeze_sink_getcaps));
+  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_set_query_type_function (self->srcpad,
+      GST_DEBUG_FUNCPTR (gst_image_freeze_src_query_type));
+  gst_pad_use_fixed_caps (self->sinkpad);
+  gst_element_add_pad (GST_ELEMENT (self), self->srcpad);
+
+  gst_image_freeze_reset (self);
+}
+
+static void
+gst_image_freeze_finalize (GObject * object)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (object);
+
+  gst_image_freeze_reset (self);
+
+  G_OBJECT_CLASS (parent_class)->finalize (object);
+}
+
+static void
+gst_image_freeze_reset (GstImageFreeze * self)
+{
+  GST_DEBUG_OBJECT (self, "Resetting internal state");
+
+  GST_OBJECT_LOCK (self);
+  gst_buffer_replace (&self->buffer, NULL);
+
+  gst_segment_init (&self->segment, GST_FORMAT_TIME);
+  self->need_segment = TRUE;
+  gst_event_replace (&self->close_segment, NULL);
+
+  self->fps_n = self->fps_d = 0;
+  self->offset = 0;
+  GST_OBJECT_UNLOCK (self);
+}
+
+static gboolean
+gst_image_freeze_sink_setcaps (GstPad * pad, GstCaps * caps)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (gst_pad_get_parent (pad));
+  gboolean ret = FALSE;
+  GstStructure *s;
+  gint fps_n, fps_d;
+  GstCaps *othercaps, *intersection;
+  guint i, n;
+
+  caps = gst_caps_make_writable (gst_caps_ref (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);
+  caps = intersection;
+  intersection = othercaps = NULL;
+
+  /* 3. Intersect with downstream peer caps */
+  othercaps = gst_pad_peer_get_caps (self->srcpad);
+  if (othercaps) {
+    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 (othercaps);
+    gst_caps_unref (caps);
+    caps = intersection;
+    intersection = othercaps = NULL;
+  }
+
+  /* 4. For every candidate check if it's accepted downstream
+   * and fixate framerate to nearest 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_pad_peer_accept_caps (self->srcpad, candidate)) {
+      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) {
+          GST_OBJECT_LOCK (self);
+          self->fps_n = fps_n;
+          self->fps_d = fps_d;
+          GST_OBJECT_UNLOCK (self);
+          GST_DEBUG_OBJECT (pad, "Setting caps %" GST_PTR_FORMAT, candidate);
+          gst_pad_set_caps (self->srcpad, candidate);
+          gst_caps_unref (candidate);
+          ret = TRUE;
+          goto done;
+        } else {
+          GST_WARNING_OBJECT (pad, "Invalid caps with framerate %d/%d", fps_n,
+              fps_d);
+        }
+      }
+    }
+    gst_caps_unref (candidate);
+  }
+
+done:
+  if (!ret)
+    GST_ERROR_OBJECT (pad, "No usable caps found");
+
+  gst_caps_unref (caps);
+  gst_object_unref (self);
+
+  return ret;
+}
+
+static GstCaps *
+gst_image_freeze_sink_getcaps (GstPad * pad)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (gst_pad_get_parent (pad));
+  GstCaps *ret, *tmp;
+
+  if (GST_PAD_CAPS (pad)) {
+    ret = gst_caps_copy (GST_PAD_CAPS (pad));
+    goto done;
+  }
+
+  tmp = gst_pad_peer_get_caps (self->srcpad);
+  if (tmp) {
+    ret = gst_caps_intersect (tmp, gst_pad_get_pad_template_caps (pad));
+    gst_caps_unref (tmp);
+  } else {
+    ret = gst_caps_copy (gst_pad_get_pad_template_caps (pad));
+  }
+
+done:
+  gst_object_unref (self);
+
+  GST_LOG_OBJECT (pad, "Returning caps: %" GST_PTR_FORMAT, ret);
+
+  return ret;
+}
+
+static gboolean
+gst_image_freeze_sink_query (GstPad * pad, GstQuery * query)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (gst_pad_get_parent (pad));
+  gboolean ret;
+  GstPad *peer = gst_pad_get_peer (self->srcpad);
+
+  GST_LOG_OBJECT (pad, "Handling query of type '%s'",
+      gst_query_type_get_name (GST_QUERY_TYPE (query)));
+
+  if (!peer) {
+    GST_INFO_OBJECT (pad, "No peer yet, dropping query");
+    ret = FALSE;
+  } else {
+    ret = gst_pad_query (peer, query);
+    gst_object_unref (peer);
+  }
+
+  gst_object_unref (self);
+  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:
+          GST_OBJECT_LOCK (self);
+          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);
+          GST_OBJECT_UNLOCK (self);
+          ret = TRUE;
+          break;
+        default:
+          break;
+      }
+    }
+    case GST_FORMAT_TIME:{
+      switch (*dest_format) {
+        case GST_FORMAT_DEFAULT:
+          GST_OBJECT_LOCK (self);
+          *dest_value =
+              gst_util_uint64_scale (src_value, self->fps_n,
+              self->fps_d * GST_SECOND);
+          GST_OBJECT_UNLOCK (self);
+          ret = TRUE;
+          break;
+        default:
+          break;
+      }
+
+    }
+    default:
+      break;
+  }
+
+  return ret;
+}
+
+static const GstQueryType *
+gst_image_freeze_src_query_type (GstPad * pad)
+{
+  static const GstQueryType types[] = {
+    GST_QUERY_POSITION,
+    GST_QUERY_DURATION,
+    GST_QUERY_SEEKING,
+    GST_QUERY_CONVERT,
+    0
+  };
+
+  return types;
+}
+
+static gboolean
+gst_image_freeze_src_query (GstPad * pad, GstQuery * query)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (gst_pad_get_parent (pad));
+  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:{
+          GST_OBJECT_LOCK (self);
+          position = self->offset;
+          GST_OBJECT_UNLOCK (self);
+          ret = TRUE;
+        }
+        case GST_FORMAT_TIME:{
+          GST_OBJECT_LOCK (self);
+          position = self->segment.last_stop;
+          GST_OBJECT_UNLOCK (self);
+          ret = TRUE;
+        }
+        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:{
+          GST_OBJECT_LOCK (self);
+          duration = self->segment.stop;
+          GST_OBJECT_UNLOCK (self);
+          ret = TRUE;
+        }
+        case GST_FORMAT_DEFAULT:{
+          GST_OBJECT_LOCK (self);
+          duration = self->segment.stop;
+          if (duration != -1)
+            duration =
+                gst_util_uint64_scale (duration, self->fps_n,
+                GST_SECOND * self->fps_d);
+          GST_OBJECT_UNLOCK (self);
+          ret = TRUE;
+        }
+        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;
+    }
+    default:
+      ret = FALSE;
+      break;
+  }
+
+  gst_object_unref (self);
+  return ret;
+}
+
+
+static gboolean
+gst_image_freeze_sink_event (GstPad * pad, GstEvent * event)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (gst_pad_get_parent (pad));
+  gboolean ret;
+
+  GST_LOG_OBJECT (pad, "Got %s event", GST_EVENT_TYPE_NAME (event));
+
+  switch (GST_EVENT_TYPE (event)) {
+    case GST_EVENT_EOS:
+    case GST_EVENT_NEWSEGMENT:
+      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;
+  }
+
+  gst_object_unref (self);
+  return ret;
+}
+
+static gboolean
+gst_image_freeze_src_event (GstPad * pad, GstEvent * event)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (gst_pad_get_parent (pad));
+  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;
+
+      gst_event_parse_seek (event, &rate, &format, &flags, &start_type, &start,
+          &stop_type, &stop);
+      gst_event_unref (event);
+
+      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 ((flags & GST_SEEK_FLAG_FLUSH)) {
+        GstEvent *e;
+
+        e = gst_event_new_flush_start ();
+        gst_pad_push_event (self->srcpad, e);
+      } else {
+        gst_pad_pause_task (self->srcpad);
+      }
+
+      GST_PAD_STREAM_LOCK (self->srcpad);
+
+      GST_OBJECT_LOCK (self);
+      gst_event_replace (&self->close_segment, NULL);
+      self->close_segment =
+          gst_event_new_new_segment_full (TRUE, self->segment.rate,
+          self->segment.applied_rate, self->segment.format, self->segment.start,
+          self->segment.last_stop, self->segment.time);
+
+      gst_segment_set_seek (&self->segment, rate, format, flags, start_type,
+          start, stop_type, stop, NULL);
+      self->need_segment = TRUE;
+      last_stop = self->segment.last_stop;
+
+      GST_OBJECT_UNLOCK (self);
+
+      if ((flags & GST_SEEK_FLAG_FLUSH)) {
+        GstEvent *e;
+
+        e = gst_event_new_flush_stop ();
+        gst_pad_push_event (self->srcpad, e);
+      }
+
+      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);
+      }
+
+      GST_PAD_STREAM_UNLOCK (self->srcpad);
+
+      GST_DEBUG_OBJECT (pad, "Seek successful");
+
+      gst_pad_start_task (self->srcpad,
+          (GstTaskFunction) gst_image_freeze_src_loop, self->srcpad);
+      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;
+  }
+
+  gst_object_unref (self);
+  return ret;
+}
+
+static GstFlowReturn
+gst_image_freeze_sink_chain (GstPad * pad, GstBuffer * buffer)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (GST_PAD_PARENT (pad));
+  GstFlowReturn ret = GST_FLOW_OK;
+
+  GST_OBJECT_LOCK (self);
+  if (self->buffer) {
+    GST_DEBUG_OBJECT (pad, "Already have a buffer, dropping");
+    gst_buffer_unref (buffer);
+    GST_OBJECT_UNLOCK (self);
+    return ret;
+  }
+
+  self->buffer = buffer;
+  GST_OBJECT_UNLOCK (self);
+
+  gst_pad_start_task (self->srcpad, (GstTaskFunction) gst_image_freeze_src_loop,
+      self->srcpad);
+  return ret;
+}
+
+static void
+gst_image_freeze_src_loop (GstPad * pad)
+{
+  GstImageFreeze *self = GST_IMAGE_FREEZE (GST_PAD_PARENT (pad));
+  GstBuffer *buffer;
+  GstClockTime timestamp, duration;
+  gint64 cstart, cstop;
+  gboolean in_seg, eos;
+
+  GST_OBJECT_LOCK (self);
+  if (!self->buffer) {
+    GST_ERROR_OBJECT (pad, "Have no buffer yet");
+    GST_OBJECT_UNLOCK (self);
+    gst_pad_pause_task (self->srcpad);
+    return;
+  }
+  buffer = gst_buffer_ref (self->buffer);
+  buffer = gst_buffer_make_metadata_writable (buffer);
+  GST_OBJECT_UNLOCK (self);
+
+  if (self->close_segment) {
+    GST_DEBUG_OBJECT (pad, "Closing previous segment");
+    gst_pad_push_event (self->srcpad, self->close_segment);
+    self->close_segment = NULL;
+  }
+
+  if (self->need_segment) {
+    GstEvent *e;
+
+    GST_DEBUG_OBJECT (pad, "Pushing NEWSEGMENT event: %" GST_SEGMENT_FORMAT,
+        &self->segment);
+    e = gst_event_new_new_segment_full (FALSE, self->segment.rate,
+        self->segment.applied_rate, self->segment.format, self->segment.start,
+        self->segment.stop, self->segment.start);
+
+    GST_OBJECT_LOCK (self);
+    self->offset =
+        gst_util_uint64_scale (self->segment.start, self->fps_n,
+        self->fps_d * GST_SECOND);
+    GST_OBJECT_UNLOCK (self);
+
+    self->need_segment = FALSE;
+
+    gst_pad_push_event (self->srcpad, e);
+  }
+
+  GST_OBJECT_LOCK (self);
+  if (self->fps_n != 0) {
+    timestamp =
+        gst_util_uint64_scale (self->offset, self->fps_d * GST_SECOND,
+        self->fps_n);
+    duration = gst_util_uint64_scale_int (GST_SECOND, self->fps_d, self->fps_n);
+  } else {
+    timestamp = 0;
+    duration = GST_CLOCK_TIME_NONE;
+  }
+  eos = (self->segment.stop != -1 && timestamp > self->segment.stop) ||
+      (self->fps_n == 0 && self->offset > 0);
+
+  if (self->fps_n == 0 && self->offset > 0)
+    in_seg = FALSE;
+  else
+    in_seg =
+        gst_segment_clip (&self->segment, GST_FORMAT_TIME, timestamp,
+        timestamp + duration, &cstart, &cstop);
+
+  if (in_seg)
+    gst_segment_set_last_stop (&self->segment, GST_FORMAT_TIME, cstart);
+
+  self->offset++;
+  GST_OBJECT_UNLOCK (self);
+
+  GST_DEBUG_OBJECT (pad, "Handling buffer with timestamp %" GST_TIME_FORMAT,
+      GST_TIME_ARGS (timestamp));
+
+  if (eos) {
+    if ((self->segment.flags & GST_SEEK_FLAG_SEGMENT)) {
+      GstMessage *m;
+
+      GST_DEBUG_OBJECT (pad, "Sending segment done at end of segment");
+      m = gst_message_new_segment_done (GST_OBJECT_CAST (self),
+          GST_FORMAT_TIME, self->segment.stop);
+      gst_element_post_message (GST_ELEMENT_CAST (self), m);
+    } else {
+      GST_DEBUG_OBJECT (pad, "Sending EOS at end of segment");
+      gst_pad_push_event (self->srcpad, gst_event_new_eos ());
+    }
+    gst_pad_pause_task (self->srcpad);
+  }
+
+  if (in_seg) {
+    GstFlowReturn ret;
+
+    GST_BUFFER_TIMESTAMP (buffer) = cstart;
+    GST_BUFFER_DURATION (buffer) = cstop - cstart;
+    gst_buffer_set_caps (buffer, GST_PAD_CAPS (self->srcpad));
+    ret = gst_pad_push (self->srcpad, buffer);
+    GST_DEBUG_OBJECT (pad, "Pushing buffer resulted in %s",
+        gst_flow_get_name (ret));
+    if (ret != GST_FLOW_OK)
+      gst_pad_pause_task (self->srcpad);
+  } else {
+    gst_buffer_unref (buffer);
+  }
+}
+
+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)

gst/imagefreeze/gstimagefreeze.h

@@ -0,0 +1,69 @@
+/* GStreamer
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __GST_IMAGE_FREEZE_H__
+#define __GST_IMAGE_FREEZE_H__
+
+#include <gst/gst.h>
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_IMAGE_FREEZE \
+  (gst_image_freeze_get_type())
+#define GST_IMAGE_FREEZE(obj) \
+  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_IMAGE_FREEZE,GstImageFreeze))
+#define GST_IMAGE_FREEZE_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_IMAGE_FREEZE,GstImageFreezeClass))
+#define GST_IMAGE_FREEZE_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj),GST_TYPE_IMAGE_FREEZE,GstImageFreezeClass))
+#define GST_IS_IMAGE_FREEZE(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_IMAGE_FREEZE))
+#define GST_IS_IMAGE_FREEZE_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_IMAGE_FREEZE))
+
+typedef struct _GstImageFreeze GstImageFreeze;
+typedef struct _GstImageFreezeClass GstImageFreezeClass;
+
+struct _GstImageFreeze
+{
+  GstElement parent;
+
+  /* < private > */
+  GstPad *sinkpad;
+  GstPad *srcpad;
+
+  GstBuffer *buffer;
+  gint fps_n, fps_d;
+
+  GstSegment segment;
+  gboolean need_segment;
+  GstEvent *close_segment;
+
+  guint64 offset;
+};
+
+struct _GstImageFreezeClass
+{
+  GstElementClass parent_class;
+};
+
+GType gst_image_freeze_get_type (void);
+
+G_END_DECLS
+
+#endif /* __GST_IMAGE_FREEZE_H__ */