gstreamer/sys/d3d11/gstd3d11desktopdupsrc.c

/*
 * GStreamer
 * Copyright (C) 2020 Seungha Yang <seungha@centricular.com>
 *
 * 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-d3d11desktopdupsrc
 * @title: d3d11desktopdupsrc
 *
 * This element uses DXGI Desktop Duplication API.
 * The default is capturing the whole desktop, but #GstD3D11DesktopDupSrc:x,
 * #GstD3D11DesktopDupSrc:y, #GstD3D11DesktopDupSrc:width and
 * #GstD3D11DesktopDupSrc:height can be used to select a particular region.
 *
 * ## Example pipelines
 * |[
 * gst-launch-1.0 d3d11desktopdupsrc ! queue ! d3d11videosink
 * ]| Capture the desktop and display it.
 */

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

#include "gstd3d11desktopdupsrc.h"
#include "gstd3d11desktopdup.h"

#include <string.h>

GST_DEBUG_CATEGORY_EXTERN (gst_d3d11_desktop_dup_debug);
#define GST_CAT_DEFAULT gst_d3d11_desktop_dup_debug

enum
{
  PROP_0,
  PROP_MONITOR_INDEX,
  PROP_SHOW_CURSOR,

  PROP_LAST,
};

static GParamSpec *properties[PROP_LAST];

#define DEFAULT_MONITOR_INDEX -1
#define DEFAULT_SHOW_CURSOR FALSE

static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE_WITH_FEATURES
        (GST_CAPS_FEATURE_MEMORY_D3D11_MEMORY, "BGRA")
    ));

struct _GstD3D11DesktopDupSrc
{
  GstPushSrc src;

  guint64 last_frame_no;
  GstClockID clock_id;
  GstVideoInfo video_info;

  GstD3D11Device *device;
  GstD3D11DesktopDup *dupl;

  gint adapter;
  gint monitor_index;
  gboolean show_cursor;

  gboolean flushing;
  GstClockTime min_latency;
  GstClockTime max_latency;
};

static void gst_d3d11_desktop_dup_src_dispose (GObject * object);
static void gst_d3d11_desktop_dup_src_set_property (GObject * object,
    guint prop_id, const GValue * value, GParamSpec * pspec);
static void gst_d3d11_desktop_dup_src_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec);

static void gst_d3d11_desktop_dup_src_set_context (GstElement * element,
    GstContext * context);

static GstCaps *gst_d3d11_desktop_dup_src_get_caps (GstBaseSrc * bsrc,
    GstCaps * filter);
static GstCaps *gst_d3d11_desktop_dup_src_fixate (GstBaseSrc * bsrc,
    GstCaps * caps);
static gboolean gst_d3d11_desktop_dup_src_set_caps (GstBaseSrc * bsrc,
    GstCaps * caps);
static gboolean gst_d3d11_desktop_dup_src_decide_allocation (GstBaseSrc * bsrc,
    GstQuery * query);
static gboolean gst_d3d11_desktop_dup_src_start (GstBaseSrc * bsrc);
static gboolean gst_d3d11_desktop_dup_src_stop (GstBaseSrc * bsrc);
static gboolean gst_d3d11_desktop_dup_src_unlock (GstBaseSrc * bsrc);
static gboolean gst_d3d11_desktop_dup_src_unlock_stop (GstBaseSrc * bsrc);
static gboolean
gst_d3d11_desktop_dup_src_src_query (GstBaseSrc * bsrc, GstQuery * query);

static GstFlowReturn gst_d3d11_desktop_dup_src_fill (GstPushSrc * pushsrc,
    GstBuffer * buffer);

#define gst_d3d11_desktop_dup_src_parent_class parent_class
G_DEFINE_TYPE (GstD3D11DesktopDupSrc, gst_d3d11_desktop_dup_src,
    GST_TYPE_PUSH_SRC);

static void
gst_d3d11_desktop_dup_src_class_init (GstD3D11DesktopDupSrcClass * klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
  GstBaseSrcClass *basesrc_class = GST_BASE_SRC_CLASS (klass);
  GstPushSrcClass *pushsrc_class = GST_PUSH_SRC_CLASS (klass);

  gobject_class->dispose = gst_d3d11_desktop_dup_src_dispose;
  gobject_class->set_property = gst_d3d11_desktop_dup_src_set_property;
  gobject_class->get_property = gst_d3d11_desktop_dup_src_get_property;

  properties[PROP_MONITOR_INDEX] =
      g_param_spec_int ("monitor-index", "Monitor Index",
      "Zero-based index for monitor to capture (-1 = primary monitor)",
      -1, G_MAXINT, DEFAULT_MONITOR_INDEX,
      G_PARAM_READWRITE | GST_PARAM_MUTABLE_READY | G_PARAM_STATIC_STRINGS);

  properties[PROP_SHOW_CURSOR] =
      g_param_spec_boolean ("show-cursor",
      "Show Mouse Cursor", "Whether to show mouse cursor",
      DEFAULT_SHOW_CURSOR, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);

  g_object_class_install_properties (gobject_class, PROP_LAST, properties);

  element_class->set_context =
      GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_set_context);

  gst_element_class_set_static_metadata (element_class,
      "Direct3D11 desktop duplication src", "Source/Video",
      "Capture desktop image by using Desktop Duplication API",
      "Seungha Yang <seungha@centricular.com>");

  gst_element_class_add_static_pad_template (element_class, &src_template);

  basesrc_class->get_caps =
      GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_get_caps);
  basesrc_class->fixate = GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_fixate);
  basesrc_class->set_caps =
      GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_set_caps);
  basesrc_class->decide_allocation =
      GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_decide_allocation);
  basesrc_class->start = GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_start);
  basesrc_class->stop = GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_stop);
  basesrc_class->unlock = GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_unlock);
  basesrc_class->unlock_stop =
      GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_unlock_stop);
  basesrc_class->query =
      GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_src_query);

  pushsrc_class->fill = GST_DEBUG_FUNCPTR (gst_d3d11_desktop_dup_src_fill);
}

static void
gst_d3d11_desktop_dup_src_init (GstD3D11DesktopDupSrc * self)
{
  gst_base_src_set_live (GST_BASE_SRC (self), TRUE);
  gst_base_src_set_format (GST_BASE_SRC (self), GST_FORMAT_TIME);

  /* FIXME: investigate non-zero adapter use case */
  self->adapter = 0;
  self->monitor_index = DEFAULT_MONITOR_INDEX;
  self->show_cursor = DEFAULT_SHOW_CURSOR;
  self->min_latency = GST_CLOCK_TIME_NONE;
  self->max_latency = GST_CLOCK_TIME_NONE;
}

static void
gst_d3d11_desktop_dup_src_dispose (GObject * object)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (object);

  gst_clear_object (&self->dupl);
  gst_clear_object (&self->device);

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

static void
gst_d3d11_desktop_dup_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (object);

  switch (prop_id) {
    case PROP_MONITOR_INDEX:
      self->monitor_index = g_value_get_int (value);
      break;
    case PROP_SHOW_CURSOR:
      self->show_cursor = g_value_get_boolean (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  };
}

static void
gst_d3d11_desktop_dup_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (object);

  switch (prop_id) {
    case PROP_MONITOR_INDEX:
      g_value_set_int (value, self->monitor_index);
      break;
    case PROP_SHOW_CURSOR:
      g_value_set_boolean (value, self->show_cursor);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  };
}

static void
gst_d3d11_desktop_dup_src_set_context (GstElement * element,
    GstContext * context)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (element);

  gst_d3d11_handle_set_context (element, context, self->adapter, &self->device);

  GST_ELEMENT_CLASS (parent_class)->set_context (element, context);
}

static GstCaps *
gst_d3d11_desktop_dup_src_get_caps (GstBaseSrc * bsrc, GstCaps * filter)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);
  GstCaps *caps = NULL;
  guint width, height;
  RECT desktop_coordinates;

  if (!self->dupl) {
    GST_DEBUG_OBJECT (self, "Duplication object is not configured yet");
    return gst_pad_get_pad_template_caps (GST_BASE_SRC_PAD (bsrc));
  }

  if (!gst_d3d11_desktop_dup_get_coordinates (self->dupl, &desktop_coordinates)) {
    GST_ELEMENT_ERROR (self, RESOURCE, OPEN_READ,
        ("Cannot query supported resolution"), (NULL));
    return NULL;
  }

  width = desktop_coordinates.right - desktop_coordinates.left;
  height = desktop_coordinates.bottom - desktop_coordinates.top;

  caps =
      gst_caps_new_simple ("video/x-raw", "format", G_TYPE_STRING, "BGRA",
      "width", G_TYPE_INT, width,
      "height", G_TYPE_INT, height,
      "framerate", GST_TYPE_FRACTION_RANGE, 1, 1, G_MAXINT, 1, NULL);
  gst_caps_set_features (caps, 0,
      gst_caps_features_new (GST_CAPS_FEATURE_MEMORY_D3D11_MEMORY, NULL));

  if (filter) {
    GstCaps *tmp =
        gst_caps_intersect_full (filter, caps, GST_CAPS_INTERSECT_FIRST);
    gst_caps_unref (caps);

    caps = tmp;
  }

  return caps;
}

static GstCaps *
gst_d3d11_desktop_dup_src_fixate (GstBaseSrc * bsrc, GstCaps * caps)
{
  GstStructure *structure;

  caps = gst_caps_make_writable (caps);

  structure = gst_caps_get_structure (caps, 0);

  gst_structure_fixate_field_nearest_fraction (structure, "framerate", 30, 1);

  return GST_BASE_SRC_CLASS (parent_class)->fixate (bsrc, caps);
}

static gboolean
gst_d3d11_desktop_dup_src_set_caps (GstBaseSrc * bsrc, GstCaps * caps)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);

  GST_DEBUG_OBJECT (self, "Set caps %" GST_PTR_FORMAT, caps);

  gst_video_info_from_caps (&self->video_info, caps);

  return TRUE;
}

static gboolean
gst_d3d11_desktop_dup_src_decide_allocation (GstBaseSrc * bsrc,
    GstQuery * query)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);
  GstBufferPool *pool = NULL;
  GstStructure *config;
  GstD3D11AllocationParams *d3d11_params;
  GstCaps *caps;
  guint min, max, size;
  gboolean update_pool;
  GstVideoInfo vinfo;

  gst_query_parse_allocation (query, &caps, NULL);

  if (!caps) {
    GST_ERROR_OBJECT (self, "No output caps");
    return FALSE;
  }

  gst_video_info_from_caps (&vinfo, caps);

  if (gst_query_get_n_allocation_pools (query) > 0) {
    gst_query_parse_nth_allocation_pool (query, 0, &pool, &size, &min, &max);
    update_pool = TRUE;
  } else {
    size = GST_VIDEO_INFO_SIZE (&vinfo);

    min = max = 0;
    update_pool = FALSE;
  }

  if (!pool || !GST_IS_D3D11_BUFFER_POOL (pool)) {
    gst_clear_object (&pool);
    pool = gst_d3d11_buffer_pool_new (self->device);
  }

  config = gst_buffer_pool_get_config (pool);

  gst_buffer_pool_config_set_params (config, caps, size, min, max);
  gst_buffer_pool_config_add_option (config, GST_BUFFER_POOL_OPTION_VIDEO_META);

  d3d11_params = gst_buffer_pool_config_get_d3d11_allocation_params (config);
  if (!d3d11_params) {
    d3d11_params = gst_d3d11_allocation_params_new (self->device, &vinfo, 0,
        D3D11_BIND_RENDER_TARGET);
  } else {
    d3d11_params->desc[0].BindFlags |= D3D11_BIND_RENDER_TARGET;
  }

  gst_buffer_pool_config_set_d3d11_allocation_params (config, d3d11_params);
  gst_d3d11_allocation_params_free (d3d11_params);

  gst_buffer_pool_set_config (pool, config);

  /* buffer size might be recalculated by pool depending on
   * device's stride/padding constraints */
  size = GST_D3D11_BUFFER_POOL (pool)->buffer_size;

  if (update_pool)
    gst_query_set_nth_allocation_pool (query, 0, pool, size, min, max);
  else
    gst_query_add_allocation_pool (query, pool, size, min, max);

  gst_object_unref (pool);

  return TRUE;
}

static gboolean
gst_d3d11_desktop_dup_src_start (GstBaseSrc * bsrc)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);

  /* FIXME: this element will use only the first adapter, but
   * this might cause issue in case of multi-gpu environment and
   * some monitor is connected to non-default adapter */
  if (!gst_d3d11_ensure_element_data (GST_ELEMENT_CAST (self), self->adapter,
          &self->device)) {
    GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
        ("D3D11 device with adapter index %d is unavailble", self->adapter),
        (NULL));

    return FALSE;
  }

  self->dupl = gst_d3d11_desktop_dup_new (self->device, self->monitor_index);
  if (!self->dupl) {
    GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
        ("Failed to prepare duplication for output index %d",
            self->monitor_index), (NULL));

    return FALSE;
  }

  self->last_frame_no = -1;
  self->min_latency = self->max_latency = GST_CLOCK_TIME_NONE;

  return TRUE;
}

static gboolean
gst_d3d11_desktop_dup_src_stop (GstBaseSrc * bsrc)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);

  gst_clear_object (&self->dupl);
  gst_clear_object (&self->device);

  return TRUE;
}

static gboolean
gst_d3d11_desktop_dup_src_unlock (GstBaseSrc * bsrc)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);

  GST_OBJECT_LOCK (self);
  if (self->clock_id) {
    GST_DEBUG_OBJECT (self, "Waking up waiting clock");
    gst_clock_id_unschedule (self->clock_id);
  }
  self->flushing = TRUE;
  GST_OBJECT_UNLOCK (self);

  return TRUE;
}

static gboolean
gst_d3d11_desktop_dup_src_unlock_stop (GstBaseSrc * bsrc)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);

  GST_OBJECT_LOCK (self);
  self->flushing = FALSE;
  GST_OBJECT_UNLOCK (self);

  return TRUE;
}

static gboolean
gst_d3d11_desktop_dup_src_src_query (GstBaseSrc * bsrc, GstQuery * query)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (bsrc);

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_CONTEXT:
      if (gst_d3d11_handle_context_query (GST_ELEMENT_CAST (self), query,
              self->device)) {
        return TRUE;
      }
      break;
    case GST_QUERY_LATENCY:
      if (GST_CLOCK_TIME_IS_VALID (self->min_latency)) {
        gst_query_set_latency (query,
            TRUE, self->min_latency, self->max_latency);
        return TRUE;
      }
      break;
    default:
      break;
  }

  return GST_BASE_SRC_CLASS (parent_class)->query (bsrc, query);
}

static GstFlowReturn
gst_d3d11_desktop_dup_src_fill (GstPushSrc * pushsrc, GstBuffer * buffer)
{
  GstD3D11DesktopDupSrc *self = GST_D3D11_DESKTOP_DUP_SRC (pushsrc);
  ID3D11Texture2D *texture;
  ID3D11RenderTargetView *rtv = NULL;
  gint fps_n, fps_d;
  GstMapInfo info;
  GstMemory *mem;
  GstD3D11Memory *dmem;
  GstFlowReturn ret = GST_FLOW_OK;
  GstClock *clock = NULL;
  GstClockTime base_time;
  GstClockTime next_capture_ts;
  GstClockTime before_capture;
  GstClockTime after_capture;
  GstClockTime latency;
  GstClockTime dur;
  gboolean update_latency = FALSE;
  gint64 next_frame_no;
  gboolean draw_mouse;

  if (!self->dupl) {
    GST_ELEMENT_ERROR (self, RESOURCE, OPEN_READ,
        ("Couldn't configure DXGI Desktop Duplication capture object"), (NULL));
    return GST_FLOW_NOT_NEGOTIATED;
  }

  fps_n = GST_VIDEO_INFO_FPS_N (&self->video_info);
  fps_d = GST_VIDEO_INFO_FPS_D (&self->video_info);

  if (fps_n <= 0 || fps_d <= 0)
    return GST_FLOW_NOT_NEGOTIATED;

again:
  clock = gst_element_get_clock (GST_ELEMENT_CAST (self));
  if (!clock) {
    GST_ELEMENT_ERROR (self, RESOURCE, FAILED,
        ("Cannot operate without a clock"), (NULL));
    return GST_FLOW_ERROR;
  }

  /* Check flushing before waiting clock because we are might be doing
   * retry */
  GST_OBJECT_LOCK (self);
  if (self->flushing) {
    ret = GST_FLOW_FLUSHING;
    GST_OBJECT_UNLOCK (self);
    goto out;
  }

  base_time = GST_ELEMENT_CAST (self)->base_time;
  next_capture_ts = gst_clock_get_time (clock);
  next_capture_ts -= base_time;

  next_frame_no = gst_util_uint64_scale (next_capture_ts,
      fps_n, GST_SECOND * fps_d);

  if (next_frame_no == self->last_frame_no) {
    GstClockID id;
    GstClockReturn ret;

    /* Need to wait for the next frame */
    next_frame_no += 1;

    /* Figure out what the next frame time is */
    next_capture_ts = gst_util_uint64_scale (next_frame_no,
        fps_d * GST_SECOND, fps_n);

    id = gst_clock_new_single_shot_id (GST_ELEMENT_CLOCK (self),
        next_capture_ts + base_time);
    self->clock_id = id;

    /* release the object lock while waiting */
    GST_OBJECT_UNLOCK (self);

    GST_LOG_OBJECT (self, "Waiting for next frame time %" GST_TIME_FORMAT,
        GST_TIME_ARGS (next_capture_ts));
    ret = gst_clock_id_wait (id, NULL);
    GST_OBJECT_LOCK (self);

    gst_clock_id_unref (id);
    self->clock_id = NULL;

    if (ret == GST_CLOCK_UNSCHEDULED) {
      /* Got woken up by the unlock function */
      ret = GST_FLOW_FLUSHING;
      GST_OBJECT_UNLOCK (self);
      goto out;
    }
    /* Duration is a complete 1/fps frame duration */
    dur = gst_util_uint64_scale_int (GST_SECOND, fps_d, fps_n);
  } else {
    GstClockTime next_frame_ts;

    GST_LOG_OBJECT (self, "No need to wait for next frame time %"
        GST_TIME_FORMAT " next frame = %" G_GINT64_FORMAT " prev = %"
        G_GINT64_FORMAT, GST_TIME_ARGS (next_capture_ts), next_frame_no,
        self->last_frame_no);

    next_frame_ts = gst_util_uint64_scale (next_frame_no + 1,
        fps_d * GST_SECOND, fps_n);
    /* Frame duration is from now until the next expected capture time */
    dur = next_frame_ts - next_capture_ts;
  }

  self->last_frame_no = next_frame_no;
  GST_OBJECT_UNLOCK (self);

  /* FIXME: handle fallback case
   * (e.g., texture belongs to other device, RTV is unavailable) */
  mem = gst_buffer_peek_memory (buffer, 0);
  dmem = (GstD3D11Memory *) mem;
  draw_mouse = self->show_cursor;
  rtv = gst_d3d11_memory_get_render_target_view (dmem, 0);
  if (draw_mouse && !rtv) {
    GST_ERROR_OBJECT (self, "Render target view is unavailable");
    ret = GST_FLOW_ERROR;
    goto out;
  }

  if (!gst_memory_map (mem, &info, GST_MAP_WRITE | GST_MAP_D3D11)) {
    GST_ERROR_OBJECT (self, "Failed to map d3d11 memory");
    ret = GST_FLOW_ERROR;
    goto out;
  }

  texture = (ID3D11Texture2D *) info.data;
  before_capture = gst_clock_get_time (clock);
  ret = gst_d3d11_desktop_dup_capture (self->dupl, texture, rtv, draw_mouse);
  gst_memory_unmap (mem, &info);

  GST_BUFFER_DTS (buffer) = GST_CLOCK_TIME_NONE;
  GST_BUFFER_PTS (buffer) = next_capture_ts;
  GST_BUFFER_DURATION (buffer) = dur;

  if (ret == GST_D3D11_DESKTOP_DUP_FLOW_EXPECTED_ERROR) {
    GST_WARNING_OBJECT (self, "Got expected error, try again");
    gst_clear_object (&clock);
    goto again;
  }

  after_capture = gst_clock_get_time (clock);
  latency = after_capture - before_capture;
  if (!GST_CLOCK_TIME_IS_VALID (self->min_latency)) {
    self->min_latency = self->max_latency = latency;
    update_latency = TRUE;
    GST_DEBUG_OBJECT (self, "Initial latency %" GST_TIME_FORMAT,
        GST_TIME_ARGS (latency));
  }

  if (latency > self->max_latency) {
    self->max_latency = latency;
    update_latency = TRUE;
    GST_DEBUG_OBJECT (self, "Updating max latency %" GST_TIME_FORMAT,
        GST_TIME_ARGS (latency));
  }

  if (update_latency) {
    gst_element_post_message (GST_ELEMENT_CAST (self),
        gst_message_new_latency (GST_OBJECT_CAST (self)));
  }

out:
  gst_clear_object (&clock);

  return ret;
}