static GstFlowReturn
gst_gdiscreencapsrc_create (GstPushSrc * push_src, GstBuffer ** buf)
{
  GstGDIScreenCapSrc *src = GST_GDISCREENCAPSRC (push_src);
  GstBuffer *new_buf;
  gint new_buf_size;
  GstClock *clock;
  GstClockTime buf_time, buf_dur;
  guint64 frame_number;

  if (G_UNLIKELY (!src->info.bmiHeader.biWidth ||
          !src->info.bmiHeader.biHeight)) {
    GST_ELEMENT_ERROR (src, CORE, NEGOTIATION, (NULL),
        ("format wasn't negotiated before create function"));
    return GST_FLOW_NOT_NEGOTIATED;
  }

  new_buf_size = GST_ROUND_UP_4 (src->info.bmiHeader.biWidth * 3) *
      (-src->info.bmiHeader.biHeight);

  GST_LOG_OBJECT (src,
      "creating buffer of %d bytes with %dx%d image",
      new_buf_size, (gint) src->info.bmiHeader.biWidth,
      (gint) (-src->info.bmiHeader.biHeight));

  new_buf = gst_buffer_new_and_alloc (new_buf_size);

  clock = gst_element_get_clock (GST_ELEMENT (src));
  if (clock != NULL) {
    GstClockTime time, base_time;

    /* Calculate sync time. */

    time = gst_clock_get_time (clock);
    base_time = gst_element_get_base_time (GST_ELEMENT (src));
    buf_time = time - base_time;

    if (src->rate_numerator) {
      frame_number = gst_util_uint64_scale (buf_time,
          src->rate_numerator, GST_SECOND * src->rate_denominator);
    } else {
      frame_number = -1;
    }
  } else {
    buf_time = GST_CLOCK_TIME_NONE;
    frame_number = -1;
  }

  if (frame_number != -1 && frame_number == src->frame_number) {
    GstClockID id;
    GstClockReturn ret;

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

    /* Figure out what the next frame time is */
    buf_time = gst_util_uint64_scale (frame_number,
        src->rate_denominator * GST_SECOND, src->rate_numerator);

    id = gst_clock_new_single_shot_id (clock,
        buf_time + gst_element_get_base_time (GST_ELEMENT (src)));
    GST_OBJECT_LOCK (src);
    src->clock_id = id;
    GST_OBJECT_UNLOCK (src);

    GST_DEBUG_OBJECT (src, "Waiting for next frame time %" G_GUINT64_FORMAT,
        buf_time);
    ret = gst_clock_id_wait (id, NULL);
    GST_OBJECT_LOCK (src);

    gst_clock_id_unref (id);
    src->clock_id = NULL;
    if (ret == GST_CLOCK_UNSCHEDULED) {
      /* Got woken up by the unlock function */
      GST_OBJECT_UNLOCK (src);
      return GST_FLOW_FLUSHING;
    }
    GST_OBJECT_UNLOCK (src);

    /* Duration is a complete 1/fps frame duration */
    buf_dur =
        gst_util_uint64_scale_int (GST_SECOND, src->rate_denominator,
        src->rate_numerator);
  } else if (frame_number != -1) {
    GstClockTime next_buf_time;

    GST_DEBUG_OBJECT (src, "No need to wait for next frame time %"
        G_GUINT64_FORMAT " next frame = %" G_GINT64_FORMAT " prev = %"
        G_GINT64_FORMAT, buf_time, frame_number, src->frame_number);
    next_buf_time = gst_util_uint64_scale (frame_number + 1,
        src->rate_denominator * GST_SECOND, src->rate_numerator);
    /* Frame duration is from now until the next expected capture time */
    buf_dur = next_buf_time - buf_time;
  } else {
    buf_dur = GST_CLOCK_TIME_NONE;
  }
  src->frame_number = frame_number;

  GST_BUFFER_TIMESTAMP (new_buf) = buf_time;
  GST_BUFFER_DURATION (new_buf) = buf_dur;

  /* Do screen capture and put it into buffer... */
  gst_gdiscreencapsrc_screen_capture (src, new_buf);

  gst_object_unref (clock);

  *buf = new_buf;
  return GST_FLOW_OK;
}
static GstFlowReturn
gst_gdiscreencapsrc_create (GstPushSrc * push_src, GstBuffer ** buf)
{
  GstGDIScreenCapSrc *src = GST_GDISCREENCAPSRC (push_src);
  GstBuffer *new_buf;
  GstFlowReturn res;
  gint new_buf_size;
  GstClock *clock;
  GstClockTime time;
  GstClockTime base_time;

  if (G_UNLIKELY (!src->info.bmiHeader.biWidth ||
          !src->info.bmiHeader.biHeight)) {
    GST_ELEMENT_ERROR (src, CORE, NEGOTIATION, (NULL),
        ("format wasn't negotiated before create function"));
    return GST_FLOW_NOT_NEGOTIATED;
  } else if (G_UNLIKELY (src->rate_numerator == 0 && src->frames == 1)) {
    GST_DEBUG_OBJECT (src, "eos: 0 framerate, frame %d", (gint) src->frames);
    return GST_FLOW_UNEXPECTED;
  }

  new_buf_size = GST_ROUND_UP_4 (src->info.bmiHeader.biWidth * 3) *
      (-src->info.bmiHeader.biHeight);

  GST_LOG_OBJECT (src,
      "creating buffer of %lu bytes with %dx%d image for frame %d",
      new_buf_size, src->info.bmiHeader.biWidth,
      -src->info.bmiHeader.biHeight, (gint) src->frames);

  res =
      gst_pad_alloc_buffer_and_set_caps (GST_BASE_SRC_PAD (src),
      GST_BUFFER_OFFSET_NONE, new_buf_size,
      GST_PAD_CAPS (GST_BASE_SRC_PAD (push_src)), &new_buf);
  if (res != GST_FLOW_OK) {
    GST_DEBUG_OBJECT (src, "could not allocate buffer, reason %s",
        gst_flow_get_name (res));
    return res;
  }

  clock = gst_element_get_clock (GST_ELEMENT (src));
  if (clock) {
    /* Calculate sync time. */
    GstClockTime frame_time =
        gst_util_uint64_scale_int (src->frames * GST_SECOND,
        src->rate_denominator, src->rate_numerator);

    time = gst_clock_get_time (clock);
    base_time = gst_element_get_base_time (GST_ELEMENT (src));
    GST_BUFFER_TIMESTAMP (new_buf) = MAX (time - base_time, frame_time);
  } else {
    GST_BUFFER_TIMESTAMP (new_buf) = GST_CLOCK_TIME_NONE;
  }

  /* Do screen capture and put it into buffer... */
  gst_gdiscreencapsrc_screen_capture (src, new_buf);

  if (src->rate_numerator) {
    GST_BUFFER_DURATION (new_buf) =
        gst_util_uint64_scale_int (GST_SECOND,
        src->rate_denominator, src->rate_numerator);
    if (clock) {
      GST_BUFFER_DURATION (new_buf) =
          MAX (GST_BUFFER_DURATION (new_buf),
          gst_clock_get_time (clock) - time);
    }
  } else {
    /* NONE means forever */
    GST_BUFFER_DURATION (new_buf) = GST_CLOCK_TIME_NONE;
  }

  GST_BUFFER_OFFSET (new_buf) = src->frames;
  src->frames++;
  GST_BUFFER_OFFSET_END (new_buf) = src->frames;

  gst_object_unref (clock);

  *buf = new_buf;
  return GST_FLOW_OK;
}