gstbasesrc.c

GStreamer是一个开源的多媒体框架库。利用它

 * the clock it must unblock when going from PLAYING to the PAUSED state and call
 * this method before continuing to produce the remaining data.
 *
 * This function will block until a state change to PLAYING happens (in which
 * case this function returns #GST_FLOW_OK) or the processing must be stopped due
 * to a state change to READY or a FLUSH event (in which case this function
 * returns #GST_FLOW_WRONG_STATE).
 *
 * Since: 0.10.12
 *
 * Returns: #GST_FLOW_OK if @src is PLAYING and processing can
 * continue. Any other return value should be returned from the create vmethod.
 */
GstFlowReturn
gst_base_src_wait_playing (GstBaseSrc * src)
{
  /* block until the state changes, or we get a flush, or something */
  GST_LIVE_LOCK (src);
  if (src->is_live) {
    while (G_UNLIKELY (!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 so that we don't
     * have to grab another lock. */
    GST_OBJECT_LOCK (src->srcpad);
    if (G_UNLIKELY (GST_PAD_IS_FLUSHING (src->srcpad)))
      goto flushing;
    GST_OBJECT_UNLOCK (src->srcpad);
  }
  GST_LIVE_UNLOCK (src);

  return GST_FLOW_OK;

  /* ERRORS */
flushing:
  {
    GST_DEBUG_OBJECT (src, "pad is flushing");
    GST_OBJECT_UNLOCK (src->srcpad);
    GST_LIVE_UNLOCK (src);
    return GST_FLOW_WRONG_STATE;
  }
}

/**
 * gst_base_src_set_live:
 * @src: base source instance
 * @live: new live-mode
 *
 * If the element listens to a live source, @live should
 * be set to %TRUE. 
 *
 * A live source will not produce data in the PAUSED state and
 * will therefore not be able to participate in the PREROLL phase
 * of a pipeline. To signal this fact to the application and the 
 * pipeline, the state change return value of the live source will
 * be GST_STATE_CHANGE_NO_PREROLL.
 */
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);
}

/**
 * gst_base_src_query_latency:
 * @src: the source
 * @live: if the source is live
 * @min_latency: the min latency of the source
 * @max_latency: the max latency of the source
 *
 * Query the source for the latency parameters. @live will be TRUE when @src is
 * configured as a live source. @min_latency will be set as the latency between
 * calling the create function and the timestamp on the resulting buffer.
 * @max_latency is always the undefined value of -1.
 *
 * This function is mostly used by subclasses. 
 *
 * Returns: TRUE if the query succeeded.
 *
 * Since: 0.10.13
 */
gboolean
gst_base_src_query_latency (GstBaseSrc * src, gboolean * live,
    GstClockTime * min_latency, GstClockTime * max_latency)
{
  GST_LIVE_LOCK (src);
  if (live)
    *live = src->is_live;
  if (min_latency)
    *min_latency = 0;
  if (max_latency)
    *max_latency = -1;
  GST_LIVE_UNLOCK (src);

  return TRUE;
}

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 void
gst_base_src_fixate (GstPad * pad, GstCaps * caps)
{
  GstBaseSrcClass *bclass;
  GstBaseSrc *bsrc;

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

  if (bclass->fixate)
    bclass->fixate (bsrc, caps);

  gst_object_unref (bsrc);
}

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_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;
    }
    case GST_QUERY_LATENCY:
    {
      GstClockTime min, max;
      gboolean live;

      /* Subclasses should override and implement something usefull */
      res = gst_base_src_query_latency (src, &live, &min, &max);

      gst_query_set_latency (query, live, min, max);
      break;
    }
    case GST_QUERY_JITTER:
    case GST_QUERY_RATE:
    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;
}

#define SEEK_TYPE_IS_RELATIVE(t) (((t) != GST_SEEK_TYPE_NONE) && ((t) != GST_SEEK_TYPE_SET))

static gboolean
gst_base_src_default_prepare_seek_segment (GstBaseSrc * src, GstEvent * event,
    GstSegment * segment)
{
  /* By default, we try one of 2 things:
   *   - For absolute seek positions, convert the requested position to our 
   *     configured processing format and place it in the output segment \
   *   - For relative seek positions, convert our current (input) values to the
   *     seek format, adjust by the relative seek offset and then convert back to
   *     the processing format
   */
  GstSeekType cur_type, stop_type;
  gint64 cur, stop;
  GstSeekFlags flags;
  GstFormat seek_format, dest_format;
  gdouble rate;
  gboolean update;
  gboolean res = TRUE;

  gst_event_parse_seek (event, &rate, &seek_format, &flags,
      &cur_type, &cur, &stop_type, &stop);
  dest_format = segment->format;

  if (seek_format == dest_format) {
    gst_segment_set_seek (segment, rate, seek_format, flags,
        cur_type, cur, stop_type, stop, &update);
    return TRUE;
  }