gstreamer/ext/closedcaption/gstcccombiner.c

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/*
* GStreamer
* Copyright (C) 2018 Sebastian Dröge <sebastian@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.
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <gst/gst.h>
#include <gst/base/base.h>
#include <gst/video/video.h>
#include <string.h>
#include "gstcccombiner.h"
GST_DEBUG_CATEGORY_STATIC (gst_cc_combiner_debug);
#define GST_CAT_DEFAULT gst_cc_combiner_debug
static GstStaticPadTemplate sinktemplate = GST_STATIC_PAD_TEMPLATE ("sink",
GST_PAD_SINK,
GST_PAD_ALWAYS,
GST_STATIC_CAPS_ANY);
static GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE ("src",
GST_PAD_SRC,
GST_PAD_ALWAYS,
GST_STATIC_CAPS_ANY);
static GstStaticPadTemplate captiontemplate =
GST_STATIC_PAD_TEMPLATE ("caption",
GST_PAD_SINK,
GST_PAD_REQUEST,
GST_STATIC_CAPS
("closedcaption/x-cea-608,format={ (string) raw, (string) s334-1a}; "
"closedcaption/x-cea-708,format={ (string) cc_data, (string) cdp }"));
G_DEFINE_TYPE (GstCCCombiner, gst_cc_combiner, GST_TYPE_AGGREGATOR);
#define parent_class gst_cc_combiner_parent_class
typedef struct
{
GstVideoCaptionType caption_type;
GstBuffer *buffer;
} CaptionData;
static void
caption_data_clear (CaptionData * data)
{
gst_buffer_unref (data->buffer);
}
static void
gst_cc_combiner_finalize (GObject * object)
{
GstCCCombiner *self = GST_CCCOMBINER (object);
g_array_unref (self->current_frame_captions);
self->current_frame_captions = NULL;
G_OBJECT_CLASS (parent_class)->finalize (object);
}
#define GST_FLOW_NEED_DATA GST_FLOW_CUSTOM_SUCCESS
static GstFlowReturn
gst_cc_combiner_collect_captions (GstCCCombiner * self, gboolean timeout)
{
GstAggregatorPad *src_pad =
GST_AGGREGATOR_PAD (GST_AGGREGATOR_SRC_PAD (self));
GstAggregatorPad *caption_pad;
GstBuffer *video_buf;
g_assert (self->current_video_buffer != NULL);
caption_pad =
GST_AGGREGATOR_PAD_CAST (gst_element_get_static_pad (GST_ELEMENT_CAST
(self), "caption"));
/* No caption pad, forward buffer directly */
if (!caption_pad) {
GST_LOG_OBJECT (self, "No caption pad, passing through video");
video_buf = self->current_video_buffer;
self->current_video_buffer = NULL;
gst_aggregator_selected_samples (GST_AGGREGATOR_CAST (self),
GST_BUFFER_PTS (video_buf), GST_BUFFER_DTS (video_buf),
GST_BUFFER_DURATION (video_buf));
goto done;
}
GST_LOG_OBJECT (self, "Trying to collect captions for queued video buffer");
do {
GstBuffer *caption_buf;
GstClockTime caption_time;
CaptionData caption_data;
caption_buf = gst_aggregator_pad_peek_buffer (caption_pad);
if (!caption_buf) {
if (gst_aggregator_pad_is_eos (caption_pad)) {
GST_DEBUG_OBJECT (self, "Caption pad is EOS, we're done");
break;
} else if (!timeout) {
GST_DEBUG_OBJECT (self, "Need more caption data");
gst_object_unref (caption_pad);
return GST_FLOW_NEED_DATA;
} else {
GST_DEBUG_OBJECT (self, "No caption data on timeout");
break;
}
}
caption_time = GST_BUFFER_PTS (caption_buf);
if (!GST_CLOCK_TIME_IS_VALID (caption_time)) {
GST_ERROR_OBJECT (self, "Caption buffer without PTS");
gst_buffer_unref (caption_buf);
gst_object_unref (caption_pad);
return GST_FLOW_ERROR;
}
caption_time =
gst_segment_to_running_time (&caption_pad->segment, GST_FORMAT_TIME,
caption_time);
if (!GST_CLOCK_TIME_IS_VALID (caption_time)) {
GST_DEBUG_OBJECT (self, "Caption buffer outside segment, dropping");
gst_aggregator_pad_drop_buffer (caption_pad);
gst_buffer_unref (caption_buf);
continue;
}
if (gst_buffer_get_size (caption_buf) == 0 &&
GST_BUFFER_FLAG_IS_SET (caption_buf, GST_BUFFER_FLAG_GAP)) {
/* This is a gap, we can go ahead. We only consume it once its end point
* is behind the current video running time. Important to note that
* we can't deal with gaps with no duration (-1)
*/
if (!GST_CLOCK_TIME_IS_VALID (GST_BUFFER_DURATION (caption_buf))) {
GST_ERROR_OBJECT (self, "GAP buffer without a duration");
gst_buffer_unref (caption_buf);
gst_object_unref (caption_pad);
return GST_FLOW_ERROR;
}
gst_buffer_unref (caption_buf);
if (caption_time + GST_BUFFER_DURATION (caption_buf) <
self->current_video_running_time_end) {
gst_aggregator_pad_drop_buffer (caption_pad);
continue;
} else {
break;
}
}
/* Collected all caption buffers for this video buffer */
if (caption_time >= self->current_video_running_time_end) {
gst_buffer_unref (caption_buf);
break;
} else if (GST_CLOCK_TIME_IS_VALID (self->previous_video_running_time_end)) {
if (caption_time < self->previous_video_running_time_end) {
GST_WARNING_OBJECT (self,
"Caption buffer before end of last video frame, dropping");
gst_aggregator_pad_drop_buffer (caption_pad);
gst_buffer_unref (caption_buf);
continue;
}
} else if (caption_time < self->current_video_running_time) {
GST_WARNING_OBJECT (self,
"Caption buffer before current video frame, dropping");
gst_aggregator_pad_drop_buffer (caption_pad);
gst_buffer_unref (caption_buf);
continue;
}
/* This caption buffer has to be collected */
GST_LOG_OBJECT (self,
"Collecting caption buffer %p %" GST_TIME_FORMAT " for video buffer %p",
caption_buf, GST_TIME_ARGS (caption_time), self->current_video_buffer);
caption_data.caption_type = self->current_caption_type;
caption_data.buffer = caption_buf;
g_array_append_val (self->current_frame_captions, caption_data);
gst_aggregator_pad_drop_buffer (caption_pad);
} while (TRUE);
gst_aggregator_selected_samples (GST_AGGREGATOR_CAST (self),
GST_BUFFER_PTS (self->current_video_buffer),
GST_BUFFER_DTS (self->current_video_buffer),
GST_BUFFER_DURATION (self->current_video_buffer));
if (self->current_frame_captions->len > 0) {
guint i;
GST_LOG_OBJECT (self, "Attaching %u captions to buffer %p",
self->current_frame_captions->len, self->current_video_buffer);
video_buf = gst_buffer_make_writable (self->current_video_buffer);
self->current_video_buffer = NULL;
for (i = 0; i < self->current_frame_captions->len; i++) {
CaptionData *caption_data =
&g_array_index (self->current_frame_captions, CaptionData, i);
GstMapInfo map;
gst_buffer_map (caption_data->buffer, &map, GST_MAP_READ);
gst_buffer_add_video_caption_meta (video_buf, caption_data->caption_type,
map.data, map.size);
gst_buffer_unmap (caption_data->buffer, &map);
}
g_array_set_size (self->current_frame_captions, 0);
} else {
GST_LOG_OBJECT (self, "No captions for buffer %p",
self->current_video_buffer);
video_buf = self->current_video_buffer;
self->current_video_buffer = NULL;
}
gst_object_unref (caption_pad);
done:
src_pad->segment.position =
GST_BUFFER_PTS (video_buf) + GST_BUFFER_DURATION (video_buf);
return gst_aggregator_finish_buffer (GST_AGGREGATOR_CAST (self), video_buf);
}
static GstFlowReturn
gst_cc_combiner_aggregate (GstAggregator * aggregator, gboolean timeout)
{
GstCCCombiner *self = GST_CCCOMBINER (aggregator);
GstFlowReturn flow_ret = GST_FLOW_OK;
/* If we have no current video buffer, queue one. If we have one but
* its end running time is not known yet, try to determine it from the
* next video buffer */
if (!self->current_video_buffer
|| !GST_CLOCK_TIME_IS_VALID (self->current_video_running_time_end)) {
GstAggregatorPad *video_pad;
GstClockTime video_start;
GstBuffer *video_buf;
video_pad =
GST_AGGREGATOR_PAD_CAST (gst_element_get_static_pad (GST_ELEMENT_CAST
(aggregator), "sink"));
video_buf = gst_aggregator_pad_peek_buffer (video_pad);
if (!video_buf) {
if (gst_aggregator_pad_is_eos (video_pad)) {
GST_DEBUG_OBJECT (aggregator, "Video pad is EOS, we're done");
/* Assume that this buffer ends where it started +50ms (25fps) and handle it */
if (self->current_video_buffer) {
self->current_video_running_time_end =
self->current_video_running_time + 50 * GST_MSECOND;
flow_ret = gst_cc_combiner_collect_captions (self, timeout);
}
/* If we collected all captions for the remaining video frame we're
* done, otherwise get called another time and go directly into the
* outer branch for finishing the current video frame */
if (flow_ret == GST_FLOW_NEED_DATA)
flow_ret = GST_FLOW_OK;
else
flow_ret = GST_FLOW_EOS;
} else {
flow_ret = GST_FLOW_OK;
}
gst_object_unref (video_pad);
return flow_ret;
}
video_start = GST_BUFFER_PTS (video_buf);
if (!GST_CLOCK_TIME_IS_VALID (video_start)) {
gst_buffer_unref (video_buf);
gst_object_unref (video_pad);
GST_ERROR_OBJECT (aggregator, "Video buffer without PTS");
return GST_FLOW_ERROR;
}
video_start =
gst_segment_to_running_time (&video_pad->segment, GST_FORMAT_TIME,
video_start);
if (!GST_CLOCK_TIME_IS_VALID (video_start)) {
GST_DEBUG_OBJECT (aggregator, "Buffer outside segment, dropping");
gst_aggregator_pad_drop_buffer (video_pad);
gst_buffer_unref (video_buf);
gst_object_unref (video_pad);
return GST_FLOW_OK;
}
if (self->current_video_buffer) {
/* If we already have a video buffer just update the current end running
* time accordingly. That's what was missing and why we got here */
self->current_video_running_time_end = video_start;
gst_buffer_unref (video_buf);
GST_LOG_OBJECT (self,
"Determined end timestamp for video buffer: %p %" GST_TIME_FORMAT
" - %" GST_TIME_FORMAT, self->current_video_buffer,
GST_TIME_ARGS (self->current_video_running_time),
GST_TIME_ARGS (self->current_video_running_time_end));
} else {
/* Otherwise we had no buffer queued currently. Let's do that now
* so that we can collect captions for it */
gst_buffer_replace (&self->current_video_buffer, video_buf);
self->current_video_running_time = video_start;
gst_aggregator_pad_drop_buffer (video_pad);
gst_buffer_unref (video_buf);
if (GST_BUFFER_DURATION_IS_VALID (video_buf)) {
GstClockTime end_time =
GST_BUFFER_PTS (video_buf) + GST_BUFFER_DURATION (video_buf);
if (video_pad->segment.stop != -1 && end_time > video_pad->segment.stop)
end_time = video_pad->segment.stop;
self->current_video_running_time_end =
gst_segment_to_running_time (&video_pad->segment, GST_FORMAT_TIME,
end_time);
} else if (self->video_fps_n != 0 && self->video_fps_d != 0) {
GstClockTime end_time =
GST_BUFFER_PTS (video_buf) + gst_util_uint64_scale_int (GST_SECOND,
self->video_fps_d, self->video_fps_n);
if (video_pad->segment.stop != -1 && end_time > video_pad->segment.stop)
end_time = video_pad->segment.stop;
self->current_video_running_time_end =
gst_segment_to_running_time (&video_pad->segment, GST_FORMAT_TIME,
end_time);
} else {
self->current_video_running_time_end = GST_CLOCK_TIME_NONE;
}
GST_LOG_OBJECT (self,
"Queued new video buffer: %p %" GST_TIME_FORMAT " - %"
GST_TIME_FORMAT, self->current_video_buffer,
GST_TIME_ARGS (self->current_video_running_time),
GST_TIME_ARGS (self->current_video_running_time_end));
}
gst_object_unref (video_pad);
}
/* At this point we have a video buffer queued and can start collecting
* caption buffers for it */
g_assert (self->current_video_buffer != NULL);
g_assert (GST_CLOCK_TIME_IS_VALID (self->current_video_running_time));
g_assert (GST_CLOCK_TIME_IS_VALID (self->current_video_running_time_end));
flow_ret = gst_cc_combiner_collect_captions (self, timeout);
/* Only if we collected all captions we replace the current video buffer
* with NULL and continue with the next one on the next call */
if (flow_ret == GST_FLOW_NEED_DATA) {
flow_ret = GST_FLOW_OK;
} else {
gst_buffer_replace (&self->current_video_buffer, NULL);
self->previous_video_running_time_end =
self->current_video_running_time_end;
self->current_video_running_time = self->current_video_running_time_end =
GST_CLOCK_TIME_NONE;
}
return flow_ret;
}
static gboolean
gst_cc_combiner_sink_event (GstAggregator * aggregator,
GstAggregatorPad * agg_pad, GstEvent * event)
{
GstCCCombiner *self = GST_CCCOMBINER (aggregator);
switch (GST_EVENT_TYPE (event)) {
case GST_EVENT_CAPS:{
GstCaps *caps;
GstStructure *s;
gst_event_parse_caps (event, &caps);
s = gst_caps_get_structure (caps, 0);
if (strcmp (GST_OBJECT_NAME (agg_pad), "caption") == 0) {
self->current_caption_type = gst_video_caption_type_from_caps (caps);
} else {
gint fps_n, fps_d;
fps_n = fps_d = 0;
gst_structure_get_fraction (s, "framerate", &fps_n, &fps_d);
if (fps_n != self->video_fps_n || fps_d != self->video_fps_d) {
GstClockTime latency;
latency = gst_util_uint64_scale (GST_SECOND, fps_d, fps_n);
gst_aggregator_set_latency (aggregator, latency, latency);
}
self->video_fps_n = fps_n;
self->video_fps_d = fps_d;
gst_aggregator_set_src_caps (aggregator, caps);
}
break;
}
case GST_EVENT_SEGMENT:{
if (strcmp (GST_OBJECT_NAME (agg_pad), "sink") == 0) {
const GstSegment *segment;
gst_event_parse_segment (event, &segment);
gst_aggregator_update_segment (aggregator, segment);
}
break;
}
default:
break;
}
return GST_AGGREGATOR_CLASS (parent_class)->sink_event (aggregator, agg_pad,
event);
}
static gboolean
gst_cc_combiner_stop (GstAggregator * aggregator)
{
GstCCCombiner *self = GST_CCCOMBINER (aggregator);
self->video_fps_n = self->video_fps_d = 0;
self->current_video_running_time = self->current_video_running_time_end =
self->previous_video_running_time_end = GST_CLOCK_TIME_NONE;
gst_buffer_replace (&self->current_video_buffer, NULL);
g_array_set_size (self->current_frame_captions, 0);
self->current_caption_type = GST_VIDEO_CAPTION_TYPE_UNKNOWN;
return TRUE;
}
static GstFlowReturn
gst_cc_combiner_flush (GstAggregator * aggregator)
{
GstCCCombiner *self = GST_CCCOMBINER (aggregator);
GstAggregatorPad *src_pad =
GST_AGGREGATOR_PAD (GST_AGGREGATOR_SRC_PAD (aggregator));
self->current_video_running_time = self->current_video_running_time_end =
self->previous_video_running_time_end = GST_CLOCK_TIME_NONE;
gst_buffer_replace (&self->current_video_buffer, NULL);
g_array_set_size (self->current_frame_captions, 0);
src_pad->segment.position = GST_CLOCK_TIME_NONE;
return GST_FLOW_OK;
}
static GstAggregatorPad *
gst_cc_combiner_create_new_pad (GstAggregator * aggregator,
GstPadTemplate * templ, const gchar * req_name, const GstCaps * caps)
{
GstCCCombiner *self = GST_CCCOMBINER (aggregator);
GstAggregatorPad *agg_pad;
if (templ->direction != GST_PAD_SINK)
return NULL;
if (templ->presence != GST_PAD_REQUEST)
return NULL;
if (strcmp (templ->name_template, "caption") != 0)
return NULL;
GST_OBJECT_LOCK (self);
agg_pad = g_object_new (GST_TYPE_AGGREGATOR_PAD,
"name", "caption", "direction", GST_PAD_SINK, "template", templ, NULL);
self->current_caption_type = GST_VIDEO_CAPTION_TYPE_UNKNOWN;
GST_OBJECT_UNLOCK (self);
return agg_pad;
}
static gboolean
gst_cc_combiner_src_query (GstAggregator * aggregator, GstQuery * query)
{
GstPad *video_sinkpad =
gst_element_get_static_pad (GST_ELEMENT_CAST (aggregator), "sink");
gboolean ret;
switch (GST_QUERY_TYPE (query)) {
case GST_QUERY_POSITION:
case GST_QUERY_DURATION:
case GST_QUERY_URI:
case GST_QUERY_CAPS:
case GST_QUERY_ALLOCATION:
ret = gst_pad_peer_query (video_sinkpad, query);
break;
case GST_QUERY_ACCEPT_CAPS:{
GstCaps *caps;
GstCaps *templ = gst_static_pad_template_get_caps (&srctemplate);
gst_query_parse_accept_caps (query, &caps);
gst_query_set_accept_caps_result (query, gst_caps_is_subset (caps,
templ));
ret = TRUE;
break;
}
default:
ret = GST_AGGREGATOR_CLASS (parent_class)->src_query (aggregator, query);
break;
}
gst_object_unref (video_sinkpad);
return ret;
}
static gboolean
gst_cc_combiner_sink_query (GstAggregator * aggregator,
GstAggregatorPad * aggpad, GstQuery * query)
{
GstPad *video_sinkpad =
gst_element_get_static_pad (GST_ELEMENT_CAST (aggregator), "sink");
GstPad *srcpad = GST_AGGREGATOR_SRC_PAD (aggregator);
gboolean ret;
switch (GST_QUERY_TYPE (query)) {
case GST_QUERY_POSITION:
case GST_QUERY_DURATION:
case GST_QUERY_URI:
case GST_QUERY_ALLOCATION:
if (GST_PAD_CAST (aggpad) == video_sinkpad) {
ret = gst_pad_peer_query (srcpad, query);
} else {
ret =
GST_AGGREGATOR_CLASS (parent_class)->src_query (aggregator, query);
}
break;
case GST_QUERY_CAPS:
if (GST_PAD_CAST (aggpad) == video_sinkpad) {
ret = gst_pad_peer_query (srcpad, query);
} else {
GstCaps *filter;
GstCaps *templ = gst_static_pad_template_get_caps (&captiontemplate);
gst_query_parse_caps (query, &filter);
if (filter) {
GstCaps *caps =
gst_caps_intersect_full (filter, templ, GST_CAPS_INTERSECT_FIRST);
gst_query_set_caps_result (query, caps);
gst_caps_unref (caps);
} else {
gst_query_set_caps_result (query, templ);
}
gst_caps_unref (templ);
ret = TRUE;
}
break;
case GST_QUERY_ACCEPT_CAPS:
if (GST_PAD_CAST (aggpad) == video_sinkpad) {
ret = gst_pad_peer_query (srcpad, query);
} else {
GstCaps *caps;
GstCaps *templ = gst_static_pad_template_get_caps (&captiontemplate);
gst_query_parse_accept_caps (query, &caps);
gst_query_set_accept_caps_result (query, gst_caps_is_subset (caps,
templ));
ret = TRUE;
}
break;
default:
ret = GST_AGGREGATOR_CLASS (parent_class)->src_query (aggregator, query);
break;
}
gst_object_unref (video_sinkpad);
return ret;
}
static GstSample *
gst_cc_combiner_peek_next_sample (GstAggregator * agg,
GstAggregatorPad * aggpad)
{
GstAggregatorPad *caption_pad, *video_pad;
GstCCCombiner *self = GST_CCCOMBINER (agg);
GstSample *res = NULL;
caption_pad =
GST_AGGREGATOR_PAD_CAST (gst_element_get_static_pad (GST_ELEMENT_CAST
(self), "caption"));
video_pad =
GST_AGGREGATOR_PAD_CAST (gst_element_get_static_pad (GST_ELEMENT_CAST
(self), "sink"));
if (aggpad == caption_pad) {
if (self->current_frame_captions->len > 0) {
GstCaps *caps = gst_pad_get_current_caps (GST_PAD (aggpad));
GstBufferList *buflist = gst_buffer_list_new ();
guint i;
for (i = 0; i < self->current_frame_captions->len; i++) {
CaptionData *caption_data =
&g_array_index (self->current_frame_captions, CaptionData, i);
gst_buffer_list_add (buflist, gst_buffer_ref (caption_data->buffer));
}
res = gst_sample_new (NULL, caps, &aggpad->segment, NULL);
gst_caps_unref (caps);
gst_sample_set_buffer_list (res, buflist);
gst_buffer_list_unref (buflist);
}
} else if (aggpad == video_pad) {
if (self->current_video_buffer) {
GstCaps *caps = gst_pad_get_current_caps (GST_PAD (aggpad));
res = gst_sample_new (self->current_video_buffer,
caps, &aggpad->segment, NULL);
gst_caps_unref (caps);
}
}
if (caption_pad)
gst_object_unref (caption_pad);
if (video_pad)
gst_object_unref (video_pad);
return res;
}
static void
gst_cc_combiner_class_init (GstCCCombinerClass * klass)
{
GObjectClass *gobject_class;
GstElementClass *gstelement_class;
GstAggregatorClass *aggregator_class;
gobject_class = (GObjectClass *) klass;
gstelement_class = (GstElementClass *) klass;
aggregator_class = (GstAggregatorClass *) klass;
gobject_class->finalize = gst_cc_combiner_finalize;
gst_element_class_set_static_metadata (gstelement_class,
"Closed Caption Combiner",
"Filter",
"Combines GstVideoCaptionMeta with video input stream",
"Sebastian Dröge <sebastian@centricular.com>");
gst_element_class_add_static_pad_template_with_gtype (gstelement_class,
&sinktemplate, GST_TYPE_AGGREGATOR_PAD);
gst_element_class_add_static_pad_template_with_gtype (gstelement_class,
&srctemplate, GST_TYPE_AGGREGATOR_PAD);
gst_element_class_add_static_pad_template_with_gtype (gstelement_class,
&captiontemplate, GST_TYPE_AGGREGATOR_PAD);
aggregator_class->aggregate = gst_cc_combiner_aggregate;
aggregator_class->stop = gst_cc_combiner_stop;
aggregator_class->flush = gst_cc_combiner_flush;
aggregator_class->create_new_pad = gst_cc_combiner_create_new_pad;
aggregator_class->sink_event = gst_cc_combiner_sink_event;
aggregator_class->negotiate = NULL;
aggregator_class->get_next_time = gst_aggregator_simple_get_next_time;
aggregator_class->src_query = gst_cc_combiner_src_query;
aggregator_class->sink_query = gst_cc_combiner_sink_query;
aggregator_class->peek_next_sample = gst_cc_combiner_peek_next_sample;
GST_DEBUG_CATEGORY_INIT (gst_cc_combiner_debug, "cccombiner",
0, "Closed Caption combiner");
}
static void
gst_cc_combiner_init (GstCCCombiner * self)
{
GstPadTemplate *templ;
GstAggregatorPad *agg_pad;
templ = gst_static_pad_template_get (&sinktemplate);
agg_pad = g_object_new (GST_TYPE_AGGREGATOR_PAD,
"name", "sink", "direction", GST_PAD_SINK, "template", templ, NULL);
gst_object_unref (templ);
gst_element_add_pad (GST_ELEMENT_CAST (self), GST_PAD_CAST (agg_pad));
self->current_frame_captions =
g_array_new (FALSE, FALSE, sizeof (CaptionData));
g_array_set_clear_func (self->current_frame_captions,
(GDestroyNotify) caption_data_clear);
self->current_video_running_time = self->current_video_running_time_end =
self->previous_video_running_time_end = GST_CLOCK_TIME_NONE;
self->current_caption_type = GST_VIDEO_CAPTION_TYPE_UNKNOWN;
}