cccombiner: implement samples selection API

Call gst_aggregator_selected_samples() after identifying the
caption buffers that will be added as a meta on the next video
buffer.

Implement GstAggregator.peek_next_sample.

Add an example that demonstrates usage of the new API in
combination with the existing buffer-consumed signal.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1390>

1 files changed, 42 insertions, 0 deletions

diff --git a/tests/check/elements/cccombiner.c b/tests/check/elements/cccombiner.c
index 92d1d46bd..82533e926 100644
--- a/tests/check/elements/cccombiner.c
+++ b/tests/check/elements/cccombiner.c
@@ -66,6 +66,36 @@ GST_START_TEST (no_captions)
 
 GST_END_TEST;
 
+GstBuffer *expected_video_buffer = NULL;
+GstBuffer *expected_caption_buffer = NULL;
+
+static void
+samples_selected_cb (GstAggregator * agg)
+{
+  GstBufferList *buflist;
+  GstPad *caption_pad =
+      gst_element_get_static_pad (GST_ELEMENT (agg), "caption");
+  GstPad *video_pad = gst_element_get_static_pad (GST_ELEMENT (agg), "sink");
+  GstSample *video_sample =
+      gst_aggregator_peek_next_sample (agg, GST_AGGREGATOR_PAD (video_pad));
+  GstSample *captions_sample =
+      gst_aggregator_peek_next_sample (agg, GST_AGGREGATOR_PAD (caption_pad));
+
+  fail_unless (video_sample != NULL);
+  fail_unless (captions_sample != NULL);
+
+  fail_unless (gst_sample_get_buffer (video_sample) == expected_video_buffer);
+  gst_sample_unref (video_sample);
+
+  buflist = gst_sample_get_buffer_list (captions_sample);
+  fail_unless_equals_int (gst_buffer_list_length (buflist), 1);
+  fail_unless (gst_buffer_list_get (buflist, 0) == expected_caption_buffer);
+  gst_sample_unref (captions_sample);
+
+  gst_object_unref (caption_pad);
+  gst_object_unref (video_pad);
+}
+
 GST_START_TEST (captions_and_eos)
 {
   GstHarness *h, *h2;
@@ -73,6 +103,7 @@ GST_START_TEST (captions_and_eos)
   GstPad *caption_pad;
   GstCaps *caps;
   GstVideoCaptionMeta *meta;
+  GstBuffer *second_video_buf, *second_caption_buf;
 
   h = gst_harness_new_with_padnames ("cccombiner", "sink", "src");
   h2 = gst_harness_new_with_element (h->element, NULL, NULL);
@@ -80,6 +111,10 @@ GST_START_TEST (captions_and_eos)
   gst_harness_add_element_sink_pad (h2, caption_pad);
   gst_object_unref (caption_pad);
 
+  g_object_set (h->element, "emit-signals", TRUE, NULL);
+  g_signal_connect (h->element, "samples-selected",
+      G_CALLBACK (samples_selected_cb), NULL);
+
   gst_harness_set_src_caps_str (h, foo_bar_caps.string);
   gst_harness_set_src_caps_str (h2, cea708_cc_data_caps.string);
 
@@ -87,11 +122,13 @@ GST_START_TEST (captions_and_eos)
   buf = gst_buffer_new_and_alloc (128);
   GST_BUFFER_PTS (buf) = 0;
   GST_BUFFER_DURATION (buf) = 40 * GST_MSECOND;
+  expected_video_buffer = buf;
   gst_harness_push (h, buf);
 
   buf = gst_buffer_new_and_alloc (128);
   GST_BUFFER_PTS (buf) = 0;
   GST_BUFFER_DURATION (buf) = 40 * GST_MSECOND;
+  expected_caption_buffer = buf;
   gst_harness_push (h2, buf);
 
   /* And another one: the first video buffer should be retrievable
@@ -99,17 +136,22 @@ GST_START_TEST (captions_and_eos)
   buf = gst_buffer_new_and_alloc (128);
   GST_BUFFER_PTS (buf) = 40 * GST_MSECOND;
   GST_BUFFER_DURATION (buf) = 40 * GST_MSECOND;
+  second_video_buf = buf;
   gst_harness_push (h, buf);
 
   buf = gst_buffer_new_and_alloc (128);
   GST_BUFFER_PTS (buf) = 40 * GST_MSECOND;
   GST_BUFFER_DURATION (buf) = 40 * GST_MSECOND;
+  second_caption_buf = buf;
   gst_harness_push (h2, buf);
 
   /* Pull the first output buffer */
   outbuf = gst_harness_pull (h);
   fail_unless (outbuf != NULL);
 
+  expected_video_buffer = second_video_buf;
+  expected_caption_buffer = second_caption_buf;
+
   meta = gst_buffer_get_video_caption_meta (outbuf);
   fail_unless (meta != NULL);
   fail_unless_equals_int (meta->caption_type,