audiorate: convert next_ts to new segment instead of restarting from 0

When receiving a new segment we should not restart PTS from the new
segment' start. Instead convert current position into the new segment if
possible.

Fixes: #4060
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7977>

subprojects/gst-plugins-base/gst/audiorate/gstaudiorate.c

@@ -292,6 +292,24 @@ gst_audio_rate_fill_to_time (GstAudioRate * audiorate, GstClockTime time)
   gst_audio_rate_chain (audiorate->sinkpad, GST_OBJECT_CAST (audiorate), buf);
 }
 
+/* FIXME: videorate has a copy, should it be public API? */
+static guint64
+convert_position (GstSegment * old_segment, GstSegment * new_segment,
+    guint64 position)
+{
+  g_return_val_if_fail (old_segment->format == new_segment->format, -1);
+  if (position == -1)
+    return -1;
+  position += old_segment->base;
+  if (position < new_segment->base)
+    return -1;
+  position -= new_segment->base;
+  if (position < new_segment->start || (new_segment->stop != -1
+          && position > new_segment->stop))
+    return -1;
+  return position;
+}
+
 static gboolean
 gst_audio_rate_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
 {
@@ -321,30 +339,28 @@ gst_audio_rate_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
     case GST_EVENT_SEGMENT:
     {
       gst_event_copy_segment (event, &audiorate->sink_segment);
-
-      GST_DEBUG_OBJECT (audiorate, "handle NEWSEGMENT");
-#if 0
-      /* FIXME: bad things will likely happen if rate < 0 ... */
-      if (!update) {
-        /* a new segment starts. We need to figure out what will be the next
-         * sample offset. We mark the offsets as invalid so that the _chain
-         * function will perform this calculation. */
-        gst_audio_rate_fill_to_time (audiorate, audiorate->src_segment.stop);
-#endif
-        audiorate->next_offset = -1;
-        audiorate->next_ts = -1;
-#if 0
-      } else {
-        gst_audio_rate_fill_to_time (audiorate, audiorate->src_segment.start);
-      }
-#endif
-
       GST_DEBUG_OBJECT (audiorate, "updated segment: %" GST_SEGMENT_FORMAT,
           &audiorate->sink_segment);
 
+      GstSegment old_segment;
+      gst_segment_copy_into (&audiorate->src_segment, &old_segment);
+
       /* Copy sink_segment into src_segment and convert to TIME format. */
       gst_audio_rate_convert_segments (audiorate);
 
+      /* Convert next_ts to new segment. */
+      audiorate->next_ts =
+          convert_position (&old_segment, &audiorate->src_segment,
+          audiorate->next_ts);
+      if (audiorate->next_ts != -1) {
+        audiorate->next_offset =
+            gst_util_uint64_scale_int_round (audiorate->next_ts,
+            GST_AUDIO_INFO_RATE (&audiorate->info), GST_SECOND);
+      } else {
+        /* Current position is outside the new segment, _chain will resync. */
+        audiorate->next_offset = -1;
+      }
+
       /* Push updated segment */
       guint32 seqnum = gst_event_get_seqnum (event);
       gst_event_take (&event, gst_event_new_segment (&audiorate->src_segment));
@@ -467,14 +483,14 @@ gst_audio_rate_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
   if (bpf == 0)
     goto not_negotiated;
 
-  /* we have a new pending segment */
   if (audiorate->next_offset == -1) {
     gint64 pos;
 
-    /* first buffer, we are negotiated and we have a segment, calculate the
+    /* first buffer, or previous buffer's position was outside of new segment,
-     * current expected offsets based on the segment.start, which is the first
+     * calculate the current expected offsets based on the segment.start, which
-     * media time of the segment and should match the media time of the first
+     * is the first media time of the segment and should match the media time of
-     * buffer in that segment, which is the offset expressed in DEFAULT units.
+     * the first buffer in that segment, which is the offset expressed in
+     * DEFAULT units.
      */
     /* convert first timestamp of segment to sample position */
     pos = gst_util_uint64_scale_int_round (audiorate->src_segment.start,

subprojects/gst-plugins-base/gst/audiorate/gstaudiorate.h

@@ -54,7 +54,6 @@ struct _GstAudioRate
 
   gboolean discont;
 
-  gboolean new_segment;
   /* we accept all formats on the sink */
   GstSegment sink_segment;
   /* we output TIME format on the src */

subprojects/gst-plugins-base/tests/check/elements/audiorate.c

@@ -564,6 +564,102 @@ GST_START_TEST (test_rate_change_down)
 
 GST_END_TEST;
 
+static GstPadProbeReturn
+segment_update_probe_cb (GstPad * pad,
+    GstPadProbeInfo * info, gpointer user_data)
+{
+  GstEvent *event = GST_PAD_PROBE_INFO_EVENT (info);
+  GList **events = user_data;
+
+  *events = g_list_append (*events, gst_event_ref (event));
+  return GST_PAD_PROBE_OK;
+}
+
+GST_START_TEST (test_segment_update)
+{
+  GstElement *audiorate;
+  GstCaps *caps;
+  GstPad *srcpad, *sinkpad;
+  GstBuffer *buf;
+
+  audiorate = gst_check_setup_element ("audiorate");
+  caps = gst_caps_new_simple ("audio/x-raw",
+      "format", G_TYPE_STRING, GST_AUDIO_NE (F32),
+      "layout", G_TYPE_STRING, "interleaved",
+      "channels", G_TYPE_INT, 1, "rate", G_TYPE_INT, 44100, NULL);
+  srcpad = gst_check_setup_src_pad (audiorate, &srctemplate);
+  sinkpad = gst_check_setup_sink_pad (audiorate, &sinktemplate);
+
+  gst_pad_set_active (srcpad, TRUE);
+  gst_check_setup_events (srcpad, audiorate, caps, GST_FORMAT_TIME);
+  gst_pad_set_active (sinkpad, TRUE);
+  fail_unless (gst_element_set_state (audiorate,
+          GST_STATE_PLAYING) == GST_STATE_CHANGE_SUCCESS,
+      "failed to set audiorate playing");
+
+  /* Initial segment is [0, -1], first buffer has PTS=0 */
+  GstClockTime pts = 0;
+  gsize frame_size = sizeof (gfloat) * 1;
+  buf = gst_buffer_new_and_alloc (frame_size);
+  GST_BUFFER_TIMESTAMP (buf) = pts;
+  gst_pad_push (srcpad, buf);
+  fail_unless_equals_int (g_list_length (buffers), 1);
+  fail_unless_equals_int64 (GST_BUFFER_PTS (buffers->data), pts);
+  gst_check_drop_buffers ();
+
+  GList *events = NULL;
+  gst_pad_add_probe (srcpad,
+      GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM,
+      (GstPadProbeCallback) segment_update_probe_cb, &events, NULL);
+
+  /* Set segment base time to 2nd frame's PTS */
+  GstSegment seg;
+  gst_segment_init (&seg, GST_FORMAT_TIME);
+  seg.base = GST_FRAMES_TO_CLOCK_TIME (1, 44100);
+  gst_pad_push_event (srcpad, gst_event_new_segment (&seg));
+  fail_unless_equals_int (g_list_length (events), 1);
+  g_clear_list (&events, (GDestroyNotify) gst_event_unref);
+
+  /* PTS=0 is correct because of the segment base time */
+  pts = 0;
+  buf = gst_buffer_new_and_alloc (frame_size);
+  GST_BUFFER_TIMESTAMP (buf) = pts;
+  gst_pad_push (srcpad, buf);
+  fail_unless_equals_int (g_list_length (buffers), 1);
+  fail_unless_equals_int64 (GST_BUFFER_PTS (buffers->data), pts);
+  gst_check_drop_buffers ();
+
+  /* Push [0, -1] segment again with base time back to 0 */
+  gst_segment_init (&seg, GST_FORMAT_TIME);
+  gst_pad_push_event (srcpad, gst_event_new_segment (&seg));
+  fail_unless_equals_int (g_list_length (events), 1);
+  g_clear_list (&events, (GDestroyNotify) gst_event_unref);
+
+  /* PTS of 3rd frame because base time is back to 0.
+   * +1 because of rounding error.
+   * audiorate used to output a buffer with PTS back to segment.start instead of
+   * continuing from its current position. */
+  pts = GST_FRAMES_TO_CLOCK_TIME (2, 44100) + 1;
+  buf = gst_buffer_new_and_alloc (frame_size);
+  GST_BUFFER_TIMESTAMP (buf) = pts;
+  gst_pad_push (srcpad, buf);
+  fail_unless_equals_int (g_list_length (buffers), 1);
+  fail_unless_equals_int64 (GST_BUFFER_PTS (buffers->data), pts);
+  gst_check_drop_buffers ();
+
+  gst_element_set_state (audiorate, GST_STATE_NULL);
+  gst_caps_unref (caps);
+
+  g_clear_list (&events, (GDestroyNotify) gst_event_unref);
+  gst_check_drop_buffers ();
+  gst_check_teardown_sink_pad (audiorate);
+  gst_check_teardown_src_pad (audiorate);
+
+  gst_object_unref (audiorate);
+}
+
+GST_END_TEST;
+
 static Suite *
 audiorate_suite (void)
 {
@@ -581,6 +677,7 @@ audiorate_suite (void)
   tcase_add_test (tc_chain, test_perfect_stream_drop45_inject25);
   tcase_add_test (tc_chain, test_large_discont);
   tcase_add_test (tc_chain, test_rate_change_down);
+  tcase_add_test (tc_chain, test_segment_update);
 
   return s;
 }