From 2d57bec92047feef06c317733e375c4bffbbb74b Mon Sep 17 00:00:00 2001
From: Edward Hervey <edward@centricular.com>
Date: Mon, 18 Dec 2023 09:23:14 +0100
Subject: [PATCH] decodebin3: Don't send sticky events to unlinked decoder

This causes a lot of nasty side effects (like decoders assuming they are
actually linked downstream).

The reason why this was done was to check whether a decoder could handle the
actual caps, but this is the wrong way to do it.

The proper way to query whether a decoder can handle certain caps is via
`GST_QUERY_ACCEPT_CAPS` which is already done just before.

Partially reverts !4677 and partially fixes #3160

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5821>
---
 .../gst/playback/gstdecodebin3.c              | 45 +------------------
 1 file changed, 2 insertions(+), 43 deletions(-)

diff --git a/subprojects/gst-plugins-base/gst/playback/gstdecodebin3.c b/subprojects/gst-plugins-base/gst/playback/gstdecodebin3.c
index 396a1aeabf..974180b8bd 100644
--- a/subprojects/gst-plugins-base/gst/playback/gstdecodebin3.c
+++ b/subprojects/gst-plugins-base/gst/playback/gstdecodebin3.c
@@ -899,37 +899,6 @@ decode_pad_set_target (GstGhostPad * pad, GstPad * target)
   return res;
 }
 
-typedef struct
-{
-  gboolean ret;
-  GstPad *peer;
-} SendStickyEventsData;
-
-static gboolean
-send_sticky_event (GstPad * pad, GstEvent ** event, gpointer user_data)
-{
-  SendStickyEventsData *data = user_data;
-
-  data->ret &= gst_pad_send_event (data->peer, gst_event_ref (*event));
-
-  return data->ret;
-}
-
-static gboolean
-send_sticky_events (GstDecodebin3 * dbin, GstPad * pad)
-{
-  SendStickyEventsData data;
-
-  data.ret = TRUE;
-  data.peer = gst_pad_get_peer (pad);
-
-  gst_pad_sticky_events_foreach (pad, send_sticky_event, &data);
-
-  gst_object_unref (data.peer);
-
-  return data.ret;
-}
-
 static CandidateDecoder *
 add_candidate_decoder (GstDecodebin3 * dbin, GstElement * element)
 {
@@ -3008,24 +2977,14 @@ reconfigure_output_stream (DecodebinOutputStream * output,
         goto try_next;
       }
 
-      /* First lock element's sinkpad stream lock so no data reaches
-       * the possible new element added when caps are sent by element
-       * while we're still sending sticky events */
-      GST_PAD_STREAM_LOCK (output->decoder_sink);
-
       if (gst_element_set_state (output->decoder,
-              GST_STATE_PAUSED) == GST_STATE_CHANGE_FAILURE ||
-          !send_sticky_events (dbin, slot->src_pad)) {
-
-        GST_PAD_STREAM_UNLOCK (output->decoder_sink);
-        GST_WARNING_OBJECT (dbin,
-            "Decoder '%s' failed to reach PAUSED state",
+              GST_STATE_PAUSED) == GST_STATE_CHANGE_FAILURE) {
+        GST_WARNING_OBJECT (dbin, "Decoder '%s' failed to reach PAUSED state",
             GST_ELEMENT_NAME (output->decoder));
         decoder_failed = TRUE;
         goto try_next;
       } else {
         /* Everything went well */
-        GST_PAD_STREAM_UNLOCK (output->decoder_sink);
         output->linked = TRUE;
         GST_DEBUG ("created decoder %" GST_PTR_FORMAT, output->decoder);