When requesting an asset from different threads we had no
guarantee that during the time we lookup an asset (which didn't exist)
and the time we create the asset with the same type/ID another thread
could not end up doing the same thing. In turns we could end up with
2 different threads loading the exact same asset and the cache
basically forgetting about one of the entries meaning that the user
would never get notified about one of those being ready to be used.
There was also the case when requesting "sync" where the user was
requesting an asset while another thread is creating it so it was
still in "ASSET_INITIALIZING" state, meaning that the returned asset
would be NULL which would be considered as an error in apps.
Since the cache lock is recursive we can just take it during the whole
ges_asset_request_async call and have other method still hold it.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5732>
When a new discoverer was created for a thread so discovery could
recurse we could end up removing the wrong discoverer info from the
cache leading to freeing it while it was still discovering URIS, which
lead to the following assertion:
``` bt
Thread 1 (Thread 0x7fcc2e1a5840 (LWP 1855496)):
#0 __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
#1 0x00007fcc2e9d98a3 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
#2 0x00007fcc2e9878ee in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3 0x00007fcc2e96f8ff in __GI_abort () at abort.c:79
#4 0x00007fcc2ed80056 in g_assertion_message (domain=domain@entry=0x7fcc2f2c19f9 "GES", file=file@entry=0x7fcc2f2dfd68 "../subprojects/gst-editing-services/ges/ges-discoverer-manager.c", line=line@entry=20, func=func@entry=0x7fcc2f2e0030 <__func__.7> "ges_discoverer_data_free", message=message@entry=0x12dab70 "assertion failed: (data->n_uri == 0)") at ../glib/gtestutils.c:3497
#5 0x00007fcc2ede1d87 in g_assertion_message_expr (domain=domain@entry=0x7fcc2f2c19f9 "GES", file=file@entry=0x7fcc2f2dfd68 "../subprojects/gst-editing-services/ges/ges-discoverer-manager.c", line=line@entry=20, func=func@entry=0x7fcc2f2e0030 <__func__.7> "ges_discoverer_data_free", expr=expr@entry=0x7fcc2f2dfcf1 "data->n_uri == 0") at ../glib/gtestutils.c:3523
#6 0x00007fcc2f2bd5c5 in ges_discoverer_data_free (data=0x160e430) at ../subprojects/gst-editing-services/ges/ges-discoverer-manager.c:20
#7 0x00007fcc2ed8509d in g_atomic_rc_box_release_full (clear_func=0x7fcc2f2bd4f0 <ges_discoverer_data_free>, mem_block=0x160e430) at ../glib/garcbox.c:355
#8 g_atomic_rc_box_release_full (mem_block=0x160e430, clear_func=0x7fcc2f2bd4f0 <ges_discoverer_data_free>) at ../glib/garcbox.c:338
#9 0x00007fcc2eda6809 in g_hash_table_remove_internal (notify=1, key=0x10448a0, hash_table=0x12e0be0) at ../glib/ghash.c:1776
#10 g_hash_table_remove (hash_table=0x12e0be0, key=0x10448a0) at ../glib/ghash.c:1804
#11 0x00007fcc2f2bd95f in cleanup_discoverer_cb (discoverer_data=discoverer_data@entry=0x13e7000) at ../subprojects/gst-editing-services/ges/ges-discoverer-manager.c:379
#12 0x00007fcc2edbc759 in g_timeout_dispatch (source=0x15a6060, callback=0x7fcc2f2bd910 <cleanup_discoverer_cb>, user_data=0x13e7000) at ../glib/gmain.c:5121
#13 0x00007fcc2edbbe1c in g_main_dispatch (context=0x1044700) at ../glib/gmain.c:3476
#14 g_main_context_dispatch_unlocked (context=0x1044700) at ../glib/gmain.c:4284
#15 0x00007fcc2ee16d78 in g_main_context_iterate_unlocked.isra.0 (context=0x1044700, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4349
#16 0x00007fcc2edbd407 in g_main_loop_run (loop=0x12ccbd0) at ../glib/gmain.c:4551
#17 0x00007fcc2f285791 in ges_uri_clip_asset_request_sync (uri=uri@entry=0x12d7980 "file:///var/home/phil/gstreamer/build/subprojects/gst-integration-testsuites/logs/ges/scenarios/check_seek_on_very_deeply_nested_timeline/nested_timeline_depth6.xges", error=error@entry=0x7fff499015a8) at ../subprojects/gst-editing-services/ges/ges-uri-asset.c:688
#18 0x00007fcc2f28949b in ges_project_create_asset_sync (project=0x12c1c70, id=id@entry=0x12d7980 "file:///var/home/phil/gstreamer/build/subprojects/gst-integration-testsuites/logs/ges/scenarios/check_seek_on_very_deeply_nested_timeline/nested_timeline_depth6.xges", extractable_type=extractable_type@entry=Python Exception <class 'gdb.error'>: value has been optimized out , error=error@entry=0x7fff499015a8) at ../subprojects/gst-editing-services/ges/ges-project.c:959
#19 0x00007fcc2f2ba484 in _ges_get_asset_from_timeline (timeline=timeline@entry=0x12bdc80, type=type@entry=Python Exception <class 'gdb.error'>: value has been optimized out , id=id@entry=0x12d7980 "file:///var/home/phil/gstreamer/build/subprojects/gst-integration-testsuites/logs/ges/scenarios/check_seek_on_very_deeply_nested_timeline/nested_timeline_depth6.xges", error=error@entry=0x7fff49901728) at ../subprojects/gst-editing-services/ges/ges-structured-interface.c:540
#20 0x00007fcc2f2ba9b2 in _ges_add_clip_from_struct (timeline=0x12bdc80, structure=0x157f690, error=0x7fff49901728) at ../subprojects/gst-editing-services/ges/ges-structured-interface.c:697
#21 0x00007fcc2f2b6a9d in _validate_action_execute (scenario=0x15f7620, action=0x157f500) at ../subprojects/gst-editing-services/ges/ges-validate.c:922
#22 0x00007fcc2eef5c9c in gst_validate_execute_action (action=0x157f500, action_type=0x13e0500) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2541
#23 gst_validate_execute_action (action_type=0x13e0500, action=0x157f500) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2507
#24 0x00007fcc2eef8ce3 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2782
#25 0x00007fcc2eef9dee in _action_set_done (action=0x157efb0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#26 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157efb0, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#27 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157efb0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#28 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#29 0x00007fcc2eef9dee in _action_set_done (action=0x157ea60) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#30 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157ea60, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#31 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157ea60) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#32 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#33 0x00007fcc2eef9dee in _action_set_done (action=0x157e510) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#34 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157e510, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#35 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157e510) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#36 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#37 0x00007fcc2eef9dee in _action_set_done (action=0x157df10) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#38 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157df10, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#39 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157df10) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#40 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#41 0x00007fcc2eef9dee in _action_set_done (action=0x157d9e0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#42 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157d9e0, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#43 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157d9e0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#44 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#45 0x00007fcc2eef9dee in _action_set_done (action=0x157d3e0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#46 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157d3e0, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#47 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157d3e0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#48 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#49 0x00007fcc2eef9dee in _action_set_done (action=0x157cf70) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#50 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157cf70, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#51 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157cf70) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#52 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#53 0x00007fcc2eef9dee in _action_set_done (action=0x157cb00) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#54 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157cb00, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#55 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157cb00) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#56 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#57 0x00007fcc2eef9dee in _action_set_done (action=0x157c690) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#58 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157c690, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#59 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157c690) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#60 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#61 0x00007fcc2eef9dee in _action_set_done (action=0x157c220) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#62 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x157c220, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#63 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x157c220) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#64 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#65 0x00007fcc2eef9dee in _action_set_done (action=0x15233c0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#66 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x15233c0, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#67 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x15233c0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#68 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#69 0x00007fcc2eef9dee in _action_set_done (action=0x1522f80) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#70 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x1522f80, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#71 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x1522f80) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#72 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#73 0x00007fcc2eef9dee in _action_set_done (action=0x1522ae0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#74 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x1522ae0, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#75 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x1522ae0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#76 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#77 0x00007fcc2eef9dee in _action_set_done (action=0x1522190) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#78 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x1522190, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#79 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x1522190) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#80 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#81 0x00007fcc2eef9dee in _action_set_done (action=0x1520ea0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6368
#82 0x00007fcc2edbd26d in g_main_context_invoke_full (context=0x1044700, priority=200, function=0x7fcc2eef9ab0 <_action_set_done>, data=0x1520ea0, notify=0x7fcc2eeea5d0 <gst_validate_action_unref>) at ../glib/gmain.c:6533
#83 0x00007fcc2eef6cf2 in gst_validate_action_set_done (action=0x1520ea0) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:6411
#84 0x00007fcc2eef9018 in execute_next_action_full (scenario=<optimized out>, message=<optimized out>) at ../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c:2803
#85 0x00007fcc2edbc759 in g_timeout_dispatch (source=0x14b6340, callback=0x7fcc2eef99c0 <execute_next_action>, user_data=0x15f7620) at ../glib/gmain.c:5121
#86 0x00007fcc2edbbe1c in g_main_dispatch (context=0x1044700) at ../glib/gmain.c:3476
#87 g_main_context_dispatch_unlocked (context=0x1044700) at ../glib/gmain.c:4284
#88 0x00007fcc2ee16d78 in g_main_context_iterate_unlocked.isra.0 (context=context@entry=0x1044700, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4349
#89 0x00007fcc2edb9a93 in g_main_context_iteration (context=context@entry=0x1044700, may_block=may_block@entry=1) at ../glib/gmain.c:4414
#90 0x00007fcc2ec14c3d in g_application_run (application=application@entry=0x1042ab0, argc=argc@entry=4, argv=argv@entry=0x7fff499031e8) at ../gio/gapplication.c:2577
#91 0x0000000000405dfd in real_main (argv=0x7fff499031e8, argc=4) at ../subprojects/gst-editing-services/tools/ges-launch.c:38
#92 main (argc=4, argv=0x7fff499031e8) at ../subprojects/gst-editing-services/tools/ges-launch.c:56
```
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5619>
The manager keeps track of one discoverer per thread and in large applications
with hundreds of threads this can significantly increase memory pressure. So we
need to periodically clean-up the unused discoverers.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5608>
When using deeply nested timelines with the `ges:` protocol the
formatters ends up trying to do discovery from the same thread current
discovery happens, leading to infinite freeze as GstDiscoverer can't run
several discoveries at the same time.
By ensuring that when calling `gst_discoverer_discover_uri_async` no
`GstDiscoverer` is set as "thread discoverer" we know that another
discoverer will be created if discovery recurses, effectively removing
the freeze.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5608>
Formatters might call "loaded" from the `gessrc` streaming thread
meaning that the `->formatters` field need to be protected.
Several other APIs are called from gesbasedemux, in some radom
thread, so we should ensure that this is all MT. safe, and the API
makes it simple.
Co-authored-by: Philippe Normand <philn@igalia.com>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5431>
ges-timeline-element property getter handler was using
g_value_take_object() with internal pointers of the element as
arguments, instead of g_value_set_object().
g_value_take_object() moves the ownership of the reference; hence,
when reading "timeline" the reference ownership of timeline is moved
away from the ges-timeline-element and into the GValue.
Since GValues are temporaries that are often discarded quickly after,
this can easily lead to a double free. This was causing
gst-editing-services / pythontests to crash when running
TestTrackElements.test_ungroup_regroup() because of an innocent read of
`clip2.props.timeline` around the end of the test.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4924>
Allowing better control over the way discovery happens and allowing
us to expose a proper API.
This also adds the potential of implementing more multi-threaded
discovery in a clean way in the future.
This allows us to cleanly expose the new
GstDiscoverer::load-serialize-info signal.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3911>
When uridecodebin exposes pads for its streams, we immediately ghost
the relevant (selected) one and let composition send a seek as soon as a
buffer is probed.
This means that sometimes uridecodebin is still linking elements
internally (for non-selected streams) and sees flush events travel down
the elements it is still busy trying to link / forward sticky events to.
This causes all sorts of nasty issues, which can be avoided by simply
blocking all data flow from the source until no-more-pads has been
emitted by uridecodebin (or whatever sub_element is wrapped).
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3971>
This most likely never caused any issues as we don't connect to
no-more-pads in the first place, and the element isn't directly exposed
to the user, but emitting it makes no sense, and we are actually going
to connect to no-more-pads in a subsequent commit.
The call was added in 86b893e54c, a patch
by me in 2013, I have no idea why but I probably didn't have a firm
grasp on what I was doing then.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3971>
There are cases where user might want to be in full control of the
timeline and not be limited by the checks that are being done by GES
to go from one timeline layout to another, this should be doable as
it is a valid use case.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3501>
The previous code was storing container children in reverse
addition order, this was mitigated by the fact that track elements
were also stored in reverse order, thus restoring the original
order, but it seems more consistent to preserve order throughout,
the extra cost of append operations is negligible.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1549>
This transition is meant to be very similar to crossfade, but
instead of fading out the background video at the same time as the
foreground fades in, the background video stays at 100% opacity
during the whole transition.
This essentially "restores" the old crossfade behaviour that was changed in:
eb48faf342
but using a new type enum, so that both behaviours are available,
letting applications choose.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2385>
