1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
---
title: Porting 0.8 applications to 0.10
...
# Porting 0.8 applications to 0.10
This section of the appendix will discuss shortly what changes to
applications will be needed to quickly and conveniently port most
applications from GStreamer-0.8 to GStreamer-0.10, with references to
the relevant sections in this Application Development Manual where
needed. With this list, it should be possible to port simple
applications to GStreamer-0.10 in less than a day.
## List of changes
- Most functions returning an object or an object property have been
changed to return its own reference rather than a constant reference
of the one owned by the object itself. The reason for this change is
primarily thread safety. This means, effectively, that return values
of functions such as `gst_element_get_pad ()`, `gst_pad_get_name ()`
and many more like these have to be free'ed or unreferenced after
use. Check the API references of each function to know for sure
whether return values should be free'ed or not. It is important that
all objects derived from GstObject are ref'ed/unref'ed using
gst\_object\_ref() and gst\_object\_unref() respectively (instead of
g\_object\_ref/unref).
- Applications should no longer use signal handlers to be notified of
errors, end-of-stream and other similar pipeline events. Instead,
they should use the `GstBus`, which has been discussed in
[Bus](manual-bus.md). The bus will take care that the messages will
be delivered in the context of a main loop, which is almost
certainly the application's main thread. The big advantage of this
is that applications no longer need to be thread-aware; they don't
need to use `g_idle_add
()` in the signal handler and do the actual real work in the
idle-callback. GStreamer now does all that internally.
- Related to this, `gst_bin_iterate ()` has been removed. Pipelines
will iterate in their own thread, and applications can simply run a
`GMainLoop` (or call the mainloop of their UI toolkit, such as
`gtk_main
()`).
- State changes can be delayed (ASYNC). Due to the new fully threaded
nature of GStreamer-0.10, state changes are not always immediate, in
particular changes including the transition from READY to PAUSED
state. This means two things in the context of porting applications:
first of all, it is no longer always possible to do
`gst_element_set_state ()` and check for a return value of
GST\_STATE\_CHANGE\_SUCCESS, as the state change might be delayed
(ASYNC) and the result will not be known until later. You should
still check for GST\_STATE\_CHANGE\_FAILURE right away, it is just
no longer possible to assume that everything that is not SUCCESS
means failure. Secondly, state changes might not be immediate, so
your code needs to take that into account. You can wait for a state
change to complete if you use GST\_CLOCK\_TIME\_NONE as timeout
interval with `gst_element_get_state ()`.
- In 0.8, events and queries had to manually be sent to sinks in
pipelines (unless you were using playbin). This is no longer the
case in 0.10. In 0.10, queries and events can be sent to toplevel
pipelines, and the pipeline will do the dispatching internally for
you. This means less bookkeeping in your application. For a short
code example, see [Position tracking and
seeking](manual-queryevents.md). Related, seeking is now
threadsafe, and your video output will show the new video position's
frame while seeking, providing a better user experience.
- The `GstThread` object has been removed. Applications can now simply
put elements in a pipeline with optionally some “queue” elements in
between for buffering, and GStreamer will take care of creating
threads internally. It is still possible to have parts of a pipeline
run in different threads than others, by using the “queue” element.
See [Threads](manual-threads.md) for details.
- Filtered caps -\> capsfilter element (the pipeline syntax for
gst-launch has not changed though).
- libgstgconf-0.10.la does not exist. Use the “gconfvideosink” and
“gconfaudiosink” elements instead, which will do live-updates and
require no library linking.
- The “new-pad” and “state-change” signals on `GstElement` were
renamed to “pad-added” and “state-changed”.
- `gst_init_get_popt_table ()` has been removed in favour of the new
GOption command line option API that was added to GLib 2.6.
`gst_init_get_option_group ()` is the new GOption-based equivalent
to `gst_init_get_ptop_table ()`.
|
