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