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