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>Chapter 21. Threads</H1
><P
>
GStreamer has support for multithreading through the use of
the <CODE
CLASS="classname"
>GstThread</CODE
> object. This object is in fact
a special <CODE
CLASS="classname"
>GstBin</CODE
> that will become a thread when started.
</P
><P
>
To construct a new thread you will perform something like:
</P
><P
> <PRE
CLASS="programlisting"
> GstElement *my_thread;
/* create the thread object */
my_thread = gst_thread_new ("my_thread");
/* you could have used gst_element_factory_make ("thread", "my_thread"); */
g_return_if_fail (my_thread != NULL);
/* add some plugins */
gst_bin_add (GST_BIN (my_thread), GST_ELEMENT (funky_src));
gst_bin_add (GST_BIN (my_thread), GST_ELEMENT (cool_effect));
/* link the elements here... */
...
/* start playing */
gst_element_set_state (GST_ELEMENT (my_thread), GST_STATE_PLAYING);
</PRE
>
</P
><P
> The above program will create a thread with two elements in it. As soon
as it is set to the PLAYING state, the thread will start to iterate
itself. You never need to explicitly iterate a thread.
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><H1
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><A
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>21.1. Constraints placed on the pipeline by the GstThread</A
></H1
><P
> Within the pipeline, everything is the same as in any other bin. The
difference lies at the thread boundary, at the link between the
thread and the outside world (containing bin). Since GStreamer is
fundamentally buffer-oriented rather than byte-oriented, the natural
solution to this problem is an element that can "buffer" the buffers
between the threads, in a thread-safe fashion. This element is the
queue, described more fully in <A
HREF="chapter-queues.html"
>Chapter 22</A
>. It doesn't
matter if the queue is placed in the containing bin or in the thread
itself, but it needs to be present on one side or the other to enable
inter-thread communication.
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