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manual: add dynamic capsfilter example

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This commit is contained in:
Wim Taymans 2012-10-04 11:50:58 +02:00
parent fc5849ef11
commit e11ca04ae7
2 changed files with 91 additions and 1 deletions
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87
docs/manual/advanced-dataaccess.xml
View file

@ -1050,14 +1050,99 @@ main (int argc, char *argv[])
</para>
<para>
Below is an example of how you can change the caps of a pipeline
while in the PLAYING state.
while in the PLAYING state:
</para>
<programlisting>
<!-- example-begin dynformat.c -->
<![CDATA[
#include <stdlib.h>
#include <gst/gst.h>
#define MAX_ROUND 100
int
main (int argc, char **argv)
{
GstElement *pipe, *filter;
GstCaps *caps;
gint width, height;
gint xdir, ydir;
gint round;
GstMessage *message;
gst_init (&argc, &argv);
pipe = gst_parse_launch_full ("videotestsrc ! capsfilter name=filter ! "
"ximagesink", NULL, GST_PARSE_FLAG_NONE, NULL);
g_assert (pipe != NULL);
filter = gst_bin_get_by_name (GST_BIN (pipe), "filter");
g_assert (filter);
width = 320;
height = 240;
xdir = ydir = -10;
for (round = 0; round < MAX_ROUND; round++) {
gchar *capsstr;
g_print ("resize to %dx%d (%d/%d) \r", width, height, round, MAX_ROUND);
/* we prefer our fixed width and height but allow other dimensions to pass
* as well */
capsstr = g_strdup_printf ("video/x-raw, width=(int)%d, height=(int)%d",
width, height);
caps = gst_caps_from_string (capsstr);
g_free (capsstr);
g_object_set (filter, "caps", caps, NULL);
gst_caps_unref (caps);
if (round == 0)
gst_element_set_state (pipe, GST_STATE_PLAYING);
width += xdir;
if (width >= 320)
xdir = -10;
else if (width < 200)
xdir = 10;
height += ydir;
if (height >= 240)
ydir = -10;
else if (height < 150)
ydir = 10;
message =
gst_bus_poll (GST_ELEMENT_BUS (pipe), GST_MESSAGE_ERROR,
50 * GST_MSECOND);
if (message) {
g_print ("got error \n");
gst_message_unref (message);
}
}
g_print ("done \n");
gst_object_unref (filter);
gst_element_set_state (pipe, GST_STATE_NULL);
gst_object_unref (pipe);
return 0;
}
]]>
<!-- example-end dynformat.c -->
</programlisting>
<para>
Note how we use <function>gst_bus_poll()</function> with a
small timeout to get messages and also introduce a short
sleep.
</para>
<para>
It is possible to set multiple caps for the capsfilter separated
with a ;. The capsfilter will try to renegotiate to the first
possible format from the list.
</para>
</sect2>
</sect1>

5
tests/examples/manual/Makefile.am
View file

@ -39,6 +39,7 @@ EXAMPLES = \
probe \
appsrc \
appsink \
dynformat \
playbin \
decodebin
@ -55,6 +56,7 @@ BUILT_SOURCES = \
probe.c \
appsrc.c \
appsink.c \
dynformat.c \
playbin.c decodebin.c
CLEANFILES = core core.* test-registry.* *.gcno *.gcda $(BUILT_SOURCES)
@ -99,6 +101,9 @@ appsrc.c: $(top_srcdir)/docs/manual/advanced-dataaccess.xml
appsink.c: $(top_srcdir)/docs/manual/advanced-dataaccess.xml
$(PERL_PATH) $(srcdir)/extract.pl $@ $<
dynformat.c: $(top_srcdir)/docs/manual/advanced-dataaccess.xml
$(PERL_PATH) $(srcdir)/extract.pl $@ $<
playbin.c decodebin.c: $(top_srcdir)/docs/manual/highlevel-components.xml
$(PERL_PATH) $(srcdir)/extract.pl $@ $<