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Add some class/init example code (on request of zeenix)

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Original commit message from CVS:
Add some class/init example code (on request of zeenix)
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Ronald S. Bultje 2003-08-29 06:50:56 +00:00
parent ae97ea085f
commit 68d336393e
1 changed files with 66 additions and 1 deletions
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67
docs/random/interfaces
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@ -170,6 +170,69 @@ Name for in the element list: "mixer". Gstaudio provides wrapper
functions for each of the class' virtual functions. Possibly also
some macros for GST_MIXER_CHANNEL_HAS_FLAG () or _get_channel ().
How to register these? Let's say that we use osssrc as an example.
typedef struct _GstOssMixer {
GstMixer mixer;
GstElement *element;
[.. more? ..]
} GstOssMixer;
typedef struct _GstOssMixerClass {
GstMixerClass klass;
} GstOssMixerClass;
[..]
static void
gst_ossmixer_class_init (GstOssMixerClass *klass)
{
GstMixerClass *mix_klass = (GstMixerClass *) klass;
[.. set virtual functions to their oss/mixer counterparts here ..]
}
[..]
static void
gst_osssrc_init (GstOssSrc *osssrc)
{
[..]
gst_element_register_interface (GST_ELEMENT (osssrc),
"mixer",
gst_osssrc_get_interface);
[..]
}
static GstInterface *
gst_osssrc_get_interface (GstElement *element,
const gchar *name)
{
GstOssMixer *mixer;
g_assert (strcmp (name, "mixer") == 0);
mixer = g_object_new (GST_TYPE_OSS_MIXER, NULL);
mixer->element = element;
[..]
return (GstInterface *) mixer;
}
And yes, that's quite a piece of code, but you didn't expect
that we could make a mixer in five lines of code, did you?
However, applications now *can*!
There might be some refcounting issues here: get_interface ()
should ref () the element, and we should set a mixer dispose
handler to unref () it again. Then, too, we could add a pointer
to the file descriptor in the osssrc/osssink, too, and we'd
have full access to the device.
However, that's implementation. Let's first worry about general
design.
4b) overlay
-----------
Overlay is used in both in- and output, too. Think of v4lsrc,
@ -215,9 +278,11 @@ typedef struct _GstOverlayClass {
GstOverlayNorm *norm);
const gchar * (* get_norm) (GstOverlay *overlay);
void (* set_xwindowid) (GstOverlay *overlay,
XWindowID xid);
XID xid);
} GstOverlayClass;
That's all!
4c) user input
--------------
And yes, user input could be an interface too. Even better, it