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56 lines
1.8 KiB
Markdown
56 lines
1.8 KiB
Markdown
---
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title: Specifying the pads
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...
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# Specifying the pads
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As explained before, pads are the port through which data goes in and
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out of your element, and that makes them a very important item in the
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process of element creation. In the boilerplate code, we have seen how
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static pad templates take care of registering pad templates with the
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element class. Here, we will see how to create actual elements, use an
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`_event
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()`-function to configure for a particular format and how to register
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functions to let data flow through the element.
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In the element `_init ()` function, you create the pad from the pad
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template that has been registered with the element class in the
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`_class_init ()` function. After creating the pad, you have to set a
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`_chain ()` function pointer that will receive and process the input
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data on the sinkpad. You can optionally also set an `_event ()` function
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pointer and a `_query ()` function pointer. Alternatively, pads can also
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operate in looping mode, which means that they can pull data themselves.
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More on this topic later. After that, you have to register the pad with
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the element. This happens like this:
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``` c
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static void
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gst_my_filter_init (GstMyFilter *filter)
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{
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/* pad through which data comes in to the element */
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filter->sinkpad = gst_pad_new_from_static_template (
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&sink_template, "sink");
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/* pads are configured here with gst_pad_set_*_function () */
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gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
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/* pad through which data goes out of the element */
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filter->srcpad = gst_pad_new_from_static_template (
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&src_template, "src");
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/* pads are configured here with gst_pad_set_*_function () */
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gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
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/* properties initial value */
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filter->silent = FALSE;
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}
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```
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