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> Plugin Writer's Guide (0.10.36)</TH
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><H1
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><A
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>2.2. Pads</A
></H1
><P
> <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>Pads</I
></SPAN
> are used to negotiate links and data flow
between elements in <SPAN
CLASS="application"
>GStreamer</SPAN
>. A pad can be viewed as a
<SPAN
CLASS="QUOTE"
>"place"</SPAN
> or <SPAN
CLASS="QUOTE"
>"port"</SPAN
> on an element where
links may be made with other elements, and through which data can
flow to or from those elements. Pads have specific data handling
capabilities: A pad can restrict the type of data that flows
through it. Links are only allowed between two pads when the
allowed data types of the two pads are compatible.
</P
><P
> An analogy may be helpful here. A pad is similar to a plug or jack on a
physical device. Consider, for example, a home theater system consisting
of an amplifier, a DVD player, and a (silent) video projector. Linking
the DVD player to the amplifier is allowed because both devices have audio
jacks, and linking the projector to the DVD player is allowed because
both devices have compatible video jacks. Links between the
projector and the amplifier may not be made because the projector and
amplifier have different types of jacks. Pads in <SPAN
CLASS="application"
>GStreamer</SPAN
> serve the
same purpose as the jacks in the home theater system.
</P
><P
> For the most part, all data in <SPAN
CLASS="application"
>GStreamer</SPAN
> flows one way through a link
between elements. Data flows out of one element through one or more
<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>source pads</I
></SPAN
>, and elements accept incoming data through
one or more <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>sink pads</I
></SPAN
>. Source and sink elements have
only source and sink pads, respectively.
</P
><P
> See the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>GStreamer Library Reference</I
></SPAN
> for the current implementation details of a <A
HREF="../../gstreamer/html/GstPad.html"
TARGET="_top"
><CODE
CLASS="classname"
>GstPad</CODE
></A
>.
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