<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML
><HEAD
><TITLE
>The Optimal Scheduler</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
REL="HOME"
TITLE="GStreamer Plugin Writer's Guide"
HREF="index.html"><LINK
REL="UP"
TITLE="How scheduling works"
HREF="chapter-loopbased-sched.html"><LINK
REL="PREVIOUS"
TITLE="How scheduling works"
HREF="chapter-loopbased-sched.html"><LINK
REL="NEXT"
TITLE="How a loopfunc works"
HREF="chapter-loopbased-loopfn.html"></HEAD
><BODY
CLASS="sect1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
><SPAN
CLASS="application"
>GStreamer</SPAN
> Plugin Writer's Guide</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="chapter-loopbased-sched.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 11. How scheduling works</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="chapter-loopbased-loopfn.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="section-sched-opt"
>11.2. The Optimal Scheduler</A
></H1
><P
> The <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>optimal</I
></SPAN
> scheduler takes advantage of the fact that
several elements can be linked together in one thread, with one element
controlling the other. This works as follows: in a series of chain-based
elements, each element has a function that accepts one piece of data, and
it calls a function that provides one piece of data to the next element.
The optimal scheduler will make sure that the <CODE
CLASS="function"
>gst_pad_push ()</CODE
>
function of the first element <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>directly</I
></SPAN
> calls the
chain-function of the second element. This significantly decreases the
latency in a pipeline. It takes similar advantage of other possibilities
of short-cutting the data path from one element to the next.
</P
><P
> The disadvantage of the optimal scheduler is that it is not fully
implemented. Also it is badly documented; for most developers, the opt
scheduler is one big black box. Features that are not implemented
include pad-unlinking within a group while running, pad-selecting
(i.e. waiting for data to arrive on a list of pads), and it can't really
cope with multi-input/-output elements (with the elements linked to each
of these in-/outputs running in the same thread) right now.
</P
><P
> Some of our developers are intending to write a new scheduler, similar to
the optimal scheduler (but better documented and more completely
implemented).
</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="chapter-loopbased-sched.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="chapter-loopbased-loopfn.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>How scheduling works</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="chapter-loopbased-sched.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>How a loopfunc works</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
