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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>Pure Data Packet</title></head>
<body>
<h1>Pure Data Packet</h1>
<h2>Introduction</h2>
<p>Pure Data Packet (PDP) is an extension library for the computer music
program <a href="http://www.pure-data.org">Pure Data</a> (PD), by <a href =
"http://www-crca.ucsd.edu/~msp/software.html">Miller Puckette</a> and
others. Its goal is to provide a way to use arbitrary data types (data
packets) as messages that can be passed around inside PD, along side the
standard PD numbers and symbol types. In short it puts any data object on
the same level as a float or a symbol.
<p>PDP runs on Linux and OSX. The OSX version depends on <a
href="http://fink.sourceforge.net/">Fink</a>. There is no
windows version.
<p> Currently, PDP's focus is on images and video, but there is no reason it
should stay like that. There is limited support for matrix processing
included in the main library (like Jitter or Gridflow). There is an
extension library for 1D and 2D binary cellular automata, opengl rendering
(like Gem). Some plans include audio buffers (like Vasp), ascii packets,
text buffers, ... Finally there's a library that enables you to connect a
scheme interpreter (guile) to PD/PDP. For more image processing objects,
have a look at Yves Degoyon's <a
href="http://ydegoyon.free.fr/pidip.html">PiDiP</a> library.
<h2>Getting Started</h2>
If you're used to working with PD, the the documentation and example
patches should be enough to get you started. Have a look at the README file
in the distribution to find out how to compile and setup. The file
<code>doc/reference.txt</code> contains a list of objects. If you have installed PDP
properly, you can just press the right mouse button on an object and select
help to get a help patch. If this doesn't work, look in the directory
<code>doc/objects</code> for a collection of help patches. The directory <code>doc/examples</code>
contains some more demos. The directory <code>doc/objects</code> contains two
abstractions that are used to setup the input and output in the help
patches. You might want to cut and connect some wires to use the
input/output setup that works for you.
<h2>Packets and Types</h2>
<p> PDP is about packets and operations on packets. Packets are just chunks
of dumb data. The interpretation of this data depends on its type name.
There are several types of packets. The default type for most
objects is <code><b>image/YCrCb/320x240</b></code>. This is a single video
frame, encoded in the internal 16bit YUV format, measuring 320 by 240
pixels. Another image type is the grayscale image
<code><b>image/grey/320x240</b></code>. Important notes: All image processing objects that
combine two or more packets need to be fed with the same packet types, i.e.
encoding (YCrCb/grey) and dimensions need to be the same. Image dimensions need to be a
multiple of <code><b>8x8</b></code>.
<p> The
<code><b>bitmap/*/*</b></code> type is another image representation type
supporting several encodings. I.e. <code><b>bitmap/rgb/*</b></code>,
<code><b>bitmap/rgba/*</b></code>, <code><b>bitmap/yv12/*</b></code>, ...
This type cannot be processed directly by most of the image processing
objects, but it can be used to store in delay lines, or to send over the
network. It's main use is to support all kinds of input/output devices, and
opengl textures, without introducing too many conversions, but it can serve
as a space and bandwidth saver too (especially
<code><b>bitmap/yv12/*</b></code>).
<p> One of the interesting
features in PD is the possibility of connecting everything with everything.
If you want to generalize this to all kinds of media objects, the complexity
of managing the different types starts to grow quite fast. Therefore PDP has
a type conversion system that can take care of most of the conversions
using the <code><b>[pdp_convert]</b></code> object. You can manually convert
packets to a certain type by specifying a type template as a creation
argument. I.e. <code><b>[pdp_convert image/grey/*]</b></code> will convert
any packet to a greyscale image. Most of the conversion will become
automatic later on.
<p> An example: You can use the basic PDP library together with the
cellular automata library and the opengl rendering library to use a cellular
automaton as an input to a video processing chain. You can convert the
processed image to a texture that can be applied to a 3d object, which then
can be drawn to the screen, captured as a texture, converted back to an
image, which can then be converted to a sound, processed and converted back
to an image, etc... You get the point. The possibilities are endless.
<p> Over the last couple of years, PDP has given birth to a forked off project called
<a href="http://zwizwa.goto10.org/zwikizwaki.php?page=PacketForth">Packet Forth</a>.
This is a programming laguage based on ideas from Forth and Lisp. It's aim is
loosely to be a kind of 'media Perl'.
<hr>
<address><a href="mailto:pdp@zzz.kotnet.org">Tom Schouten</a></address>
<!-- Created: Thu Apr 24 22:21:03 CEST 2003 -->
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Last modified: Thu Jan 25 23:56:07 CEST 2006
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