The Bongo Media Player
**********************

Bongo is a flexible and usable media player for GNU Emacs.  This manual describes how to use Bongo and some of how to customize and extend it.

Copyright © 2007  Daniel Brockman

Copyright © 2007  Daniel Jensen

     Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU FDL''.

Introduction
************

You are reading about Bongo, a flexible and usable media player for GNU Emacs.  Bongo is flexible because it does not assume that you want to do things in a certain way.

On the other hand, its default settings and key bindings are good and carefully thought-out.  So Bongo is usable because it does not force you to come up with your own way of doing things.

To open a Bongo buffer, use M-x bongo RET.  To switch between playlist and library, use the h (bongo-switch-buffers) command.  There are a few different ways to go from here.

  * One way to use Bongo is to go to a playlist, insert some tracks, and just play those tracks in some order (see Playing Tracks).

  * Another way is to insert a lot of tracks into a library, and pick out some of them into a playlist (see Enqueuing Tracks).

  * Yet another way is to let Bongo continuously pick out fresh random tracks from the library into the playlist (see Sprinkle Mode).

Five ideas central to Bongo are tracks, which represent media resources; backends, which are applications used to play media; players, which are instances of backends; and playlists and libraries, which are buffers used to organize tracks.

The following sections explain these basic ideas in turn.

Tracks
======

Bongo is a media player; its job is to play things.  The things that it plays are called tracks.  Bongo tracks can represent local audio and video files, remote media streams (such as internet radio stations), audio CD tracks and DVD chapters.

There are even tracks that perform arbitrary actions when played (see Action Tracks).  Such tracks may be used, for example, to force playback to stop at certain points in a playlist.

To insert a local file track into a playlist or library, use i. Other kinds can be inserted using I (see Inserting Tracks).

Backends
========

Instead of actually attempting to decode media files to produce sound and display video, Bongo relies on external applications to do this. The applications it uses for this purpose are called backends.

The term ``backend'' is used loosely to refer to either an external application, or to the glue code in Bongo specific to that application, or even to both the application and the glue code seen as a whole. (This usage is quite natural and normally does not cause any confusion.)

Bongo currently ships with backends for VLC, mpg123, ogg123, speexdec, TiMidity and MikMod.  Unfortunately, only VLC and mpg123 support fast-forwarding and rewinding (see Seeking).

Players
=======

Instances of backends (see Backends) are called players (or backend players).  Every time a track starts playing, a new backend player is created.  Multiple players may exist simultaneously.

For example, while there is only one VLC backend, there may be multiple VLC players at any given time --- each probably playing a different track.

Every player has an associated process (which does the actual work of playing) and an associated buffer (from which it may be controlled). Bongo buffers designed to hold players are called playlist buffers.

Playlists
=========

Playlist buffers, or simply playlists, are buffers specifically designed to hold and control backend players (see Players).

Playlists have a number of commands used to control playback: play the track at point (RET), pause/resume playback (SPC), go to the next track (C-c C-n), go to the previous track (C-c C-p), stop playback (C-c C-s), and so on (see Playing Tracks).

Some backends support fast-forwarding and rewinding (see Seeking).

Libraries
=========

Library buffers, or simply libraries, are buffers specifically designed to hold tracks for convenient insertion into playlist buffers.

After inserting tracks into a library (using i and I), you may enqueue into the nearest playlist using the e command (which appends to the end of the playlist) and the E command (which inserts into the playlist directly after the currently playing track).

All the commands for controlling playback (see Playlists) are also available in library buffers, where they simply control playback in the most recently used, or nearest, playlist buffer.  Similarily, if you attempt to play a track in a library (using RET), the track will be enqueued into the nearest playlist and played there instead.

You may prefer to use Bongo without library buffers, simply inserting tracks directly into playlists.  There is no problem with that: libraries are provided only as a convenience.

Inserting Tracks
****************

i
     Insert a file or directory (bongo-insert-file).

I
     Insert one or more non-file tracks (bongo-insert-special).

If you try to insert a directory with subdirectories, Bongo will ask whether you want to recursively insert them too.  To get rid of this question, customize the variable bongo-insert-whole-directory-trees.

The I command prompts for the type of thing to insert --- an action track, a CD, a URI, or the contents of a PLS or an M3U playlist. These special insert commands are described individually below.

I action RET
     Insert an action track (bongo-insert-action).

     This command prompts for an Emacs Lisp form to be evaluated when the action track is played.  Emacs Lisp Reference (GNU Emacs Lisp Reference Manual)

I cd RET
     Insert one track for each audio track on the CD in the tray (bongo-insert-cd).  If the track information is unavailable, insert a single track representing the entire disc.

     The customization group bongo-audio-cd covers this feature. Easy Customization (GNU Emacs Manual)

I uri RET
     Insert a URI track (bongo-insert-uri).

     This commands prompts for the URI (or URL) and for an optional title. If specified, the title will be displayed instead of the URI.  For most internet radio streams, leaving out the title enables the radio station to specify a title on its own.

I playlist RET
     Insert the contents of a PLS or an M3U playlist file (bongo-insert-playlist-contents).

     The type of the playlist is determined by its file extension:

       * pls for PLS playlists;

       * m3u or m3u8 (forces UTF-8) for M3U playlists.

     While PLS files are rather complex, M3U files are simple lists of file names (one per line, except that lines starting with # are comments).

Playing Tracks
**************

To play some particular track, move point to it and hit RET (or click on it).  Doing that on a section header will just collapse the section; to play a section, use g (bongo-play).

RET
     Play the track at point.  If point is on a section header, collapse or expand the section.

g
     Play the track or section at point, unless there is an active region or marking (see Marking Tracks).

     In choosing which tracks and sections to play, this command follows the prefix/region/marking (see The P/R/M Convention), so it may not actually always play the track or section at point.

1 g
     Play the track or section at point, even if there is an active region or marking.

Since libraries are not meant to play tracks, the RET and g commands enqueue into the nearest playlist and play there instead when used in a library buffer.

Pausing Playback
================

It is often useful to temporarily pause playback without killing the backend process.  The SPC command toggles the paused state of the currently playing track.

SPC
     Pause or resume playback (bongo-pause/resume).

Some backends (e.g., VLC and mpg123) support pausing by talking to the backend process through a pipe.  For backends where this is not possible (due to lack of any such remote control facility), pausing is implemented using SIGTSTP (or SIGSTOP) and SIGCONT, which forces the entire process to stop (just as C-z would in a job control shell).

Stopping Playback
=================

The C-c C-s command stops playback and kills the backend process. However, if nothing is being played, then C-c C-s instead starts playing the first track.

C-c C-s
     Start or stop playback (bongo-start/stop).

C-u C-c C-s
     Switch to start/stop playback mode, in which playback stops whenever any track finishes playing (see Playback Modes).

1 C-c C-s
     Insert a stopping action track (see Action Tracks) immediately after the current track.  (``Stop after playing this track.'')

5 C-c C-s
     Insert a stopping action track five tracks below the current track. (``Stop after playing these five tracks.'')

C-u C-u C-c C-s
     Insert a stopping action track at point.

Fast-forwarding and Rewinding
=============================

Some backends support fast-forwarding and rewinding --- often referred to as seeking forward or backward.  This allows you to skip over some part of a track or go back and play some part of it again.

f, b
     Fast-forward or rewind the current track 1 second (or N seconds, given a prefix argument N).

F, B, S-right, S-left
     Fast-forward or rewind 3 seconds (or 3 N seconds).

M-F, M-B, M-S-right, M-S-left
     Fast-forward or rewind 10 seconds (or 10 N seconds).

C-M-F, C-M-B, C-M-S-right, C-M-S-left
     Fast-forward or rewind 60 seconds (or N minutes).

     While C-M-B and C-M-F cannot be typed in all terminals, you may use the following commands as substitutes:

     60 b, 60 f
          Seek 60 seconds.

     C-u C-u C-u b, C-u C-u C-u f
          Seek 64 seconds.

To seek a specific number of seconds, give a numeric prefix argument to f or b.  (For example, 27 f would seek 27 seconds forward.)

To seek to a specific position, use the s (bongo-seek) command with a numeric prefix argument.  (For example, 80 s would jump directly to 1 minute and 20 seconds from the beginning of the track.)  Giving just C-u as the prefix argument to s will prompt for the position to seek to and allows you to say things like ``1:20''.

Unfortunately, not all backends support seeking.  Among the ones in the Bongo distribution, VLC and mpg123 do support it, whereas ogg123, speexdec, TiMidity and MikMod do not.

Seek Mode
---------

Typing s (bongo-seek) without any prefix argument takes you into a special mode dedicated to seeking.  In this mode, all the seeking commands work as usual, but you can drop most of the S- modifiers. For example, S-left still works, but left does the same thing.

s
     Enter seek mode.  Use RET or C-g to exit.

In seek mode, playback status is shown continuously in the echo area, and the following extra key bindings are available:

a, e, home, end
     These are shortcuts for C-c C-a (bongo-replay-current) and C-c C-e (bongo-skip-current).

p, n, r
     These are shortcuts for C-c C-p (bongo-play-previous), C-c C-n (bongo-play-next), and C-c C-r (bongo-play-random).

Seek mode uses its own command loop, so you cannot do anything other than seeking (and a handful of other things) until you quit seek mode. If you don't like this, set bongo-seek-electric-mode to nil.

Volume
======

The volume control facility is provided by the volume library (http://www.brockman.se/software/volume-el/).

The v (volume) command

Switching Tracks
================

The C-c C-n, C-c C-p and C-c C-r commands are used to start playing another track (stopping any currently playing track first).

C-c C-n
     Play the next track (bongo-play-next).

C-c C-p
     Play the previous track (bongo-play-previous).

C-c C-r
     Play a random track (bongo-play-random).

5 C-c C-n
     Skip four tracks downwards and play the one after that.

5 C-c C-p
     Skip four tracks upwards and play the one before that.

Though 0 C-c C-n may be used to play the current track again, it is easier to use the C-c C-a command.

C-c C-a
     Play the current track again (bongo-replay-current).

Just as the regular C-a command in Emacs has a counterpart C-e, so C-c C-a has a counterpart C-c C-e.

C-c C-e
     Skip the current track (bongo-skip-current).  Proceed according to the current playback mode (see Playback Modes).

Playback Modes
==============

Whenever a track finishes playing (or is skipped using C-c C-e), normally, the next track in the playlist will be played.  This is the default behavior, but it can be changed.  The way Bongo chooses which track to play next is called the playback mode.

There are five built-in playback modes.  Switching to one of them is easily done by giving a C-u prefix argument to the corresponding playback command:

C-u C-c C-n
     In progressive playback, the default playback mode, tracks are played in the usual top-to-bottom order.

C-u C-c C-p
     In regressive playback, tracks are played in reverse order, bottom-to-top.

C-u C-c C-a
     In repeating playback, the same track is played over and over.

C-u C-c C-s
     In start/stop playback, playback is stopped after each track.

     For example, this is often nice when your playlist contains videos that would otherwise keep popping up, covering your Emacs frame.

C-u C-c C-r
     In random playback, tracks are played in random order.  For an alternative to random playback mode, Sprinkle Mode.

When a non-progressive playback mode is in effect, this is indicated in the mode line:

  * Playlist[reverse] for regressive playback;

  * Playlist[repeat] for repeating playback;

  * Playlist[stop] for start/stop playback;

  * Playlist[random] for random playback;

  * Playlist[custom] for custom playback modes (to change this for some specific custom playback mode, put the string to be used as the indicator on the bongo-playback-mode-indicator property of the symbol naming the function used for bongo-next-action).

Sprinkle Mode
=============

Enqueuing Tracks
****************

The following commands are used to enqueue tracks into the playlist:

e
     Append a track to the end of the playlist.

E
     Insert a track into the playlist directly after the currently playing track (in order to have it played next).

Marking Tracks
**************

Saving and Loading
******************

The Prefix/Region/Marking Convention
************************************

Many Bongo commands follow a certain convention, called the P/R/M convention, which makes it possible to predict which objects a command will operate on.

Normally, a command operates on the track or section under point. However, if any tracks are marked (see Marking Tracks), the command operates on those instead---unless there is an active region, in which case the command operates on the tracks and sections in the region.  All of this may be overridden by giving a numeric prefix argument, which tells the command how many tracks or sections to operate on, counting from point.  Most commands allow negative prefix arguments for operating on tracks before point.

Note that giving a prefix argument of `1' tells a command to operate on the track or section under point regardless of any marking or region that may be in effect.

&
     Force the next command to use the P/R/M convention (bongo-universal-prefix/region/marking-object-command).

M-&
     Force the next command to use the P/R/M convention, but to operate only on tracks---never on sections (bongo-universal-prefix/region/marking-track-command).

Action Tracks
*************

Internals
*********

Writing Backends
****************

The predefined backends support commonly used media files and players. To use other programs with Bongo, you can define your own custom backends.  This involves some Emacs Lisp, but simple non-interactive backends are easy to define.  See Emacs Lisp Reference (GNU Emacs Lisp Reference Manual), for help with writing Lisp.

As an example, here is a minimal backend for displaying PostScript and PDF files with Evince, a GNOME document viewer.  We don't need interactive controls for Evince; we only want to launch it.

     (eval-after-load 'bongo
       '(define-bongo-backend evince
          :matcher '(local-file "ps" "pdf")))

define-bongo-backend is used to define backends.  The definition is wrapped inside an eval-after-load form so that it will execute after Bongo has loaded.  You don't need this if you load Bongo at startup, but it will work in both cases.

The first argument names the backend.  As a side effect, it also defines the executable file evince to be used with the backend. In most cases, this default behavior is fine.  If you want to customize the invocation of Evince, use M-x customize-group RET bongo-evince RET.  The define-bongo-backend macro automatically defines customizable options for this.

The second argument, the keyword :matcher, and the third argument define a matcher for the backend.  Files with suffixes ps and pdf can now be inserted in Bongo buffers, and Bongo will select the new backend to display them.  The Evince backend is now ready for use.

For information on how to write more advanced backend definitions, refer to the description of define-bongo-backend below. Examples can be found in bongo.el.

 -- Macro: define-bongo-backend name [keyword value]...
     Defines a new backend named NAME.  More specifically, defines variables used by the backend, a constructor function that will be invoked to play tracks with the backend and optionally matchers and translators for the backend.  The default definitions can be overridden with keyword arguments.  The NAME argument is not evaluated.

     define-bongo-backend accepts the following optional keywords:

     :pretty-name STRING
          The name used to described the backend to the user.  The default is to use NAME.

     :matcher MATCHER
          A backend matcher expression.  This keyword can be supplied multiple times, specifying multiple matchers.  There is no default matcher.

     :file-name-transformer EXPRESSION
          A file name transformer for the backend, to be used by bongo-transform-file-name to manipulate file names.  This keyword can be supplied multiple times, specifying multiple transformers.  There is no default file name transformer.

     :program-name STRING
          The file name of the executable program for the backend.  The default is the symbol-name of NAME.

     :program-name-variable VARIABLE
          The variable specifying the backend executable.  The default defines a variable bongo-NAME-program-name, bound to the value of PROGRAM-NAME.

     :program-arguments LIST
          A list of program arguments, to be processed by bongo-evaluate-program-arguments.  The default is (EXTRA-PROGRAM-ARGUMENTS-VARIABLE bongo-extra-arguments bongo-file-name).

     :extra-program-arguments-variable VARIABLE-NAME
          The name of the variable specifying extra command line arguments to pass to the program.  This variable will be defined with defcustom, if its name is mentioned in PROGRAM-ARGUMENTS. The default defines a variable bongo-NAME-extra-arguments.

     :extra-program-arguments LIST
          The initial value for the EXTRA-PROGRAM-ARGUMENTS-VARIABLE variable.  The default is nil.

     :constructor FUNCTION
          The function that will create and invoke the backend player.  It must be a function of two arguments, a file name and a list of extra arguments.  It shall return a player, represented by a cons (name . properties) where properties is an alist.

          The default defines a function bongo-start-NAME-player which calls bongo-start-simple-player.

     :pause-signal SIGCODE
          The signal used with signal-process to pause the player process.  The default is SIGSTOP.

GNU General Public License
**************************

Version 2, June 1991

     Copyright © 1989, 1991 Free Software Foundation, Inc.
     51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

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========

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     NO WARRANTY

 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs
=============================================

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program.  It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the ``copyright'' line and a pointer to where the full notice is found.

     ONE LINE TO GIVE THE PROGRAM'S NAME AND AN IDEA OF WHAT IT DOES.
     Copyright (C) YYYY  NAME OF AUTHOR

     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     as published by the Free Software Foundation; either version 2
     of the License, or (at your option) any later version.

     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.

     You should have received a copy of the GNU General Public License along
     with this program; if not, write to the Free Software Foundation, Inc.,
     51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

     Gnomovision version 69, Copyright (C) YYYY NAME OF AUTHOR
     Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
     type `show w'.  This is free software, and you are welcome
     to redistribute it under certain conditions; type `show c'
     for details.

The hypothetical commands show w and show c should show the appropriate parts of the General Public License.  Of course, the commands you use may be called something other than show w and show c; they could even be mouse-clicks or menu items---whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a ``copyright disclaimer'' for the program, if necessary.  Here is a sample; alter the names:

     Yoyodyne, Inc., hereby disclaims all copyright
     interest in the program `Gnomovision'
     (which makes passes at compilers) written
     by James Hacker.

     SIGNATURE OF TY COON, 1 April 1989
     Ty Coon, President of Vice

This General Public License does not permit incorporating your program into proprietary programs.  If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library.  If this is what you want to do, use the GNU Lesser General Public License instead of this License.

GNU Free Documentation License
******************************

Version 1.2, November 2002

     Copyright © 2000, 2001, 2002  Free Software Foundation, Inc.
     51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

 0. PREAMBLE

     The purpose of this License is to make a manual, textbook, or other functional and useful document ``free'' in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

     This License is a kind of ``copyleft,'' which means that derivative works of the document must themselves be free in the same sense.  It complements the GNU General Public License, which is a copyleft license designed for free software.

     We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does.  But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book.  We recommend this License principally for works whose purpose is instruction or reference.

 1. APPLICABILITY AND DEFINITIONS

     This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License.  Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein.  The ``Document,'' below, refers to any such manual or work.  Any member of the public is a licensee, and is addressed as ``you.''  You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

     A ``Modified Version'' of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

     A ``Secondary Section'' is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject.  (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.)  The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

     The ``Invariant Sections'' are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.  If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant.  The Document may contain zero Invariant Sections.  If the Document does not identify any Invariant Sections then there are none.

     The ``Cover Texts'' are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.  A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

     A ``Transparent'' copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters.  A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text.  A copy that is not ``Transparent'' is called ``Opaque.''

     Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification.  Examples of transparent image formats include PNG, XCF and JPG.  Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

     The ``Title Page'' means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page.  For works in formats which do not have any title page as such, ``Title Page'' means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

     A section ``Entitled XYZ'' means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language.  (Here XYZ stands for a specific section name mentioned below, such as ``Acknowledgements,'' ``Dedications,'' ``Endorsements,'' or ``History.'')  To ``Preserve the Title'' of such a section when you modify the Document means that it remains a section ``Entitled XYZ'' according to this definition.

     The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document.  These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

 2. VERBATIM COPYING

     You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License.  You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute.  However, you may accept compensation in exchange for copies.  If you distribute a large enough number of copies you must also follow the conditions in section 3.

     You may also lend copies, under the same conditions stated above, and you may publicly display copies.

 3. COPYING IN QUANTITY

     If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover.  Both covers must also clearly and legibly identify you as the publisher of these copies.  The front cover must present the full title with all words of the title equally prominent and visible.  You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

     If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

     If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

     It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

 4. MODIFICATIONS

     You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it.  In addition, you must do these things in the Modified Version:

      A. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document).  You may use the same title as a previous version if the original publisher of that version gives permission.

      B. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.

      C. State on the Title page the name of the publisher of the Modified Version, as the publisher.

      D. Preserve all the copyright notices of the Document.

      E. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

      F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

      G. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.

      H. Include an unaltered copy of this License.

      I. Preserve the section Entitled ``History,'' Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page.  If there is no section Entitled ``History'' in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

      J. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on.  These may be placed in the ``History'' section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

      K. For any section Entitled ``Acknowledgements'' or ``Dedications,'' Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

      L. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles.  Section numbers or the equivalent are not considered part of the section titles.

      M. Delete any section Entitled ``Endorsements.''  Such a section may not be included in the Modified Version.

      N. Do not retitle any existing section to be Entitled ``Endorsements'' or to conflict in title with any Invariant Section.

      O. Preserve any Warranty Disclaimers.

     If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant.  To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

     You may add a section Entitled ``Endorsements,'' provided it contains nothing but endorsements of your Modified Version by various parties---for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

     You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version.  Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity.  If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

     The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

 5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy.  If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

     In the combination, you must combine any sections Entitled ``History'' in the various original documents, forming one section Entitled ``History''; likewise combine any sections Entitled ``Acknowledgements,'' and any sections Entitled ``Dedications.''  You must delete all sections Entitled ``Endorsements.''

 6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

     You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

 7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an ``aggregate'' if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

 8. TRANSLATION

     Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections.  You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers.  In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

     If a section in the Document is Entitled ``Acknowledgements,'' ``Dedications,'' or ``History,'' the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

 9. TERMINATION

     You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License.  Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License.  However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

 10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time.  Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.  See http://www.gnu.org/copyleft/.

     Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License ``or any later version'' applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation.  If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

ADDENDUM: How to use this License for your documents
====================================================

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

     Copyright (C) YEAR  YOUR NAME.
     Permission is granted to copy, distribute and/or modify this document
     under the terms of the GNU Free Documentation License, Version 1.2
     or any later version published by the Free Software Foundation;
     with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
     A copy of the license is included in the section entitled ``GNU
     Free Documentation License.''

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the ``with...Texts.'' line with this:

     with the Invariant Sections being LIST THEIR TITLES, with the
     Front-Cover Texts being LIST, and with the Back-Cover Texts being
     LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.