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in a swift and cunning move thomasvs leaps up to the front of the pack in the race to the biggest commit of the week

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Original commit message from CVS:
in a swift and cunning move thomasvs leaps up to the front of the pack in the
race to the biggest commit of the week
This commit is contained in:
Thomas Vander Stichele 2002-10-19 09:15:52 +00:00
parent d91bb1bca4
commit 4c055db51d
12 changed files with 734 additions and 0 deletions
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DOC=gstreamer-faq
MAIN=$(DOC).xml
XML=$(wildcard *.xml)
XSLFO=$(srcdir)/../xsl/fo.xsl
XSLFOMODS=$(srcdir)/../xsl/ulink.xsl $(srcdir)/../xsl/keycombo.xsl
XSLHTML=$(srcdir)/../xsl/html.xsl
XSLHTMLMODS=$(srcdir)/../xsl/fileext.xsl $(srcdir)/../xsl/admon.xsl \
$(srcdir)/../xsl/keycombo.xsl $(srcdir)/../xsl/css.xsl
XSLS=$(XSLFO) $(XSLFOMODS) $(XSLHTML) $(XSLHTMLMODS)
SRC=$(XML)
CSS=base.css
EXTRA_DIST = $(XML) $(CSS)
include $(srcdir)/../manuals.mak

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pre.programlisting {
background: #E8E8FF;
}

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<sect1 id="chapter-dependencies">
<title id="title-dependencies">Dependencies</title>
<qandaset>
<qandaentry>
<question id="dependencies-why-so-many">
<para>Why are there so many dependencies ?</para>
</question>
<answer>
<para>
Making a full-featured media framework is a huge undertaking in itself.
By using the work done by others, we both reduce the amount of redundant work
being done and leave ourselves free to work on the architecture itself
instead of working on the low-level stuff. We would be stupid not to reuse
the code others have written.
</para>
<para>
However, do realize that in no way you are forced to have all dependencies
installed. Nono of the core developers has all of them installed. GStreamer
has only a few obligate dependencies : GLib 2.0, popt >= 1.6.0, and very
common stuff like glibc, a C compiler, and so on. All of the other
dependencies are optional.
</para>
<para>
So, in closing, let's rephrase the question to
<quote>Why are you giving me so many choices and such a rich environment ?
</quote>
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="dependencies-glib">
<para>
Does GStreamer use GTK+ 1.2/GLib 1.2 or GLib 2.0 ?
</para>
</question>
<answer>
<para>
Since the 0.3.3 release of GStreamer, we use GLib 2.0 as the core library
for GStreamer, which features a move of GObject from GTK+ 2.0 to GLib 2.0.
If you want to compile using GTK+ 1.2/GLib 1.2, you need to get the
0.3.1 or earlier release. It is of course not supported.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="dependencies-dxr">
<para>
Does GStreamer offer support for DVD decoder cards like dxr2/3 ?
</para>
</question>
<answer>
<para>
We do have support for the dxr3, although dxr2 support is unkown.
GStreamer can easily accomodate hardware acceleration by writing new
device-specific elements.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="dependencies-x">
<para>Is GStreamer X independent ?</para>
</question>
<answer>
<para>
Yes, we have no X dependency in any of our core modules. There are GStreamer
applications that run fine without any need for X. However, until our Linux
Framebuffer or libsvga plugin is ready, you will not be able to play videos
without X. In the future, there will probably be lots of different output
plugins for video available.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="dependencies-ladspa">
<para>What is GStreamer's position on efforts such as LADSPA ?</para>
</question>
<answer>
<para>
GStreamer actively supports such efforts, and in the case of
<ulink url="http://ladspa.org/"><citetitle>LADPSA</citetitle></ulink>,
we already have a wrapper plugin. This wrapper plug-in detects the LADSPA
plugins present on your system at register time.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="dependencies-midi">
<para>Does GStreamer support MIDI ?</para>
</question>
<answer>
<para>
Not yet. The GStreamer architecture should be able to support the needs of
MIDI applications very well however. If you are a developer interested in
adding MIDI support to GStreamer we are very interested in getting in touch
with you.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="dependencies-gnome">
<para>Does GStreamer depend on GNOME ?</para>
</question>
<answer>
<para>
No. But many of the applications developed for GStreamer do, including our
sample applications. There is nothing hindering people from developing
applications using other toolkits however and we would happily help promote
such efforts. A good example of an application using GStreamer, but which is
not using GNOME is the
<ulink url="http://mozstreamer.mozdev.org"><citetitle>
Mozstreamer</citetitle></ulink> which uses Mozilla XUL.
</para>
</answer>
</qandaentry>
</qandaset>
</sect1>

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<sect1 id="chapter-developing">
<title id="title-developing">Developing applications with GStreamer</title>
<qandaset defaultlabel="qandaset-developing">
<qandaentry>
<question id="developing-compile-programs">
<para>How do I compile programs that use GStreamer ?</para>
</question>
<answer>
<para>
GStreamer uses pkg-config to assist applications with compilationa and
linking flags.
pkg-config is already used by GTK+, GNOME, SDL, and others; so if you are
familiar with using it for any of those, you're set.
</para>
<para>
If you're not familiar with pkg-config to compile and link a small
one-file program, pass the --cflags and --libs arguments to pkg-config.
For example:
<programlisting>
$ gcc `pkg-config --cflags --libs gstreamer` -o myprog myprog.c
</programlisting>
would be sufficient for a gstreamer-only program.
If (for example) your app also used GTK+ 2.0, you could use
<programlisting>
$ gcc `pkg-config --cflags --libs gstreamer gtk+-2.0` -o myprog myprog.c
</programlisting>
Those are back-ticks (on the same key with the tilde on US keyboards),
not single quotes.
</para>
<para>
For bigger projects, you should integrate pkg-config use in your Makefile,
or integrate with autoconf using the pkg.m4 macro.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="developing-gconf">
<para>How can I use GConf to get the system-wide defaults ?</para>
</question>
<answer>
<para>
It's a good idea to use GConf to use default ways of outputting audio and
video. Since GStreamer's GConf keys can be more than
just one element, but a whole pipeline, it would be a good idea
to use the gstgconf library. It provides functions to parse the GConf key
to a usable pipeline.
</para>
<para>
To link against gstgconf, use pkg-config to query the gstreamer-libs.pc file
for link flags, and add -lgstgconf to the link flags.
This fragment of configure.ac shows how to use pkg-config to get the LIBS:
</para>
<programlisting>
dnl check for GStreamer helper libs
PKG_CHECK_MODULES(GST_HELPLIBS, gstreamer-libs >= $GSTREAMER_REQ,,exit)
AC_SUBST(GST_HELPLIBS_LIBS)
AC_SUBST(GST_HELPLIBS_CFLAGS)
</programlisting>
<para>
This fragment of a Makefile.am file shows how to make your application link
to it:
</para>
<programlisting>
bin_PROGRAMS = application
application_LDADD = $(GST_LIBS) $(GST_HELPLIBS_LIBS) -lgstgconf
application_CFLAGS = $(GST_CFLAGS) $(GST_HELPLIBS_CFLAGS)
</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question id="developing-libtool-scripts">
<para>
How do I debug these funny shell scripts that libtool makes ?
</para>
</question>
<answer>
<para>
When you link a program against uninstalled GStreamer using libtool,
funny shell scripts are made to modify your shared object search path
and then run your program. For instance, to debug gst-launch, try
<programlisting>
libtool gdb /path/to/gstreamer-launch
</programlisting>.
If this does not work, you're probably using a broken version of libtool.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="developing-mail-gstreamer-devel">
<para>Why is mail traffic so low on gstreamer-devel ?</para>
</question>
<answer>
<para>
Our main arena for coordination and discussion is IRC, not email.
Join us in #gstreamer on irc.freenode.net
For larger picture questions or getting more input from more persons,
a mail to gstreamer-devel is never a bad idea.
However, we do archive our IRC discussions, which you may find in the
gstreamer-daily mailing list archives.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="developing-versioning">
<para>What kind of versioning scheme does GStreamer use ?</para>
</question>
<answer>
<para>
For public releases, GStreamer uses a standard MAJOR.MINOR.MICRO version
scheme. If the release consists of mostly bug fixes or incremental changes,
the MICRO version is incremented.
If the release contains big changes, the MINOR version is incremented.
If we're particularly giddy, we might even increase the MAJOR number.
Don't hold your breath for that though.
</para>
<para>
During the development cycle, GStreamer also uses a fourth or NANO number.
If this number is 1, then it's a CVS version.
Any tarball or package that has a nano number of 1 is made from CVS and thus
not supported. Additionally, if you didn't get this package or tarball from
the GStreamer team, don't have high hopes on it doing whatever you want it
to do.
</para>
<para>
If the number is 2 or higher, it's an official pre-release in preparation
of an actual complete release. Your help in testing these tarballs and
packages is very much appreciated.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="developing-coding-style">
<para>What is the coding style for GStreamer core ?</para>
</question>
<answer>
<para>
The core is basically coded in K&amp;R with 2-space indenting.
Just follow what's already there and you'll be fine.
The core could use a code cleanup though at this point.
</para>
<para>
Individual plugins in gst-plugins or plugins that you want considered for
addition to the gst-plugins module should be coded in the same style.
It's easier if everything is consistent. Consistency is, of course, the goal.
</para>
<para>
If you use emacs, try these lines:
<programlisting>
(defun gstreamer-c-mode ()
"C mode with adjusted defaults for use with GStreamer."
(interactive)
(c-mode)
(c-set-style "K&amp;R")
(setq c-basic-offset 2))
(setq auto-mode-alist (cons '("gst.*/.*\\.[ch]$" . gstreamer-c-mode)
auto-mode-alist))
</programlisting>
</para>
<para>
Or, run your code through
<programlisting>
indent -br -bad -cbi0 -cli2 -bls -l100 -ut -ce
</programlisting>
before submitting a patch (FIXME: check if these are indeed the proper options).
</para>
<para>
As for the code itself, the
<ulink url="http://developer.gnome.org/doc/guides/programming-guidelines/book1.html">GNOME coding guidelines</ulink> is a good read.
Where possible, we try to adhere to the spirit of GObject and use similar
coding idioms.
</para>
</answer>
</qandaentry>
</qandaset>
</sect1>

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<sect1 id="chapter-general">
<title id="title-general">General</title>
<qandaset>
<qandaentry>
<question id="general-media-player">
<para>Is GStreamer a media player ?</para>
</question>
<answer>
<para>
No, GStreamer is a development framework for creating applications like
media players, video editors, streaming media broadcasters and so on.
That said, very good media players can easily be built on top
of GStreamer and we even include a simple yet functional media player
with GStreamer, called gst-player.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-why-c">
<para>
Why is GStreamer written in C ? Why not C++/Objective-C/... ?
</para>
</question>
<answer>
<para>
We like C. Aside from "personal preference", there are a number of technical
reasons why C is nice in this project:
<itemizedlist>
<listitem>C is extremely portable.</listitem>
<listitem>C is fast.</listitem>
<listitem>It is easy to make language bindings for libraries written in C.
</listitem>
<listitem>The GObject object system provided by GLib implements objects in C,
in a portable, powerful way. This library provides for introspection and
runtime dynamic typing. It is a full OO system, but without the syntactic
sugar. If you want sugar, take a look at
<ulink url="http://www.5z.com/jirka/gob.html">GOB</ulink>.</listitem>
<listitem>Use of C integrates nicely with Gtk+ and GNOME. Some people like
this a lot, but neither Gtk+ nor GNOME are required by GStreamer.</listitem>
</itemizedlist>
</para>
<para>
So, in closing, we like C. If you don't, that's fine; if you still want to
help out on GStreamer, we always need more language binding people. And if
not, don't bother us; we're working :-)
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-applications">
<para>What applications are available for GStreamer ?</para>
</question>
<answer>
<para>
GStreamer is still very early in its development, but already we see some
really nice applications being developed in parallel with GStreamer.
Both gst-player and gst-editor are very closely linked to GStreamer itself
for obvious reasons.
For a list of some of the more advanced projects, look at the list
in our <ulink url="http://gstreamer.net/status/">Status table</ulink>.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-licensing">
<para>
What are the exact licensing terms for GStreamer and its plugins ?
</para>
</question>
<answer>
<para>
All of GStreamer, including our own plugin code, is licensed under the
<ulink url="http://www.gnu.org/licenses/lgpl.html">GNU LGPL</ulink> license.
Some of the libraries we use for some of the plugins are however under the
GPL, which means that those plugins can not be used by a non-GPL-compatible
application.
</para>
<para>
As part of the GStreamer source download you find a file called
license_README. That file contains information in the exact licensing
terms of the libraries we use. As a general rule, GStreamer aims at using
only LGPL or BSD licensed libraries if available and only use GPL or
proprietary libraries where no good LGPL or BSD alternatives are available.
</para>
From GStreamer 0.4.2 on, we implemented a license field for all of the plugins,
and in the future we might have the application enforce a stricter policy
(much like tainting in the kernel).
<para>
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-sound-server">
<para>Is GStreamer a sound server ?</para>
</question>
<answer>
<para>
No, GStreamer is not a soundserver. GStreamer does however have plugins
supporting most of the major soundservers available today, including
ESD, aRTSd, and to some extent Jack. Support for MAS is also planned.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-platforms">
<para>
Will GStreamer be available for platforms other than Unix ?
</para>
</question>
<answer>
<para>
Depends. Our main target is the Unix platform. That said, interest has been
expressed in porting GStreamer to other platforms and the GStreamer core
team will gladly accept patches to accomplish this.
Please refer to the
<ulink url="http://gstreamer.net/status/?category=7">
platform support status table</ulink>
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-gnome">
<para>What is GStreamer's relationship with the GNOME community ?</para>
</question>
<answer>
<para>
While GStreamer is operated as an independent project, we do have a close
relationship with the GNOME community. Many of our hackers consider
themselves also to be members of the GNOME community. There are plans to
make (some part of) GStreamer an official part of the development framework
of GNOME. This does not exclude use of GStreamer by other communities at
all, of course.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-kde">
<para>What is GStreamer's relationship with the KDE community ?</para>
</question>
<answer>
<para>
The GStreamer community wants to have as good a relationship as possible
with KDE, and we hope that someday KDE decides to adopt GStreamer as their
multimedia API, just like the GNOME community plans on doing.
There have been contacts from time to time between the GStreamer community
and KDE and we do already have support for the aRTSd sound server used by KDE.
Also, some of the KDE hackers have created Qt bindings of GStreamer
and made a simple video player.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="general-my-application">
<para>
I'm considering adding GStreamer output to my application...
</para>
</question>
<answer>
<para>
That doesn't really make sense. GStreamer is not a sound server, so you don't
output directly to GStreamer, and it's not an intermediate API between
audio data and different kinds of audio sinks. It is a fundamental design
decision to use GStreamer in your app; there are no easy ways of somehow
'transfering' data from your app to GStreamer. Instead, your app would have
to use or implement a number of GStreamer elements, string them together, and
tell them to run. In that manner the data would all be internal to the
GStreamer pipeline.
</para>
<para>
That said, it is possible to write a plugin specific to your app that can get
at the audio data.
</para>
</answer>
</qandaentry>
</qandaset>
</sect1>

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<sect1 id="chapter-getting">
<title id="title-getting">Getting GStreamer</title>
<qandaset>
<qandaentry>
<question id="getting-gstreamer">
<para>How do I get GStreamer ?</para>
</question>
<answer>
<para>
You either ask us nicely for it or pay us big bucks.
</para>
</answer>
</qandaentry>
</qandaset>
</sect1>

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<?xml version="1.0"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" [
<!ENTITY START SYSTEM "start.xml">
<!ENTITY GENERAL SYSTEM "general.xml">
<!ENTITY DEPENDENCIES SYSTEM "dependencies.xml">
<!ENTITY GETTING SYSTEM "getting.xml">
<!ENTITY USING SYSTEM "using.xml">
<!ENTITY DEVELOPING SYSTEM "developing.xml">
<!ENTITY TROUBLESHOOTING SYSTEM "troubleshooting.xml">
]>
<article class="faq">
<articleinfo>
<title>GStreamer FAQ</title>
<abstract>
<para>
This is the FAQ for GStreamer, a multimedia framework.
Questions and answers range from general information to
deep-down-and-dirty compilation issues.
</para>
</abstract>
<revhistory>
<revision>
<revnumber>0.1</revnumber>
<date>2002-10-01</date>
<revremark>Initial conversion from FAQ database.</revremark>
</revision>
</revhistory>
</articleinfo>
&START;
&GENERAL;
&DEPENDENCIES;
&GETTING;
&USING;
&DEVELOPING;
&TROUBLESHOOTING;
</article>

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<!ENTITY magic "pdf">

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<!ENTITY magic "png">

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<sect1 id="start">
<title id="start-title">Getting Started</title>
<para>
So you're eager to get started learning about GStreamer.
There's a few ways you can get started.
<itemizedlist>
<listitem>If you want to learn by reading about it, start with
<xref linkend="title-general" endterm="title-general"/></listitem>
<listitem>
If you'd rather learn by trying it out, start with
<xref linkend="title-getting" endterm="title-getting"/>
</listitem>
</itemizedlist>
</para>
</sect1>

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<sect1 id="chapter-troubleshooting">
<title id="title-troubleshooting">Troubleshooting GStreamer</title>
<qandaset>
<qandaentry>
<question id="troubleshooting-wiki">
<para>
I'm having problems building or installing GStreamer. What should I do ?
</para>
</question>
<answer>
<para>
We've started a step-by-step
<ulink url="http://gstreamer.net/wiki/?DichotomousKey">
troubleshooting guide</ulink>.
Look there before asking, your problem might already have been solved by
someone else.
</para>
</answer>
</qandaentry>
</qandaset>
</sect1>

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<sect1 id="chapter-using">
<title id="title-using">Using GStreamer</title>
<qandaset>
<qandaentry>
<question id="using-gst-inspect">
<para>How do I tell what GStreamer plugins I have on my system ?</para>
</question>
<answer>
<para>
To do this you use the gst-inspect
command-line tool, which comes standard with GStreamer.
Invoked without any arguments,
<programlisting>
$ gst-inspect
</programlisting>
will print out a listing of installed plugins.
To learn more about a particular plugin, pass its name on the command line.
For example,
<programlisting>
$ gst-inspect volume
</programlisting>
will give you information about the volume plugin.
</para>
<para>
Also, if you install the gst-editor package, you will have a graphical
plugin browser available, gst-inspect-gui.
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="using-bugs">
<para>Where should I report bugs ?</para>
</question>
<answer>
<para>
Bug management is now hosted on GNOME's Bugzilla at
<ulink url="http://bugzilla.gnome.org">http://bugzilla.gnome.org</ulink>,
under the product GStreamer.
Using bugzilla you can view past bug history, report new bugs, etc.
Bugzilla requires you to make an account here, which might seem cumbersome,
but allows us to at least have a chance at contacting you for further
information, as we will most likely have to.
</para>
<para>
When doing a bug report, you should at least describe
<itemizedlist>
<listitem>your distribution</listitem>
<listitem>
how you installed GStreamer (from cvs, source, packages, which ?)</listitem>
<listitem>if you installed GStreamer before</listitem>
</itemizedlist>
</para>
<para>
If you're new to GStreamer, it also is useful for us if you attach output of
the gst-feedback command to your bug report.
If you're having problem with a specific application (either one of ours,
somebody else's, or your own), please also provide a log of gst-mask by
running
<programlisting>
myapp --gst-mask=-1 > mask.log 2>&amp;1
gzip mask.log
</programlisting>
(interrupting the program if it doesn't stop by itself)
and attach mask.log.gz to your bug report
</para>
</answer>
</qandaentry>
<qandaentry>
<question id="using-gst-launch">
<para>How do I use the GStreamer command line interface ?</para>
</question>
<answer>
<para>
You access the GStreamer command line interface using the command gst-launch.
To decode an mp3 and play it through OSS, you could use
<programlisting>
gst-launch filesrc location=thesong.mp3 ! mad ! osssink
</programlisting>.
More examples can be found in the gst-launch man page.
</para>
<para>
To automatically detect the right codec in a pipeline, try
<programlisting>
gst-launch filesrc location=my-random-media-file.mpeg ! spider ! osssink
</programlisting>.
Try replacing osssink with sdlvideosink and see what happens.
</para>
<para>
We also have a simple tool called gst-launch-ext used for debugging,
which has predefined pipelines for you. This means you can just write
<programlisting>
gst-launch-ext (filename)
</programlisting>
and it will play the file if the extension is supported. Note that no effort
has been made for uninterrupted synchronized playback using this tool.
</para>
</answer>
</qandaentry>
</qandaset>
</sect1>