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198 lines
8.4 KiB
Markdown
198 lines
8.4 KiB
Markdown
# Developing applications with GStreamer
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## How do I compile programs that use GStreamer?
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<!-- FIXME: update for windows, macOS, and meson build, get rid of libtool things -->
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This depends all a bit on what your development environment and target
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operating system is. The following is mostly aimed at Linux/unix setups.
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GStreamer uses the `pkg-config` utility to provide applications with the right
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compiler and linker flags. `pkg-config` is a standard build tool that is widely
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used in unix systems to locate libraries and retrieve build settings. If
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you're already familiar with it, then you're basically set.
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If you're not familiar with `pkg-config`, to compile and link a small
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one-file program, pass the `--cflags` and `--libs` arguments to `pkg-config`.
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The following should be sufficient for a gstreamer-only program:
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```
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$ libtool --mode=link gcc `pkg-config --cflags --libs gstreamer-1.0` -o myprog myprog.c
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```
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If your application also used GTK+ 3.0, you could use
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```
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$ libtool --mode=link gcc `pkg-config --cflags --libs gstreamer-1.0 gtk+-3.0` -o myprog myprog.c
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```
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Those are back-ticks (on the same key with the tilde on US keyboards),
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not single quotes.
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For bigger projects, you should integrate `pkg-config` use in your
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Makefile, or with autoconf using the pkg.m4 macro (providing
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`PKG_CONFIG_CHECK`).
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## How do I develop against an uninstalled GStreamer copy?
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It is possible to develop and compile against an uninstalled copy of GStreamer
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and its plugins, for example, against git checkouts. This enables you to test
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the latest version of GStreamer without interfering with your system-wide
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installation.
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There are two ways to achieve such a setup:
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1. [`gst-build`][gst-build] is our new meta-build module based on the
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[Meson build system][meson]. This is the shiny new option. It's fast and
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simple to get started with, but you will need a recent version of Meson
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installed. Just check out the git repository and run the `setup.py` script.
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Once the initial Meson configure stage has passed, you can enter an
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uninstalled environment by running `ninja uninstalled` in the build
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directory. This will make sure tools and plugins from the uninstalled build
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tree are used. Any problems, let us know.
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2. [`gst-uninstalled`][gst-uninstalled] is our traditional autotools
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and libtool-based uninstalled setup tool, but it requires a few extra steps,
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like manually downloading the needed GStreamer repositories. The
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[`create-uninstalled-setup.sh`][create-uninstalled] script automates this
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process. Run `create-uninstalled.sh` and follow its instructions to gain
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access to an environment where uninstalled GStreamer tools and plugins are
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used by default. Also, `pkg-config` will prefer uninstalled library copies
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over installed ones.
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Multiple uninstalled setups can be used in parallel, e.g. one for the
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latest stable branch and one for git master. Have a look at the
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[gst-uninstalled][gst-uninstalled] script to see how it determines which
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environment is used.
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[gst-build]: https://gitlab.freedesktop.org/gstreamer/gst-build/
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[meson]: http://mesonbuild.com
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[gst-uninstalled]: https://gitlab.freedesktop.org/gstreamer/gstreamer/tree/master/scripts/gst-uninstalled
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[create-uninstalled]: https://gitlab.freedesktop.org/gstreamer/gstreamer/tree/master/scripts/create-uninstalled-setup.sh
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## How can I use GConf to get the system-wide defaults?
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<!-- FIXME: Consider removing. GConf was deprecated half a decade ago -->
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GStreamer used to have GConf-based elements but these were removed in 2011,
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after `GConf` itself was deprecated in favor of `GSettings`.
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If what you want is automatic audio/video sinks, consider using the
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`autovideosink` and `autoaudiosink` elements.
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## How do I debug these funny shell scripts that libtool makes?
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When you link a program against uninstalled GStreamer using
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libtool, funny shell scripts are made to modify your shared object
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search path and then run your program. For instance, to debug
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`gst-launch`, try:
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```
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libtool --mode=execute gdb /path/to/gst-launch
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```
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If this does not work, you're probably using a broken version of
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libtool.
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If you build GStreamer using the Meson build system, libtool will not
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be used and this is not a problem. You can run `gdb`, `valgrind` or any
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debugging tools directly on the binaries Meson creates in the build
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directory.
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## Why is mail traffic so low on gstreamer-devel?
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Our main arenas for coordination and discussion are IRC and Gitlab, not
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the mailing lists. Join us in [`#gstreamer`][irc-gstreamer] on irc.freenode.net.
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There is also a [webchat interface][webchat-gstreamer]. For larger picture
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questions or getting more input from more people, a mail to the gstreamer-devel
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mailing list is never a bad idea, however.
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[irc-gstreamer]: irc://irc.freenode.net/#gstreamer
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[webchat-gstreamer]: https://webchat.freenode.net
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## What kind of versioning scheme does GStreamer use?
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For public releases, GStreamer uses a standard MAJOR.MINOR.MICRO
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version scheme. If the release consists of mostly bug fixes or
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incremental changes, the MICRO version is incremented. If the release
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contains big changes, the MINOR version is incremented. A change in the
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MAJOR version indicates incompatible API or ABI changes, which happens
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very rarely (the last one dates back to 2012). This is also known as
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[semantic versioning](http://semver.org).
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Even MINOR numbers indicate *stable releases*: 1.0.x, 1.2.x, 1.4.x, 1.6.x,
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1.8.x, and 1.10.x are our stable release series. Odd MINOR numbers are used
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for *unstable development releases* and *prereleases* which should only be
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used temporarily for testing; your help in testing these tarballs and packages
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is very much appreciated!
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During the development cycle, GStreamer also uses a fourth or NANO
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number. If this number is 1, then it's a git development version. Any
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tarball or package that has a nano number of 1 is made from git and thus
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not supported. Additionally, if you didn't get this package or tarball
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from the GStreamer team, don't have high hopes on it doing whatever you
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want it to do.
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## What is the coding style for GStreamer code?
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Basically, the core and almost all plugin modules use K\&R with 2-space
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indenting. Just follow what's already there and you'll be fine. We only require
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code files to be indented, header may be indented manually for better
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readability. Please use spaces for indenting, not tabs, even in header files.
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Individual plugins in gst-plugins-\* or plugins that you want considered
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for addition to these modules should use the same style. It's easier if
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everything is consistent. Consistency is, of course, the goal.
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One way to make sure you are following our coding style is to run your code
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(remember, only the `*.c` files, not the headers) through GNU Indent using the
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following options:
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```
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indent \
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--braces-on-if-line \
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--case-brace-indentation0 \
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--case-indentation2 \
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--braces-after-struct-decl-line \
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--line-length80 \
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--no-tabs \
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--cuddle-else \
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--dont-line-up-parentheses \
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--continuation-indentation4 \
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--honour-newlines \
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--tab-size8 \
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--indent-level2
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```
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There is also a `gst-indent` script in the GStreamer core source tree in the
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tools directory which wraps GNU Indent and uses the right options.
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The easiest way to get the indenting right is probably to develop against a git
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checkout. The local git commit hook will ensure correct indentation.
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Comments should be in `/* ANSI C comment style */` and code should generally
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be compatible with ANSI C89, so please declare all variables at the beginning
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of the block, etc.
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Merge requests should ideally be made against git master or a recent release.
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Please don't send patches to the mailing list. They will likely get lost there.
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See [How to submit patches][submit-patches] for more details.
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[submit-patches]: contribute/index.md#how-to-submit-patches
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## How do I get my translations included?
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I have translated one of the module .po files into a new language. How do I get it included?
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GStreamer translations are uniformly managed through the
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[Translation Project](http://translationproject.org). There are some
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instructions on how to join the Translation Project team and submit new
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translations at http://translationproject.org/html/translators.html.
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New translations submitted via the Translation Project are merged
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periodically into git by the maintainers by running `make download-po`
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in the various modules when preparing a new release.
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We don't merge new translations or translation fixes directly, everything
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must go via the Translation Project.
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