Commit 40948819 authored by Nicolas George's avatar Nicolas George

doc/faq: explain pkg-config basic setup.

parent 32c836cb
...@@ -90,6 +90,56 @@ To build FFmpeg, you need to install the development package. It is usually ...@@ -90,6 +90,56 @@ To build FFmpeg, you need to install the development package. It is usually
called @file{libfoo-dev} or @file{libfoo-devel}. You can remove it after the called @file{libfoo-dev} or @file{libfoo-devel}. You can remove it after the
build is finished, but be sure to keep the main package. build is finished, but be sure to keep the main package.
@section How do I make @command{pkg-config} find my libraries?
Somewhere along with your libraries, there is a @file{.pc} file (or several)
in a @file{pkgconfig} directory. You need to set environment variables to
point @command{pkg-config} to these files.
If you need to @emph{add} directories to @command{pkg-config}'s search list
(typical use case: library installed separately), add it to
@code{$PKG_CONFIG_PATH}:
@example
export PKG_CONFIG_PATH=/opt/x264/lib/pkgconfig:/opt/opus/lib/pkgconfig
@end example
If you need to @emph{replace} @command{pkg-config}'s search list
(typical use case: cross-compiling), set it in
@code{$PKG_CONFIG_LIBDIR}:
@example
export PKG_CONFIG_LIBDIR=/home/me/cross/usr/lib/pkgconfig:/home/me/cross/usr/local/lib/pkgconfig
@end example
If you need to know the library's internal dependencies (typical use: static
linking), add the @code{--static} option to @command{pkg-config}:
@example
./configure --pkg-config-flags=--static
@end example
@section How do I use @command{pkg-config} when cross-compiling?
The best way is to install @command{pkg-config} in your cross-compilation
environment. It will automatically use the cross-compilation libraries.
You can also use @command{pkg-config} from the host environment by
specifying explicitly @code{--pkg-config=pkg-config} to @command{configure}.
In that case, you must point @command{pkg-config} to the correct directories
using the @code{PKG_CONFIG_LIBDIR}, as explained in the previous entry.
As an intermediate solution, you can place in your cross-compilation
environment a script that calls the host @command{pkg-config} with
@code{PKG_CONFIG_LIBDIR} set. That script can look like that:
@example
#!/bin/sh
PKG_CONFIG_LIBDIR=/path/to/cross/lib/pkgconfig
export PKG_CONFIG_LIBDIR
exec /usr/bin/pkg-config "$@@"
@end example
@chapter Usage @chapter Usage
@section ffmpeg does not work; what is wrong? @section ffmpeg does not work; what is wrong?
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