Zirconium Linux From Scratch - Version r12.4-45-systemd

Chapter 13. Preparing FFMpeg and Support Libraries

Liba52-0.8.0

Introduction to Liba52

a52dec is a free library for decoding ATSC A/52 (also known as AC-3) streams. The A/52 standard is used in a variety of applications, including digital television and DVD.

This package is known to build and work properly using an LFS 12.4 platform.

Package Information

Optional

djbfft

Editor Notes: https://wiki.linuxfromscratch.org/blfs/wiki/a52dec

Installation of Liba52

Prepare a52dec by running the following commands: 

./configure --prefix=/usr           \
            --mandir=/usr/share/man \
            --enable-shared         \
            --disable-static        \
            CFLAGS="${CFLAGS:--g -O3} -fPIC"
make

To test the results, issue: 

make check

Now Install the package, as the root user: 

make install
cp a52dec/a52_internal.h /usr/include/a52dec
install -v -m644 -D doc/a52dec.txt /usr/share/doc/a52dec-0.8.0/a52dec.txt

Command Explanations

CFLAGS="${CFLAGS:--g -O3} -fPIC": This appends -fPIC to CFLAGS but use -g -O3 (the default of this package) instead of an empty string when CFLAGS is not set. This is needed to compile a52dec without runtime text relocation. Runtime text relocation is prohibited on x86_64 so -fPIC is strictly required. On 32-bit x86 runtime text relocation is allowed but it's insecure and it may waste physical RAM, so -fPIC is still better.

cp a52dec/a52_internal.h ...: Copying this header file into /usr/include/a52dec allows some other programs (such as xine-lib) to compile and link against a system installed a52dec.

Contents

Installed Programs: a52dec and extract_a52
Installed Library: a52dec.so
Installed Directories: /usr/include/a52dec and /usr/share/doc/a52dec-0.8.0

Short Descriptions

a52dec

plays ATSC A/52 audio streams

extract_a52

extracts ATSC A/52 audio from an MPEG stream

a52dec.so

provides functions for the programs dealing with ATSC A/52 streams