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Audio/MPEG
==========

I have been building a fairly extensive MP3 library, and decided to write
some software to help manage the collection. It's turned out to be a rather
cool piece of software (incidentally, I will be releasing it under the GPL
shortly), with both a web and command line interface, good searching,
integrated ripping, archive statistics, etc.

However, I also wanted to be able to stream audio, and verify the integrity
of files in the archive. It is certainly possible to stream audio (even
with re-encoding at a different bitrate) without resorting to writing
interface glue like this module, but verification of the files was
clumsy at best (e.g. scanning stdout/err for strings), and useless at worst.

Writing Audio::MPEG was my solution for this problem. It it Perl module
interface to the MAD and LAME libraries for decoding/encoding MP3 files.

This module will allow a Perl program to verify an MP3 file (fixed and
variable bitrate), decode it into a high-resolution (24 bit) PCM stream,
apply filtering effects to the data (stereo->mono, fade in/out, equalizer),
transform that stream into an audio stream (M$ WAV, Sun AU, integer PCM,
floating point PCM), and finally encode a PCM stream as an MP3.

The interface is quite Perl-like, and treats the data stream as an opaque
blob of data (however it is simple to transform, using unpack and pack,
between the opaque data and a Perl array - recipes are given in the man
page).

It should be possible, given a reasonably modern computer, to
decode/filter/re-encode an MP3 file in real-time.

PLATFORM

This module has been tested under Linux 2.4.x (PowerPC and Pentium III),
and FreeBSD 4.3 (Pentium III). As both big and littlen endian machines
work, I anticipate no serious problems getting this module to work under
any of the Un*x variants (however, I have not tested it on a 64 bit integer
machine - there may be some problems there...)

In addition, being that I'm very down on Windows, I won't bother testing
on this platform. However, since both MAD and LAME should compile under
Windows, I'm guessing that this module could probably be coaxed to work.
If anyone out there does manage to get this working under Windows, please
let me know any special instructions, and I'll include this information.
Also, if there are any code changes, please send me the patches. Note:
if the libraries require patching, please send the patches to the respective
authors, and not me, as I'm not maintaining those libraries.

INSTALLATION

This module requires Perl 5.00503 or later.

Before this module may be installed, MAD and LAME libraries must be in
installed (see DEPENDENCIES below). The following instructions may not
be optimal for your installation, so please be sure to read the respective
installation notes for each library. In addition, before pulling your hair
out debugging this module, make sure both MAD and LAME work correctly
by using their supplied programs (madplay(1) and lame(1) respectively) and
verifying that those programs work as expected.

To install MAD (see DEPENDENCIES below) expand the MAD tarball, and
type the following in the MAD source directory:

    ./configure
    make
    make install

If you (like me) prefer shared libraries, add --enable-shared=yes to
the configure command.

To install LAME (see DEPENDENCIES below) expand the LAME tarball, and
type the following in the LAME source directory:

    ./configure --disable-gtktest --disable-analyzer-hooks --disable-decoder \
       --disable-decoder-layer1 --disable-decoder-layer2 --with-vorbis=no \
       --enable-brhist=no
    make
    make install

If you (like me) prefer shared libraries, add --enable-shared=yes to
the configure command.

To install this module type the following:

    perl Makefile.PL
    make
    make test
    make install

DEPENDENCIES

If you haven't figured it out yet, installation of this module will require
a C compiler...

This module requires these other libraries:

    MAD - MPEG Audio Decoder
    Version:  0.13.0 (beta) or later
    Location: http://www.mars.org/home/rob/proj/mpeg/

    LAME - Lame Ain't MP3 Encoder
    Version:  3.88 (beta 1)