Audio File
Processing
Welcome to the Audio File Processing page. You
will find here some hints about the manipulation of the most common audio file
formats available on the Internet.
Jump to one
of the sections bellow, depending on which file manipulation you intend to
perform:
Converting WAVE or MP3 files to MIDI
Extracting WAVE files from Audio CDs
Converting MIDI to WAVE
MIDI stands
for Musical Instrument Digital Interface. It is a standard by which various
electronic musical instruments (such as keyboards, synthesizers, computer
soundcards, etc.) can communicate with each other. MIDI can be also used to
connect a computer to a musical instrument so that the computer can control the
instrument. For example, the computer can play the whole song on an electronic
instrument via MIDI. The information on how the song is played is stored in a
MIDI file.
Midi files
are a very compact for of audio data representation; the MIDI files
corresponding to an Audio-CD (650 Mb) would normally take just a few Kilobytes.
The main reason for being so is that most of the information is not really
contained in the MIDI file; it is assumed to be elsewhere.
In fact, a
MIDI file doesn’t contain any audio data; it’s just a bunch of commands for
sound generating equipment (synthesizers). These commands are like: “Play note
C using a guitar sound”; the equipment that executes these commands must know
how to generate the guitar sound.
Therefore
to obtain a WAVE from a MIDI file, one cannot really talk about “converting”
because the contents of the WAVE file will bear little relation to the MIDI
file. The correct term is “rendering”.
To render a
MIDI file you can use a hardware synthesizer like the one in your sound card,
or use a software only solution. MidiSyn and MidiKare are examples of the
latter.
If all you
want to do is to render a MIDI file to WAVE so that you can put it on an audio
CD or convert it to MP3, you have two options:
·
For a
simple program that will just convert your MIDI file to wave using a Sound Font
based softsynth you should go to the MidiSyn main page.
·
For a
more professional approach, you should go to the MidiKare main page.
MidiKare has the same Sound Font based softsynth that MidiSyn has but it also
allows you to use any standard MIDI synthesizer, soft or hardware based,
internal or external. Besides, it includes a series of tools that can be very
useful in this kind of work: A file player, a recorder, an audio mixer and an
MP3 converter.
For more
information on MIDI files, Sound Fonts and synthesis methods you can read the
very well organised and maintained FAQ for the alt.music.midi newsgroup, available here.
Converting .KAR to WAVE
Karaoke is
a very popular form of entertainment whereby people get to sing accompanied by
what can be best described as a virtual orchestra, provided by some electronic
sound reproducing equipment. Most systems also provide some way of showing, in
a synchronised way, the lyrics associated with the song, to guide people while
they sing.
.KAR files
provide this type of entertainment based on MIDI capable sound producing
devices. There are tons of these files all over the Net, and plenty of players
that use the soundcard of your computer.
.KAR files
are just plain MIDI files to which there has been added special features to
store the lyrics associated with the song.
To convert
a .KAR file to WAVE you can use MidiSyn for a basic
approach but the ideal tool is MidiKare. This
program has the ability to show the lyrics included in the .KAR file,
synchronised with the music. This allows you for instance to record yourself
singing while the .KAR file is playing and the lyrics are displayed in a
window. Then you can mix the vocal track with the sounds resulting from the
conversion of the .KAR file with a mixing tool. The resulting WAVE file can
then be recorded on an Audio-CD or you can use the MP3 tool, also included in
MidiKare, to obtain an MP3 from the WAVE file.
Converting
WAVE files to MP3
The WAVE
file format is the MS-Windows standard format for audio data. It affords a
CD-Audio like quality and has many variants but the most used is the
uncompressed 44.1 Khz/ 16 bit stereo, precisely the equivalent of CD-Audio.
Almost any
Windows program that manipulates audio information recognizes this file format.
Its main drawback is that the files are huge: each minute of sound takes about
10Mb.
Wave files
can be burn into a CD-R or CD-RW in CD-Audio format (see bellow) or converted
to MP3. The conversion to MP3 is lossy (will cause some audio data to be
dismissed) but the resulting file will be much smaller (usually by 1:10 factor)
while still maintaining very good sound quality.
To convert WAVE files to MP3 you can use the MP3 tool included in MidiKare.
Converting MP3 files to
WAVE
The MP3 file format is the Internet standard
for audio data interchange. It has been made popular by Napster and its
derivatives. This format uses lossy compression but it represents a very good
compromise between sound quality and file size. One minute of sound takes about
1 Mb, instead of 10Mb for the WAVE file format.
Most CD burning software accepts only files in
WAVE format when creating an Audio-CD. Each track in the Audio-CD corresponds
to a WAVE file. Therefore you need to convert your MP3 files to WAVE before you
can put them in a CD-audio that you can listen to in your hi-fi or your car.
To convert MP3 files to WAVE you can use the MP3 tool included in MidiKare.
Converting WAVE or MP3
files to MIDI
Short
answer: It cannot be done, you should forget about it. I’m sorry to disappoint
you. Long answer follows.
Converting
a WAVE file to MIDI is akin to recover a recipe from a baked cake: A specialist
can do it to a certain extent by trial and error, but there is not an automated
process of doing it.
In certain
cases it could even be impossible for a specialist: Imagine that the cake has a
very unusual ingredient that is not available to everybody; or in the case of a
WAVE file that the original artist used a customized instrument. It would be
very difficult for someone else to duplicate that sound.
There are
some programs that claim to perform this kind of conversion in a very limited
way. From what I hear from people who have tried them the results are not that
great.
You don’t
believe me? Look at what they say in the FAQ for the alt.music.midi newsgroup, available here.
Extracting WAVE files from
Audio CDs
It is
possible to create a WAVE file with the sound data corresponding to a track of
an Audio-cd. This process, called “ripping” maintains the sound quality of the
original.
Here you
have some examples of software that can be used to extract WAVE files from
audio-CDs:
¨
MPAction MP3 Tools available here. MPAction Rip'n'Coder
is a CDA files “Ripper” and an MP3 Encoder in one application. Allows the user
to rip and encode CD to MP3, CD to Wave or Wave to MP3.
¨
YAMP available here. YAMP is an award-winning
program for compressing audio WAV files and saving them in MP3 format. It
offers both constant and variable bit rate encoding, batch processing,
selection of existing or creation of new output folders, WAV and MP3 files
preview, creating or removing ID3 tags, filtering (both low-pass and high-pass
filters are available) and selection of output mode (mono, stereo or joint
stereo). YAMP also includes additional tools: WAV finder, MP3 to WAV converter
and CD ripper. In case you wonder: YAMP stands for Yet Another MP3 Program.
¨
Audiograbber available here. Audiograbber is a
beautiful piece of software that grabs digital audio from CDs. It copies the
audio digitally - not through the soundcard - which enables you to make perfect
copies of the originals. It can even perform a test to see that the copies
really are perfect. Audiograbber can also automatically normalise the music,
delete silence from the start and/or end of tracks, and send them to L3enc or
Fraunhofer acm codec for automatic creation of MP3's. This is also the only
CD-Ripper that can grab audio through both ASPI and MSCDEX calls. Note: It has
an MP3 encoder in a DLL.
Creating Audio CDs
To burn
audio data into a CD-R or CD-RW in CD-Audio format you need first to get the
WAVE files that will correspond to each track of your CD (There is however
software that can burn Audio-CDs directly from MP3 files, doing the conversion
to WAVE on the fly). See above for some of the more usual file conversions that
you may need.
You can
then use the software that came bundled with your CD-Writer to burn the CD in
CD-Audio format, compatible with your hi-fi system or car-stereo.
There are
alternatives to the CD-Writer software that you can use. Here you have some of
them:
¨
MP3Bee available here. Burn Audio CD's out of your MP3
music files with ease! Select some MP3 files and click Burn... That's all! The
CDs will be burned in high quality audio and can be played back in regular CD
players like Discmans and Stereo Towers. This easy-to-use program has a Windows
Explorer-style (drag 'n drop) interface, with built-in tools like an Audio
player and an ID3 tag editor.
¨
MP3 CD Maker available here. MP3 CD Maker burns MP3 files into audio
CDs so you can listen to them in ordinary CD players. It is very small, easy to
use and supports many popular CD recorders.
¨
CDcopy available here. Windows ripper/encoder.
¨
CDRWIN available here. Golden Hawk Technology offers two
different versions of its CD recording software whose first version was
released in 1995. For Windows 9x/ME/NT/2000 and Alpha NT CDRWIN features with a
graphic user-friendly interface. For users preferring the command line prompt
in DOS there is a DOS version of DAO (16- and 32-bit) that is
keyboard-controlled and is therefore easily integrated into your own
batch-oriented applications.
Feedback
Comments, suggestions and bug reports are welcome and should be sent to fadevelop@clix.pt
This page last modified 2003-03-15 - Copyright
© 2000-2003 ACE