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:
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, MidiKare and KarVCD 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.
· If what you intend is to create a karaoke VCD, then you should go to the KarVCD main page. KarVCD has the same features that MidiKare has but it also allows you to create AVI files and convert them to MPEG. These can be burn to a VCD that you can play on a CD or DVD player that is VCD compatible.
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.
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 KarVCD, to obtain an MP3 from the WAVE file.
If what you intend is to create a karaoke VCD, then you should use KarVCD. KarVCD has the same features that MidiKare has but it also allows you to create AVI files and convert them to MPEG. These can be burn to a VCD that you can play on a CD or DVD player that is VCD compatible.
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.
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.
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.
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.
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.
To create a karaoke VCD you need to get the MPEG file with the movie that contains the sound and the associated lyrics. The MPEG file is usually obtained by encoding an AVI file. The best way to get the AVI file is to use KarVCD. This program can extract the lyrics contained in a KAR file and combine them with a WAVE file into an AVI file. It can also create the WAVE file from a MIDI or KAR file.
Once you get the MPEG file, you can then use the software that came bundled with your CD-Writer to create the VCD. It is not enough to create a data CD with the MPEG file, your CD-burning software must be able to create the special format required by the VCD standard; not all CD-burning programs can do that.
Comments, suggestions and bug reports are welcome and should be sent to firstname.lastname@example.org
This page last modified 2003-07-28 - Copyright © 2000-2003 ACE