The Audio Plug-ins
|Definition of a Plug-in
A plug-in is a software unit, generally not functioning by itself, which
comes to be grafted on a more complex program and enhances the functions of
this welcoming program. Initially appeared on graphic creation software
like Photoshop with its filters, XPress with its Xtensions, the concept of
the plug-in was then transposed in the digital audio domain, with the
effects plug-ins (adding audio effects such as reverb to the MIDI/Audio
sequencers and the digital audio software) and more recently with the
instruments plug-ins (adding a synthesizer or a virtual sampler to its
Midi/Audio program). For the user the advantages are many: creation of a
modular software configuration, according to his needs, consequently
reducing the cost of its configuration. On the other hand the use of these
plug-ins require a powerful computer (Mac G3 or Pentium II 450 MHz
|Native or DSP
Each plug-in is composed of a whole of data-processing codes constituting a
sound processing module or a synthesis sound module. These codes are
written to be executed by:
- either DSP circuits being on a special card in PCI format located inside
the computer. In this case the plug-ins have a stand-alone processing, not
much depending on the power of the computer processor, but on the number
and power of these DSP circuits installed on the card. This gives a very
reliable professional quality system but rather expensive because of the
aquisition of the card. It is the case of the Digidesign Pro Tools systems,
the Creamw@re Pulsar system or more recently of the TC Works PowerCore
system and the UAD-1 by Mackie/Universal Audio.
- either the intern processor of the computer: it is the solution known as
"native". In this case the use of the plug-ins is related to the power of
the computer. The native solution has many advantages as the the lack of
DSP cards and more attractive prices, as well as a multitude of offers. But
this solution involves also risks when the total working power of the
computer is reached.This condition occurs in the case of an activity
overload occuring at the time of a multitrack recording with the reading of
other audio tracks when there is a certain number of plug-ins running. It
is for that reason some plug-ins writtenin native version are "limited" to
voluntarily limit the computing power necessary to the use of these
plug-ins. The result is: on very greedy algorithms like reverbs , the
difference in quality can be significant between a DSP version and the
native version of the same plug-in.
|The main formats of audio Plug-ins
Since the emergence of the Audio and Audio/MIDI softwares, the various
editors have shown their desire to each propose a personal format of
plug-ins of which these are the most common :
AudioSuite and RTAS :
The native format of Audiosuite effects plug-ins
launched by Digidesign uses an architecture of recalculation processing
and uses the computing power of the computer to apply postpone effects on a
sound file . This format is found in the following softwares: Audio Logic,
Peak and of course Pro Tools. With the arrival of Pro Tools 5 this format
evolved in real time format RTAS: Real Time AudioSuite.
This new format of "AudioUnit" plug-ins launched by Apple for
Mac OS X, might quickly become a standard in the world of the audio on the
Mac. This plug-in format, which has the advantage of being compatible with
any application of the system, uses Mac OS X?s CoreAudio. For the moment
only Logic Audio and in a soon to appear Digital Performer for Mac OS X
handles this format.
Direct X :
It is the more used standard of audio plug-ins on the Windows
platform and the following softwares: Cakewalk Pro Audio, Sound Forge,
Wavelab, Audio Quartz Master Pro, Acid, Samplitude etc.
Native format of 32 bits plug-ins created by Mark Of The Unicorn
(MOTU) intended for the company softwares meaning : Digital Performer and
AudioDesk. These quality plug-ins has the advantage of being able to be
used in real time or postponed.
Native format of effect plug-ins created by Adobe for the
virtual editing software Premiere. This format is recognized by the
sequencers Digital Performer, Logic Audio, Studio Vision in recalculation
and Peak in real time.
Format of real time audio Plug-ins created by Digidesign for Pro
Tools. It uses the DSP being on the hardware Pro Tools cards. It is a
professional format of quality at a substancial price.
Standard of real time native Plug-ins, , multi platform (Mac and PC
but warning! A PC VST plug-in does not function on Mac and vice versa) used
by a very great number of audio softwares: Cubase VST, Logic Audio, Studio
Vision, Sparks and SonicWORX and soon Peak. In addition the developer
Amulet proposes an adapter making it possible to use on PC any VST plug-in
with the applications using the Direct X format. Another developer on Mac
(AudioEase) had the same idea with VST Wrapper which makes it possible to
the users of DigitalPerformer to use any plug-in at the VST format.
|The " effect " plug-in
Most of the of the plug-ins used in the digital audio domain are effect
plug-ins which are the "software" equivalents of effect racks. The most
common effects are: reverbs, chorus, equalizers, compressors, delay etc.
Two main categories of plug-ins are to be distinguished:
Real time plug-ins
It is the most interesting category of plug-ins for the musician since it
makes it possible to listen in real time to all the modifications of the
sound that occur progressively.
The plug-ins that do not function in real time are known as recalculation
plug-ins. The principle is simple: the plug-in handles the sound of a
selected audio area and creates a new file containing the processed sound .
This new file comes to replace the original, which is not erased and can be
used elsewhere in the piece. This type of processing makes it possible to
save on the power of the host computer?s processor.
|The " instrument Plug-ins " or Virtual Instruments
Recently appeared,these softwares are the virtual equivalents of the
synthetizers, the expanders and the "hardware" samplers. They can take
various forms: "Tool Box" allowing to build its own modular synth,
multitimbral expander, Fender Rhodes electric piano, experimental sampler
etc. They can be used on a traditional computer (Mac or PC) rather than to
be integrated into a whole of electronic components which constitute an
"hardware" instrument. The interfacing is also virtual, since it is carried
out within the software domain (OS, sequencer MIDI + Audio etc). They are
controllable by MIDI, thanks to a master keyboard . They often ask a very
great consumption of the computer?s processor power, and need an important
RAM capacity to be used as a complement to the MIDI+ Audio sequencer.
There are two ways of using them:
- In "Stand alone" mode which means the synthetizer is launched like a
traditional software. In this case, it is it which manages the MIDI and
Audio inputs/outputs, it is independent of any other software and can be
MIDI controlled in by a master keyboard. In this case you can :
* either dedicate this instrument to a computer, and use a sequencer on another
computer connected to this one by MIDI,
* either at the same time use these virtual instruments with a MIDI + Audio sequencer as Cubase, Logic, or Digital Performer thanks to the ReWire 2.0 connection or the DirectConnect
connection with Pro Tools. The ReWire 2.0 connection is a technology
developed by Propellerhead Software, which makes it possible to transmit
the MIDI but also the audio datas between two compatible applications.
ReWire 2.0 becomes a true virtual cable being able to transport MIDI and
audio datas, of a virtual synthetizer towards a MIDI+ Audio sequencer. This
technology also makes it possible to synchronize these two applications.
The DirectConnect connection developed by Digidesign allows the same thing
with Pro Tools.
- In "Plug-In" mode : if you use a sequencer as Cubase, Logic, Digital
Performer, Pro Tools or Sonar to compose music, it is preferable to use
this method. You can install virtual instruments on the mixing board of
your sequencer with a simple click and you can control them by MIDI thanks
to a master keyboard. There are various proprietary formats of virtual
instruments in form of plug-ins: VSTi (VST instrument), DXi (DirectX
instrument), MAS 2.0, and RTAS:
* VSTi are used in Cubase, Logic (for Mac
OS 9) and all compatible VST sequencers
* DXi as for them are used in Sonar
or Sonar XL, and are in the Microsoft DirectX format
* The instruments in
the format MAS 2.0 are designed for the MOTU sequencer : Digital Performer
* The instruments in the format RTAS were created for the Digidesign?s
It is important to understand that to use these virtual instruments in an
optimal and comfortable way, it is necessary to use a well conceived audio
interface or audio card and an efficient driver (the ASIO 2.0 drivers are
often well suited). Otherwise you will have have to deal with an audible
latency time not suitable with a "live" use of these instruments. This
means mostly a delay between what is played and what is heard that gets
quickly unbearable when the instrument is played directly through a MIDI
keyboard. A good adjustment can be obtained by decreasing the number of
"sample per buffer" of the audio card drivers knowing that this reduction
requires an additional effort of the computer?s processor. As mentionned
earlier these virtual instruments often ask a very great consumption of the
computer?s processor, and need an important RAM to be used in complement of
MIDI+ Audio sequencer.
The virtual instruments families
"Sample player" synthetizers: These virtual instruments use sound samples
stored on the hard drive (then in RAM to be used in real time). These are
like multi purpose expanders or specialized in a particular style.
Examples: SampleTank, the PlugSound series, Edirol Hypercanvas etc.
"Modeling" synthetizers: The programmers of this kind of synthetizers try
to imitate analog instruments in the most faithful possible way. They
modelise for that purpose in a simplified way each electronic component (or
groups of components) of the analog instrument to be imitated, then connect
(always virtually) these components between them. The result is often
rather successful and close to the original. The first model to appear on
the market of this kind of virtual synth was Rebirth from Propellerheads
(imitation of TB-303 Roland?s TB 303), followed by many others synths or
vintage instruments (the products Native Instruments FM7, Pro53 or B4,
Bitheadz Retro AS-1 etc).
Virtual samplers: These virtual instruments emulate the hardware samplers
and you thus find on these instruments the functions of the hardware
samplers. The main difference with the "sampler player" synthetizers is
that the virtual samplers read about any kind of sample format (WAV, AIFF,
SDII or proprietary formats) and are compatible with the various banks of
sound samples which appear regularly on the market. Furthermore, they have
at their disposal many processing functions on the samples (in particular
filters). Examples of virtual samplers: HaLion, Kontakt, EXS24, Gigasampler
etc. NB: the difference between the sample players and the samplers is less
obvious in the virtual field than in the "hardware" world, insofar as one
of the great differences in the hardware world between the
synths/expanders and the samplers is the samples? storage capacity. Perhaps
the difference which still remains relates to the processing possibilities
of a sampler which are higher than those of sample player.
Virtual Drum machines, they are either dedicated samplers to the sounds of
drums and other percussion instruments, or specialized synthetizers in
modeling the sounds of drums or percussions. Examples of virtual drums
machines: Battery, Gamma 9000, Voodoo etc.
Virtual studios: These are all in one software, a kind of virtual rack
which contains all the devices that are found in an electronic music
studio: an analog synthetizer, a sampler, a drum machine, a loop player,
effects processors, a sequencer and a mixing board. Examples of virtual
studios: Reason, Studio 9000, Storm etc.
If you want to discover more informations and read all my articles (especially about midi) please come on my home page at: http://perso.club-internet.fr/clborne
Translated from french by Dominique ZBIEGIEL, aka DOMZ
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