http://en.wikipedia.org/wiki/Pro_Tools
"Pro Tools is a Digital Audio Workstation platform for Mac OS and Microsoft Windows operating systems, developed and manufactured by Digidesign, a division of Avid Technology. It is widely used by professionals throughout the audio industries for recording and editing in music production, film scoring, television and post production. Pro Tools has three levels of software; HD, LE, and M-powered. HD is the premier package and is an integration of hardware and software. The hardware includes an external A/D converter and internal PCI or PCIe audio cards with onboard DSP.
Fundamentally, Pro Tools is similar to a multitrack tape recorder and mixer, with additional features that can only be performed in the digital medium. The most highly specified version supports sample rates of up to 192 kHz and bit depths of 16 and 24 bit, opens WAV, AIFF, mp3 and SDII audio files and QuickTime video files, and features Time Code, tempo maps, automation and surround sound capabilities.
Most of Pro Tools' basic functions can be controlled within the Edit or Mix windows. The Edit window displays audio and MIDI tracks, and provides graphical representation of the information recorded or imported. Here, audio can be edited in a non-linear, non-destructive fashion to the level of individual samples. MIDI information can also be manipulated. The Mix window displays each track's fader channel and allows for the adjustment of a channel's volume and pan, as well as being the usual place to insert plug-in effects and route audio to and from different outputs and inputs.
Effects processing and virtual instruments in Pro Tools are achieved through the use of plug-ins, which are either processed by the DSP chips as TDM plug-ins, or the host computer as RTAS plug-ins."
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