Audio System Basics Part II

Review Audio input/output (i/o) is generally handled through system extensions. Audio systems define the bounds of what is possible. Applications must be written to use specific audio systems. Applications communicate with hardware through the use of device drivers. The audio system in use determines what drivers are available to an application. Device drivers are usually located in the extensions folder.

Other Possibilities Proprietary ASIO

Proprietary Audio Drivers Proprietary audio drivers are generally designed to be used only by software from one company. ProTools is a prime example. Non-Digi applications must use a 3rd-party system to access Digi hardware. MOTU and Digital Performer.

ASIO The opposite of Proprietary. Audio Stream Input/Output (Steinberg) An example of what happens when OS developers fail to address certain computing features that many users want. 3rd-Party mediator between application and hardware Applications can be written to use ASIO as their “audio system.”

ASIO cont’d Applications communicate with an ASIO driver written for either a specific audio interface, or a family of interfaces made by a single manufacturer. Once ASIO has been chosen as the Audio Output, a pop- up menu appears asking you to select from a list of ASIO drivers contained in that application’s ASIO Drivers folder. The specific chosen ASIO driver communicates with a device driver in the extensions folder. Each ASIO-aware app has it’s own ASIO Drivers folder. Drivers must be copied and placed in each folder.

Audio Communication Software applications communicate with the audio system (extension), ASIO, or a proprietary driver. Drivers allow an audio system (extension) or application to communicate with a specific hardware interface. Settings for the system and interface are usually changed with a control panel, except for ASIO drivers. Settings for ASIO drivers are changed through the ASIO Drivers pop-up window in each application. Audio setup in an application usually involves choosing what audio driver you want to use as your audio out.

One Potential Problem Some audio device drivers are “single-client”—that is, only one application at a time can be using it. MOTU Firewire Audio, MOTU PCI-324 Audio, and Digidesign Direct I/O are all single-client. If one application is open and has selected any of these drivers, then another application cannot use them. If you try, you might find that neither app can use it. Since ASIO drivers and Sound Manager drivers both access the proprietary driver, the same limitations apply. The built-in sound out of the first four Mac’s are all hooked into the mixers as tape in.

Examples Sound Manager (Sound Manager Drivers) Peak (Sound Manager—direct to Driver, ASIO, MAS) Digital Performer (MAS Proprietary, ASIO, Sound Manager) ProTools and PT/LE (Proprietary) ProTools Free (Sound Manager) Max/MSP (Sound Manager, ASIO) Kontakt (Sound Manager, ASIO, MAS) Windows—future presentation

Homework Reading (All from Roads) –Ch. 1, Oversampling, pp (multiple-bit only) –Ch. 3, Background through Table-lookup Noise and Interpolating Oscillators, pp –Ch. 5, Subractive Synthesis, pp Pay attention to the Math!