![]() Hence OpenAL cannot be used for time difference of arrival calculations unless that functionality is added in separately. The distance to a sound source only translates into an amplitude effect (attenuation) and not a delay. OpenAL also fails to take into account sound propagation delays (the speed of sound is used for the Doppler effect only). ![]() In these cases a multiple listener model is required. The single listener model in OpenAL is tailored to a single human user and is not fit for artificial intelligence or robotic simulations or multiple human participants as in collaborative musical performances. ARB extensions have the prospect of being added to the core API after a period of time.įor advanced digital signal processing and hardware-accelerated sound effects, the EFX (Effects Extension) or environmental audio extensions (EAX) can be used. Extensions can be promoted to ARB (Architecture Review Board) status, indicating a standard extension which will be maintained for backwards compatibility. Individual vendors are thereby able to include their own extensions into distributions of OpenAL, commonly for the purpose of exposing additional functionality on their proprietary hardware. In order to provide additional functionality in the future, OpenAL utilizes an extension mechanism. There is also an 'ALUT' (Audio Library Utility Toolkit) library that provides higher level 'convenience' functions - exactly analogous to OpenGL's ' GLUT'. Unlike the OpenGL specification, the OpenAL specification includes two subsections of the API: the core consisting of the actual OpenAL function calls, and the ALC (Audio Library Context) API which is used to manage rendering contexts, resource usage and locking in a cross platform manner. From a programmer's perspective, very little additional work is required to make this happen in an existing OpenGL-based 3D graphical application. The net result of all of this for the end user is that in a properly written OpenAL application, sounds behave quite naturally as the user moves through the three-dimensional space of the virtual world. The rendering engine performs all necessary calculations as far as distance attenuation, Doppler effect, etc. Buffers contain audio data in PCM format, either 8- or 16-bit, in either monaural or stereo format. The listener object contains the velocity, position and direction of the listener, and the general gain applied to all sound. A source object contains a pointer to a buffer, the velocity, position and direction of the sound, and the intensity of the sound. The general functionality of OpenAL is encoded in source objects, audio buffers and a single listener. However, OpenAL Soft is a widely used open source alternative. Since 1.1, the implementation by Creative has turned proprietary, with the last releases in free licenses still accessible through the project's Subversion source code repository. While the OpenAL charter says that there will be an "Architecture Review Board" (ARB) modeled on the OpenGL ARB, no such organization has ever been formed and the OpenAL specification is generally handled and discussed via email on its public mailing list. ![]() It is now hosted (and largely developed) by Creative Technology with on-going support from Apple, Blue Ripple Sound via their Rapture3D OpenAL Driver, and individual open-source developers. After the demise of Loki, the project was maintained for a time by the free software/ open source community, and implemented on NVIDIA nForce sound cards and motherboards. OpenAL was originally developed in 2000 by Loki Software to help them in their business of porting Windows games to Linux. While the reference implementation later became proprietary, there are open source implementations such as OpenAL Soft available. OpenAL aimed to originally be an open standard and open-source replacement for proprietary (and generally incompatible with one another) 3D audio APIs such as DirectSound and Core Audio, though in practice has largely been implemented on various platforms as a wrapper around said proprietary APIs or as a proprietary and vendor-specific fork. OpenAL is an environmental 3D audio library, which can add realism to a game by simulating attenuation (degradation of sound over distance), the Doppler effect (change in frequency as a result of motion), and material densities. Its API style and conventions deliberately resemble those of OpenGL. It is designed for efficient rendering of multichannel three-dimensional positional audio. OpenAL ( Open Audio Library) is a cross-platform audio application programming interface (API). Proprietary since v1.1, LGPL before v1.1, BSD in early versions
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