Features
ALSA was designed to use some features which were not, at the time of its conception, supported by the Open Sound System (OSS):
- Hardware-based MIDI synthesis.
- Hardware mixing of multiple channels.
- Full-duplex operation.
- Multiprocessor-friendly, thread-safe device drivers.
ALSA has a larger and more complex API than OSS, so it can be harder to develop an application that uses ALSA as its sound technology. While ALSA may be configured to provide an OSS emulation layer, such functionality is no longer available in many Linux distributions.
Besides the sound device drivers, ALSA bundles a user space library for application developers who want to use driver features through an interface that is higher level than the interface provided for direct interaction with the kernel drivers; unlike the kernel API, which tries to reflect the capabilities of the hardware directly, ALSA's user space library presents an abstraction which remains as standardized as possible across disparate underlying hardware. This goal is achieved in part by using software plugins. For example, many modern soundcards or built-in sound chips don't have a "master volume" control; for these devices, the user space library instead provides a software volume control using the "softvol" plugin, and ordinary application software need not care whether such a control is implemented by actual underlying hardware or software emulation of such underlying hardware.
Read more about this topic: Advanced Linux Sound Architecture
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