Pulse Audio
- Abstraction layer for desktop audio
- Programmable behaviorv (API)
- Automatic Setup
- Flexibility
- Extensibility
- Protocols and networking
- Device drivers
- Sound processing
- Sample Cache
- Stream Management
- Time Management (latency)
- Power Saving
- Automatic Setup and Routing
- Desktop Integrations
- Compatibility Layers
- GUI for switching between different output/input devices
- Mixing table per application
- GUI for routing audio to remote device available in LAN
- Effects
- Compromise between latency and power saving
- Integration with any application, even if not compatible
- libpulse-simple: client library. Is a wrapper around libpulse.
- libpulse: client and server library. Provides "Asynchronous API" for applications.
- libpulsecommon: client and server library. Contains parts of libpulse that ar not part of the public API.
- libpulsecore: server library. Internal API for modules.
- modules: server extensions. Network protocols, device drivers, desktop integrations.
- Source <=> input HW device
- Source Output <=> Channel <=> input SW source
- Sink <=> Output device
- Sink Input <=> Audio playback stream <=> ex: application
- Core => 1 instance created at startup (1)
- Module <=> 1 loadable server extension (*)
- Client <=> 1 application connected to the PulseAudio server (*). Ex: media player
- Card <=> 1 physical audio device (*)
- Device: single input or output port on the card. One card can have several device ports. A port can be used by several devices on the same card
- Device: virtual device that represents an output or input device. Can have an arbitrary number of streams connected to it:
- HW device
- Virtual device or sink: represents a remote network device
- Monitor device: every sink gets automatically a monitor device (duplicate signal). Can be used to copy the signal somewhere else
- Stream: recording stream (source output) connected to source | playback stream (sink input) connected to an output device (sink)
- Application Stream: associated with a client
- Virtual Stream: not with a client. Represents a remote server or anything else.
- Sample cache is an in-memory storage for short names batches. Used for event sounds.
D-Bus API is too unstable and project has been abandoned
C API is better:
- Asynchronous API (libpulse): complicated, but complete
- Simple API (libpule-simple): easier, but synchronous.
Asynchronous API is designed around a main loop. User registers callbacks or can poll. Events can be either subscription events or stream events.