A binding for the PulseAudio system library (libpulse).

About

This binding enables Rust projects to make use of the PulseAudio client system library. It builds upon the separate raw FFI crate to provide a more “Rusty” interface.

The documentation below and throughout this crate has been largely copied (under fair-use terms) from those in the PulseAudio C API header files, and adjusted where appropriate to fit any differences, thus it should not be too unfamiliar to those of you already familiar with the C API.

Introduction

The PulseAudio API comes in two flavours to accommodate different styles of applications and different needs in complexity:

• The complete but somewhat complicated to use asynchronous API.
• The simplified, easy to use, but limited synchronous API.

Simple API

Use this if you develop your program in synchronous style and just need a way to play or record data on the sound server. This functionality is kept in the separate libpulse-simple-binding crate. See that for details.

Asynchronous API

Use this if you develop your programs in asynchronous, event loop based style or if you want to use the advanced features of the PulseAudio API. A guide can be found in the mainloop module.

By using the built-in threaded main loop, it is possible to achieve a pseudo-synchronous API, which can be useful in synchronous applications where the simple API is insufficient.

Threads

The PulseAudio client libraries are not designed to be directly thread-safe. They are however designed to be re-entrant and thread-aware.

To use the libraries in a threaded environment, you must assure that all objects are only used in one thread at a time. Normally, this means that all objects belonging to a single context must be accessed from the same thread.

The included main loop implementation is also not thread safe. Take care to make sure event objects are not manipulated when any other code is using the main loop.

Logging

You can configure different logging parameters for the PulseAudio client libraries. The following environment variables are recognized:

• PULSE_LOG: Maximum log level required. Bigger values result in a more verbose logging output. The following values are recognized:
• 0: Error messages
• 1: Warning messages
• 2: Notice messages
• 3: Info messages
• 4: Debug messages
• PULSE_LOG_SYSLOG: If defined, force all client libraries to log their output using the syslog(3) mechanism. Default behavior is to log all output to stderr.
• PULSE_LOG_JOURNAL: If defined, force all client libraries to log their output using the systemd journal. If both PULSE_LOG_JOURNAL and PULSE_LOG_SYSLOG are defined, logging to the systemd journal takes a higher precedence. Each message originating library file name and function are included by default through the journal fields CODE_FILE, CODE_FUNC, and CODE_LINE. Any backtrace attached to the logging message is sent through the PulseAudio-specific journal field PULSE_BACKTRACE. This environment variable has no effect if PulseAudio was compiled without systemd journal support.
• PULSE_LOG_COLORS: If defined, enables colored logging output.
• PULSE_LOG_TIME: If defined, include timestamps with each message.
• PULSE_LOG_FILE: If defined, include each message originating file name.
• PULSE_LOG_META: If defined, include each message originating file name and path relative to the PulseAudio source tree root.
• PULSE_LOG_LEVEL: If defined, include a log level prefix with each message. Respectively, the prefixes "E", "W", "N", "I", "D" stands for Error, Warning, Notice, Info, and Debugging.
• PULSE_LOG_BACKTRACE: Number of functions to display in the backtrace. If this variable is not defined, or has a value of zero, no backtrace is shown.
• PULSE_LOG_BACKTRACE_SKIP: Number of backtrace levels to skip, from the function printing the log message downwards.
• PULSE_LOG_NO_RATE_LIMIT: If defined, do not rate limit the logging output. Rate limiting skips certain log messages when their frequency is considered too high.

Usage

Start by adding a dependency on the crate in your program’s Cargo.toml file. Note that it is recommended that you rename the crate such that you can refer to it by a shorter name within your code (such as pulse, as used within examples within this crate’s documentation). Such renaming can be done within your Cargo.toml file with cargo version 1.31 or newer, or otherwise with extern crate statements.

See sub-modules for further information.