Working on a new network transport for PulseAudio and ALSA

Intro Last few years I was working on Roc Toolkit, an open-source solution for real-time media streaming over the network. Due to lack of free time, we postponed release several times, but now it’s almost ready. This article is, inter alia, some kind of a pre-release announcement. You can read more about the project here. …

Ephemeral ports and SO_REUSEADDR

Ephemeral ports The ephemeral port range is a range of ports used by the kernel when the user wants the socket to be bound to a random unused port. In particular, bind, listen, connect, and sendto may automatically allocate an ephemeral port for AF_INET and AF_INET6 sockets. This behavior is described in the ip_local_port_range …

PulseAudio under the hood

Table of contents Preface About PulseAudio High-level components Key abstractions D-Bus API C API Protocols and networking Device drivers Sound processing Sample cache Stream management Time management Power saving Automatic setup and routing Desktop integrations Compatibility layers Server internals Module list GUI tools …

Using MiniSAPServer and MiniSAPListener for SAP/SDP

MiniSAPServer is a small program that periodically sends SAP/SDP messages, given a config file and destination address. I’ve prepared a complementary MiniSAPListener program which listens for SAP/SDP messages, and prints them to stdout or passes to a shell command. The source code is mostly extracted from PulseAudio RTP …

File locking in Linux

Table of contents Introduction Advisory locking Common features Differing features File descriptors and i-nodes BSD locks (flock) POSIX record locks (fcntl) lockf function Open file description locks (fcntl) Emulating Open file description locks Test program Command-line tools Mandatory locking Example usage Introduction …

Reusing UNIX domain socket (SO_REUSEADDR for AF_UNIX)

Unix domain sockets are a networkless version of Internet sockets. They have several advantages: Unix domain sockets are files, so file-system permissions may be used for them when one end is closed (e.g. process exits), SIGPIPE is delivered to another end performance may be up to 2x better See details here. Lack of …

Decoding and playing audio files in Linux

Table of contents Overview FFmpeg SoX ALSA (libasound) PulseAudio libsndfile Other libraries Notes Overview I was playing with various media libraries recently and have prepared several snippets demonstrating how one can decode and play an audio file in two separate steps. The source code is available on GitHub here and there. …

Xlib usage examples

Table of contents What is Xlib? Printing pressed keys Embedding window What is Xlib? Xlib (also known as libX11) is an X11 client library. It contains functions for interacting with an X server. This page provides several code snippets implementing complete X11 programs. Printing pressed keys The source code is available on …

Detecting USB devices with libudev

Below you can find code snippets that match USB devices using libudev. A good tutorial is available here: libudev and Sysfs Tutorial. Listing and monitoring USB devices The snippet first prints all detected USB devices, and then enters monitoring mode and prints USB devices when they are inserted or removed. Source code on …