Articles on Victor Gaydov

Roc Toolkit 0.4 + updated tutorial for live audio streaming

Sat, 15 Jun 2024 00:00:00 +0000

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What’s in this release

Roc Toolkit implements real-time streaming over unreliable networks like Internet and Wi-Fi, with high quality and low latency.

It can connect audio apps and devices across network, which run PipeWire, PulseAudio, bare ALSA, macOS CoreAudio, and Android. You can use it via C library, bindings, CLI tools, sound server extensions, and Android app.

Roc Toolkit 0.3 is out!

Wed, 22 Nov 2023 00:00:00 +0000

What’s new

Roc Toolkit implements real-time streaming over unreliable networks like Internet and Wi-Fi. It works on Linux and macOS and provides C library, CLI tools, modules for PulseAudio and PipeWire, and Android app.

The 0.3 release was focused on:

reducing minimum allowed latency
running in CPU-constrained environments
extending C API

Full changelog is available here.

Latency

To allow lower latencies, two changes were made:

All pipeline elements were reworked to accept arbitrary frame sizes. Earlier, some of them were using frames of fixed size which put limitations on the minimum possible latency.

Two C++17 projects open for contributions

Wed, 20 Sep 2023 00:00:00 +0000

Signal Estimator

This one implements a tool (both CLI and GUI) for measuring audio latency and glitches.

The idea behind the tool is simple: you have an audio loopback that connects audio output to audio input; the tool writes impulses to the output, waits until the same impulses are received from the input, and measures the delay or other properties.

I’m using this tool at work for measuring latency of various audio software. Here is an example of a real-world usage, a test bench for measuring latency of audio streaming between two boards over Ethernet:

Debian Linux on Dell XPS 15

Wed, 15 Mar 2023 00:00:00 +0000

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This is a small report and how-to on running Debian on Dell XPS 15 9520.

TL;DR:

on the whole, it works well
use Debian Bookworm or later
be aware of sound quality issues of built-in speakers on Linux
be aware of possible issues with dock station after hibernation

Installing Debian

First of all, open BIOS (press F12 after turning on) and adjust a few settings:

Updated tutorial for Roc 0.2

Mon, 27 Feb 2023 00:00:00 +0000

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UPDATE

You can find tutorial updated for 0.4.x release series in this article.

What’s new?

This article is an updated version of previous tutorial. An overview of the new release is available here.

There are two main changes that affect users:

PulseAudio modules moved to a separate repo and have their own build system and new build instructions.
Command-line tools now use universal URI notation for network endpoints and audio devices.

This table provides examples of old and new notation.

Roc Toolkit 0.2 released

Sun, 26 Feb 2023 00:00:00 +0000

What is Roc?

Roc is a toolkit for real-time streaming over unreliable networks. It works with desktop and embedded Linux, ALSA, PulseAudio, PipeWire, macOS, and Android.

For a quick intro, see project repo and two previous articles: 1, 2.

Summary

Full changelog is available here.

The main focus of this release was:

polishing C API
creating bindings for Go and Java
Android support
preparing internals for control and signaling protocols

We also created a small Android app.

A step-by-step tutorial for live audio streaming with Roc

Wed, 14 Aug 2019 00:00:00 +0000

Table of contents

UPDATE

You can find tutorial updated for 0.4.x release series in this article.

What is Roc?

Roc is an open-source toolkit for real-time audio streaming over the network. You can learn about the project here: overview, features, usage.

Among other things, Roc can be used as a network transport for PulseAudio, ALSA, or macOS CoreAudio, and connect audio applications and devices across the network. Roc has the following benefits in this case:

Roc 0.1 released: real-time streaming over the network

Tue, 28 May 2019 00:00:00 +0000

What is Roc?

I’m happy to announce the first release of Roc Toolkit, version 0.1.0!

Roc provides a C API for real-time audio transport. The user just writes a stream to the one end and reads it from another end. Roc, in turn, performs encoding and decoding, and, more importantly, deals with the problems related to the real-time delivery: counters network jitter and packet reordering, maintains constant latency, restores lost packets, compensates the clocks difference.

Working on a new network transport for PulseAudio and ALSA

Fri, 03 May 2019 00:00:00 +0000

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. The project scope is quite wide. It provides a general-purpose library and tools that can be used in numerous use-cases. However, to start with something feasible and practical, we decided to focus the first few releases on the home audio use-case.

Ephemeral ports and SO_REUSEADDR

Sun, 03 Dec 2017 00:00:00 +0000

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 section of the ip(7) man page.

This feature is not specified in POSIX but is available in many operating systems that implement BSD sockets, including Linux.

PulseAudio under the hood

Thu, 21 Sep 2017 00:00:00 +0000

Table of contents

Preface

I’m working on the Roc Toolkit open-source project, a development kit for realtime audio streaming over the network. You can read more about the project in these two articles: 1, 2.

Using MiniSAPServer and MiniSAPListener for SAP/SDP

Fri, 09 Dec 2016 00:00:00 +0000

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 receiver.

To send custom SAP/SDP messages, one should create two configuration files for MiniSAPServer, one with SAP configuration, and another with an SDP message.

File locking in Linux

Fri, 29 Jul 2016 00:00:00 +0000

Introduction

File locking is a mutual-exclusion mechanism for files. Linux supports two major kinds of file locks:

advisory locks
mandatory locks

Below we discuss all lock types available in POSIX and Linux and provide usage examples.

Reusing UNIX domain socket (SO_REUSEADDR for AF_UNIX)

Thu, 07 Jul 2016 00:00:01 +0000

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 SO_REUSEADDR

A socket file is created by bind(2) call. If the file already exists, EADDRINUSE is returned.

Decoding and playing audio files in Linux

Thu, 07 Jul 2016 00:00:00 +0000

Table of contents

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.

The following libraries are used:

Each snippet is a small program. There are two kinds of them:

SCons rebuilds generated source files every launch

Wed, 06 Jul 2016 00:00:00 +0000

Problem

In a large project that uses SCons, VariantDir, and source code generation, happens one of the following:

generated source files are rebuilt every time when scons is launched
if .sconsign.dblite is removed manually, scons crashes with the following trace:

OSError: [Errno 2] No such file or directory: '.sconsign.dblite':
  File "/usr/lib64/python2.7/site-packages/SCons/Script/Main.py", line 1372:
    _exec_main(parser, values)
  File "/usr/lib64/python2.7/site-packages/SCons/Script/Main.py", line 1335:
    _main(parser)
  File "/usr/lib64/python2.7/site-packages/SCons/Script/Main.py", line 1099:
    nodes = _build_targets(fs, options, targets, target_top)
  File "/usr/lib64/python2.7/site-packages/SCons/Script/Main.py", line 1297:
    jobs.run(postfunc = jobs_postfunc)
  File "/usr/lib64/python2.7/site-packages/SCons/Job.py", line 113:
    postfunc()
  File "/usr/lib64/python2.7/site-packages/SCons/Script/Main.py", line 1294:
    SCons.SConsign.write()
  File "/usr/lib64/python2.7/site-packages/SCons/SConsign.py", line 109:
    syncmethod()
  File "/usr/lib64/python2.7/site-packages/SCons/dblite.py", line 127:
    self._os_unlink(self._file_name)
Exception OSError: OSError(2, 'No such file or directory') in
  <bound method dblite.__del__ of <SCons.dblite.dblite object at 0x7fa287435c10>> ignored

Unfortunately, I was unable to reproduce this outside of my project.

Xlib usage examples

Tue, 05 Jul 2016 00:00:01 +0000

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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 GitHub: xlib_hello.c.

The snippet creates a new window and handles X11 events:

prints all received events to stdout
prints pressed keys into a graphical window
quits when the close button is pressed

Some documentation that was useful for me:

Detecting USB devices with libudev

Tue, 05 Jul 2016 00:00:00 +0000

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 GitHub: udev_monitor_usb.c

Example output:

$ ./a.out
usb usb_device exists 1d6b:0001 /dev/bus/usb/002/001
usb usb_device exists 046d:c05b /dev/bus/usb/002/002
usb usb_device exists 1d6b:0001 /dev/bus/usb/003/001
usb usb_device exists 1d6b:0001 /dev/bus/usb/004/001
usb usb_device exists 1d6b:0001 /dev/bus/usb/005/001
usb usb_device exists 1d6b:0002 /dev/bus/usb/001/001
usb usb_device    add 8564:1000 /dev/bus/usb/001/026
usb usb_device remove 0000:0000 /dev/bus/usb/001/026
^C

Listing USB storage devices

The snippet prints detected USB storage devices.

httpexpect.v1: end-to-end HTTP API testing for Go

Mon, 04 Jul 2016 00:00:00 +0000

httpexpect is a new Go package for end-to-end HTTP and REST API testing.

It provides convenient chainable helpers for building HTTP request, sending it, and inspecting received HTTP response and its payload.

Links:

The key point is that request construction and response assertions become concise and declarative:

// create httpexpect instance
e := httpexpect.New(t, "http://example.com")

// check that "GET /fruits" returns empty JSON array
e.GET("/fruits").
    Expect().
    Status(http.StatusOK).JSON().Array().Empty()

You can find more examples in the Quick Start.