DOCSLIB.ORG

Audio in Embedded Linux Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Audio in embedded Linux systems Audio in embedded Linux systems Free Electrons 1 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Rights to copy © Copyright 2004-2009, Free Electrons [email protected] Document sources, updates and translations: http://free-electrons.com/docs/audio Corrections, suggestions, contributions and translations are welcome! Attribution ± ShareAlike 3.0 Latest update: Sep 15, 2009 You are free to copy, distribute, display, and perform the work to make derivative works to make commercial use of the work Under the following conditions Attribution. You must give the original author credit. Share Alike. If you alter, transform, or build upon this work, you may distribute the resulting work only under a license identical to this one. For any reuse or distribution, you must make clear to others the license terms of this work. Any of these conditions can be waived if you get permission from the copyright holder. Your fair use and other rights are in no way affected by the above. License text: http://creativecommons.org/licenses/by-sa/3.0/legalcode 2 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Scope of this training Audio in embedded Linux systems This training targets the development of audio-capable embedded Linux systems. Though it can be useful to playing or creating sound on GNU/Linux desktops, it is not meant to cover everything about audio on GNU/Linux. Linux 2.6 This training only targets new systems based on the Linux 2.6 kernel. This way, you leverage the most advanced technology and don©t learn about something getting obsolete. 3 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Contents (1) Introduction Advanced Linux Sound Glossary Architecture (ALSA) Audio codecs and file formats ALSA kernel drivers Kernel low latency requirements System perspective ALSA userspace interface System overview Sound servers 4 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Contents (2) Free Software audio Audio players for the embedded target Audio encoders Creating your own applications Miscellaneous Speech synthesis Audio distributions References 5 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Quick Glossary PCM: Pulse Code Modulation Digital audio encoding, representing the amplitude of a signal at uniform intervals. Codec: coder / decoder Program or device coding and / or decoding a data stream or a signal. MIDI: Musical Instrument Digital Interface. Standard to control electronic musical instruments. See http://wikipedia.org for details! 6 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Audio in embedded Linux systems Free Software Audio Audio codecs and file formats 7 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com MP3 MPEG-1 Audio Layer III The most popular. Users have lots from the Fraunhofer Society of files in this format. Lossy audio format Free Software encoders and decoders exist Bitrates from 32 to 320 kbit/s But relies on patented algorithms. Quality depends on the bitrate: Depending on which country you 128-192: good, 192-224: very sell to, you may have to pay for a good, 224-320: excellent license. Depends also pretty much on the Licenses can apply to encoding, encoder and on the source. decoding or even songs! Depends on the listener too! Ask for legal advice! See http://en.wikipedia.org/wiki/Mp3 for details 8 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com AAC Advanced Audio Coding Used on some on-line music stores MPEG-4 Audio (Apple iTunes) and portable players (Apple iPod). Standard format from the MPEG group: Dolby, Fraunhofer, AT&T, Also burdened by patents, like MP3. Sony, and Nokia License needed to encode and read this format. Lossy audio format Free Software decoders available. Designed to replace MP3. Consistently better audio quality Just one Free Software encoder than MP3 at lower bitrates. available (faac). Can be DRM encrypted (FairPlay). More details on http://en.wikipedia.org/wiki/Advanced_Audio_Coding 9 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com RealAudio From RealNetworks Free Software decoder available: http://realnetworks.com/ mplayer Mainly used for streaming, used by Lossy audio format a significant number of on-line Proprietary format media. Useful for mobile devices Designed for connecting to these media. very low bandwidth connections. Only proprietary encoders. Bitrates: 12 to 800 kbit/s RealNetworks encoder free of Now uses AAC at 128 kbit/s and charge only for personal use. more. Lossless format also supported More details on http://en.wikipedia.org/wiki/Real_Audio 10 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com WMA Windows Media Audio Now supported by more and more digital players and on-line music Microsoft proprietary, as a stores. Users may ask for WMA alternative to MP3 (patented by playing capability. somebody else) and now AAC. Lack of Free Software players Almost always encapsulated in an (except libavcodec) and Advanced Systems Format (ASF) encoders. file. Relies on patented algorithms. File extensions: asf or wma Licenses may apply to encoding, Supports constant and variable decoding or even songs, though MS bitrates, and lossless compression. is still very tolerant so far (to achieve Can be DRM encrypted. dominance). See http://en.wikipedia.org/wiki/WMA for details 11 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Ogg Vorbis From the Xiph foundation Growing in popularity. More and http://xiph.org/ more hardware players available. Ogg: container for multimedia Xiph.org releases libraries under a streams BSD-style license and GPL for tools. Vorbis: lossy audio format Various Free Software decoders Open, patent and royalty free! and encoders available. Supported by many proprietary players too. Bitrates from 45 to 500 kbit/s Variable bitrate Achieves better quality than MP3 at low bitrates. See for http://en.wikipedia.org/wiki/Ogg_vorbis details 12 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Ogg Speex From the Xiph foundation Constant or variable bitrate, http://www.speex.org/ from 2 to 44 kbit/s. Ogg: container Listen to samples on Usual file extension: .spx http://speex.org/samples/. Speex: lossy audio dedicated to Free Software encoder, speech encoding. decoders and applications available. Targets Voice over IP applications, voice mail Even supported by proprietary archival, audio books... tools (e.g. MS NetMeeting). Open, patent and royalty free! See http://en.wikipedia.org/wiki/Speex for details 13 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Flac http://flac.sourceforge.net/ Libraries available under a BSD- Supported by Xiph.org like license, and tools under the GPL. Lossless audio compression format Free Software players available. Compress audio files at no risk! Even starts to be supported by Preferred format for trading live hardware players. music on-line. Supports streaming. Ogg: also used as a container. Integer-only coder and decoder available. See http://en.wikipedia.org/wiki/FLAC for details 14 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Compression rate example comparison (1) Format / 64 kbit/s 128 kbit/s 192 kbit/s 256 kbit/s bitrate Wav 100.00% MP3 4.6% (22:1) 9.1% (11:1) 13.6% (7:1) 18.2% (5:1) (lame 3.96.1) Ogg Vorbis 4.3% (23:1) 8.5% (12:1) 12.7% (8:1) 17.7 % (6:1) (oggenc 1.0.1) Flac (flac 1.1.0) 56.30% bzip2 (1.0.2) 89.50% Source: Omara Portuondo, Flor de Amor (Cuban Salsa) 15 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Compression rate example comparison (2) Compression rate (same example) 120 100 Wav 80 MP3 Ogg Vorbis Flac 60 bzip2 40 20 0 64 kbit/s 128 kbit/s 192 kbit/s 256 kbit/s 16 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Audio in embedded Linux systems System perspective 17 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com Traditional system architecture App1 App2 App3 User applications (concurrent access to resources) Sound driver devices (/dev) Linux kernel Sound drivers Hardware 18 Free Electrons. Kernel, drivers and embedded Linux development, consulting, training and support. http//free-electrons.com OSS The Open Sound System http://www.4front-tech.com/oss.html Old sound card support system in Linux versions up to 2.4. Still used for some cards in 2.6 (porting to ALSA in progress). Originates from the Linux driver for the Sound Blaster 16 sound card. Extended to support other (often compatible) sound cards. Was also made available
Recommended publications
  • Proceedings 2005

    Proceedings 2005

    LAC2005 Proceedings 3rd International Linux Audio Conference April 21 – 24, 2005 ZKM | Zentrum fur¨ Kunst und Medientechnologie Karlsruhe, Germany Published by ZKM | Zentrum fur¨ Kunst und Medientechnologie Karlsruhe, Germany April, 2005 All copyright remains with the authors www.zkm.de/lac/2005 Content Preface ............................................ ............................5 Staff ............................................... ............................6 Thursday, April 21, 2005 – Lecture Hall 11:45 AM Peter Brinkmann MidiKinesis – MIDI controllers for (almost) any purpose . ....................9 01:30 PM Victor Lazzarini Extensions to the Csound Language: from User-Defined to Plugin Opcodes and Beyond ............................. .....................13 02:15 PM Albert Gr¨af Q: A Functional Programming Language for Multimedia Applications .........21 03:00 PM St´ephane Letz, Dominique Fober and Yann Orlarey jackdmp: Jack server for multi-processor machines . ......................29 03:45 PM John ffitch On The Design of Csound5 ............................... .....................37 04:30 PM Pau Arum´ıand Xavier Amatriain CLAM, an Object Oriented Framework for Audio and Music . .............43 Friday, April 22, 2005 – Lecture Hall 11:00 AM Ivica Ico Bukvic “Made in Linux” – The Next Step .......................... ..................51 11:45 AM Christoph Eckert Linux Audio Usability Issues .......................... ........................57 01:30 PM Marije Baalman Updates of the WONDER software interface for using Wave Field Synthesis . 69 02:15 PM Georg B¨onn Development of a Composer’s Sketchbook ................. ....................73 Saturday, April 23, 2005 – Lecture Hall 11:00 AM J¨urgen Reuter SoundPaint – Painting Music ........................... ......................79 11:45 AM Michael Sch¨uepp, Rene Widtmann, Rolf “Day” Koch and Klaus Buchheim System design for audio record and playback with a computer using FireWire . 87 01:30 PM John ffitch and Tom Natt Recording all Output from a Student Radio Station .
  • Free C Ulture Forum

    Free C Ulture Forum

    Free C ulture Free C ulture Forum March 23, 2006 11:30 am - 2:30 pm 450 Dodge Hall, Northeastern University PROGRAM Welcome Dani Capalbo NU Student, Class of 2010 Edward A. Warro Dean of Libraries Introduction of Panelists Marcus Breen Communication Studies Panelists Lawrence Lessig Derek Slater Nelson Pavlosky Will Wakeling Bios Additional Resources Lawrence Lawrence Lessig is a Professor of Law at Stanford Law School and founder of the school's The World Wide Web holds many examples of projects whose intent is to facilitate Center for Internet and Society. Prior to joining the Stanford faculty, he was the Berkman the sharing of ideas, scholarly research and creative works. Professor of Law at Harvard Law School and a Professor at the University of Chicago. He clerked for Judge Richard Posner on the 7th Circuit Court of Appeals and Justice Antonin Scalia on the United States Supreme Court. Professor Lessig represented web site operator Creative Commons (http://creativecommons.org/) is a nonprofit organization that Eric Eldred in the ground-breaking case Eldred v. Ashcroft, a challenge to the 1998 Sonny offers flexible copyright licenses for original works; creators may choose from a range Bono Copyright Term Extension Act. He has won numerous awards, including the Free of protections and freedoms. Software Foundation's Freedom Award, and was named one of Scientific American's Top 50 Visionaries, for arguing "against interpretations of copyright that could stifle innovation and Creative Commons Education (http://creativecommons.org/education/) helps with online discourse online." Professor Lessig is the author of Free Culture (2004), The Future of Ideas publishing of educational materials.
  • Enable USB Drivers on Linux

    Enable USB Drivers on Linux

    Enable USB drivers on Linux INTHISDOCUMENT · Enable USB driver on system with USBFS support · Enable USB driver on system without USBFS support · Additional notes for FTDI/XTAG debug adapters The XMOS tools interface to development boards using USB debug adapters. USB driver support is provided natively on Linux, but in some cases, the driver must be enabled. The method required to enable the driver depends on the Linux distribution you are using and the kernel version. Linux distributions known to provide USBFS support include: · Ubuntu 9.04 or older · Ubuntu 9.10 with kernel 2.6.31-19-server · CentOS 4.8 and 5.4 · Generally, any distribution with kernel version < 2.6.32 Linux distributions known to not provide USBFS support include: · Ubuntu 10.04 · Generally, any distribution with kernel version >= 2.6.32 1 Enable USB driver on system with USBFS support If your distribution provides USBFS support, use the following command to enable the Linux driver: · mount -t usbfs none /proc/bus/usb -o devmode=0666 To automatically enable the driver on boot, add the following line to the file /etc/fstab: none /proc/bus/usb usbfs defaults,devmode=0666 0 0 Publication Date: 2012/10/30 Document Number: X2612A XMOS © 2012, All Rights Reserved Enable USB drivers on Linux 2/3 2 Enable USB driver on system without USBFS support If you distribution does not provide USBFS support, you must configure udev to recognise the device. To configure udev, follow these steps: 1. Create a file /etc/udev/rules.d/99-xmos.rules with the following contents: SUBSYSTEM!="usb|usb_device", GOTO="xmos_rules_end" ACTION!="add", GOTO="xmos_rules_end" # 20b1:f7d1 for xmos xtag2 ATTRS{idVendor}=="20b1", ATTRS{idProduct}=="f7d1", MODE="0666", SYMLINK+="xtag2-%n" # 0403:6010 for XC-1 with FTDI dual-uart chip ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6010", MODE="0666", SYMLINK+="xc1-%n" LABEL="xmos_rules_end" The ATTRS, MODE and SYMLINK stanzas must be all on one line, as each rule can only be on one line.
  • CD/DVD Player

    CD/DVD Player

    4-277-895-11(1) CD/DVD Player Operating Instructions DVP-NS638P DVP-NS648P © 2011 Sony Corporation Precautions Notes about the discs Safety • To keep the disc clean, handle WARNING To prevent fire or shock hazard, do the disc by its edge. Do not touch not place objects filled with the surface. Dust, fingerprints, or To reduce the risk of fire or liquids, such as vases, on the scratches on the disc may cause electric shock, do not expose apparatus. it to malfunction. this apparatus to rain or moisture. Installing To avoid electrical shock, do • Do not install the unit in an not open the cabinet. Refer inclined position. It is designed servicing to qualified to be operated in a horizontal personnel only. position only. The mains lead must only be • Keep the unit and discs away changed at a qualified from equipment with strong service shop. magnets, such as microwave Batteries or batteries ovens, or large loudspeakers. installed apparatus shall not • Do not place heavy objects on be exposed to excessive heat the unit. such as sunshine, fire or the like. Lightning For added protection for this set • Do not expose the disc to direct CAUTION during a lightning storm, or when it sunlight or heat sources such as is left unattended and unused for hot air ducts, or leave it in a car The use of optical instruments with long periods of time, unplug it parked in direct sunlight as the this product will increase eye from the wall outlet. This will temperature may rise hazard. As the laser beam used in prevent damage to the set due to considerably inside the car.
  • Release Notes for Debian GNU/Linux 5.0 (Lenny), Alpha

    Release Notes for Debian GNU/Linux 5.0 (Lenny), Alpha

    Release Notes for Debian GNU/Linux 5.0 (lenny), Alpha The Debian Documentation Project (http://www.debian.org/doc/) November 11, 2010 Release Notes for Debian GNU/Linux 5.0 (lenny), Alpha Published 2009-02-14 This document is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2, as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; with- out even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. The license text can also be found at http://www.gnu.org/copyleft/gpl.html and /usr/ share/common-licenses/GPL-2 on Debian GNU/Linux. ii Contents 1 Introduction 3 1.1 Reporting bugs on this document . .3 1.2 Contributing upgrade reports . .3 1.3 Sources for this document . .4 2 What’s new in Debian GNU/Linux 5.05 2.1 What’s new in the distribution? . .5 2.1.1 Package management . .7 2.1.2 The proposed-updates section . .7 2.2 System improvements . .8 2.3 Major kernel-related changes . .8 2.3.1 Changes in kernel packaging . .8 2.4 Emdebian 1.0 (based on Debian GNU/Linux lenny 5.0) . .9 2.5 Netbook support .
  • Flexible Lustre Management

    Flexible Lustre Management

    Flexible Lustre management Making less work for Admins ORNL is managed by UT-Battelle for the US Department of Energy How do we know Lustre condition today • Polling proc / sysfs files – The knocking on the door model – Parse stats, rpc info, etc for performance deviations. • Constant collection of debug logs – Heavy parsing for common problems. • The death of a node – Have to examine kdumps and /or lustre dump Origins of a new approach • Requirements for Linux kernel integration. – No more proc usage – Migration to sysfs and debugfs – Used to configure your file system. – Started in lustre 2.9 and still on going. • Two ways to configure your file system. – On MGS server run lctl conf_param … • Directly accessed proc seq_files. – On MSG server run lctl set_param –P • Originally used an upcall to lctl for configuration • Introduced in Lustre 2.4 but was broken until lustre 2.12 (LU-7004) – Configuring file system works transparently before and after sysfs migration. Changes introduced with sysfs / debugfs migration • sysfs has a one item per file rule. • Complex proc files moved to debugfs • Moving to debugfs introduced permission problems – Only debugging files should be their. – Both debugfs and procfs have scaling issues. • Moving to sysfs introduced the ability to send uevents – Item of most interest from LUG 2018 Linux Lustre client talk. – Both lctl conf_param and lctl set_param –P use this approach • lctl conf_param can set sysfs attributes without uevents. See class_modify_config() – We get life cycle events for free – udev is now involved. What do we get by using udev ? • Under the hood – uevents are collect by systemd and then processed by udev rules – /etc/udev/rules.d/99-lustre.rules – SUBSYSTEM=="lustre", ACTION=="change", ENV{PARAM}=="?*", RUN+="/usr/sbin/lctl set_param '$env{PARAM}=$env{SETTING}’” • You can create your own udev rule – http://reactivated.net/writing_udev_rules.html – /lib/udev/rules.d/* for examples – Add udev_log="debug” to /etc/udev.conf if you have problems • Using systemd for long task.
  • C-Based Hardware Design of Imdct Accelerator for Ogg Vorbis Decoder

    C-Based Hardware Design of Imdct Accelerator for Ogg Vorbis Decoder

    C-BASED HARDWARE DESIGN OF IMDCT ACCELERATOR FOR OGG VORBIS DECODER Shinichi Maeta1, Atsushi Kosaka1, Akihisa Yamada1, 2, Takao Onoye1, Tohru Chiba1, 2, and Isao Shirakawa1 1Department of Information Systems Engineering, 2Sharp Corporation Graduate School of Information Science and Technology, 2613-1 Ichinomoto, Tenri, Nara, 632-8567 Japan Osaka University phone: +81 743 65 2531, fax: +81 743 65 3963, 2-1 Yamada-oka, Suita, Osaka, 565-0871 Japan email: [email protected], phone: +81 6 6879 7808, fax: +81 6 6875 5902, [email protected] email: {maeta, kosaka, onoye, sirakawa}@ist.osaka-u.ac.jp ABSTRACT ARM7TDMI is used as the embedded processor since it has This paper presents hardware design of an IMDCT accelera- come into wide use recently. tor for an Ogg Vorbis decoder using a C-based design sys- tem. Low power implementation of audio codec is important 2. OGG VORBIS CODEC in order to achieve long battery life of portable audio de- 2.1 Ogg Vorbis Overview vices. Through the computational cost analysis of the whole decoding process, it is found that Ogg Vorbis requires higher Figure 1 shows a block diagram of the Ogg Vorbis codec operation frequency of an embedded processor than MPEG processes outlined below. Audio. In order to reduce the CPU load, an accelerator is designed as specific hardware for IMDCT, which is detected MDCT Psycho Audio Remove Channel Acoustic VQ as the most computation-intensive functional block. Real- Signal Floor Coupling time decoding of Ogg Vorbis is achieved with the accelera- FFT Model Ogg Vorbis tor and an embedded processor both run at 36MHz.
  • Version 7.8-Systemd

    Version 7.8-Systemd

    Linux From Scratch Version 7.8-systemd Created by Gerard Beekmans Edited by Douglas R. Reno Linux From Scratch: Version 7.8-systemd by Created by Gerard Beekmans and Edited by Douglas R. Reno Copyright © 1999-2015 Gerard Beekmans Copyright © 1999-2015, Gerard Beekmans All rights reserved. This book is licensed under a Creative Commons License. Computer instructions may be extracted from the book under the MIT License. Linux® is a registered trademark of Linus Torvalds. Linux From Scratch - Version 7.8-systemd Table of Contents Preface .......................................................................................................................................................................... vii i. Foreword ............................................................................................................................................................. vii ii. Audience ............................................................................................................................................................ vii iii. LFS Target Architectures ................................................................................................................................ viii iv. LFS and Standards ............................................................................................................................................ ix v. Rationale for Packages in the Book .................................................................................................................... x vi. Prerequisites
  • The GNOME Census: Who Writes GNOME?

    The GNOME Census: Who Writes GNOME?

    The GNOME Census: Who writes GNOME? Dave Neary & Vanessa David, Neary Consulting © Neary Consulting 2010: Some rights reserved Table of Contents Introduction.........................................................................................3 What is GNOME?.............................................................................3 Project governance...........................................................................3 Why survey GNOME?.......................................................................4 Scope and methodology...................................................................5 Tools and Observations on Data Quality..........................................7 Results and analysis...........................................................................10 GNOME Project size.......................................................................10 The Long Tail..................................................................................11 Effects of commercialisation..........................................................14 Who does the work?.......................................................................15 Who maintains GNOME?................................................................17 Conclusions........................................................................................22 References.........................................................................................24 Appendix 1: Modules included in survey...........................................25 2 Introduction What
  • State of Linux Audio in 2009 Linux Plumbers Conference 2009

    State of Linux Audio in 2009 Linux Plumbers Conference 2009

    State of Linux Audio in 2009 Linux Plumbers Conference 2009 Lennart Poettering [email protected] September 2009 Lennart Poettering State of Linux Audio in 2009 Who Am I? Software Engineer at Red Hat, Inc. Developer of PulseAudio, Avahi and a few other Free Software projects http://0pointer.de/lennart/ [email protected] IRC: mezcalero Lennart Poettering State of Linux Audio in 2009 Perspective Lennart Poettering State of Linux Audio in 2009 So, what happened since last LPC? Lennart Poettering State of Linux Audio in 2009 RIP: EsounD is officially gone. Lennart Poettering State of Linux Audio in 2009 (at least on Fedora) RIP: OSS is officially gone. Lennart Poettering State of Linux Audio in 2009 RIP: OSS is officially gone. (at least on Fedora) Lennart Poettering State of Linux Audio in 2009 Audio API Guide http://0pointer.de/blog/projects/guide-to-sound-apis Lennart Poettering State of Linux Audio in 2009 We also make use of high-resolution timers on the desktop by default. We now use realtime scheduling on the desktop by default. Lennart Poettering State of Linux Audio in 2009 We now use realtime scheduling on the desktop by default. We also make use of high-resolution timers on the desktop by default. Lennart Poettering State of Linux Audio in 2009 2s Buffers Lennart Poettering State of Linux Audio in 2009 Mixer abstraction? Due to user-friendliness, i18n, meta data (icons, ...) We moved a couple of things into the audio server: Timer-based audio scheduling; mixing; flat volume/volume range and granularity extension; integration of volume sliders; mixer abstraction; monitoring Lennart Poettering State of Linux Audio in 2009 We moved a couple of things into the audio server: Timer-based audio scheduling; mixing; flat volume/volume range and granularity extension; integration of volume sliders; mixer abstraction; monitoring Mixer abstraction? Due to user-friendliness, i18n, meta data (icons, ...) Lennart Poettering State of Linux Audio in 2009 udev integration: meta data, by-path/by-id/..
  • Command-Line Sound Editing Wednesday, December 7, 2016

    Command-Line Sound Editing Wednesday, December 7, 2016

    21m.380 Music and Technology Recording Techniques & Audio Production Workshop: Command-line sound editing Wednesday, December 7, 2016 1 Student presentation (pa1) • 2 Subject evaluation 3 Group picture 4 Why edit sound on the command line? Figure 1. Graphical representation of sound • We are used to editing sound graphically. • But for many operations, we do not actually need to see the waveform! 4.1 Potential applications • • • • • • • • • • • • • • • • 1 of 11 21m.380 · Workshop: Command-line sound editing · Wed, 12/7/2016 4.2 Advantages • No visual belief system (what you hear is what you hear) • Faster (no need to load guis or waveforms) • Efficient batch-processing (applying editing sequence to multiple files) • Self-documenting (simply save an editing sequence to a script) • Imaginative (might give you different ideas of what’s possible) • Way cooler (let’s face it) © 4.3 Software packages On Debian-based gnu/Linux systems (e.g., Ubuntu), install any of the below packages via apt, e.g., sudo apt-get install mplayer. Program .deb package Function mplayer mplayer Play any media file Table 1. Command-line programs for sndfile-info sndfile-programs playing, converting, and editing me- Metadata retrieval dia files sndfile-convert sndfile-programs Bit depth conversion sndfile-resample samplerate-programs Resampling lame lame Mp3 encoder flac flac Flac encoder oggenc vorbis-tools Ogg Vorbis encoder ffmpeg ffmpeg Media conversion tool mencoder mencoder Media conversion tool sox sox Sound editor ecasound ecasound Sound editor 4.4 Real-world
  • Pipewire: a Low-Level Multimedia Subsystem

    Pipewire: a Low-Level Multimedia Subsystem

    Proceedings of the 18th Linux Audio Conference (LAC-20), SCRIME, Université de Bordeaux, France, November 25–27, 2020 PIPEWIRE: A LOW-LEVEL MULTIMEDIA SUBSYSTEM Wim Taymans ∗ Principal Software Engineer Red Hat, Spain [email protected] ABSTRACT 2. LINUX AUDIO LANDSCAPE PipeWire is a low-level multimedia library and daemon that facili- Audio support on Linux first appeared with the Open Sound System tates negotiation and low-latency transport of multimedia content be- (OSS) [6] and was until the 2.4 kernel the only audio API available tween applications, filters and devices. It is built using modern Linux on Linux. It was based around the standard Unix open/close/read- infrastructure and has both performance and security as its core de- /write/ioctl system calls. sign guidelines. The goal is to provide services such as JACK and OSS was replaced by the Advanced Linux Sound Architecture PulseAudio on top of this common infrastructure. PipeWire is media (ALSA) [7]from Linux 2.5. ALSA improved on the OSS API and agnostic and supports arbitrary compressed and uncompressed for- included a user space library that abstracted many of the hardware mats. A common audio infrastructure with backwards compatibility details. The ALSA user-space library also includes a plugin infras- that can support Pro Audio and Desktop Audio use cases can poten- tructure that can be used to create new custom devices and plugins. tially unify the currently fractured audio landscape on Linux desk- Unfortunately, the plugin system is quite static and requires editing tops and workstations and give users and developers a much better of configuration files.