Linux command line basics audacity

Introduction

Recording a good podcast is as much about good voice training and delivery, as much as it is about the technology used to record it. As with other things, you only get better with practice.

In this article we will use Linux command line tools and optionally Audacity to create a quick, no-frills podcast with a background music track. The only other GUI-based tool we will manipulate, will be the ALSA Mixer . The mixer has a command-line interface too, but the GUI is intuitive and quicker. The emphasis is on quick turnaround.

If you are the type that attaches a quick voice message to an e-mail for impact, (“We simply must get this done by Friday!!”) then the podcast creation method outlined here should appeal to you.

If you are new to podcasting and audio mixer setups, the next few sections might be tedious. But towards the end of this article, we will see how quickly one can run down these steps so that you spend more time recording your message than wrestling with technology or complicated screens.

The Recording Setup

A stereo headset with a microphone works best for making or listening to podcasts; but do not despair if you have a desktop microphone and a pair of speakers. You can always upgrade your setup later. For now just make sure that the sound from the speakers does not directly reach the microphone and cause feedback.

Place the microphone towards the lower right of your mouth as you speak, away from your nose. This avoids breathing sounds getting captured. Minimizing ambient noise by choosing a quieter time of the day is also a good idea.

Recording Tips

All through the recording and mixing process, there are a couple of things to keep in mind.

First, stay above the noise floor. The signal should be recorded high enough to stay above the background noise and hiss. If your audio signals are like little, beautiful flowers growing in a grassy field, make sure their stalks are tall enough to tower over the field. Else you would lose the flowers in the prickly grass just as your audio signal would be lost in the background hiss and noise.

Second, stay below the clipping or overload level of the audio channels. If your audio channels were like open water canals, then overloading them past the clipping limit would have a similar undesirable effect on your audio experience as a canal overflowing its banks — puddles around your feet or a jarring quality to your sound.

Since sound level is a dynamic quantity, record your audio at a level of around 80% keeping some margin (or headroom) against clipping.

Setting up the Audio Mixer Connections

An audio mixer application helps us record our podcast by allowing us to mix various signal sources in the right proportion. You can bring up the sound mixer from the Linux start menu by getting into the Sound and Video category.

To those who are new to the red and green lights of the Linux ALSA mixer, let us run a quick intro. There are audio signal sources and there are destinations. An audio mixer allows you to route one or more sources after adjusting their relative levels to one or more destinations and achieve your project goal. The project goal might be listening to music — the destination in this case being a pair of headphones or speakers; or it might be a recording device, say, to capture a podcast as we will do presently.

Once the ALSA mixer or Kmix is up, select the Output tab. Make sure the Master output channel as well as the PCM channel is switched on (click over the green lights so they turn on) and their gains — the slider positions — are at the maximum.

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Linux Command Line Basics

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We have built this course for beginners who have no experience with the Linux system and the command-line interface.

In this course, you’ll learn the basics of the command line interface of a Linux server: the terminal and shell (GNU Bash). This course includes an introduction to files and directories in the Linux filesystem.

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Get Into the Shell

• Learn about the terminal user interface.
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Shell Commands

• Different kinds of shell commands that work with the terminal in different ways
• Use the Linux manual (manpages) to expand your knowledge of shell commands.

The Linux Filesystem

• Working with files and directories is a big part of using the shell.
• Learn basic commands for interacting with the filesystem.

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To take this course, you should have beginner-level experience in a programming languages such as Python or JavaScript. While this course does not involve doing any programming, it does use concepts that are familiar to the beginning programmer such as «function», «expression», and «string».

Note: This course is intended for beginners to the shell environment. If you have done shell scripting or other extensive use of the shell before, this course will probably be too introductory for you. You might want to check out our Configuring Linux Web Servers course.

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Audacity

The manual page and help for the audacity linux command. Audacity is a graphical audio editor.

Man page output

audacity(1) General Commands Manual audacity(1) NAME audacity - Graphical cross-platform audio editor SYNOPSIS audacity -help audacity -version audacity [-blocksize nnn] -test audacity [-blocksize nnn] [ AUDIO-FILE ] . DESCRIPTION Audacity is a graphical audio editor. This man page does not describe all of the features of Audacity or how to use it; for this, see the html documentation that came with the pro‐ gram, which should be accessible from the Help menu. This man page describes the Unix- specific features, including special files and environment variables. Audacity currently uses libsndfile to open many uncompressed audio formats such as WAV, AIFF, and AU, and it can also be linked to libmad, libvorbis, and libflac, to provide sup‐ port for opening MP2/3, Ogg Vorbis, and FLAC files, respectively. LAME, libvorbis, libflac and libtwolame provide facilities to export files to all these formats as well. Audacity is primarily an interactive, graphical editor, not a batch-processing tool. Whilst there is a basic batch processing tool it is experimental and incomplete. If you need to batch-process audio or do simple edits from the command line, using sox or eca‐ sound driven by a bash script will be much more powerful than audacity. OPTIONS -help display a brief list of command line options -version display the audacity version number -test run self diagnostics tests (only present in development builds) -blocksize nnn set the audacity block size for writing files to disk to nnn bytes FILES ~/.audacity-data/audacity.cfg Per user configuration file. /var/tmp/audacity-/ Default location of Audacity's temp directory, where is your username. If this location is not suitable (not enough space in /var/tmp, for example), you should change the temp directory in the Preferences and restart Audacity. Audacity is a disk-based editor, so the temp directory is very important: it should always be on a fast (local) disk with lots of free space. Note that older versions of Audacity put the temp directory inside of the user's home directory. This is undesirable on many systems, and using some directory in /tmp is recommended. On many modern Linux systems all files in /tmp/ will be deleted each time the sys‐ tem boots up, which makes recovering a recording that was going on when the system crashed much harder. This is why the default is to use a directory in /var/tmp/ which will not normally be deleted by the system. Open the Preferences to check. SEARCH PATH When looking for plug-ins, help files, localization files, or other configuration files, Audacity searches the following locations, in this order: AUDACITY_PATH Any directories in the AUDACITY_PATH environment variable will be searched before anywhere else. . The current working directory when Audacity is started. ~/.audacity-data/Plug-Ins /share/audacity The system-wide Audacity directory, where is usually /usr or /usr/local, depending on where the program was installed. /share/doc/audacity The system-wide Audacity documentation directory, where is usually /usr or /usr/local, depending on where the program was installed. For localization files in particular (i.e. translations of Audacity into other languages), Audacity also searches /share/locale PLUG-INS Audacity supports two types of plug-ins on Unix: LADSPA and Nyquist plug-ins. These are generally placed in a directory called plug-ins somewhere on the search path (see above). LADSPA plug-ins can either be in the plug-ins directory, or alternatively in a ladspa di‐ rectory on the search path if you choose to create one. Audacity will also search the di‐ rectories in the LADSPA_PATH environment variable for additional LADSPA plug-ins. Nyquist plug-ins can either be in the plug-ins directory, or alternatively in a nyquist directory on the search path if you choose to create one. VERSION This man page documents audacity version 1.3.5 LICENSE Audacity is distributed under the GPL, however some of the libraries it links to are dis‐ tributed under other free licenses, including the LGPL and BSD licenses. BUGS For details of known problems, see the release notes and the audacity wiki: http://wiki.audacityteam.org/wiki/Known_Issues To report a bug, see the instructions at http://wiki.audacityteam.org/wiki/Reporting_Bugs AUTHORS Project leaders include Dominic Mazzoni, Matt Brubeck, James Crook, Vaughan Johnson, Le‐ land Lucius, and Markus Meyer, but dozens of others have contributed, and Audacity would not be possible without wxWidgets, libsndfile, and many of the other libraries it is built upon. For the most recent list of contributors and current email addresses, see our web‐ site: http://www.audacityteam.org/about/credits/ audacity(1)

Help output

Usage: audacity [-b ] [-d ] [-h] [-t] [-v] [hang- vagy projektfájlnév. ] -b, --blocksize= legnagyobb lemezblokkméret beállítása bájtban -d, --decode= egy automatikusan mentett fájl visszafejtése -h, --help ez a súgó üzenet -t, --test öndiagnosztika futtatása -v, --version Audacity verzió megjelenítése

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