Linux FormatMay 2021的目錄

Jonni Bidwell My RetroPie set up is losing me lots of hours. But I’ve also been mesmerised by magnetic marble tracks from a local maker in Bath. They’re laser-cut from wood with stylish living hinges for the curvaceous bits. A modern take on a childhood classic. Check them out at https://deepmake.io. Nick Peers My favourite Pi project was one I documented way back in LXF239 and 240: creating a multi-room audio system with Logitech Media Server and a Pi Zero running PiCorePlayer. It’s three years since I installed it, and I’m still listening to music through it every single day. Les Pounder For me the Raspberry Pi Pico has been a runaway success, more so now that I have the Maker Pi Pico board from Cytron. For $10 I have…

“Risk analysis considers the likelihood of a risk being realised and then multiplies it by the impact of it being realised to give a “level of risk”. For example, leaving your suitcase across the top of the stairs means there’s a risk that someone may trip over it. Not very likely, but the impact of falling down the stairs is likely to be substantial (and painful!). In short, don’t do it. The likelihood of a data centre catching fire is very low, but the impact is likely to be very high. There’s little you can do (unless you’re a data centre owner) to manage the risk of fire breaking out, but you can mitigate the impact. Some people don’t have data backups that are independent of the data centre. Hopefully…

Steam Link (released in 2018) is now available for Linux devices courtesy of Flathub (you can download it from http://bit.ly/LXF275SteamLink), enabling you to stream games from another PC running Steam to that device. This is handy if you have a Linux-powered PC hooked up to your main TV, but your gaming PC is elsewhere in the house. With Steam Link, you can stream games from your gaming PC to the Linux device. Because the software streams the games from the powerful PC, it means that you can play games on devices that would usually be too underpowered to play them, and it’s great to see Linux devices now supported, along with Windows and Android devices. Attaching a game controller to the device gives you a pretty impressive experience, but while…

“This month’s main topic is a nasty data corrupting bug that struck during the course of Linux 5.12 development (and thankfully was caught before the final release). While hopefully very rare, data corrupting bugs can and do occur. The worst are those that affect the block and file systems because they not only corrupt data while it’s being used, but also destroy copies on disk. If such bugs are subtle, and take some time to be detected, things can be worse. The worst-case scenario would probably be backups ruined by virtue of slow data corruption that results in copies stored to long-term archives being in some way compromised. To avoid this, modern filesystems are increasingly turning to aggressive checksums and background “scrubbing” of volumes to look for inconsistencies. I’ve always…

Q Confused network card I’ve been using Linux Mint Cinnamon flavour for many years. I recently decided to update from version 18.3 to the latest 20.x version. I went through the procedure of going from 18.x to 19.0, then to 19.3 finally to 20.0 ensuring that I had backups and snapshots readily available. The update to version 20 failed abysmally, with no network connection and to make matters worse, substantial loss of data. I reverted to 19.3 but still had problems. The cause was eventually traced to the kernel in use as follows: Linux kernel 5.0.0-32-generic amd64 (End of Life) Everything works OK, network connects. Linux kernel 5.3.0-70-generic amd64 (End of Life) Everything works OK, network connects but shows battery symbol, “Using battery power"! Linux kernel 5.4.x-xx-generic amd64 (all versions)…

By and large, we’ve grabbed the latest, stable version of each Digital Audio Workstation (DAW). However, with music software on Linux, it’s quite often the case that the version in the official distribution repository is badly out of date. In these cases, it’s often worth checking out the latest beta, and that’s what we’ve done in the case of MusE and Ardour. We’ve installed each application and put it through its paces by using it for musical recording and composition tasks such as loading up multitrack projects and playing around with plug-ins. Having a bit of experience with the software in question is important because evaluating the feature list doesn’t give you an insight into what it’s like to try to create something with it, and music software is creative…

If you see an interesting-looking piece of Linux music software, make sure that it’s still being supported. There are many old projects that look good, but that have been abandoned by the developers. Rosegarden (www.rosegardenmusic.com) is a traditional-looking, but fully featured, MIDI sequencer with basic audio support plus scoring facilities, which is an important consideration for some. Reaper (www.reaper.fm) is a low-priced DAW that’s widely used by hobbyist musicians, and you can get the Linux build for free by hunting around on the Reaper forums. However, it’s not an official release and it’s still in beta, as of yet. Some people report good success in getting Windows DAW software working on Linux (including the Windows version of Reaper) with reasonable performance. If you’re willing to try this because you’ve got…

Multi-room audio systems can cost a pretty penny, but who needs to buy an expensive set of wireless speakers when you can use some Raspberry Pis and any 3.5mm wired speakers to achieve the same effect? We’ll use our Pi 4s and speakers/receivers (with 3.5mm audio inputs) to play music from a streaming service perfectly in sync via Bluetooth from our phone, tablet or computer. We’ll show you how to do this with a single speaker and Raspberry Pi and then replicate it in other rooms. This is an excellent project for repurposing old receivers. If you have a non-Bluetooth receiver with a 3.5mm jack input, you can connect your speakers to your receiver and your receiver to your Raspberry Pi. Instead of Raspberry Pi OS, we’ll use BalenaSoundOS to…

Register now for the Coolest Projects 2021 Individual and team entries are now open so you can show off your amazing builds to the world! Open to everyone in the world up to the age of 18, Coolest Projects showcases any and all projects created by young makers across the globe. Registration is already under way and you have until Monday 3 May to sign up for any of the contest’s six categories: hardware, Scratch, mobile apps, websites, games and advanced programming. Projects don’t even need to be completed by the registration data, Coolest Projects is all about celebrating the creation process of projects as much as finished creations. As always with the Raspberry Pi Foundation, this event is backed up with a host of learning materials and live broadcasts.…

OpAmp production is a highly competitive market. This leads to excellent datasheets and useful component selection web pages. If you feel like learning more about the magic of OpAmps, visit Analog Devices, Texas Instruments, or STMicroelectronics and see what options are available. Cheap commodity multimeters usually come with limited documentation. Lygte-Info from Denmark provides detailed analysis of low-end products. Visit https:// lygteinfo.dk/info/ DMMDesign Protection UK.html and click through to learn more. Interactions between test equipment and the device under test are a interesting phenomenon. An old Austrian adage states that the brain of the metrologist must never be switched off during metrology. Keep this in mind if something is behaving oddly, or it might be your multimeter or oscilloscope that’s affecting the circuit’s operation.…

At the risk of overextending an already slightly dubious metaphor, Kubernetes (k8s) is fast becoming the operating system of the cloud. But how did we get to this point? And how do complicated projects migrate to it? We were lucky enough to chat to Patrick McFadin, VP of developer relations at Datastax and K8ssandra (an open source, cloud-native distribution of Apache Cassandra) developer. As far as projects go, they don’t come much more complicated than the Cassandra database, it powers everything from Facebook to Netflix to the New York Times. In the past, deploying Cassandra required an expensive team of eggheads and some equally expensive infrastructure. Now, thanks to Astra – Datastax’s managed Cassandra offering – anyone can have a go. There’s even a free tier for those looking to…

In Logo we used commands to move around the screen. For example, FORWARD and LEFT. But we can shorten these commands for ease of use. FD and LT perform the exact same functions. At any time in microM8 we can click in the top-left corner of the screen, where a floppy disk icon will appear and load a menu. From here we can change applications, reboot the machine or switch to a totally different computer. Both of versions of BASIC on the Apple ][ come with tab completion – something we take for granted on Linux. Type in the first few letters of a command and you’ll see a suggestion appear. Press TAB to complete.…

IMAGE EDITOR Photoflare Version: 1.6.6 Web: https://github.com/PhotoFlare/photoflare There are several categories of open source image editors. Usually we recommend Gimp for advanced users, Krita for digital artists and a whole variety of Paint-like tools for basic drawing, cropping and other common tasks. There’s certainly a gap in the market for a beginner-friendly photo editor that’s simple to use, but contains advanced options should you need them. If you’re struggling to think of a program that meets these requirements, then struggle no more as we take a look at Photoflare, a feature-rich open source image editor for Linux. Photoflare looks like an advanced image viewer, but it’s designed for editing images instead of merely browsing them, and is ideal for quick edits and enhancements. The main window’s toolbar has an extended…

For general-purpose fluorescence photography you need a moderately high-powered UV torch. You should buy a so-called near longwave UV light source because these are fairly cheap, and because medium- and shortwave UV (as required, for example, to get some minerals to fluoresce) is more harmful. Although you’ll probably want to experiment with lots of special effects, there’s also a case for focusing on one. Many pro photographers have done this: perfected a single technique and then made it their signature style. Deliberately blurring a photo requires a moderately long exposure, but there’s a limit to how long you can achieve, even with a small aperture, if it’s a bright day. If you can’t get anywhere close to the one second we suggest, try using one or more neutral density filters…

Setting up a multiplayer game requires a client/server configuration. Open the ip_port_to_connect.txt file and alter the second line to include your player’s name or alias. The third line will be the IP address of the computer running the server program, and line four will be the port the server program is running on, awaiting connections. The first line will have to be changed from ‘no’ to ‘yes’ if you want to enable multiplayer. Launch server.py on the server machine, then get the client(s) to connect to it. If all goes well, we’ve got a multiplayer game up and running. You’ll see “Connected? Yes” on both the client and the server console if the connection was successful. We hard-coded this information into a configuration file for testing purposes The next step…

Choosing between using C and a programming language such as Go, Python or Ruby for creating system utilities isn’t a straightforward decision. If speed is your main concern then C might be the better option. Otherwise, use a programming language that will increase your productivity. A great book for learning about development in UNIX is The UNIX Programming Environment. Two other helpful books for developing system utilities are Advanced Programming in the UNIX Environment and The Linux programming interface. Although all these books use C, they’re great guides on how the UNIX OS operates.…

I remember people used to talk about market disrupters and truly the Raspberry Pi was just that. In a world that looked like it was falling into a corporate-owned walled garden of locked-down “smart” devices, like the Apple iPad and Google Nexus phones, came 10 thousand bare-naked Raspberry Pis that happened to run Linux. Who’d be mad enough to want to buy one of those? Forty million Pi sales later and here we are… It’s not like the Raspberry Pi was unique as a device. Beagle and Arduino had similar single-board computers, but at much higher prices and without necessarily the software backing it up. At the time I read a lot of Pi criticism pointing out the better specs of competing devices, while completely ignoring the software and price…

AMD and Microsoft have both announced the launch of its Secured-core Server initiative which, according to AMD’s announcement (http://bit.ly/LXF275AMDSec), will help you “boot securely, protect your device from firmware vulnerabilities, shield the operating system from attacks and prevent unauthorised access to devices and data with advanced access controls and authentication systems.” Meanwhile, Microsoft’s own announcement (http://bit.ly/LXFMicrosoftSec) reveals that Secured-core Sever “is built on three key pillars: simplified security, advanced protection, and preventative defence.” With a device running Secured-core Server, it can boot securely and avoid any firmware vulnerabilities, while protecting the OS from attacks or unauthorised access. As the AMD blog post explains, “The firmware and bootloader can load freely with the assumption that these are unprotected code and knowing that shortly after launch the system will transition into a…

Things were looking up following the slow start to this development cycle when seemingly out of the blue Linus sent a follow-up email titled “A note on the 5.12-rc1 tag.” In it, he provided a warning about a data-corrupting bug that had snuck through. This particular one affected those using swap files (but not swap partitions, which are still generally the default option in common use) and it affected them badly by destroying the filesystem they were stored on. Like most other operating systems, Linux uses the concept of “swapping” (or perhaps more technically correct “paging”) less recently used data out to disk when there’s a memory crunch that necessitates freeing up some RAM. Because application memory is “virtual” in nature, every access by a program to its memory goes…

Linux uses a system called ALSA to interface with the sound card, but most Linux music applications also support JACK (JACK Audio Connection Kit). This is a layer that sits on top of that, and it’s a key aspect of the Linux audio ecosystem. JACK is used to plug one music program into another and to keep multiple applications in sync with each other. MusE, Qtractor and Ardour are fully JACK enabled applications. Waveform and LMMS have only basic JACK support, using it for simple audio and MIDI input and output. Waveform became a bit unstable when constantly reassigning the JACK inputs while running, so it’s best to just use it as intended. Using a fully JACK-enabled program like Ardour, you could send audio from a track, have it affected…

We do love the Raspberry Pi here at LXF Towers. And so do our digital colleagues at tomshardware.com, home to our Pi User’s Les Pounder. So with their help we’ve selected the finest Pi projects for you to enjoy. We’ve got something to inspire everyone, from retro gaming to home security, or even artificially intelligent object classification. The Raspberry Pi is the perfect device for learning Linux. Its official operating system is based on Debian Linux and there’s even a build of Ubuntu for it. The Pi 4 is powerful enough that it can happily replace your desktop, and small enough that you can hide it behind the back of your monitor. If that’s not small enough, there’s always the Pi Zero, which is perfect for budding Internet of Things…

Pimoroni’s Picade arcade cabinets have a long history of quality. Coming as a laser-cut, self-assembly kit in eight- or ten-inch screen sizes, Picade is easy to build and can be used with all models of Raspberry Pi, but for best results you’ll want a Raspberry Pi 4. Because Picade uses common arcade components, it can be customised to meet your playing style and aesthetics. If you like microswitched buttons and joystick then you can easily swap to get the edge in your favourite game. The Picade X HAT attaches to the GPIO of your Raspberry Pi and provides connections for the controls, USB-C power management and an audio DAC connected to a 5W speaker for authentic arcade audio. Everything you need to build your own arcade cabinet – just add…

For especially young children, even those for whom using a block-based language might be a step too far, Bee-Bot from www.ttsgroup.co.uk (£59.94) or their Blue-Bot (£83.94) might be of interest. Referred to as programmable floor robots, and typically used with floor mats that the robots can be programmed to navigate, these devices don’t have to be programmed via a programming language at all. Instead, they can be programmed by pressing buttons on the robot’s body. So, for example, if you press the Clear button, followed by Forward twice, Right turn, Forward and Go, the robot will move forward by 300mm (2 x 150mm), turn right by 90 degrees, and finally move forward by 150mm, with a short pause between each step. While this certainly isn’t programming as we normally use…

It’s 2012. I had been a stay-at-home, home-schooling mum for 15 years already. The kids have grown up. Time for me to figure out what I would do with the rest of my life. In a time B.C. (before children) I’d been a C developer but in the tech world 15 years away is an eternity. The web revolution happened while I was home, both the original web and Web 2.0. I hadn’t coded anything in an eternity. Then I heard of this little board coming out of the UK meant for kids who were interested in computers. I ordered two (for my teenagers, obviously). The Raspberry Pis arrived in Canada between Christmas and New Year. I’m sorry to say they were a bust. I was unable to get anything…

Scratch is much more than just for making games. We can also use the GPIO from Scratch 3.0. In the bottom left of the screen there’s a blue folder icon. Click this to open the Extensions menu. Scroll down to Raspberry Pi GPIO and click to install. This adds another set of blocks to the menu. Next we need to connect an LED, 330 Ohm resistor to a breadboard, and using two male-to-female jumper wires connect to the GPIO (see download for a detailed diagram). In Scratch go to Events and drag When Green Flag Clicked into the coding area. Then from Control drag repeat 10 . From the Raspberry Pi GPIO drag set gpio 0 to output high and place it inside the loop. Change the 0 to 17…

An operational amplifier wants to have a voltage difference of zero between inverting and non-inverting input. Inputs being inputs, the OpAmp can’t affect the voltages present. Instead, it modifies the output and hopes that a feedback circuit supplied by the developer enables it to achieve its goal. In the case of our buffer circuit, the situation is simple. The output voltage is equal to the voltage at the terminal Vminus – given that the input voltage is applied to Vplus, setting Vout to Vplus satisfies the condition. Fortunately, using operational amplifiers usually doesn’t require a deep level of technical knowledge. In many cases, it’s enough to take a well-known application circuit and modify the values of the passives. A common example for this would be an adder, subtractor, inverting or…

Distributed computing isn’t something that comes naturally to most people, but the benefits, particularly to databases, are enormous. We let Patrick tell all. “Cassandra is a distributed system and I think most distributed systems come with a bit of a tax. We’ve built systems around this idea that CPU and memory are expensive resources that we have to manage carefully, and we build systems on a single servers. “Most of my career I was building things on a single server that might talk to another server for some interaction. Even though my background was in distributed computing, most of what I had to manage was on a single server. When we start talking to systems administrators about distributed systems it takes some work for us to start thinking in terms…

Choose View shortcuts from the More actions menu to reveal a slew of handy shortcuts to speed up navigating Jitsi. For example, W toggles tile view on and off, while D enables you to quickly switch between video and screen sharing. If you’re running a WordPress website and would like to extend Jitsi meeting rooms to your site’s members, then install the free Buddymeet plugin (https:// wordpress. org/plugins/buddymeet), which makes it easy to embed conference rooms into your site via shortcodes. You’ll find documentation for Jitsi Meet at https:// jitsi.github.io/ handbook. Use the Getting Started and User Guides to learn more about Jitsi’s key features, and the Self-Hosting Guide if you want to host your own Jitsi server.…

Constraints are useful when you want to keep objects in alignment. Locate the Snap icon in the top bar to limit movements to the resolution of the current grid. Movement can be limited to a single axis by pressing the x, y and z keys. Blender is a complex tool. If you want to get good with it, work through tutorial examples. Then come back later and try to do it all again from memory. If you see an interesting 3D object online, try to recreate it in Blender using the skills you have. If there’s something you do a lot of in Blender, it’s worth learning the keyboard shortcuts. If you can’t find a particular function, hit F3 to search all functions.…

Blender is free software. We used a 2.9 series (current stable) build for this tutorial. Our advice is to visit the Blender website and compare the latest release (www.blender.org) with the version in your distribution’s repository. You can go cutting edge, if you’re really curious about the latest features, but that option isn’t for the faint of heart. The safest possible option is to look at the LTS (Long Term Support) version (www.blender.org/download/lts), which will receive updates without changing significantly for two years after release. Blender can also be installed using the Snap system and it’s even available (for free) via Steam. Blender underwent major changes to its layout starting with the 2.8 series, so bear that in mind when looking up information.…

There are many other ways to emulate an Apple II. On Linux we can use LinApple (http://linapple.sourceforge.net), which is an open source Apple II emulator. It does require installation of a few extra packages, chiefly those to build the source files into an executable, but there’s plenty of help in the INSTALL and readme file. Raspberry Pi fans can use a version of LinApple for Raspberry Pi OS called Linapple-pie (https://github.com/dabonetn/linapple-pie) and there’s also a version for Windows (https://github.com/AppleWin/AppleWin). One thing to note on these emulators is that they’re all quite old, with some last receiving an update in 2015. This isn’t too much of a worry, but something to bear in mind. If your interest in the Apple II is purely game related then you’re once again in luck…

It might sound obvious if we were to say that shadows are black but, paradoxically, they aren’t always, and this is key to an artistic effect. For although shadows will be black if there’s just a single light source, if there are multiple light sources – each a different colour and illuminating a subject from a different angle – then each light will colour the shadows cast by the other lights. What’s more, if those lights are red, green and blue, the subject will be illuminated in the three primary colours. It’ll appear fairly naturally coloured, in total contrast to the bizarrely coloured shadows. Alternatively, you might find that concentrating just on the shadows and omitting the object(s) that cast them could provide an impressive and commonly abstract result. Like…

Confluence is only one of the services you can connect OnlyOffice with. You are also able to use OnlyOffice Docs with other popular sync and share platforms like Nextcloud, Alfresco, ownCloud, Seafile, Plone, SharePoint, Liferay, HumHub and many others. You can install the free version of OnlyOffice’s online editors or choose the scalable commercial build and then just connect the editors with the required service using ready-to-use integration tools. If you need professional editing features for a family-size team, opt for Home Server, a special tariff plan that’s intended specially for noncommercial home use. Detailed information about OnlyOffice Docs can be found on the official website: www.onlyoffice.com.…

You can use Go to perform the same tasks as Python 3 because Go is well suited to systems programming. The logic behind a Go version of the Python 3 utility discussed here is the same: you traverse the entire directory tree and keep visiting all directories, including symbolic links to directories, until there’s no directory left to visit. Go offers the filepath.Walk() function for traversing directory trees. However, filepath.Walk() doesn’t traverse symbolic links, so to avoid cycles we need to specifically tell the Go utility to visit symbolic links to directories by calling filepath.Walk() more times. The IsDir() method of the os package (https://golang.org/pkg/os) enables you to identify directories whereas the FileMode data type makes it possible to determine whether you’re dealing with a symbolic link or not. Finally,…

ENCHANTING DISTRO MIN SPECS: 2GB RAM, 20GB DISK Mageia 8 Mageia’s roots go way back to Mandrake and Connectiva in the late 90s, which merged to become Mandriva in the 2000s, which Mageia became a fork of in 2010. If you remember any of Mageia’s pioneering predecessors, you’ll probably find their echoes in Mageia. Perhaps in the thoughtfully customised KDE desktop (others are available) or the undeniably useful Mageia Control Centre. Mageia has a friendly installer that will have your system ready in a matter of minutes. One slightly odd thing is that users aren’t set up until after you reboot into the new OS. Then you get to make accounts for root and a regular user. Mageia doesn’t use sudo to elevate privileges, so you might need to get…

For years the Wayland display server protocol has looked like it would become a mainstream alternative to the X Window System. Yet a prime-time release always seemed one year away… Recent moves by some big industry names means that Wayland’s time could finally be upon us. The team behind the Ubuntu distro has announced that they’ll once again be attempting to use Wayland as the default session. While this has previously been attempted with Ubuntu 17.10, the team now feels confident that “now is the right time to try again,” with an aim of using Wayland as default in an LTS (Long Term Support) version. With the GNOME version of Ubuntu not being upgraded in this cycle, the team believes this will make things easier. However, in a forum post…

“KernelCI has been driving continuous integration for the Linux kernel with hundreds of commits every day since its creation in 2012 and as a Linux Foundation project since 2019. The platform can help you find and fix several problems, including regressions, build failures and merge conflicts from your patches with others. Today, KernelCI is the most complete automated testing and continuous integration tool for the Linux kernel. It can test your code on many platforms performing automatic builds in kernel trees. Builds, tests information and more can be found in its dashboard. Over the past year, the KernelCI dashboard has changed in many points, transitioning from checking basic boot reports to starting to check more advanced test reports. This has opened the way to an increased focus on testing, more…

The Fedora distro’s goal of moving from Python 2 to Python 3 is getting tantalisingly close, with the Python 2 Dropping Database (http://bit.ly/LXF275P2DD) noting that 99 per cent of Python packages in Fedora Rawhide are now using Python 3. With Python 2 entering its End of Life on 1 January, 2020, there has been a concerted effort to move popular tools in Fedora to Python 3. While this 99 per cent milestone is certainly impressive, there are still some noticeable holdouts still using Python 2, such as the Chromium browser, GIMP, SeaMonkey and Trac. There are also several ‘idle’ packages that have yet to be ported to Python 3. The Python 2 Dropping Database is asking volunteers to grab a package and help port these over to Python 3. Hopefully…

“In December, CentOS announced a new approach called CentOS Stream. Rather than having specific releases and long-term support (LTS), the new approach is based on a continuous stream of updates. Support for CentOS will end in December 2021, putting its End of Life before CentOS 7 in July 2024. Implementing a continuous update approach will help some users. For others, the reduced support for CentOS 8 will affect their future plans. Community backlash has been significant. In the world of open source, the ability to fork a project and support the community is a massive strength. Already, multiple forks of CentOS have been started, to address the gap. Changes in licences have affected data projects, also leading to forks. Organisations rely on free and open source projects. When terms change,…

Features landing in Linux 5.12 will include support for “dynamic thermal and power management”, which “is a technique to dynamically adjust the power consumption of different devices in order to ensure a global thermal constraint”. This will allow, for example, future mobile/laptop SoCs (chips) to better coordinate power use of different chip components to avoid overheating and excessive fan use. There are more advanced solutions to this perennial computing problem, but this is a useful start. 5.12 also removes support for a number of legacy platforms (and the drivers that are unique to those platforms) that no longer have active users. These include TI’s “c6x” which this author always meant to play with and never did. Perhaps the life lesson here is to procrastinate more often (my wife very likely…

We’d love to try and answer any questions you send to lxf.answers@futurenet.com, no matter what the level. We’ve all been stuck before, so don’t be shy. However, we’re only human (although many suspect Jonni is a layabout), so it’s important that you include as much information as you can. If something works on one distro but not another, then tell us. If you get an error message, please tell us the exact message and precisely what you did to invoke it. If you have, or suspect, a hardware problem, let us know about the hardware. Consider installing hardinfo or lshw. These programs list the hardware on your machine, so send us their output. If you’re unwilling, or unable, to install these, run the following commands in a root terminal and…

Not much music gets made these days without heavy use of computers, and the majority of new music that you hear on the radio was made 100 per cent ‘in the box’. That is, the sounds that you hear were either recorded into a computer and processed with software, or in the case of synthesiser sounds, entirely created inside a computer. Fortunately, Linux sports some highly professional software in this area. When recording at Abbey Road, The Beatles graduated from two- to four- and then eventually eight-track recording, and they used a special, echoey room with a microphone and a speaker to simulate reverberation. With a reasonably modern computer and some of the Digital Audio Workstation (DAW) software that we’ll be looking at here, you can create almost unlimited numbers…

Q tractor has a MIDI editor that’s clear and extensively featured with loads of the traditional MIDI sequencer tools such as rescaling, quantising, randomising and normalising. It’s a shame that, like LMMS, it lacks step-entry of notes, a feature that Waveform Pro, MusE and Ardour do have. MusE also has a dedicated mode for editing percussion tracks, as does Ardour. Ardour is a bit disappointing in the MIDI realm, with an awkward workflow. It’s good enough for, say, playing in a piano track and then making corrections, but creating a piece of trance music (an example of a style that requires a lot of editing of individual MIDI notes) with Ardour would soon become an exercise in frustration. Waveform Pro is probably the equal of Qtractor and MusE for pure…

Last issue’s monitoring feature showed how your PC’s CPU temperature could be displayed and graphed by a Pi with an LCD display. For this project we’ll take that idea a step further, and measure a range of environmental variables. Thermistors and most other components that measure such factors, are analogue in nature. So they’re not immediately suitable for the Pi, which only has digital (GPIO) inputs. However, thanks to HATs like the GrovePi, it’s easy to get your Pi talking to analogue sensors. We used a high accuracy temperature and humidity sensor, a soil moisture meter, a light sensor, but much more are available and getting them working with GrovePi is super easy. We won’t cover setting up the Pi (any model will do), but you’ll probably want to get…

Sonic Pi (https://sonic-pi.net) is described as a code-based music creation and performance tool. The tool runs under Raspberry Pi OS (it was developed in conjunction with the Raspberry Pi Foundation), as well as Windows and MacOS. It’s also referred to as a live coding environment. This means that performers write code on the fly to create music as they’re performing. We might think of it as enabling a digital jam session. Where things differ, though, is that it’s common to project the live code onto a screen during performances so the audience can share in the coding experience. It’s used by professional artists, but it also has educational value, especially for kids to whom its creative application appeals. According to its developer Sam Aaron, writing for MagPi magazine, “Sonic Pi…

Getting more value out of our little multimeter can be achieved by a variety of steps. Incidentally, selecting more accurate resistors isn’t high on the bucket list – in modern metrology, temporal stability beats accuracy every time. Instead, making maximum use of the ADCs input range would be nice. Use a more modern operational amplifier with rail-to-rail capabilities to achieve improvements in this area. Given that we already have an operational amplifier in our circuit, why not use an adder to expand the multimeter to being able to measure negative voltages. If you have an input range of, say, -1.5 V to +1.5 V, adding +1.5V yields an ADC range of 0 to 3V. Alternatively, “levitate away” the ground potential of the Raspberry Pi Pico to offset it from the…

By default, Jitsu will host all your video chats on its own meet.jit.se platform, but it’s equally at home providing you with the tools you need to build your own secure conferencing server, too. There are several compelling reasons to do so (other than the obvious – “why not?”). Aside from the privacy angle, self-hosted Jitsi servers can be configured specifically for your needs – for example, you can set up a secure domain that requires authenticated users to start new meetings to prevent drive-by users from hosting their own meetings for free at your expense. Crucially, self-hosted Jitsi servers aren’t too taxing on your hardware – they’re run by Jitsi Videobridge, which simply forwards all audio and video feeds directly to participants rather than mixing them first – that…

In the 1980s as the home computer market boomed (and eventually went bust) there was one language that dominated every machine. BASIC (Beginners’ All-purpose Symbolic Instruction Code) was the Python of the era. It was easy to read, write and could be ported across machines with very little effort. At the time there were thousands of books on the market, each offering the skills and knowledge of BASIC that we sought. Yet of all these books it was the Usborne/Scholastic books series that captured the imagination of a generation, including this author. These books taught us the syntax of BASIC via games and puzzles served up via a comic book. These books are available via auction sites, sometimes for a bargain price but often for extortionate prices. So if you…

The phrase “special effects” in photography can mean different things to different people. For some it means using an app on a phone to distort your selfie or, perhaps, to add a dog’s nose and tongue to your face. Others use PC software or smartphone apps to generate a range of pre-determined effects with a press of a button. However, there’s plenty of scope for applying effects using photo-editing software such as GIMP. This is our theme here but with one key caveat. Our emphasis is on effects that’ll exercise your grey matter rather more than, for example, just adjusting the Hue in an image’s HLS colour definition to introduce some bizarre colours. We don’t say that from a patronising or disapproving viewpoint but, quite simply, because if anything is…

A striking technique is to desaturate the background to an object in a scene, the end result being a black and white photograph with one or more objects appearing in colour. To generate this effect, you only need the one photograph, but it’s important to recognise scenes where this technique works well. All rules have their exceptions but, in the main, this effect is particularly effective in scenes that contain a single object – or perhaps just a few – that are predominantly a single bold colour, such as the novice Buddhist monk in our example. In GIMP, open your photo and open another copy of it as a second layer. Now convert one of the layers to a black and white image by reducing the saturation using the Colours>Saturation…

Most UNIX utilities are written in C or in machine code – this part of the tutorial explains the basic C system calls for working with the UNIX filesystem as well as directories and for visiting all files and directories under a given root directory. The most important system call is opendir(3) , which opens a directory and associates a directory stream with it, enabling you to process the directory’s contents. After that you should use multiple calls to the readdir(3) function that returns pointers to the directory entries of the path that was passed as an argument to opendir(3) . The readlink(2) function resolves the value of a symbolic link. Additionally, the realpath(3) system call returns the canonicalised absolute pathname of its argument. This can be useful for determining…