software

Now what does rtcirqus actually do?

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To answer that question let’s assume the following:

  • You want to do real-time audio, for instance you would like to do an overdub in a song project by using a MIDI keyboard and a soft synth.
  • You’re using a USB audio interface.
  • You’re experiencing xruns when using lower buffer sizes (64 or even lower) that result in crackling audio.

Basically all components of a desktop computer or a laptop have an IRQ. Let’s say IRQs are some sort of communication lines between the brains of your computer (the CPU) and those components. All these communication lines are more or less the same as in, none of these communication lines has priority over the other. But if you suffer from bad audio quality caused by xruns then giving the communication line that is connected to your USB device more priority than the rest could alleviate the audio issues.

This is where rtcirqus could be helpful. What rtcirqus does is detecting your USB audio interface when it gets connected, then it figures out what the IRQ of the USB bus is that your audio interface is connected to and raises the priority of the IRQ attached to that USB bus. In other words, rtcirqus gives the communication line between the USB bus that your audio interface is connected to and the CPU of your computer a higher priority. This higher priority translates into other communication lines being throttled and giving the communication line of our USB audio interface more room to transfer and receive its audio data.

rtcirqus needs to be able to prioritize that communication line though and this is where the threadirqs kernel option is for, it creates so-called threads of all available IRQs on a computer. Threads are more or less like processes running on your computer, with threadirqs enabled you can list them as such with a command like ps -eLo cmd | grep '^[irq'. So make sure this kernel option has been added to the kernel command line. In case you’re using a real-time kernel this isn’t needed as a real-time kernel uses threaded IRQs by default.

So if you find yourself in such a situation, head over to https://codeberg.org/autostatic/rtcirqus and give rtcirqus a try, maybe it helps you achieving lower latencies with your USB audio interface while retaining a clean audio output signal.

Now what does rtcirqus actually do?

Using Vim with ALE for Python linting and autocompletion

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At work we use VS Code but if possible I would prefer not to use that on my work station at home. Since I’ve been apt purging nano for ages I started looking for a way to do this with Vim. In the end it turned out to be quite simple on my Debian Bookworm install.

Prerequisites

You will need the following packages:

  • vim
  • flake8
  • python3-pylsp
  • vim-ale

Install them with sudo apt install vim flake8 python3-pylsp vim-ale.

Configuration

Add the following lines to your .vimrc and you should be good to go!

syntax on

packadd! ale
let g:ale_completion_enabled = 1
let g:ale_linters = {'python': ['pylsp']}

On Ubuntu the situation is a bit different, the linter to add for autocompletion is called pyls but the executable is called pylsp. So to have ALE load the correct executable some extra configuration is needed.

syntax on

packadd! ale
let g:ale_completion_enabled = 1
let g:ale_linters = {'python': ['pyls']}
let g:ale_python_pyls_executable = 'pylsp'
Using Vim with ALE for Python linting and autocompletion

Running your own Mastodon instance with Docker

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This is on a Ubuntu 22.04 server. Install the necessary Docker packages first.

sudo apt install docker-compose-v2

Add a mastodon user with UID and GID 991.

sudo groupadd -g 991 mastodon
sudo useradd -u 991 -g 991 -m -d /srv/mastodon -s /bin/false mastodon

Now cd to /srv/mastodon, clone the Mastodon repository and check out the current version.

git clone https://github.com/mastodon/mastodon.git .
git checkout v4.2.8

Build the Mastodon image and set correct ownership of the public directory.

docker compose build
sudo chown -R mastodon: /srv/mastodon/public

Now run the Mastodon setup step.

copy .env.production.sample .env.production
docker compose run --rm web rake mastodon:setup

Fill in the necessary details but leave the Redis password blank. Make sure the (sub)domain you want to use has a proper DNS record. The setup outputs a set of variables, copy and paste those into .env.production after having deleted the old content. Since this file contains credentials you could chmod 400 it so only the user firing up the Docker setup has read access.

Start the Mastodon stack.

docker compose up -d

And verify all containers come up healthy. Now you can put your Mastodon instance behind a reverse proxy. I’m running Apache myself and the configuration below works for me. Bear in mind it relies on a working Let’s Encrypt certificate, you will have to create one yourself.

<VirtualHost *:80>
        ServerName mastodon.yoursite.net
        ServerAdmin yourname@yoursite.net
        AssignUserID mastodon mastodon # Only applicable when using MPM-ITK

        DocumentRoot /srv/mastodon

        <Directory />
                Options FollowSymLinks
                AllowOverride None
        </Directory>

        Redirect permanent / https://mastodon.yoursite.net/

        ErrorLog ${APACHE_LOG_DIR}/mastodon.yoursite.net.error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel warn

        CustomLog ${APACHE_LOG_DIR}/mastodon.yoursite.net.access.log combined

</VirtualHost>


<VirtualHost *:443>
        ServerName mastodon.yoursite.net
        ServerAdmin yourname@yoursite.net
        AssignUserID mastodon mastodon # Only applicable when using MPM-ITK

        ProxyPreserveHost On
        ProxyPass /api/v1/streaming http://localhost:4000/
        ProxyPass / http://localhost:3000/
        ProxyPassReverse / http://localhost:3000/

        RequestHeader set X-Forwarded-Proto "https"

        SSLEngine on
        SSLProxyEngine on
        SSLCertificateFile      /etc/letsencrypt/live/mastodon.yoursite.net/cert.pem
        SSLCertificateKeyFile   /etc/letsencrypt/live/mastodon.yoursite.net/privkey.pem
        SSLCertificateChainFile /etc/letsencrypt/live/mastodon.yoursite.net/chain.pem

        # intermediate configuration, tweak to your needs
        SSLProtocol             all -SSLv3 -TLSv1 -TLSv1.1
        SSLCipherSuite          ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305
        SSLHonorCipherOrder     off
        SSLCompression    off

        # HSTS (mod_headers is required) (15768000 seconds = 6 months)
        Header always set Strict-Transport-Security "max-age=15768000"

        ErrorLog ${APACHE_LOG_DIR}/mastodon.yoursite.net.error.log
        CustomLog ${APACHE_LOG_DIR}/mastodon.yoursite.net.access.log combined
</VirtualHost>

Reload Apache and visit your Mastodon instance with the admin account you created. The result of these steps can be found here: https://mastodon.autostatic.net

References:

Running your own Mastodon instance with Docker

rtcqs v0.6.1 released

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A new version of rtcqs, a Linux audio performance analyzer, is now available. Most notable changes include:

  • Fixed inconsistent use of single and double quotes
  • Replaced audio group check with a group agnostic check (fixes #4)
  • Governor check can now deal with systems that have SMT disabled
  • Tickless check now deals with all CONFIG_NO_HZ* variants and with nohz being set on the kernel command line (fixes #8)
  • File systems check has been expanded
  • IRQ check now loops through /sys/kernel/irq instead of parsing /proc/interrupts
  • rtprio check now checks if a SCHED_FIFO priority can be set instead of a SCHED_RR priority
  • Improved preempt RT check, check if “preempt=full” is part of the kernel command line (fixes #7)
  • Refactoring, created separate classes for main app, resources and GUI
  • Moved all packaging directives into pyprojects.toml

While working on this release I found out PySimpleGUI is not open source anymore so rtcqs’ GUI has become a bit of a moving target. I’m looking at alternatives like pygubu or even popsicle but that will be something for in the long run. In the short run there are more improvements in the pipeline. The swappiness check needs some attention and same goes for the IRQ check. I’ve been working on a different project to automate prioritizing IRQs and I’m planning to to reuse some parts of that project for the IRQ check in rtcqs. The idea is to have rtcqs not only list the status of all audio related IRQs but also any audio devices attached to those IRQs.

rtcqs is available on Codeberg, PyPI and is also included in the AUR.

rtcqs v0.6.1 released

Balancing act

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At the moment everything seems a bit like a balancing act. First on a physical level, as I’m currently recovering from surgery one of the things I have to learn again is to find my balance, literally. While recovering I can’t do very much hobby stuff in the analogue domain so I swayed a bit to the digital domain again.

About 6 years ago I bought a Mixbus 32C license but found myself using Ardour more and more. During the pandemic I took a subscription and from then on I basically started using Ardour exclusively. Still remember the first time I opened up Ardour back in the 00’s, to me it was intimidating, daunting, what did all those buttons and sliders do? But like with more things in life, sometimes you just fathom the seeming complexity of something, call it an eye opener, and then you’re like, why didn’t I start using Ardour right from the beginning?

Now Ardour is my DAW of choice. It’s running on Debian 12 with a Liquorix kernel on my old, trusted BTO and I’ve never had such a stable setup before. Yes, Debian, after 14 years of Ubuntu that has become a balancing act too. The more applications are moved into Snap the more it alienates me from the OS. While I understand the concept of self-contained applications, it’s part of my job, I don’t think this concept has a real purpose on a desktop OS. It adds another layer of complexity and makes communication between applications harder. Whole different story for another time.

Ardour 8.0 has just been released and I can wholeheartedly recommend it. Installing and setting it up is a breeze and even on my old BTO it runs like a charm. The only restriction is that I can’t use too many Dragonfly Reverb plugins within a project but once I give in to my GAS to get a Framework notebook that will be resolved too.

Balancing act

rtcqs v0.4.2 released

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This release comes with a new Power Management check which checks if the audio group has read/write permissions on /dev/cpu_dma_latency. If your user is a member of the audio group and permissions are set for this group then DAW’s like Ardour and Reaper can open this file as your user, keep it open and control power management this way. This allows a user to prevent CPU sleep states for example so your CPUs are always on and instantly available which could lower the chance running into xruns.

Ardour CPU DMA latency setting Under Edit – Preferences – Performance

This release also introduces a new basic and simple tkinter-based GUI. The Qt GUI does look fancy but to use it it also needs a fancy amount of dependencies. When building binaries with PyInstaller the result of the Qt GUI is a whopping 130MB package while the tkinter version stays below 12MB.

rtcqs tkinter GUI

Future plans are to get rid of some checks:

  • Max user watches as it’s not related to the overall performance of your system
  • System timer as it’s not relevant anymore, rtcqs already checks for the more relevant stuff (high res timers and tickless kernel)
  • Background processes as it’s merely a placeholder which checks for two processes that don’t exist anymore on modern systems

I’m having my doubts about swappiness too as it’s not really applicable anymore for modern machines. But I’m curious if it still applies for smaller systems like RPi’s for example. I’d like to add a filesystem mount option check, for Ext it would check if the filesystem is mounted at least with the relatime option or even noatime for example. And maybe a disk scheduler check but I’m not conviced yet that it really makes a difference.

The new release and binary packages of rtcqs and rtcqs_simple_gui can be found on the Codeberg repo: https://codeberg.org/rtcqs/rtcqs/releases/tag/v0.4.2

rtcqs v0.4.2 released

Using Home Assistant with IR controlled devices

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When my stereo amplifier stopped working I could’ve bought a new one but after a quick look inside I was pretty sure the damage was minor so I brought it to a repair service. When I could pick it up again not only were the costs way below the price of a new amplifier but the repair service basically did a full recap with good quality capacitors so not only will it last another decade or two it also still sounds great.

But since this is a pre smart era device it only came with a bulky IR remote, so no possibility to control it via Wi-Fi. I bought a cheap Wi-Fi remote control device that could be flashed with Tasmota and integrated it with my Domoticz setup. Then we got a new thermostat that worked with Domoticz initially but after a firmware update it stopped working. With Home Assistant everything worked except for the IR remote control so for a while I used both solutions.

Not ideal so I dug a bit deeper to get the IR remote control to work with Home Assistant. Since user stories on this matter are pretty much non-existent here are the steps to get a similar solution going on your Home Assistant setup. Be warned that this is not a step-by-step walkthrough, I’m assuming you know how to flash ESP devices, that you know your way around Home Assistant and Tasmota and that you have your own MQTT server running.

First you will have to acquire a Wi-Fi remote control device that can be flashed with Tasmota. I got one from Amazon similar to this unit. Flashed it over the air with tuya-convert. Next step was to add the Pyscript HACS integration to Home Assistant. Then I added the following Python script wich I named irsend.py to the pyscripts directory.

#!/usr/bin/env python3

import paho.mqtt.client as mqtt

mqtt_server = "localhost"
topic = "ir_remote01"

# IR codes
ir_codes = {}
ir_codes['stereo_protocol'] = 'NEC'
ir_codes['stereo_volume_down'] = '0xE13E31CE'
ir_codes['stereo_volume_up'] = '0xE13E11EE'
ir_codes['stereo_off'] = '0xE13E13EC'
ir_codes['stereo_on'] = '0xE13EA45B'
ir_codes['stereo_tuner'] = '0xE13EBB44'
ir_codes['stereo_aux'] = '0xE13ED926'
ir_codes['stereo_cd'] = '0xE13EA15E'
ir_codes['stereo_video'] = '0xE13E43BC'


@service
def send_ir_code(action=None, id=None):
    log.info(f'irsend: got action {action} id {id}')
    ir_protocol = ir_codes[f'{id}_protocol']
    ir_code = ir_codes[f'{id}_{action}']
    ir_payload = f'{{"Protocol":"{ir_protocol}","Bits":32,"Data":"{ir_code}"}}'
    log.info(f'irsend: sending payload {ir_payload}')
    mqtt_client = mqtt.Client()
    mqtt_client.connect(mqtt_server)
    mqtt_publish = mqtt_client.publish(f'{topic}/cmnd/irsend', ir_payload)
    mqtt_client.disconnect()

What this script does is sending a message over MQTT to the IR remote control, the IR remote control then converts this message to an IR signal and transmits this signal. The script needs two input parameters, action and id. These parameters are made available to the script through pyscript. The Python @service decorator makes the script available as a Service in Home Assistant.

With this Service working I can add it to a View. I used a Grid card for this and added Buttons cards to this Grid.

The Grid Card Configuration looks like this.

Added a Name, an Icon and set the Tap Action to Call Service. As a Service I could select Pyscript Python scripting: send_ir_code and as Service data I entered an id and an action as a dictionary, so {id: stereo, action: on}. Did this for all the other actions and now I can control my pre smart age stereo in a smart way.

Using Home Assistant with IR controlled devices

rtcqs released

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rtcqs v0.3.1 is now available on Codeberg and Github. rtcqs is the continuation of the realtimeconfigquickscan project but then rewritten in Python. It comes with a Qt GUI and a few extra checks.

Dear all,

I’d like to announce rtcqs, the continuation of the realtimeconfigquickscan project. It’s a port to Python with some added extra’s, like a Spectre/Meltdown mitigations check and a Qt GUI. It has the approval of the original author of realtimeconfigquickscan to whom I owe a debt of gratitude, not only for the original code but also for his helpfulness with the continuation, or maybe even evolution of the project.

So check it out, indulge me with bugs, issues, improvements or any other useful feedback on the Codeberg repo which you can find at at https://codeberg.org/rtcqs/rtcqs

Happy system tuning and happy holidays!

Jeremy

While setting up a solution to fully automate the deployment of SSL certificates at work I piggybacked on the flow and focus to rewrite the realtimeconfigquickscan Perl code in Python. As part of the certificate deployment project I wrote an application to decrypt, re-encrypt and base64 encode PFX files so they can be uploaded to a vault solution. This way I ran into PySimpleGUI which enabled me to quickly put together a nice looking Qt GUI.


rtcqs main window

The code could be more terse and probably contains some typical non-programmer idiosyncracies. First improvement will be to make the code more dynamic so the GUI gets generated instead of using hardcoded values like it does now. And I’d like to add a power management check but then I first need to read up on that subject. There are also some checks that might need some more scrutiny like the swappiness and max_user_watches checks to verify if those checks are really needed for a real-time audio environment.

rtcqs released