Piping Linux audio to a file

I recently had to pipe some audio from my browser to a file. This may not be the most elegant way, but I found it works.

Using SimpleScreenRecorder

For capturing audio and video, I use SimpleScreenRecoder. It’s a pretty no-frills recording program that is intended for (among other things) streaming content from a machine. While it supports both audio and video, I only care about the audio portion for this project.

To minimize bandwidth wasted recordin video, I set “Record a fixed rectangle” and set a 2x2 rectangle at 0,0. I then enabled “Record audio” with the PulseAudio backend and a Source of Monitor of sof-hda-dsp Speaker + Headphones. That output to my computer’s main speakers.

On the next screen, I set up an Output profile declaring the destination, use of MP4 as the container, an H.264 video codec with constant rate factor of 23, superfast preset, and “Allow frame skipping”, and an Audio codec of MP3, Bit-rate 128 kbit/s). 

Once set up, I could just start recording.

Resetting my monitor in Linux

Recently, I had an Ubuntu laptop I use regularly develop a weird quirk: sometimes when I plugged it into USB-C, neither the monitor nor power would connect. I discovered I could fix this by simply running lspci on the laptop, which somehow forced both to come back.

As this made no sense, I dug down a bit more. I can’t say I found an answer, but I did find some more things worth questioning.

PCI devices

On my laptop, devices are exposed at /sys/bus/pci/devices. Searching around a bit, I found that device /sys/bus/cpi/devices/0000:3b:00.0 was reporting itself as USB controller: Intel Corporation JHL6540 Thunderbolt 3 USB Controller (C step) [Alpine Ridge 4C 2016] (rev 02). Navigating into that subdirectory, I found I could sudo -s, then echo 1 > reset, which fixed the system in apparently the same way as running lspci.

What the hell?

At this point, I don’t really know. Sometimes the Linux architecture just puzzles me. I don’t know that lspci is running a reset on devices, but perhaps when it tries to poll details on the device, the act of polling itself trips a fault in the driver (becuase the driver realizes it can’t communicate with the device) and forces a reset to heal itself? I haven’t found any code confirming or falsifying this hypothesis; it’s still an open question for me.

On not giving up

Owning a Linux machine is like this. When things go wrong, the only person who’s responsible for fixing it is the owner. This is, ultimately, true of all self-owned computers, of course.

When I was younger, the ecosystem of Linux users was too hard to find to make this task easy; certainly not as easy as it was for Windows ownership, when everyone on the block had one of those machines. But the nice thing about living in the Internet era is Linux use bloomed, and at the same time users can find each other much more easily. I learned about the existence of the PCI list poking around on various sites.

There’s much more to learn, but it’s nice that resources are far easier to find now.

Setting up Xmonad on a Lenovo ThinkPad X1 Carbon: Power Management and Sound (and Dead Ends)

This is my second post on the topic of setting up Xmonad on a Lenovo ThinkPad X1 Carbon. Previous post is here. This time around, we'll talk power management and screen geometry.

Power Management

Power management is handled by the xfce4-power-manager applet. I launch the applet in the .xsessionrc file, but when I initially launched it, it was invisible. It turns out, there were two issues:

1. By default, the tray icon doesn't show up. I had to enable it in the xfce-power-manager-settings app, which can be run from the command line.
2. The default icon in my desktop was black and I had it on a black background. That was easy enough to change out by adjusting the GNOME theme. lxappearance is the tool I used to do this; you can install it with apt-get and it then just runs on the command line. It allows me to tweak various configs, including the theming for icons; "Ubuntu-Mono-Dark" gave me a fine visible icon.

Not fancy, but it works

Once the power manager is in the tray, I can right-click on it and select "Power manager settings..." to configure the manager options. In particular, I make sure "When laptop lid is closed" is set to "Suspend" for both battery and plugged in modes. Note: this didn't work on the first try, and needed a restart to make it work. I can also use systemctl suspend to pause the machine, if needed.

Sound

Sound is notoriously complicated in Linux ecosystems. I tried a couple different options here and didn't find anything I'm completely thrilled with, but I did find some things I hated least. I ended up installing pasystray, which operates at the PulseAudio level. As a result, it's a bit options-heavy; PulseAudio lets you somewhat arbitrarily pipe audio sources to audio sinks, so I have the capability to, for example, send Zoom to my headphones while Chrome goes to my PC speaker (I don't want that, but I have it). My streams are also uhelpfully named "sof-hda-dsp HDMI1/DP1" etc. instead of, I don't know. "Computer speakers" or "Monitor output" or, uh, something sane. But it does work, and I can probably figure out (eventually) how to configure the human-readable device names.

"Sound is a solved problem in Linux"

Volume can be increased and decreased (on the default sink) via two-finger scrolling on the speaker icon (on the Carbon X1, Mod-volume-up and Mod-volume-down also work, since I configured them in Xmonad's keybindings themselves).

Final thoughts

I give this part of the configuration three out of five stars. Making the audio layer do anything that isn't space-alien is a real challenge when I step off the beaten path of Canonical's pre-configured tooling. But it is working, and I'm not unhappy with that.

Epilogue: Dead ends

Later update:I should mention some dead-ends I encountered while trying to configure everything. As always, one of the challenges of free software is there are so many options to choose from, and many aren't intended to work together.

Trying to install xmonad-extras from cabal

Directions here led me to try and configure volume control by installing xmonad-extras from cabal, the Haskell package manager. This was a detour; I later discovered the package was available in apt, but was named ligbhc-xmonad-extras-dev. Cabal isn't integrated with the apt packages in several ways (for one, its version of xmonad-extras installs in a different location that the apt install of Xmonad won't find them in; for another, xmonad-extras depends on a pile of C-written libraries that cabal can't install because it's not a universal package manager, it's only intended for Haskell code). Not worth the trouble

fdpowermon

For a brief period, I thought the power manager for xfce4-power-manager was buggy and didn't show an icon. The icon was there, but it was showing as black-on-black because of my icon theme. To work around this, I installed fdpowermon. fdpowermon has a couple of annoying issues: for one, it doesn't have a click-to-configure feature. But perhaps more annoying, the icon disappears when the laptop is plugged in and fully charged. This is a preference by the plugin's author; it can be overridden, but that's the default, to hide the whole thing! More trouble than it's worth; I uninstalled it.

volumeicon-alsa

Before settling on pasystray, I gave volumeicon-alsa a quick tour. This worked okay, but it didn't seem to want to let me switch my audio output devices. Also, I'm still a bit unclear on whether I want to be operating at the PulseAudio or ALSA layer of the audio stack. Rather than debug why internal laptop speakers, HDMI-accessible audio, and headphones weren't all showing up in volumeicon-alsa, I gave up and switched to pasystray... Even though the control it gives is overkill, it gives enough control that I can do what I want.

Setting up Xmonad on a Lenovo ThinkPad X1 Carbon: Getting Started

From time to time, I have profoundly bad ideas. One of those ideas is to change out the window manager on a Linux PC.

For many tasks (such as maintaining this blog), I keep a Lenovo ThinkPad X1 Carbon running Linux. It’s been a good little workhorse, running Ubuntu 20.04. I decided to switch my window manager to Xmonad, because I enjoy fast manipulation of my windows without needing to tell the window manager where they should live.

In principle, this should be very straightforward. In practice, it turns out that switching out your window manager causes a wide variety of seemingly-unrelated things to break. As best I understand it, this is because several basic “housekeeping” tasks of a desktop Linux environment actually route through the window manager, and when the WM goes away, the configurations that launch those tools goes with it. Here’s a short list of things that no longer “just work” when you switch off (I keep discovering more as I go):

• screen locking
• rendering the desktop (yes, if you give it no commands, the window manager just draws nothing!)
• auto-mounting of plugged-in USB storage
• sleep-on-close-screen
• layout of second monitors
• connecting second monitors
• battery indicator
• sound volume, mute, output control
• Bluetooth connections

The rest of this post will go into how to get a basic Xmonad setup done. Over the next while, I’ll fill in more information on how to get the remaining functionality back without Canonical’s default window manager in place.

First steps

I drew heavily from a beginner’s guide to Xmonad, which generally steered me in the right direction. I was able to install the relevant components with apt-get. This got me a configuration running with Xmonad, Xmobar (to display content at the top), and Stalonetray (an icon tray, which is necessary for some X11 apps to have a place to show system status).

After finishing this config, some things worked but some took some banging on. In particular,

• Xmonad has been updated since this guide was released, and the way “docks” attach has changed. My xmonad.sh factors this change in.
• xfce4-power-manager icon is black-on-black, so I thought it was missing. It was simply invisible in the default all-black color scheme of the top-bar. Switching to a dull grey helped the missing icons appear. Once I knew what the issue was, I was able to install lxappearance and run it to change the icon theme configuration; switching to “Ubuntu-Mono-Dark” provided an icon that was visible.
• To attempt to integrate with the sound control buttons on the ThinkPad, I pulled in “xmonad-extras,” which integrates against “Third party extensions for xmonad with wacky dependencies” (I’m leaving it as an exercise for the reader whether ‘controlling volume via keyboard’ should be considered “wacky,” but you do you). This proved more challenging than I expected because apt-get actually knows this package as libghc-xmonad-extras-dev, but once I found it it worked fine (though I will probably extract it for reasons I’ll get into when I drill open audio).

Put it all together and the end result so far isn’t terrible!

I don't expect it to win any awards, but it's pretty functional

The Configs

Below are the relevant config files I have so far.

How to keep your gnome-terminal from hanging in SSH connections

I've been having problems with my GNOME terminal hanging when on an extended SSH connection. Finally realized today there's probably a keepalive configuration somewhere.

There is.

Go into your ~/.ssh/config file and add this stanza under your Host config:

  ServerAliveInterval 240

(note the two spaces to make it a sub-property of Host)

If you want every SSH connection to stay alive, add the rule for every host

Host *
  ServerAliveInterval 240

FAQ

1. Why isn't this the default?
   
   Really? You're using a Linux environment and you're asking why the default isn't "Don't just break?" 

   😉