Working on a stable setup

Next step for the synth module project was to get the Raspberry Pi 2 to run in a stable manner. It seems like I’m getting close or that I’m already there. First I built a new RT kernel based on the 4.1.7 release of the RPi kernel. Therefore I had to checkout an older git commit because the RPi kernel is already at 4.1.8. The 4.1.7-rt8 patchset applied cleanly and the kernel booted right away:

pi@rpi-jessie:~$ uname -a
 Linux rpi-jessie 4.1.7-rt8-v7 #1 SMP PREEMPT RT Sun Sep 27 19:41:20 CEST 2015 armv7l GNU/Linux

After cleaning up my cmdline.txt it seems to run fine without any hiccups so far. My cmdline.txt now looks like this:

dwc_otg.lpm_enable=0 dwc_otg.speed=1 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootflags=data=writeback elevator=deadline rootwait

Setting USB speed to Full Speed (so USB1.1) by using dwc_otg.speed=1 is necessary otherwise the audio coming out of my USB DAC sounds distorted.

I’m starting ZynAddSubFX as follows:

zynaddsubfx -r 48000 -b 64 -I alsa -O alsa -P 7777 -L /usr/share/zynaddsubfx/banks/SynthPiano/0040-BinaryPiano2.xiz

With a buffer of 64 frames latency is very low and so far I haven’t run into instruments that cause a lot of xruns with this buffer size. Not even the multi-layered ones from Will Godfrey.

So I guess it’s time for the next step, creating a systemd startup unit so that ZynAddSubFX starts at boot. And it would be nice if USB MIDI devices would get connected automatically. And if you could see somehow which instrument is loaded, an LCD display would be great for this. Also I’d like to have the state of the synth saved, maybe by saving an .xmz file whenever there’s a state change or on regular intervals. And the synth module will need a housing or casing. Well, let’s get the software stuff down first.

Working on a stable setup

CarPC v1.0

As our collection of MP3 CD’s was wearing out I thought why not put a small embedded board with a big drive in our car? I dug up a Cubieboard2 that was gathering dust and started hacking. The goal:

  • Small system based on Debian Jessie
  • MPD to serve the audio files
  • Remote control via WiFi
  • Big drive
  • Acceptable boot time
  • Basic protection against file system corruption

Putting a bog standard Debian Jessie on the Cubieboard2 was quite straightforward with the help of the wiki. The board booted with the standard kernel but unfortunately no sound. Luckily I had just received some ultra-cheap PCM2704 USB audio interfaces and these worked and sounded great too. WiFi worked out of the box but the rtl8192cu driver of the 3.16 kernel for the Realtek RTL8192CU chipset has the tendency to quickly go into suspension and as this driver doesn’t have any power management options I ended up with a hacky for loop in /etc/rc.local that pings all IP’s in the DHCP range. I quickly dropped this iffy set-up as it just didn’t work out that well and ended up using a DKMS based solution that made it possible to control power management of the WiFi dongle. Next hurdle was hostapd that stopped working with this alternative driver. But with the help of the hostapd-rtl871xdrv GitHub repo I managed to cook up a fully working hostapd Debian package.

Next up was the hard drive. I first tried a USB drive but the Cubieboard2 just couldn’t provide enough juice to power the drive properly together with the WiFi dongle. I also tried with my Raspberry Pi’s but those had the same issues. So I had to resort to a SATA drive. Of course I bought a 3.5″ drive first because those are cheaper. But you can’t power a 3.5″ drive with the SATA cable that comes with the Cubieboard2 and as I had a bit of a deadline I returned it for a 2.5″ drive and that works like a charm. I installed MPD, copied my music collection to the hard drive, fired up MPD and was greeted with a segmentation fault. Apparently the Jessie MPD package has issues with the sticker database file so I installed MPD from the backports repo and that version runs without any complaints so far.

For some basic protection against corruption by sudden power loss I created separate partitions for /home and /var on the SD card that are mounted rw with a couple of options to reduce corruption (sync,commit=1,data=journal) and / is mounted ro, just like the big hard drive with the audio files. /tmp is being mounted as tmpfs in RAM. Boot time is about 15 seconds and I’m OK with that. To remotely shut down the CarPC via WiFi I use a JuiceSSH homescreen shortcut of a connection that runs a simple shutdown -h now snippet.

After I had mounted everything in our car the thing wouldn’t boot though. Swapped the 1A USB car adapter for a 2.1A version and then the CarPC came up properly. Installed MPDroid on my Nexus 5 to control MPD via WiFi and so far, so good!

Cubieboard2 based CarPC


Sometimes the CarPC became unreachable via WiFi. The culprit was that the DHCP service (udhcpd) didn’t always come up because it was sometimes started before hostapd. I fixed this by copying /var/run/systemd/generator.late/udhcpd.service to /etc/systemd/system/udhcpd-custom.service and adding hostapd.service to the After line and adding a Requires=hostapd.service line. I also added a [Install] stanza with the line I then disabled udhcpd.service and enabled udhcpd-custom.service.

Addendum 2

Hostapd didn’t always start flawlessly either so I copied /var/run/systemd/generator.late/hostapd.service to /etc/systemd/system/hostapd-custom.service and added sys-subsystem-net-devices-wlan0.device to the After and Wants lines. Also added an [Install] stanza, disabled hostapd.service and enabled hostapd-custom.service.

CarPC v1.0

Downscaling and upgrading

For years I’ve used Focusrite Firewire interfaces, first the Saffire Pro 10 IO and after that its successor, the Saffire Pro 40. Both great devices but recently I decided to make the switch to USB. The reason was twofold:

  • I was barely using more than 2 ins or outs simultaneously
  • Firewire is being phased out and my notebooks don’t have any Express Card slots either, only USB ports
  • The Pro 40 isn’t very portable

So when switching to USB I would need:

  • Same or better quality preamps and AD/DA convertors
  • At least 2 ins and outs
  • Portability
  • Possibility to achieve similar latencies as with the Pro 40
  • Works well with Linux

This narrowed down the choice significantly. I could go for a Focusrite Scarlett but from what I found on the net there were some issues with these devices. I’ve also looked at some Presonus devices but actually I had already set my mind on a different device: the RME Babyface.

RME Babyface

So when I found a webshop that offered the Babyface at a reduced price (almost 15% off) I put my Focusrite up for sale and bought the Babyface. The Focusrite was sold within a week and the Babyface easily met my expectations:

  • When in CC (Class Compliant) mode it works out of the box
  • It’s highly portable, the Babyface is actually specifically made for this purpose as it comes with a nice pouch
  • It has 2 ins and outs and the great thing is that it’s possible to extend the IO via ADAT
  • The preamps and AD/DA converters are simply top notch, they’re so good that I’m considering switching cans and studio monitors as this device is merciless, it simply doesn’t work well with my current setup
  • When connected to an USB3 port (XHCI) the Babyface can run with nominal latencies of 0.5ms (this is with 8 samples), i.e. it beats the other two OS’s mentioned on the RME product page

I can live with not being able to control the device from within Linux, almost all settings can be done on the device itself. Upgrading the firmware can be done with a VM so that’s covered too. The only real drawbacks are that it’s an USB device so it’s a bit more picky with regard to your system setup and it consumes a bit more CPU compared to Firewire. But all in all this is a great sounding device that works well with Linux when in CC mode and it fits my specific user case very well.

Downscaling and upgrading

The Infinite Repeat – Cala Del Aceite

Finally got around finishing a new track. And it’s just 65BPM so no four to the floor this time. I posted the demo a while ago, this is more or less a definitive version (definitive is a fluid term in my dictionary). … aceite.ogg

This song is about one of the most beautiful places I know on this
planet, Cala Del Aceite in the most southern part of Spain: … eConil.htm

Tools used:

  • Qtractor for recording and mixing
  • seq24 for sequencing
  • The necessary plugins:
    • drumkv1 to hold the drum samples (drum samples are all from
    • a lot of plugins that are part of Distrho or Carla: Noize Maker, Tal
    • Reverb III, ZynAddSubFX-LV2, Nekobi
    • MDA subsynth
    • FluidSynth DSSI for the Rhodes
    • linuxDSP plugins (EQ500, DYN500, MBC2B on the master bus)
    • Calf Vintage Delay
    • LADSPA comb filter, Fast Lookahead Limiter
    • GxZitaReverb

The background vocals for the choruses are sung by my wife. The ocean
sample is from Freesound:

Cádiz is pretty close to Conil, hence the choice.

Thanks to everyone for making this possible. Especially falkTX and rncbc, couldn’t have done this without your valuable work.

Making promises that I can’t keep
It’s pushing me, pushing me into a deep
State of sadness, state of doubt
A state of awareness I can’t live without

Making mistakes, so hard to bear
It’s driving me, driving me to a point where
I can’t escape, I can’t shy away
From the daemons I refuse to obey

All is forgiven, all is well…

Awaiting the day that I’ll be relieved
From this burden, this burden that has grieved
So many loved ones, so many friends
All the people on which I depend

Stand up, act now, it’s time for a change
Lingering won’t help, help to rearrange
The current imbalance, the current state
Of things so rush now don’t hesitate

All is forgiven, all is well…

Creative Commons License
Cala Del Aceite by The Infinite Repeat is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

The Infinite Repeat – Cala Del Aceite

Wolfson Audio Card for Raspberry Pi

Just ordered a Wolfson Audio Card for Raspberry Pi via RaspberryStore. I asked them about this audio interface at their stand during the NLLGG meeting where I did a presentation about doing real-time audio with the RPi and they told me they would ship it as soon as it would become available. They kept their word so I’m hoping to mount this buddy on my RPi this very week. Hopefully it will be an improvement and allow me to achieve low latencies with a more stable RPi so that I can use it in more critical environments (think live on stage). It has a mic in so I can probably set up the RPi with the Wolfson card quite easily as a guitar pedal. Just a pot after the line output, stick it in a Hammond case, put guitarix on it and rock on.

Wolfson Audio Card for Raspberry Pi

Wolfson Audio Card for Raspberry Pi

LAC2014: submission accepted!

My submission for the Linux Sound Night at LAC2014 with The Infinite Repeat has been accepted. The Call for Papers page mentions the term “danceable” so I’m going to focus on that. Making danceable music is quite a challenge for me but it should definitely be doable to produce a solid set, especially now that I’m the proud owner of a Korg Volca Keys. I’m definitely going to integrate it in my current setup as the Volca reacts great on MIDI sent from my workstation. It has some fat sounds that just scream dance floor.

Korga Volca Keys

I’m really looking forward to this year’s LAC. It seems falkTX and avlinux are going too, it’d be great to meet these guys in real life!

LAC2014: submission accepted!

LV2 gaining momentum

The number of new LV2 plugins being released is steadily growing. The last couple of months at least the following LV2 plugins have been released:

  • Bitrot (a set of LV2 and LADSPA plugins for glitch effects)
  • beatslash-lv2 (a set of plugins for live beat repeating and beat slicing)
  • deteriorate-lv2 (a set of plugins to deteriorate the sound quality of live inputs)
  • midimsg-lv2 (a set of plugins to transform midi output into usable values to control other plugins)
  • QmidiArp (LV2 plugins of the three QMidiArp modules)
  • x42-plugins (collection of LV2 plugins: tuner, oscillator, x-fader, audio-level meters, midi filters etc.)
  • BLOP-LV2 (port of the LADSPA BLOP plugins)

Haven’t tried them all of them yet but the ones I did try (the QmidiArp modules as plugins and some of the x42 plugins) proved to be very promising. Besides new plugins being released work continues on a great number of plugins, the LV2 framework itself and on tools facilitating in the creation or building of LV2 plugins. Especially falkTX is in the vanguard with his current work on getting his Carla plugin host to work as a LV2 plugin. This would open up a lot of possibilities like using it in hosts that don’t support all plugin frameworks (think Ardour and DSSI support). In the meanwhile the guitarix team continues to add great LV2 plugins to their ever growing collection and Dave Robillard, the main author of LV2, doesn’t sit still either with releasing updated versions of the building blocks that form the LV2 framework.

LV2 gaining momentum

Bitwig Studio to be released

The 26th of March Bitwig Studio will be released. From the Bitwig Studio site:

Bitwig Studio is a multi-platform music-creation system for production, remixing and performance with a focus on flexible editing tools and a super-fast workflow.

It’s being developed by folks who have worked on Ableton Live and it will also be available for Linux. It’s a cross-platform DAW which means that for the GUI a platform agnostic framework has been used. In the case of Bitwig Studio the chosen framework is most probably Java which raised some eyebrows within the Linux Audio community. The price of the upcoming product met some scepticism too as it ends up higher than initially announced. Add to this that there’s barely any support for plugins (except native Linux VST) and you’ll understand that this upcoming release has fueled a discussion or two.

I haven’t seen anything yet of Bitwig Studio so I can’t judge the quality, workflow or usability of the product. I’ve registered for a beta testing account two years ago and didn’t hear anything from the Bitwig folks until recently so to be honest I completely lost interest in the product in the meanwhile.

Really, the people from Tracktion do it a lot better in that regard I think, it’s cheaper, they communicate more and it’s based on a cross-platform toolkit that has more credibility (Juce). But you never know, maybe I’ll get blown away when I get my hands on Bitwig Studio. You’ll be the first to hear.

Bitwig Studio to be released

Resolved JACK issues on notebook

Finally got around troubleshooting the issues I was facing with JACK on my notebook, a BTO that is actually a Clevo W170ER. Somehow I couldn’t go lower than -p128 with USB audio interfaces. When I thought I had tried every option, even disabling hyperthreading, I noticed two unidentified entries in my lsusb output:

Bus 001 Device 003: ID 8087:07da Intel Corp. 
Bus 002 Device 003: ID 5986:0401 Acer, Inc

The first entry is a Bluetooth adapter and the second entry is a webcam. Both devices are unnecessary when making music so I thought, why not unbind them. First I had to figure out their respective bus ID’s:

$ tree /sys/bus/usb/drivers/usb
??? 1-1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1
??? 1-1.3 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.3
??? 2-1 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1
??? 2-1.6 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.6
??? bind
??? uevent
??? unbind
??? usb1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1
??? usb2 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2
??? usb3 -> ../../../../devices/pci0000:00/0000:00:14.0/usb3
??? usb4 -> ../../../../devices/pci0000:00/0000:00:14.0/usb4

Since the Bluetooth adapter sits on bus 1 and the webcam on bus two their respective ID’s should be 1-1 and 2-1. So I echoed the ID’s to the unbind file in the same directory:

$ echo -n "1-1" | sudo tee /sys/bus/usb/drivers/usb/unbind
$ echo -n "2-1" | sudo tee /sys/bus/usb/drivers/usb/unbind

Good riddance:

$ lsusb
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub

Then I started JACK again with -p64 using an USB audio interface connected to bus 3 (so no rate matching hub in between) and no more xruns, not even with a generic kernel and using WiFi and all. Next hurdle is the onboard sound. Below -p128 I get bursts of massive xruns and so far I didn’t manage to pinpoint the culprit.

Edit #1: I’ve found out that the Bluetooth adapter is the main bottleneck. Also, by echoing the aformentioned ID’s (1-1 and 2-1) you disable the whole USB bus apparently. To disable just the USB device echo the last ID in the respective path names, so for the Bluetooth adapter that’s 1-1.3 and for the webcam 2-1.6. This way you can still use the USB bus on which these devices are residing. In my case disabling the whole bus is not an option, this would mean I’d have to connect all my USB interfaces to bus 3 (bus 4 doesn’t have any external inputs) which could result in these devices getting in each other’s way with regard to bandwidth. After echoing the ID’s the output of the tree command looks like this:

$ tree /sys/bus/usb/drivers/usb
??? 1-1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1
??? 2-1 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1
??? bind
??? uevent
??? unbind
??? usb1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1
??? usb2 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2
??? usb3 -> ../../../../devices/pci0000:00/0000:00:14.0/usb3
??? usb4 -> ../../../../devices/pci0000:00/0000:00:14.0/usb4

The lsusb command still shows the devices though.

Edit #2: unbinding drivers like described above won’t persist across reboots. If you’d like to make the unbinding persistent you could add the unbind command to /etc/rc.local or create a script that runs at login. There are other options of course like blacklisting the Bluetooth drivers.

Resolved JACK issues on notebook

A month on a Mac

During the second job interview with my new employer I was asked if I’d like to use a Mac or a Windows PC with the assurance I’d get a Linux workstation after my probation time. Just put me behind a Mac then, that’s closer to Linux than Windows and from what I recalled it comes with a native terminal that does SSH. And what do I need more?

So there I am in front of a big, glossy screen and a tiny keyboard that lacks some familiar keys. My findings so far? Kind of neutral. I’ve got my terminal and I can run SSH from the CLI so I’m happy. There are some quirks that annoy me though (in no particular order):

  • No Compose key and I had to jump through quite some hoops to map a key as a Compose key.
  • No easy way to map a keyboard shortcut for opening a terminal. I had to resort to something called ‘Automator’ to get it working. And it still doesn’t work the way I want too. When there are no windows open pressing the shortcut doesn’t do anything. When there are open windows it works but why does it open two terminals when pressing the shortcut for the first time? Not a real big deal as I need multiple terminals anyway (I just can’t get used to tabbed terminals).
  • I prefer non-glare monitors to glossy ones.
  • No Home, End, PageDown and PageUp keys. Not a real big deal either, in fact, it’s a real good incentive to start getting accustomed to Vi(m) shortcuts since I kind of live inside Vim these days. I even bought this, great stuff.
  • Can’t get used to the default window management settings. For instance when you minimize a window and Alt+Tab to it the window doesn’t open. So I’m not minimizing any windows anymore since this is really annoying. Haven’t looked into changing this behaviour though, it’s probably something relatively simple.
  • Annoying pop-ups from updates and programs that are downloaded from the internet (“blabla” is an application downloaded from the Internet. Are you sure you want to open it?). Especially the latter ones are annoying. Disabling the pop-ups has to be done from a terminal. Wow, so much for a “user-friendly” OS.
  • Clicking the close button of an application doesn’t quit it. Cmd+Q does. This is something I won’t get used to either. Actually I don’t want to get used to the Cmd button at all.
  • I prefer a panel with a window list on it. I don’t know how other folks do it but this Alt+Tab stuff is counter-efficient in my case.

Are there things I particularly like about Mac OS X or the Mac itself? Actually no, can’t think of anything. Yeah, the keyboard feel is really nice but that pro gets nulled out because of the missing keys, ~ being placed next to the left Shift key and the Fn keys being mapped to the F1/F12 keys. Add to this the meaningless keys with all kinds of arrows on them and this key with a crossed square. No idea what they do. On a software level MacPorts is nice, it allowed me to install some of my favorite tools that I found were missing. Other than that I can’t wait to have my own workstation with Linux on it. The plan is that I get a Dell XPS 15 with a dual monitor setup. Something to look forward to.

And yes, I have to deal with quite some Windows servers now. I’m not going to dedicate a blogpost to my findings on that OS. Just one word. Meh.

A month on a Mac