The Zynthian project

November 11, 2015 jeremymodule, raspberry, raspberry pi, raspberrypi, raspberrypi2, synth, synth module, zynaddsubfx, zynthian7 Comments

Recently I found out that I was not the only one trying to build a synth module out of a Raspberry Pi with ZynAddSubFX. The Zynthian project is trying to achieve the exact same goal and so far it looks very promising. I contacted the project owner to ask if he would be interested in collaborating. I got a reply promptly and we both agreed it would be a good idea to join forces. The Zynthian project has all the things that I still had to set up already in place but I think I can still help out. The Zynthian set-up might benefit from some optimizations like a real-time kernel and things like boot time can be improved. Also I could help out testing, maybe do some packaging. And if there’s a need for things like a repository, web server or other hosting related stuff I could provide those.

Protoype of the Zynthian project — Zynthian prototype

I’m very happy with these developments of our projects converging. Check out the Zynthian blog for more information on the current state of the project.

Working on a stable setup

September 28, 2015October 24, 2015 jeremyalsa, audio, dac, folderol, godfrey, kernel, linux, midi, module, raspberry, raspberrypi, raspberrypi2, real-time, realtime, synth, synth module, systemd, usb, zynaddsubfxLeave a comment

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.

Building a synth module using a Raspberry Pi

September 13, 2015October 24, 2015 jeremyfundamental, kernel, midi, module, osc, patchset, pcm2704, raspberry, raspberry pi, raspberrypi, raspberrypi2, real_time, realtime, synth, synth module, usb, zynaddsubfx, zynaddsubfx-ext-gui5 Comments

Ever since I did an acid set with my brother in law at the now closed bar De Vinger I’ve been playing with the idea of creating some kind of synth module out of a Raspberry Pi. The Raspberry Pi 2 should be powerful enough to run a complex synth like ZynAddSubFX. When version 2.5.1 of that synth got released the idea resurfaced again since that version allows to remote control a running headless instance of ZynAddSubFX via OSC that is running on for instance a Raspberry Pi. I looked at this functionality before a few months ago but the developer was just starting to implement this feature so it wasn’t very usable yet.

But with the release of ZynAddSubFX 2.5.1 the stabilitity of the zynaddsubfx-ext-gui utility has improved to such an extent that it’s a very usable tool. In the above screenshot you can see zynaddsubfx-ext-gui running on my notebook with Ubuntu 14.04 controlling a remote instance of ZynAddSubFX running on a Raspberry Pi.

So basically all the necessary building blocks for a synth module are there. Coupled with my battered Akai MPK Mini and a cheap PCM2704 USB DAC I started setting up a test setup.

For the OS on the Raspberry Pi 2 I chose Debian Jessie as I feel Raspbian isn’t getting you the most out of your Pi. It’s running a 4.1.6 kernel with the 4.1.5-rt5 RT patch set, which applied cleanly and seems to run so far:

pi@rpi-jessie:~$ uname -a
Linux rpi-jessie 4.1.6-rt0-v7 #1 SMP PREEMPT RT Sun Sep 13 21:01:19 CEST 2015 armv7l GNU/Linux

This isn’t a very clean solution of course so let’s hope a real 4.1.6 RT patch set will happen or maybe I could give the 4.1.6 PREEMPT kernel that rpi-update installed a try. I packaged a headless ZynAddSubFX for the RPi on my notebook using pbuilder with a Jessie armhf root and installed the package for Ubuntu 14.04 from the KXStudio repos. I slightly overclocked the RPi to 1000MHz and set the CPU scaling governor to performance. The filesystem is Ext4, mounted with noatime,nobarrier,data=writeback.

To get the USB audio interface and the USB MIDI keyboard into line I had to add the following line to my /etc/modprobe.d/alsa.conf file:

options snd-usb-audio index=0,1 vid=0x08bb,0x09e8 pid=0x2704,0x007c

This makes sure the DAC gets loaded as the first audio interface, so with index 0. Before adding this line the Akai would claim index 0 and since I’m using ZynAddSubFX with ALSA it couldn’t find an audio interface. But all is fine now:

pi@rpi-jessie:~$ cat /proc/asound/cards
 0 [DAC            ]: USB-Audio - USB Audio DAC
                      Burr-Brown from TI USB Audio DAC at usb-bcm2708_usb-1.3, full speed
 1 [mini           ]: USB-Audio - MPK mini
                      AKAI PROFESSIONAL,LP MPK mini at usb-bcm2708_usb-1.5, full speed

So no JACK as the audio back-end, the output is going directly to ALSA. I’ve decided to do it this way because I will only be running one single application that uses the audio interface so basically I don’t need JACK. And JACK tends to add a bit of overhead, you barely notice this on a PC system but on small systems like the Raspberry Pi JACK can consume a noticeable amount of resources. To make ZynAddSubFX use ALSA as the back-end I’m starting it with the -O alsa option:

zynaddsubfx -r 48000 -b 256 -I alsa -O alsa -P 7777

The -r option sets the sample rate, the -b option sets the buffer size, -I is for the MIDI input and the -P option sets the UDP port on which ZynAddSubFX starts listening for OSC messages. And now that’s the cool part. If you then start zynaddsubfx-ext-gui on another machine on the network and tell it to connect to this port it starts only the GUI and sends all changes to the GUI as OSC messages to the headless instance it is connected to:

zynaddsubfx-ext-gui osc.udp://10.42.0.83:7777

Next up is stabilizing this setup and testing with other kernels or kernel configs as the kernel I’ve cooked up now isn’t a viable long-term solution. And I’d like to add a physical MIDI in and maybe a display like described on the Samplerbox site. And the project needs a casing of course.

Media units

September 12, 2015October 24, 2015 jeremydali, kodi, mk808, mpd, mpdroid, openelec, pcm2704, sl1210, somafm, technicsLeave a comment

The MK808 Android TV stick with a PCM2704 USB audio interface runs Debian Jessie with MPD and serves as our mediaplayer for audio files. It draws its power from the USB port of our cable modem so it’s always on. Most of the time Indie Pop Rocks is playing. It’s hooked up to the network via WiFi. We use MPDroid to control it.

The Raspberry Pi runs OpenELEC with Kodi. We use this for watching all kinds of video files that we stream from our NAS (an aging WD My Book Live that runs Debian Lenny) via an NFS share. It is connected to the network via ethernet.

The Chromecast is for watching Netflix. When we just got it we had some issues with connecting it to the network but after replacing our old router with an ASUS RT-AC68U it worked flawlessly.

The Technics SL-1210MK2 with Ortofon headshell and cartridge is for listening music on vinyl, you know those round black plastic units from the past with grooves in them. It doesn’t have any network connections and doesn’t run an OS. It does send electrical current to a NAD C 325BEE Stereo Integrated Amplifier with Dali Concept 2 speakers. Yeah, I’m a 2.0 guy.

The TV is an old pre Smart TV Samsung but as it still works we probably won’t replace it for the time being. It does have CEC so we can control the TV, RPi and Chromecast with a single remote.

CarPC v1.0

July 13, 2015October 24, 2015 jeremy8192cu, access, audio, car, carpc, cubieboard, cubieboard2, debian, hostapd, jessie, linux, mpd, mpdroid, pc, pcm2704, point, realtek, remote, rtl8192cu, sunxi, wifi2 Comments

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 linux-sunxi.org 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

Addendum

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 WantedBy=multi-user.target. 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.

Raspberry Pi Revisited

April 18, 2015October 24, 2015 jeremykernel, linuxsampler, raspberry, raspberry pi, raspberrypi, raspberrypi2, real_time, realtime, rpi, salamander, wolfson, zynaddsubfx23 Comments

When the Raspberry Pi 2 was released I certainly got curious. Would it be really better than it’s little brother? As soon as it got available in The Netherlands I bought it and sure this thing flies compared to the Raspberry Pi 1. The four cores and 1GB of memory are certainly an improvement. The biggest improvement though is the shift from ARMv6 to ARMv7. Now you can really run basically anything on it and thus I soon parted from Raspbian and I’m now running plain Debian Jessie armhf on the RPi.

So is everything fine and dandy with the RPi2? Well, no. It still uses the poor USB implementation and audio output. And it was quite a challenge to prepare it for its intended use: a musical instrument. To my great surprise a new version of the Wolfson Audio Card was available too for the new Raspberry Pi board layout so as soon as people reported they got it to work with the RPi2 I ordered one too.

Cirrus Logic Audio Card for Raspberry Pi

One of the first steps to make the device suitable for use as a musical device was to build a real-time kernel for it. Building the kernel itself was quite easy as the RT patchset of the kernel being used at the moment by the Raspberry Foundation (3.18) applied cleanly and it also booted without issues. But after a few minutes the RPi2 would lock up without logging anything. Fortunately there were people on the same boat as me and with the help of the info and patches provided by the Emlid community I managed to get my RPi2 stable with a RT kernel.

Next step was to get the right software running so I dusted off my RPi repositories and added a Jessie armhf repo. With the help of fundamental the latest version of ZynAddSubFX now runs like charm with very acceptable latencies, when using not all too elaborate instrument patches Zyn is happy with an internal latency of 64/48000=1.3ms. I haven’t measured the total round-trip latency but it probably stays well below 10ms. LinuxSampler with the Salamander Grand Piano sample pack also performs a lot better than on the RPi1 and when using ALSA directly I barely get any underruns with a slightly higher buffer setting.

I’d love to get Guitarix running on the RPi2 with the Cirrus Logic Audio Card so that will be the next challenge.

Downscaling and upgrading

April 6, 2014 jeremyaudio, babyface, cc, class, compliant, firewire, focusrite, interface, latency, linux, mode, pro, rme, saffire, samples, scarlett, usbLeave a comment

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.

Wolfson Audio Card for Raspberry Pi

March 19, 2014October 24, 2015 jeremyaddon, audio, card, guitar, guitarix, interface, linux, nllgg, pi, raspberry, raspberrypi, raspberrystore, rpi, sound, wolfson48 Comments

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

LAC2014: submission accepted!

February 25, 2014 jeremyaudio, avlinux, conference, falktx, infinite, keys, korg, kxstudio, lac, lac2104, linux, midi, repeat, volcaLeave a comment

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!

A week without a Mac

January 12, 2014 jeremy12.04, 13, 2i4, 3, 9333, dell, developer, edition, focusrite, k290, logitech, lts, lubuntu, pangolin, precise, scarlett, sputnik, ubuntu, usb, xps4 Comments

Got my new workstation last week. Ultimately I decided to opt for a Dell notebook system with Linux pre-installed. So that left me only one single option: the XPS 13 Developer Edition, aka Sputnik 3. After having worked with it for a week I can only say I’m very, very happy with it. Unboxing it was a joy in itself, unwrapping the amazingly sleek machine and booting it for the first time. The XPS 13 comes with Ubuntu 12.04 LTS pre-installed which is just fine for me, especially given the fact that everything seems to work flawlessly so far. I haven’t rebooted it for days for example, suspending it works brilliantly and when I open the lid the device wakes up instantly, even after having it closed for days. And even though it has an i7 CPU it can run for hours on a full battery. The touch screen is a nice bonus but I haven’t really made use of it yet, it could be quite cool for live perfomances though. I’ve tested the touch screen with seq24 and it’s quite awesome to be able to trigger sequences by pressing the sequences on your screen.

Dell XPS 13 Developer Edition

I did try a fresh install but it would take me a bit too much time to get everything working properly so in the end I opted for sticking with the default install and install the Lubuntu desktop on top of it. And the default install doesn’t get in the way so I’m all set. I’m now looking for a nice keyboard and mouse to pair with the notebook, I’d greatly appreciate any suggestions. I had already ordered a Logitech K290 but I’m sending it back because it has the function keys swapped with the media keys and I just can’t work with that. Switching tty’s with Fn+Ctrl+F[:digit:] is just impossible to do with that keyboard. I could’ve tried swapping the keys but I’ve already filled in the RMA form and repacked the keyboard so it’s going back.

Next up is configuring it for making music. I’m thinking about purchasing a new USB audio interface, preferably USB2.0, that matches well with this machine. Suggestions are very welcome. I’ve looked at the Focusrite Scarlett 2i4 but a recent thread on LAU raised some doubts. We’ll see, it’s something for later, for now I’m extremely happy with my new work horse.

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