Android in Wonderland

Modern software development is a complex task, and having an IDE that guides the developer can make this a bit more directed.  I imported the ardmix github java code into Android Studio 3.2 and converted it to kotlin, just to make life interesting.  The syntax is similar to java, but cleaner, and has a more modern feel.  Android Studio considers this a first class language and I was able to compile and run the app after a bit of tweaking.  I will not miss Java, and suspect Google feels the same.

The source is posted on gitlab ardosc, under the GPL3+ license.  It uses an OSC Library called NetUtil to handle the UDP communication to Ardour.  The java sources for de.sciss.net NetUtil were developed by Hanns Holger Rutz and licensed under LGPL 2.1 or later.  The original sources can be found at https://github.com/Sciss/NetUtil/.

I plan to release this as a free Google Play store app with no strings once I am finished testing, and will be using the app with the RPi3 in the field as part of the tests.  There is more conversion to do from Java idioms to Kotlin, as I begin to be comfortable with the syntax and best practices.  The mechanical conversion compiled and ran but lint finds lots of fluff and I know it can be much cleaner.

Controlling Ardour with OSC and Android

Now that I have a stable RPi3 running alpine linux 4.14.52-0-rpi2, jackd2 1.9.10, and ardour 5.12.0, and have the recording and playback operational; it is time to work on the remote control.  The use case I am working on is to have the RPi3 with a battery and a stereo mic in a small bag that can be placed unobtrusively in the center of a jam circle and record the session.  I want to have a small android tablet controlling the mix and transport in hand.  That will operate ardour using the OSC protocol.  

It is easy to enable OSC in Ardour, see the Ardour Manual section here. 
The more complicated part is to acquire a suitable Android app that can deal with Ardour.
Candidates include TouchOSC for Android and iPad, which looks full featured and not very expensive, and a number of other apps in various states of development or abandonment. 

As I prefer free and open source software,  I settled on ardmix, by Detlef Urban, which is a working Android app.  The app has to be built from source so my Android Studio adventure begins.

I installed and built oscchief, a very useful command line osc tool from Sebastian Ruml.  This allows me to emulate both sides of the full system, either ardour or the ardmix app.  I can see the OSC messages being sent, and send appropriate canned messages for testing and debugging.

Android development is a complex and dynamic effort.  I feel like Alice in Wonderland, 

"Now, here, you see, it takes all the running you can do to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!"

So my implicit task list has just enlarged while I refresh my Android development skill.
I also want to add the led blinking lights to my list, as the RPi3 has a red and a green LED and I think they should indicate running (green) and recording (red).  That looks like a fun diversion when the android complexities get overwhelming.

Jack configuration: running with low latency

I have been using the jack audio connection kit  on linux since I can recall and ardour since 1999, and trust them to run well together.  I tried both jack1 and jack2 on the RPi3 and both run fine, so I went with jack2 as it can use more than one cpu.  I wrote an OpenRC start/stop/status script that handles the desired ulimit settings, as I could not get pam limits.conf to work in Alpine.   I built my own jackd from jack2 git source so I could do without the dbus configuration, trying to keep this simple.

#!/sbin/openrc-run

#

# Copyright (C) 2018, Samuel S Chessman

# SPDX-License-Identifier: GPL-3.0-or-later

# Start the jackd audio daemon as root for rt/memlock

# the settings below are in /etc/conf.d/jackd

#name=jackd

#pidfile=/var/run/jackd.pid

#command_user="sam:realtime"

#command="/usr/local/bin/jackd"

#command_args="-t 200 -p 2048 -R -n default -d alsa -s -n2 -r96000 -p 512 -dhw:RPiCirrus"

#command_background=true

# set the jackd ulimit

ulimit -r 99

ulimit -l 131072

ulimit -e unlimited

# set the users ulimit on ssh login

PID=$(cat /var/run/sshd.pid)

prlimit  -p $PID  --rtprio=99

prlimit  -p $PID  --memlock=134217728

prlimit  -p $PID  --nice=-20

depend() {

        after alsa

        after sshd

}

status() {

        if [ -e ${pidfile} ] ; then

                su $user -c "jack_lsp -A"

                eend $? "jackd is not running"

        else

                eerror "jackd is not running"

        fi

}

To have this run at boot:
rc-update add jackd default

There is a status command:
/etc/init.d/jackd status
system:capture_1
   alsa_pcm:hw:RPiCirrus:out1
system:capture_2
   alsa_pcm:hw:RPiCirrus:out2
system:playback_1
   alsa_pcm:hw:RPiCirrus:in1
system:playback_2
   alsa_pcm:hw:RPiCirrus:in2    

This corresponds to what ALSA and jack_lsp are reporting.
aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vc4hdmi [vc4-hdmi], device 0: MAI PCM vc4-hdmi-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: RPiCirrus [RPi-Cirrus], device 0: WM5102 AiFi wm5102-aif1-0 []
  Subdevices: 0/1
  Subdevice #0: subdevice #0
oscar:/opt/audiopi$ jack_lsp
system:capture_1
system:capture_2
system:playback_1
system:playback_2

First sound: cirrus logic configuration

The cirrus logic audio card drive is standard in the linux 4.14.52 kernel supplied by Alpine Linux, and the driver loads when the firmware overlay is installed.  After this, it is necessary to configure the card as desired using the amixer cset capability.  The original versions have been updated for the current driver and can be found at http://www.horus.com/~hias/tmp/cirrus/cirrus-ng-scripts.tgz.  They have been rewritten to use a common function definition script file and the new register names.

I use a Sony Stereo ceramic electret condenser mic ECM-CS3 which needs a 5v mic bias.  The script Record_from_Linein_Micbias.sh sets the cirrus logic card up fine for this and recording works fine.  Playback currently through a pair of earbuds for testing.

The idea is to put the RPi, a battery and the mic in a small satchel bag and put it on the floor in the middle of the acoustic jam sessions to record the tunes.  I plan to setup an Open Sound Control interface on a tablet to adjust the mix, more on that to come.

Dependencies: Building the rest of the lot

Ardour 5.12 has lot of opensource library dependencies.  Many of them are available already built in the Alpine Linux armv7 repository, and the rest have to be built from source.  This is not trivial.  I was able to install 58 tools and libraries with the get_alpine_deps.sh script found on my audiopi gitlab repository.

The other 23 need to be configured and compiled from source.  See ardour_dep_urls.txt.

The gory details of waf, perl, configure etc are not of tremendous interest except where the default process needs a nudge.   I'll document what I did for the following to make them compile and install on Alpine Linux.  I'm using 

./configure --prefix=/usr/local
 ./waf configure --prefix=/usr/local
 perl Makefile.PL PREFIX=/usr/local

• ExtUtils-MakeMaker-6.64: needed perl-dev installed.  Updated get_alpine_deps.sh.  make test needed fakethr.h, sudo touch /usr/lib/perl5/core_perl/CORE/fakethr.h; same for sudo touch /usr/lib/perl5/core_perl/CORE/perlsfio.h
• LRDF-0.5.1-rg
• XML-Parser-2.41
• XML-Simple-2.22: needed perl-xml-namespacesupport and perl-xml-sax, perl-xml-sax-base installed.  Updated get_alpine_deps.sh
• aubio-0.3.2
• gtk-doc-1.21: needed docbook-xsl installed, Updated get_alpine_deps.sh
• gtk-engines-2.21.0
• jpeg-9a
• libart_lgpl-2.3.21
• libiconv-1.14: edited srclib/stdio.h to comment out _GL_WARN_ON_USE (gets, "gets is a security hole - use fgets instead");
• liblo-0.28
• lilv-0.24.3: needs lv2, serd, sord installed
• lv2-1.14.0: install before lilv
• nss-3.25: export NSPR_INCLUDE_DIR=/usr/local/include/nspr for nss after installing nspr
• nss-pem-1.0.2
• rdflib-4.1.2: sudo python setup.py install
• rubberband-1.8.1: needs vamp sdk installed, needs ladspa-dev installed.  Updated get_alpine_deps.sh
• serd-0.29.2: install before lilv
• sord-0.16.1: install before lilv
• sratom-0.6.0: install before lilv
• suil-0.10.0
• vamp-plugin-sdk-2.5: install before rubberband

Reboot: Alpine Linux and Ardour 5.12

Alpine Linux has a Raspberry Pi distribution with a modern kernel (4.14.52).  I installed this on a 32GB SD card and will be compiling and running Ardour 5.12 on this using the Cirrus Logic Audio Card which appears to be unavailable since 2016.   Perhaps the Blokas PiSound would work even better.

Installing Alpine Linux was not hard, following the Classic installation instructions.  To get the Cirrus Logic Audio Card driver working, the device tree overlay for wm5102 needs to be loaded.  There also is a modprobe dependency, put this in /etc/modprobe.d/cirrus.conf

softdep arizona-spi pre: arizona-ldo1

The file  /media/mmcblk0p1/config.txt needs to have the overlay added:
head /media/mmcblk0p1/config.txt
disable_splash=1
boot_delay=0
dtoverlay=vc4-kms-v3d
dtoverlay=rpi-cirrus-wm5102
dtoverlay=pi3-disable-bt
gpu_mem=256
gpu_mem_256=64

This successfully adds the device tree overlay at boot and loads the appropriate modules.

dmesg | tail -19

[ 2271.440909] snd-rpi-cirrus soc:sound: ASoC: CODEC DAI wm5102-aif1 not registered - will retry

[ 2271.444327] wm8804 1-003b: revision E

[ 2271.445857] snd-rpi-cirrus soc:sound: ASoC: CODEC DAI wm5102-aif1 not registered - will retry

[ 2271.483599] arizona spi0.1: Failed to get mclk1: -2

[ 2271.483615] arizona spi0.1: Failed to get mclk2: -2

[ 2271.483939] LDO1: supplied by RPi-Cirrus 1v8

[ 2271.484938] snd-rpi-cirrus soc:sound: ASoC: CODEC DAI wm5102-aif1 not registered - will retry

[ 2271.492410] arizona spi0.1: WM5102 revision C

[ 2271.520832] MICVDD: supplied by RPi-Cirrus 1v8

[ 2271.521795] Adding alias for supply MICVDD,(null) -> MICVDD,spi0.1

[ 2271.522102] Adding alias for supply MICVDD,(null) -> MICVDD,spi0.1

[ 2271.522109] Adding alias for supply DBVDD2,(null) -> DBVDD2,spi0.1

[ 2271.522115] Adding alias for supply DBVDD3,(null) -> DBVDD3,spi0.1

[ 2271.522121] Adding alias for supply CPVDD,(null) -> CPVDD,spi0.1

[ 2271.522130] Adding alias for supply SPKVDDL,(null) -> SPKVDDL,spi0.1

[ 2271.522144] Adding alias for supply SPKVDDR,(null) -> SPKVDDR,spi0.1

[ 2271.523659] snd-rpi-cirrus soc:sound: ASoC: CODEC DAI wm5102-aif1 not registered - will retry

[ 2271.553689] snd-rpi-cirrus soc:sound: ASoC: CODEC DAI wm5102-aif1 not registered - will retry

[ 2271.681956] snd-rpi-cirrus soc:sound: wm5102-aif1 <-> 3f203000.i2s mapping ok

aplay -l

**** List of PLAYBACK Hardware Devices ****

card 0: RPiCirrus [RPi-Cirrus], device 0: WM5102 AiFi wm5102-aif1-0 []

  Subdevices: 1/1

  Subdevice #0: subdevice #0

lsmod

Module                  Size  Used by

snd_soc_wm5102        385024  1

snd_soc_wm_adsp        40960  1 snd_soc_wm5102

gpio_arizona           16384  0

snd_soc_arizona        45056  1 snd_soc_wm5102

arizona_micsupp        16384  1

arizona_spi            16384  0

arizona_ldo1           16384  1

snd_soc_wm8804_i2c     16384  1

snd_soc_rpi_cirrus     20480  0

snd_soc_wm8804         16384  1 snd_soc_wm8804_i2c

snd_soc_bcm2835_i2s    16384  2

snd_soc_core          180224  7 snd_soc_wm8804,snd_soc_rpi_cirrus,snd_soc_wm5102,arizona_micsupp,snd_soc_bcm2835_i2s,snd_soc_arizona,snd_soc_wm_adsp

snd_compress           20480  2 snd_soc_core,snd_soc_wm_adsp

snd_pcm_dmaengine      16384  1 snd_soc_core

snd_pcm                94208  6 snd_soc_wm8804,snd_soc_rpi_cirrus,snd_pcm_dmaengine,snd_soc_bcm2835_i2s,snd_soc_arizona,snd_soc_core

spi_bcm2835            16384  0

snd_timer              32768  1 snd_pcm

i2c_bcm2835            16384  0

snd                    65536  5 snd_compress,snd_soc_rpi_cirrus,snd_timer,snd_soc_core,snd_pcm
...

The modprobe.d file can be found on my audiopi gitlab repository.

Ardour and the Pi

I was able to compile (waf) ardour4 on the Raspberry Pi3 and it works fine with the Cirrus Logic Audio Card.  I can record and play back in stereo using the onboard microphones and headphone output.  I will have to try my preamp and AKG condenser microphone and confirm the line in WORKS but I have confidence.

Compiling ardour is not for the fainthearted.  The dependency list is extensive and it took a while on the Pi3 but nothing seemed out of the ordinary for a project of this complexity.

If you are really interested, see http://ardour.org/current_dependencies.html for the dependencies and http://ardour.org/building_linux.html for the procedure.

I had to build a few of the dependencies:

• atkmm-2.22.7
• libart_lgpl-2.3.21
• liblrdf-0.5.0
• pangomm-2.28.4

 but raspbian has a working jack daemon and it runs fine.
Time to try some plugins and see if the whole system can handle signal processing.

Thanks to all the Ardour and Linux Audio developers who have made this possible!