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BlitzLoop on a dedicated x86 box (with Arch Linux)

Normally, BlitzLoop runs on OpenGL on GLX on Xorg, and uses mpv with the opengl-cb backend. However, for a dedicated system, it also supports a raw DRM backend that runs without a windowing system or compositor. This guide focuses on this mode, using Arch Linux as the base OS.

This guide is intended for x86 systems dedicated to BlitzLoop. However, feel free to take whatever bits are useful to you and customize your setup. These steps were tested on a LattePanda, but should work on basically any x86 box with proper KMS support (i.e. Intel or AMD, and perhaps Nvidia with Nouveau).

Prerequisites

  • An x86-64 machine with modern KMS/DRM graphics (e.g. Intel GPU)
  • Arch Linux x86-64

Installation

Base OS

Follow the Arch Linux installation guide.

Users and permissions

As root, add a user for BlitzLoop:

useradd -m blitz

The rest of this guide assumes you're running as the blitz user and uses sudo to refer to commands to be run as root; you can grant sudo access to the blitz user or use a separate root shell.

Grant blitz audio/video access and real-time priority for JACK:

sudo usermod -aG audio,video blitz
echo 'blitz - rtprio 99' | sudo tee -a /etc/security/limits.conf

Configure environment

Set the locale to something with UTF-8:

echo 'en_US.UTF-8 UTF-8' | sudo tee /etc/locale.gen
sudo locale-gen
echo 'LANG=en_US.UTF-8' | sudo tee /etc/locale.conf

Log out and back in.

Update system

sudo pacman -Syu

LattePanda specific configuration

Skip this section if you're not using a LattePanda. However, if you need to configure mixer controls, the last two commands may be useful on your platform too.

To make the built-in audio work, a kernel command line argument is required. You also need another argument to disable the (nonexistent) DSI panel. Edit /etc/default/grub and set:

GRUB_CMDLINE_LINUX="snd_soc_rt5645.quirk=0x31 video=DSI-1:d"

Then update the config, fix up the ALSA UCM config, set the correct mixer profile, and save the settings:

sudo grub-mkconfig -o /boot/grub/grub.cfg

# Symlink the ALSA UCM config files so alsaucm will find them.
A=AMICorporation-Defaultstring-Defaultstring-CherryTrailCR
C=chtrt5645
cd /usr/share/alsa/ucm/
sudo mkdir $A
sudo ln -s ../$C/HiFi.conf $A/HiFi.conf
sudo ln -s ../$C/$C.conf $A/$A.conf

# Set up the mixer controls as required
sudo alsaucm -c $C set _verb HiFi set _enadev Headphone

# This is useful on other platforms that need to store mixer controls too
sudo ln -s /usr/lib/systemd/system/alsa-restore.service /etc/systemd/system/multi-user.target.wants/
sudo alsactl store

We also want to disable some CPU C-states, since otherwise the latency spikes cause frame dropping:

cat <<EOF | sudo tee /etc/tmpfiles.d/10-cpuidle-control.conf
w /sys/devices/system/cpu/cpu*/cpuidle/state[2345]/disable - - - - 1
EOF

Reboot for the changes to take effect. The system should now come up with functional audio. The audio device name is hw:chtrt5645.

Install dependencies and BlitzLoop

We need a bunch of dependencies from AUR, which will be a lot easier to do with yaourt:

# Manually pull in jack2 instead of jack, which works better here
sudo pacman -S --needed base-devel jack2 alsa-tools alsa-utils wget git mpv libva-intel-driver

mkdir -p ~/pkg; cd ~/pkg
wget https://aur.archlinux.org/cgit/aur.git/snapshot/package-query.tar.gz
tar xvzf package-query.tar.gz
cd ~/pkg/package-query
MAKEFLAGS="-j4" makepkg --skippgpcheck --syncdeps
sudo pacman -U package-query-*.pkg.tar.xz

cd ~/pkg
wget https://aur.archlinux.org/cgit/aur.git/snapshot/yaourt.tar.gz
tar xvzf yaourt.tar.gz
cd ~/pkg/yaourt
MAKEFLAGS="-j4" makepkg --skippgpcheck --syncdeps
sudo pacman -U yaourt-*.pkg.tar.xz

cd ~/pkg
yaourt -S python-pympv-git # required until python-pympv-0.5.1 is in AUR
yaourt -S mpv-git # required until mpv-0.29.1 or later is released and in Arch
yaourt -S blitzloop-git

TODO: kms++ is a dependency too, get it into AUR

Configure BlitzLoop

mkdir -p ~/.config/blitzloop
cat <<EOF >~/.config/blitzloop/blitzloop.conf
display=kms
EOF

Get songs

Put your songs in /home/blitz/.local/share/blitzloop/songs/ (create it first).

Test out BlitzLoop

Run:

blitzloop --mpv-audio-device=alsa/hw:chtrt5645 --no-audioengine --mpv-extra="audio-format=s16"

Connect to TCP port 10111 and check to see if everything works properly. Note that you will not have any microphone support at this point. You should use the ALSA device short name instead of chtrt5645; check /proc/asound/cards for a list. The audio-format=s16 parameter is required to work around driver issues in LattePanda, and should not be required on other systems (but it probably won't hurt).

Systemd service

This sets up the service with a separate input card for microphones. See blitzberry.md#mic-setup for other options.

cat >~/startblitz.sh <<EOF
#!/bin/sh
cd "$(dirname "$0")"
export JACK_NO_AUDIO_RESERVATION=1
jackd -R --timeout 10000 -d alsa -P hw:chtrt5645 -r 48000 -p 240 -n 2 -o 2 -S &
jack_pid=$!
alsa_in -j mic -d hw:Receiver -c 2 -p 240 -n 2 -q 0 &
alsa_pid=$!
trap "kill $jack_pid $alsa_pid" EXIT
sleep 2
python -u /usr/bin/blitzloop --port=80 --mpv-ao=jack --mics=mic:capture_1,mic:capture_2 "$@"
EOF
chmod +x ~/startblitz.sh

cat <<EOF | sudo tee /etc/systemd/system/blitzloop.service > /dev/null
[Unit]
Description=BlitzLoop

[Service]
Type=simple
User=blitz
Group=blitz
ExecStart=/home/blitz/startblitz.sh
AmbientCapabilities=CAP_NET_BIND_SERVICE
KillMode=mixed
TimeoutStopSec=5
LimitRTPRIO=99
LimitMEMLOCK=1024000000

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl enable blitzloop
sudo systemctl start blitzloop

WiFi setup

See blitzberry.md#wifi-setup.
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