transporter

A minimal, bit-perfect Linux music player.

Bare-metal ALSA-direct playback. No sound server in the audio path, no resampling, no DSP, no software volume on the bit-perfect path. Wayland-native GUI with a software renderer — no GPU required.

Features

• Bit-perfect ALSA-direct output (hw: device, no PipeWire / PulseAudio in path)
• Hard exclusive device ownership — kernel-level lock, no sharing
• Format support: FLAC, WAV, AIFF, MP3, Ogg Vorbis, Opus, ALAC (M4A)
• Native sample-rate switching — DAC follows the track, no resampling ever
• Gapless playback via background preloading; format mismatch falls through gracefully
• Real-time audio thread (SCHED_FIFO priority 80, mlockall, CPU affinity)
• Pipeline view — live per-stage telemetry: formats, ring fill, xrun count, RT mode, bit-perfect verdict with per-condition breakdown
• Live FFT spectrum analyser (1024-point, 32 log-spaced bars, 20 Hz–20 kHz)
• Waveform amplitude envelope overlaid on seek bar
• Time-synced LRC lyrics display
• Album art thumbnails in library (cover.jpg / cover.png probed automatically)
• SQLite-backed music library with background scanner
• Play queue with shuffle and repeat (none / one / all); shows title, artist, and duration from library
• Session persistence — queue, shuffle, and repeat state survive restarts
• M3U / M3U8 playlist support in headless mode (--no-gui)
• Mini/compact mode (480×72 strip) with progress bar
• MPRIS (org.mpris.MediaPlayer2) — playback, volume, shuffle, loop status all wired; playerctl and status-bar applets work
• Wayland-native — no X11, no GPU driver stack (wl_shm software render)

Keyboard shortcuts

Key	Action
Space	Play / Pause
← / →	Seek −5 s / +5 s
Ctrl+← / Ctrl+→	Previous / Next track
+ / =	Volume +5%
−	Volume −5%
M	Toggle mute
S	Toggle shuffle
R	Cycle repeat mode (off → track → playlist)
F1–F4	Switch view (Main / Library / Pipeline / Queue)
Tab	Cycle views

XF86 media keys (play/pause, stop, next, prev, mute, vol up/down) are also handled.

Dependencies

Install on Arch:

sudo pacman -S meson ninja pkg-config \
  flac mpg123 libvorbis opus \
  alsa-lib \
  wayland wayland-protocols libxkbcommon \
  dbus sdbus-cpp \
  sqlite \
  libpng libjpeg-turbo

Install on Debian / Ubuntu:

sudo apt install \
  meson ninja-build pkg-config \
  libflac-dev libmpg123-dev libvorbis-dev libopus-dev \
  libasound2-dev \
  libwayland-dev wayland-protocols libxkbcommon-dev \
  libdbus-1-dev libsdbus-c++-dev \
  libsqlite3-dev \
  libpng-dev libjpeg-dev

Dear ImGui, toml++, doctest, and the Apple ALAC decoder are bundled under third_party/.

Build

meson setup build
ninja -C build

Binary: build/transporter.

System install:

sudo ninja -C build install

Realtime audio (recommended)

The audio thread requests SCHED_FIFO priority 80 with mlockall and CPU affinity. Grant it without root:

sudo gpasswd -a "$USER" audio

Create /etc/security/limits.d/99-transporter.conf:

@audio  -  rtprio  95
@audio  -  memlock unlimited

Log out and back in. transporter detects the granted capability at startup; falls back to SCHED_OTHER and reports the actual mode in the Pipeline view.

Usage

transporter [OPTIONS] [FILE]

Play a file:

transporter /path/to/track.flac

Open the library browser (no file argument):

transporter

Pin a specific DAC:

transporter --device hw:CARD=Topping_E70,DEV=0

Headless playback (no GUI, exits when done):

transporter --no-gui /path/to/track.flac

Config file

~/.config/transporter/config.toml

[device]
# hw: string for the DAC to claim at startup. Saved automatically when you
# pick a device in the GUI; you rarely need to set this manually.
preferred = "hw:CARD=Topping_E70,DEV=0"

[audio]
# ALSA period size in milliseconds and number of periods per ring.
# Total latency ≈ period_ms × period_count. Defaults: 12 ms × 4 = ~50 ms.
period_ms = 12
period_count = 4
# RT scheduling policy: "auto" tries SCHED_FIFO, falls back to SCHED_OTHER;
# "fifo" requires RT capability (fails hard if not granted); "other" disables RT.
rt_policy = "auto"

[library]
roots = ["/home/user/Music"]
# Glob patterns to skip during scanning (e.g. hidden dirs, sample packs).
ignore_patterns = [".*", "Samples"]

[theme]
# Follow Hyprland border/gap colours from ~/.config/hypr/hyprland.conf.
follow_hyprland = true
# Override with a custom theme TOML file (disables Hyprland detection when set).
# override_file = "~/.config/transporter/theme.toml"

[ui]
# View shown at startup: "main", "library", or "pipeline".
default_view = "main"

[dbus]
enabled = true

License

GPL-3.0-or-later. See LICENSE.