Phosphor

A software XY oscilloscope for everything your PC plays.

Phosphor watches "oscilloscope music" (Jerobeam Fenderson et al.) draw its hidden pictures, and makes any system audio look good. In XY mode the left channel moves the beam horizontally and the right channel moves it vertically; scope music is composed so this traces actual drawings. Beam brightness falls as the beam moves faster and the phosphor decays in two layers (a blue-white flash where the beam lands, a colored glow that lingers) — P7 phosphor physics, the details that make it look like the real instrument.

The animation above is a real Phosphor capture, exported straight from the app's own clip recorder.

Drawn by sound

A few real captures, straight from Phosphor's snapshot button — each shape is just a stereo audio file, traced live by the beam:

In use

The full window — headerbar transport, source picker, and the slider rail down the side — running on a normal Linux desktop:

And the mini player: a borderless, always-on-top square you tuck into a corner while you work. Snapshots (S) drop into ~/Pictures/Phosphor and browse like any other folder.

_{“Made with Claude Fable 5 — finished the last prompt before the feds took it down. Amazing model…” — Ben
Shipped to GitHub by Claude Opus 4.8, the day Fable 5 went dark (12 June 2026).}

Install

Debian / Ubuntu / Linux Mint — prebuilt package

Download the .deb from the latest release, then:

sudo apt install ./phosphor_2.6.0_all.deb

That installs the Phosphor launcher (applications menu + desktop icon) and pulls in the dependencies below automatically. (A harmless N: Download is performed unsandboxed… note just means apt couldn't read the file as its sandbox user from your home directory — the install still succeeds; install from /tmp to avoid it.)

From source

git clone https://github.com/RamenFast/phosphor.git
cd phosphor
python3 phosphor.py

Dependencies, all in the stock Mint / Ubuntu repositories:

sudo apt install python3-gi python3-gi-cairo gir1.2-gtk-3.0 \
                 pulseaudio-utils ffmpeg python3-numpy

• PyGObject + GTK 3 — the application and its UI
• parec / pacat (pulseaudio-utils) — audio capture and playback, over PulseAudio or PipeWire
• ffmpeg — audio-file decoding and clip (mp4) export
• numpy (optional) — vectorizes the signal path (~7× faster, comfortably feeding high-refresh monitors); a pure-python fallback keeps working without it

The GPU renderer binds OpenGL through GTK's own libepoxy with ctypes — no PyOpenGL needed. Phosphor targets Linux desktops (X11 or Wayland) running PipeWire or PulseAudio.

Build the package yourself

packaging/build-deb.sh     # -> packaging/dist/phosphor_<version>_all.deb

Panel applet (Cinnamon)

A live vectorscope right in your Cinnamon panel — like a CPU monitor, but it draws your audio. It reuses Phosphor's exact signal path through a tiny headless feed, so the panel traces the signal identically to the full app.

applet/install.sh   # then add "Phosphor Scope" from Menu -> Applets

Hover for a bigger scope, switch modes, follow your panel theme or pick a Phosphor colour (AMOLED background included), set the refresh rate to match your monitor, and a ⏻ toggle gives it a proper CRT power-off. See applet/README.md.

What to scope

The source picker offers three kinds of target:

• APP — one playing application (game audio without the music player, or vice versa); these come and go, the refresh button re-scans
• OUT — everything a given output plays (default: your default output)
• IN — microphones (hum into the Q2U for live Lissajous figures)

Or skip capture entirely: open an audio file (O, the folder button, or the right-click menu) and Phosphor decodes it with ffmpeg, plays it out loud, and scopes it directly — no separate player needed. Opening a file discovers every track in its folder: transport buttons (⏮ ⏯ ⏭) and a seek slider with an elapsed/total readout appear in the title bar, tracks auto-advance, and pause freezes decode and playback in place. A speaker/mic/app icon beside the source picker shows what kind of target is selected.

Compose (draw your own oscilloscope music)

The scope, run in reverse. Hit the ✏ pencil (or D), draw a shape on the screen, release — Phosphor resamples your path into a closed audio loop traversed at constant speed (left channel = X, right channel = Y), plays it out loud, and the scope draws it back. Draw a mushroom, hear the mushroom.

• scroll retunes the loop frequency (20–400 Hz): same shape, new pitch
• draw again to replace the shape; Esc or the pencil exits
• right-click → Export drawing as WAV writes 10 s to ~/Music/Phosphor/ — that file draws your shape on any XY oscilloscope (or in Phosphor itself, or sent to a friend)
• snapshots (S) and clips (C) work while a loop plays, so you can keep a picture or a video of your drawing drawing itself

App targets are remembered by application name, not stream number — when Chrome finishes a song its stream dies, and Phosphor now waits for that same app to play again and re-grabs it automatically (up to 3 min) instead of dumping you onto another source.

Modes

Mode	What it's for
XY (scope art)	Oscilloscope music. The real deal.
XY · goniometer	Ordinary songs: raw XY collapses stereo music into a diagonal line; rotated 45° the mono energy stands upright and stereo width blooms sideways.
XY · dots	The same XY field as discrete sample dots, like a vectorscope's dot display — shows where the beam dwells.
Waveform	Dual trace with rising-edge triggering so pitched sounds hold still.
Spectrum	Log-frequency bars, fast attack / phosphor fall.
Spectrum · radial	The same analysis swept around a circle, bass at twelve o'clock.

Controls

• ⏻ Live — capture on/off, with the status readout right beside it. Off = stream closed, render loop stopped, ~0% CPU.

• Title bar — open file, mini view, pin-above (hideable in settings), and the settings gear, sysmon-style.

• 📷 / ⏺ — snapshot to ~/Pictures/Phosphor, save the last 10 s as mp4 with sound to ~/Videos/Phosphor. Both re-render the captured audio offline, so exports look exactly like the screen did.

• Sliders — Gain / Glow / Beam, each with an editable percent box: click and type an exact value. Scroll the scope to zoom gain; the graticule grows and shrinks with it, octave-stepped like a volts/div switch. Or flip on Auto gain (settings or right-click) and the trace autosizes to the screen: gain follows the signal's peak — instant attack when something would clip off-screen, slow glide as it fades.

• ⚙ settings — renderer (GPU/CPU), GPU quality (2×/3× supersampling) and CPU resolution selectors, Scope detail (feed sample rate: 48/96/192 kHz — higher rates resample with proper sinc reconstruction, so the scope traces the true curves between samples and fine scope-art detail stops washing out), beam Focus (sharper beams keep dense scope-art scenes from washing out), themes (P7 Green, Amber, Ice Blue, White, Vaporwave, Red Phosphor, Ultraviolet, Solar Gold, Cyan Tube, Custom), grid, AMOLED scope background, UI style (System / Dark / Light / AMOLED pink-on-black chrome with yellow selected states), FPS overlay (now also shows python ms per frame — if that's tiny and fps is below refresh, the GPU or compositor is the limit), and a Max FPS cap (leave at 0 to follow the monitor's refresh rate; setting it equal to the refresh rate makes the cap race vsync and drop frames).

  The GPU beam uses an analytic erf line integral (the woscope trick): consecutive segments join without double-depositing energy, which is what keeps complex scenes like 72 Pantera from blooming into fuzz. Compositing happens in linear light with output dithering: faint trail detail is no longer crushed by display gamma, and dark glow falloff has no banding rings.

• Mini — borderless always-on-top square. Drag to move, drag the bottom-right corner or Ctrl+scroll to resize (square stays square, up to 1000 px), right-click for the full menu (modes, themes, grid, pin, sizes up to Extra large…), double-click to restore. Window positions, sizes, and all settings are remembered in ~/.config/phosphor/settings.json, including whether you quit in mini.

• Keys — Space capture · O open file · D compose (draw) · M mini · F11 fullscreen scope (chrome-less; also the path to the monitor's full refresh rate, since compositors unredirect fullscreen windows) · S snapshot · C clip · P pin · G grid · F fps · scroll = gain (pitch while composing) · Q/Esc quit.

Trails grade continuously in time: each sample's deposit is pre-decayed by its age within the frame, so slowly drifting sweeps blend the way real phosphor does instead of leaving stepped duplicate lines.

Resource behavior (measured)

State	CPU
Capture off	~0% (parec killed, render loop removed, PipeWire suspends the source)
Armed but silent	<1% (silence detected by content; monitors deliver zeros, so an empty-buffer check doesn't work)
Live, GPU renderer	~10% of one core
Live, CPU renderer	~25–35% of one core (signal math + phosphor decay now run on a worker thread, so the UI stays smooth and slow frames drop instead of queueing)

Things to try

• Jerobeam Fenderson — How To Draw Mushrooms; whole albums at https://oscilloscopemusic.com
• Put on any normal song in XY · goniometer and watch the stereo image dance.

Future

See FUTURE.md — compose mode shipped in 2.4; next candidates: SVG import for compose, GL bloom, multi-app mixing, a Cinnamon applet.

License

GPL-3.0-or-later — see LICENSE. Free as in phosphorescence: use it, read it, change it, share it; derivatives stay free too.