echobuf

Audio instant-replay buffer for Linux. Continuously records system audio into a rolling RAM buffer — hit a hotkey and the last N seconds are saved to a WAV file. Like ShadowPlay, but for audio.

Install

pip install echobuf

Requires Python 3.11+ and either PipeWire or PulseAudio.

Optional extras:

pip install echobuf[tray]      # system tray icon
pip install echobuf[hotkey]    # built-in global hotkey via pynput
pip install echobuf[dev]       # pytest for development

Quick start

# Start the daemon
echobuf daemon &

# Save the last 10 seconds of audio
echobuf save

# Save with a label
echobuf save --label "cool_riff"

# Check status
echobuf status

# Stop the daemon
echobuf quit

Saved files go to ~/samples/ by default, organized by date.

Binding to your WM

The recommended way to trigger saves is by binding echobuf save in your window manager. The daemon doesn't need to know about input devices — your WM handles that better than we can.

i3 / sway:

bindsym $mod+Shift+s exec --no-startup-id echobuf save
bindsym $mod+Shift+d exec --no-startup-id echobuf save --label dialogue
bindsym $mod+Shift+m exec --no-startup-id echobuf save --label "$(rofi -dmenu -p tag)"

GNOME: Settings → Keyboard → Custom Shortcuts → add echobuf save

KDE: System Settings → Shortcuts → Custom Shortcuts → add echobuf save

Configuration

Config lives at ~/.config/echobuf/config.toml. Created with defaults on first use via the tray icon, or create it manually:

[buffer]
seconds = 10              # rolling buffer length
post_seconds = 0          # extra seconds captured after save

[capture]
backend = "auto"          # auto | pipewire | pulse
source = "system"         # system | app:<name>
sample_rate = 48000
channels = 2

[output]
directory = "~/samples"
template = "%(date)s/%(time)s_%(counter)03d.%(ext)s"
format = "wav"
sanitize = true

[hotkey]
binding = ""              # e.g. "<ctrl>+<shift>+s" (requires echobuf[hotkey])

[notifications]
enabled = true
sound = true

[logging]
level = "info"

Output templates

File paths use yt-dlp–style tokens:

Default values: %(label|untitled)s falls back to untitled when no label is given.

CLI reference

echobuf daemon              Run the capture daemon in foreground
echobuf save [--label NAME] Trigger a save
echobuf status              Print daemon status (backend, buffer, saves)
echobuf sources             List available capture sources (system + apps)
echobuf set-source <spec>   Switch source: "system" or "app:<name>"
echobuf pause               Pause capture (daemon keeps running)
echobuf resume              Resume capture
echobuf quit                Stop the daemon
echobuf tray                Launch the system tray icon

Per-app capture

Capture audio from a specific application instead of the full system mix:

# Via config
[capture]
source = "app:firefox"

# At runtime
echobuf set-source app:spotify
echobuf set-source system          # switch back

On PipeWire, per-app capture uses native graph linking — the app's audio is tapped without any routing changes, so there's no latency penalty and the user keeps hearing audio normally.

On PulseAudio, a null sink + loopback is created. The user still hears audio, but through a loopback with ~30ms latency.

System tray

echobuf tray

Requires echobuf[tray]. Provides a menu to save, pause/resume, open the save folder, edit config, and quit the daemon.

systemd service

A unit file is included at contrib/echobuf.service. To install:

cp contrib/echobuf.service ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user enable --now echobuf

The tray icon should be started separately via your desktop environment's autostart.

Architecture

┌──────────────────────────────────────────────┐
│                echobuf daemon                │
│                                              │
│  Audio Source ──▶ Ring Buffer ──▶ WAV Writer  │
│  (parec/pw-record)  (numpy)    (on trigger)  │
│                                              │
│  IPC Server (Unix socket, JSON)              │
└──────────┬───────────────────────────────────┘
           │
    CLI / Tray / WM binding

• Ring buffer: preallocated NumPy array, ~22 MB for 60s of 48kHz stereo
• Backends: PipeWire (pw-record) auto-detected, PulseAudio (parec) fallback
• IPC: Unix socket at $XDG_RUNTIME_DIR/echobuf.sock, line-delimited JSON
• Output: 16-bit PCM WAV via libsndfile

License

MIT