Captioneer/README.md

# Captioneer

Captioneer creates local, live English captions for audio playing through the current default PulseAudio or PipeWire output device. It captures the sink's monitor source and transcribes it with Parakeet TDT v2; VAD mode uses Silero to find speech boundaries.

Audio and captions stay on your machine. Nothing is uploaded after the one-time model download.

Captioneer provides two commands:

- `captioneer` is the lightweight, terminal-only command and has no GTK dependency.
- `captioneer-desktop` adds a GTK4 subtitle overlay and can output to the overlay, terminal, or both. It is built with the `gtk` build tag.

## Setup

The terminal command requires Linux x86_64, Go 1.26.2 or newer, `pactl`, and `parec`. The desktop command additionally needs GTK4 and GTK4 Layer Shell development/runtime libraries. PipeWire works through its PulseAudio compatibility layer.

Download the large recognition models once:

```bash
./scripts/download-models.sh
```

This creates `models/parakeet-tdt-v2/` and `models/silero_vad_v5.onnx`. They are intentionally excluded from Git.

## Terminal captions

VAD mode is recommended for normal use. It redraws a provisional caption while speech is active and commits a timestamped caption after the utterance ends:

```bash
go run ./src/cmd/captioneer --mode=vad
```

Fixed mode transcribes independent, exact-duration chunks:

```bash
go run ./src/cmd/captioneer --mode=fixed --chunk-duration=1s
```

Build and run the terminal binary:

```bash
go build -o build/captioneer ./src/cmd/captioneer
./build/captioneer --mode=vad
```

Final captions use stdout; diagnostics and overload warnings use stderr. This makes redirection useful:

```bash
./build/captioneer --mode=vad > captions.txt
```

Press <kbd>Ctrl</kbd>+<kbd>C</kbd> to stop. Captioneer stops `parec` and flushes pending audio before exiting.

## Desktop overlay

The simplest Bazzite development command is:

```bash
./scripts/distrobox/run.sh --mode=vad --output=overlay
```

Use `--output=both` to keep terminal output as well:

```bash
./scripts/distrobox/run.sh --mode=vad --output=both
```

In VAD mode, a 500 ms pause finalizes the current caption and starts the next line. The overlay keeps up to six completed lines above the active provisional caption; each completed line remains visible for at least three seconds. If a seventh line arrives sooner, the hard six-line cap removes the oldest. Text is left-aligned inside the centered, fixed-width dark bubble. Pointer input passes through the window by default. Empty completed captions hide the overlay.

To build outside the helper script, install GTK4 and GTK4 Layer Shell development packages, then run:

```bash
go build -tags gtk -o build/captioneer-desktop ./src/cmd/captioneer-desktop
./build/captioneer-desktop --mode=vad --output=overlay
```

### Wayland and X11 behavior

On KDE Plasma Wayland, GTK4 Layer Shell places Captioneer in the overlay layer near the bottom center without taking keyboard focus. With automatic monitor selection, the compositor chooses the recently active output. A numeric monitor index or connector name can be selected explicitly.

A normal GTK window does work on Wayland. What generic Wayland does **not** provide is a portable way for that window to force itself above all other windows or choose an exact screen position. If Layer Shell is unavailable, Captioneer uses a normal undecorated window and prints an explicit warning; compositor window rules may improve its stacking behavior. It never silently switches to XWayland—use `--overlay-backend=x11` when that route is wanted.

On X11/XWayland, Captioneer selects the monitor containing the mouse cursor in automatic mode and requests notification, keep-above, skip-taskbar, and skip-pager window-manager hints.

Layer Shell and X11 hints are requests, not universal guarantees. Same-layer windows, exclusive-fullscreen games, compositor policy, screenshots, screen sharing, and recording software can all behave differently. Captioneer does not attempt capture exclusion in this version.

## Command-line options

`--mode` is required for both commands. `captioneer-desktop` also requires `--output`.

### Transcription options

| Option | Default | Meaning |
| --- | --- | --- |
| `--mode=vad|fixed` | required | Speech-aware utterances or independent fixed chunks. |
| `--chunk-duration=1s` | `1s` | Fixed chunk length or VAD preview refresh interval. Accepts Go durations such as `500ms` or `2s`. |
| `--models-dir=models` | `models` | Directory containing `parakeet-tdt-v2/` and `silero_vad_v5.onnx`. |
| `--threads=2` | `2` | CPU threads used by recognition and VAD. |
| `--preview-threshold-dbfs=-45` | `-45` | RMS threshold that starts a provisional VAD caption. Raise it to reject background audio; lower it for quiet speech. |

### Desktop-only options

| Option | Default | Meaning |
| --- | --- | --- |
| `--output=terminal|overlay|both` | required | Select desktop-command renderers. `both` falls back to terminal if GTK initialization fails. |
| `--overlay-backend=auto|wayland|x11` | `auto` | Let GTK detect the backend, or require one explicitly. |
| `--overlay-opacity=0.90` | `0.90` | Dark bubble opacity from `0` to `1`. |
| `--overlay-font-size=28` | `28` | Font size in logical pixels. |
| `--overlay-bottom-margin=100` | `100` | Bottom margin in logical pixels. |
| `--overlay-max-width=1200` | `1200` | Fixed caption-bubble width; it is capped at 80% of the selected monitor. |
| `--overlay-monitor=auto` | `auto` | `auto`, a zero-based monitor index, or a connector name such as `DP-1`. |
| `--overlay-final-timeout=3s` | `3s` | Completed-caption lifetime; it must be `0s` or at least `3s`. `0s` keeps lines until the six-line cap removes them. |
| `--overlay-click-through=true` | `true` | Use an empty input region where the display backend supports it. |

Examples:

```bash
# Larger text, longer final-caption visibility
./scripts/distrobox/run.sh --mode=vad --output=overlay \
  --overlay-font-size=34 --overlay-final-timeout=6s

# Explicit XWayland/X11 route on the cursor's monitor
./scripts/distrobox/run.sh --mode=vad --output=both --overlay-backend=x11

# Fixed two-second captions on a named monitor
./scripts/distrobox/run.sh --mode=fixed --chunk-duration=2s \
  --output=overlay --overlay-monitor=DP-1
```

## Bazzite development with Distrobox

The helper scripts keep GTK development packages off the immutable host. They create and reuse `captioneer-dev` from the pinned `registry.fedoraproject.org/fedora-toolbox:44` image, install only missing packages, enter this mounted repository, and reuse the host's `models/` directory.

Run the desktop command from source:

```bash
./scripts/distrobox/run.sh --mode=vad --output=overlay
```

Build both binaries into the host-visible `build/` directory:

```bash
./scripts/distrobox/build.sh
```

The results are `build/captioneer` and `build/captioneer-desktop`. The terminal binary can normally run directly on Bazzite. The desktop binary is dynamically linked to GTK4 Layer Shell; run it through `run.sh` unless matching runtime libraries are available on the host.

The scripts recognize these environment variables:

| Variable | Default | Meaning |
| --- | --- | --- |
| `CAPTIONEER_DISTROBOX_NAME` | `captioneer-dev` | Dedicated Distrobox container name. |
| `CAPTIONEER_DISTROBOX_IMAGE` | `registry.fedoraproject.org/fedora-toolbox:44` | Container image. Override it to test a newer Fedora release deliberately. |
| `GSK_RENDERER` | `cairo` in `run.sh` only | GTK renderer. The safe software default avoids host/container GPU DMABUF mismatches; an explicit value is preserved. |

Captioneer itself has no environment-based application configuration; use the command-line flags above. The Fedora image is pinned for reproducibility and will not advance automatically. The name and image overrides apply when creating or selecting the container; an existing named container is reused. Update the image intentionally when Fedora 44 is no longer supported. Distrobox provides the normal home, display, session bus, PipeWire/PulseAudio, and runtime-directory integration; the scripts add no broad socket or device mounts.

## Troubleshooting

- **Missing model files:** run `./scripts/download-models.sh` or correct `--models-dir`.
- **`pactl` or `parec` missing:** install PulseAudio utilities, or use the Distrobox scripts.
- **No captions:** confirm the current sink with `pactl get-default-sink`; Captioneer listens to `<sink>.monitor`.
- **Processing overload warning:** inference fell behind and the oldest 100 ms packet was dropped. Try more `--threads` or a longer `--chunk-duration`.
- **Overlay is not always above other windows:** read the backend warning. On Wayland this usually means the compositor lacks Layer Shell; add a compositor rule for the `Captioneer Overlay` window if supported.
- **Overlay initialization fails:** `--output=overlay` exits with the error. `--output=both` warns and continues terminal-only.
- **Desktop binary misses shared libraries on Bazzite:** use `scripts/distrobox/run.sh`; container-built GTK binaries are not self-contained.

## Development

The transcription pipeline emits presentation-neutral events. `output/terminal` and `output/overlay` consume those events independently; GTK stays on its main OS thread while capture and recognition run on a worker.

```text
src/app/                 capture/model/process lifecycle
src/captions/            caption events and fixed/VAD coordination
src/output/terminal/     terminal renderer
src/output/overlay/      private GTK4/Layer Shell CGO adapter
src/cmd/captioneer/      terminal command
src/cmd/captioneer-desktop/ GTK-tagged desktop command
```

Run non-GTK verification on the host:

```bash
go test ./...
go build -o build/captioneer ./src/cmd/captioneer
```

Run full verification in the prepared Distrobox:

```bash
repo_root="$(pwd -P)"
distrobox enter --no-workdir captioneer-dev -- bash -lc '
  cd -- "$1"
  go test -tags gtk ./...
  shellcheck scripts/distrobox/common.sh scripts/distrobox/build.sh scripts/distrobox/run.sh
' captioneer-verify "$repo_root"
./scripts/distrobox/build.sh
```

Run this from the repository root. The build and run helpers resolve that path automatically.

## License

Captioneer is licensed under the [Apache License 2.0](LICENSE). Sherpa-Onnx is Apache-2.0 licensed, GTK4 is LGPL-2.1-or-later, and GTK4 Layer Shell is MIT licensed. Captioneer links to the system GTK libraries rather than copying their source into the project.

Version 1 intentionally has no animation, persisted caption history, runtime dragging, background-free mode, capture exclusion, Flatpak, desktop entry, or autostart integration.