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.
The terminal command requires Linux x86_64, Go 1.26.2 or newer, `pactl`, and `parec`. Building the desktop command from source additionally needs GTK4 and GTK4 Layer Shell development libraries. Published release archives carry the desktop runtime libraries. PipeWire works through its PulseAudio compatibility layer.
VAD mode is recommended for normal use. It redraws a provisional caption only after Silero detects speech and commits a timestamped caption after the utterance ends:
Sherpa recognition, Silero VAD, and audio capture run in an isolated worker process. The terminal or GTK process stays responsive if native inference crashes or hangs: Captioneer restarts the worker automatically after a failure, and Ctrl+C force-kills only that worker if it cannot flush within the configured shutdown timeout. Send `SIGHUP` to the parent Captioneer PID to hot-reload the models without closing the terminal or overlay:
```bash
kill -HUP <captioneer-parent-pid>
```
An automatic or manual restart begins a fresh capture/transcription session; audio being processed by the failed worker cannot be recovered.
In VAD mode, a 500 ms pause finalizes the current speech segment. Captioneer splits that transcript again at sentence punctuation and at word-safe boundaries of at most 64 characters, so continuous speech does not become one enormous paragraph. The live provisional view keeps the latest three digestible chunks and grows vertically without ellipsizing them. Completed chunks remain visible for at least three seconds, receive extra time based on their word count, and gradually fade from white to a restrained gray as they age. When several chunks finalize together, their removal is staggered in reading order instead of deleting the whole block at once. Up to six completed chunks remain above the provisional text; if a seventh arrives, the oldest is removed. Blank recognition results never erase completed text before its reading lifetime expires.
The expensive Parakeet recognizer stays idle during silence and audio that Silero does not classify as speech. A small rolling preview window also prevents long continuous audio from making each refresh progressively slower. Silero itself continues receiving the live stream because it needs the quiet frames to detect when speech ends and when it starts again.
Text is left-aligned inside the centered, fixed-width dark bubble and wraps at its configured width instead of extending off-screen. Pointer input passes through the window by default.
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`.
| `--preview-threshold-dbfs=-45` | `-45` | RMS gate below which recognition stays idle. Raise it to reject quiet background noise; lower it for quiet speech. In fixed mode, gated chunks are not sent to Parakeet. |
| `--vad-threshold=0.5` | `0.5` | Silero speech confidence from `0` to `1`. Raise it to reject more music/noise; lower it if real speech is missed. Applies to VAD mode. |
| `--model-auto-restart=true` | `true` | Restart the isolated model worker after a crash, capture failure, or timeout. Set `false` to report the failure and exit instead. |
| `--model-timeout=30s` | `30s` | Maximum model startup, continuously busy processing time, or missing-heartbeat period before the worker is considered hung. `0s` disables hang detection. |
| `--model-shutdown-timeout=2s` | `2s` | Time allowed for pending-audio flush and model cleanup after Ctrl+C or reload before the worker is force-killed. |
| `--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. |
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.
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:
| `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`.
- **Music/noise produces captions:** use VAD mode and try `--vad-threshold=0.65`. Increase it in small steps if false detections continue. `--preview-threshold-dbfs=-40` can also reject quiet background audio, but an RMS gate cannot distinguish loud music from speech. Singing may still be treated as speech.
- **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.
- **A locally built desktop binary misses shared libraries:** use `scripts/distrobox/run.sh` or install the matching GTK4 and GTK4 Layer Shell runtime packages. The desktop command in a published release carries these application libraries in its private `lib/` directory; keep the extracted directory together.
- **The model worker repeatedly restarts:** inspect the warning on stderr. Slow machines may need a larger `--model-timeout`; use `--model-auto-restart=false` when diagnosing a persistent crash so Captioneer exits on the first failure.
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, VAD, and recognition run in a supervised child process. Caption events and health messages cross a private pipe, and the child is placed in its own process group so its `parec` process can be stopped or replaced with it.
The `Tests` workflow runs the normal and GTK-tagged Go tests, `go vet`, and ShellCheck for every pull request and branch push. To make it mandatory for pull requests, open the repository's **Settings → Branches**, edit the protection rule for `master`, enable required status checks, and select **Tests / Go and GTK tests** after its first run. Workflow files can report the check, but the branch-protection rule is what prevents merging when it fails.
Pushing a tag that exactly follows `vMAJOR.MINOR.BUG` runs the same test suite first, then builds and publishes a Gitea release:
The release contains a checksummed Linux x86_64 archive with `captioneer`, `captioneer-desktop`, and a private runtime containing GTK4, GTK4 Layer Shell, Sherpa/ONNX, and their linked non-glibc dependencies. Extract the whole archive and run `./captioneer-desktop`; do not move the executable away from its adjacent `lib/` directory. Models, `pactl`, `parec`, host fonts, the display server, graphics drivers, and glibc remain host-provided.
The release workflow uses Gitea's built-in `GITEA_TOKEN`; no personal token is required. In **Settings → Actions → General**, allow the workflow token `Read` access to code and `Write` access to releases. Gitea clamps workflow permissions to those repository settings, so a more restrictive maximum produces an actionable HTTP 403 during publishing.
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. Release archives dynamically link and redistribute the required shared libraries; `RUNTIME-LIBRARIES.tsv` records their source packages and `third-party-licenses/` contains the installed license notices supplied by those packages. Local source builds continue to link against the system libraries.
