> ## Documentation Index
> Fetch the complete documentation index at: https://docs.efference.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# efference-viewer

> View live video and IMU data

`efference-viewer` displays decoded video, frame count, acceleration, and
angular velocity.

```sh theme={null}
efference-viewer [--codec raw|h264|h264hq|h265|h265hq] [--h264|--h265]
                 [--ble MAC] [--password PW] [--udp HOST[:PORT]]
                 [--flip on|off|auto] [--headless]
```

`--h264` and `--h265` are shorthands for `--codec h264` / `--codec h265`.

* **Wired:** run without connection flags; USB is the default.
* **Wireless:** pass `--ble <MAC> --udp <linux-host-ip>`.
* **Headless:** `--headless` (alias `--no-window`) opens and holds the session
  without a local window. Combine it with `--udp <host>` to have the device push
  video and IMU to a remote host. Without `--udp` there is nothing to display or
  forward, so every frame is discarded. `--flip` is a host-side display transform
  and has no effect on a forwarded stream.
* **Quit:** press `Q` or `Esc`, close the window, or press Ctrl-C.

This tool requires an SDK built with OpenCV and FFmpeg, both installed by the
initial `./build.sh --deps` run. CMake omits the tool if either is missing.

If the video shows persistent corruption over USB, confirm that `ef-cli info`
reports a SuperSpeed connection.