# DVD support

DVD support is optional per classroom and off by default.

## Enabling a room

Edit `/etc/ekklesia-classroom/device.conf` on that endpoint:

```
DVD_ENABLED=true
```

Then restart the session (reboot, or restart `classroom-dock`).

With `DVD_ENABLED=false`, or the key absent, the DVD button is not built
at all and no drive polling happens. Older endpoints get a commented
`DVD_ENABLED=false` appended on upgrade so the option is discoverable,
which leaves their behaviour unchanged.

## Behaviour

The dock polls the drive every two seconds with the `CDROM_DRIVE_STATUS`
ioctl. That is a status query, so it does not spin the disc up.

| State | Dock icon | Clicking the button |
| --- | --- | --- |
| No drive connected | DVD logo held back at 55% | "No DVD drive is connected to this classroom computer." |
| Drive present, no disc | DVD logo held back at 55% | "No disc is in the drive. Insert a disc to get started." |
| Tray open | held back | "The disc tray is open. Insert a disc to get started." |
| Disc still being read | held back | "Reading the disc. Please try again in a moment." |
| Disc ready | DVD logo at full strength | Plays the disc |

When a disc becomes ready, a **DVD Ready** notification is shown once.
Discs never play on their own; playback always needs a button press.

The first poll after login only records what is already in the drive, so
a disc left in over the week does not announce itself at every boot.

## Playback

Playback is VLC, chosen over mpv because mpv dropped DVD menu support.
VLC's `dvdnav` path gives working menus, chapters and audio tracks.

`classroom-dvd toggle` hands the disc to VLC through `classroom-window`,
so the DVD player behaves like any other classroom application: the DVD
button focuses it, minimises it, and restores it. `Super+M` minimises it
too. VLC starts fullscreen; `Esc` leaves fullscreen.

## Commercial (CSS encrypted) discs

Most retail DVDs are CSS encrypted, and Debian cannot ship the
decryption library. Unencrypted discs — curriculum discs, home-burned
video — play without any extra work.

For commercial discs, run once per endpoint, as root:

```
sudo classroom-dvd-css-setup
```

That enables the Debian `contrib` component, installs `libdvd-pkg` and
builds `libdvdcss`. It needs network access and it compiles a package,
which is why it is deliberately not run from the package `postinst`: the
postinst runs while dpkg already holds the apt lock during an OTA update.

**Commercial DVD playback has not been verified on hardware yet.** Test
with an actual disc before relying on it for a service.

## Command line

```
classroom-dvd status    # drive node, drive state, whether VLC is installed
classroom-dvd toggle    # what the dock button does
classroom-dvd play      # start playback even if the drive is unsure
classroom-dvd eject     # open the tray
```

## Permissions

Reading the drive needs group `cdrom`. The postinst adds the `classroom`
user to it; that takes effect at the next login, which the OTA reboot
provides. Without it the drive reads as absent.