reStream

reMarkable screen sharing over SSH.

Installation

Requirements

On your host machine

• Any POSIX-shell (e.g. bash)
• ffmpeg (with ffplay)
• ssh
• lz4

Unix

1. Install lz4 on your host with your usual package manager.
   On Ubuntu, apt install liblz4-tool will do the trick.
2. Set up an SSH key and add it to the ssh-agent, then add your key to the reMarkable with ssh-copy-id [email protected].

Note: the reMarkable 2 doesn't support ed25519 keys, those users should generate and rsa key. Try out ssh [email protected], it should not prompt for a password.

Windows

1. Install ffmpeg for windows.
2. Download lz4 for windows and extract the zip to a folder where you'll remember it (e.g. C:\Users\{username}\lz4).
3. Add the ffmpeg and lz4 directories to the windows Path environment. Here is a quick guide how.
   • Control Panel > Edit the system environment variables > Environment Variables
   • Find the Path variable under System variables, click edit.
   • Add two New entries: one to the bin directory in the ffmpeg directory, and one to the lz4 directory you created.
   • Click OK
4. (Re)start bash so the new Path is used.
5. Generate a new ssh-key using ssh-keygen.
6. Send the public key to the reMarkable (connect trough USB cable) using ssh-copy-id -i ~/.ssh/id_rsa [email protected]
7. Try out ssh [email protected], it should not prompt for a password.

reStream installation

The instructions below will install the files from the latest release. In particular, reStream.sh is the executable on the host, and restream.arm.static is the binary which has to be moved to the reMarkable with the name restream.

Host

Download reStream.sh and make it executable

$ chmod +x reStream.sh

Tip
If you save reStream.sh in a PATH directory as reStream, you can launch it as reStream.
On Ubuntu, list these folders with echo $PATH. One should be/usr/local/bin.
As root, download the executable there:

# wget https://github.com/rien/reStream/releases/latest/download/reStream.sh -O /usr/local/bin/reStream
# chmod +x /usr/local/bin/reStream

reMarkable

You can install restream on reMarkable in three ways.

• Install via toltec if you use it.

$ ssh [email protected] 'opkg install restream'

• If you have access to internet on your reMarkable, download directly the binary onto it:

$ ssh [email protected] 'wget https://github.com/rien/reStream/releases/latest/download/restream.arm.static -O /home/root/restream && chmod +x /home/root/restream'

• Download the restream binary onto your host, move it to reMarkable and make it executable.

$ scp restream.arm.static [email protected]:/home/root/restream
$ ssh [email protected] 'chmod +x /home/root/restream'

Usage

1. Connect your reMarkable with the USB cable.
2. Make sure you can open an SSH connection.
3. Run ./reStream.sh in the script directory or reStream if you've installed it in your PATH
4. A screen will pop-up on your local machine, with a live view of your reMarkable!

Options

• -h --help: show usage information
• -p --portrait: shows the reMarkable screen in portrait mode (default: landscape mode, 90 degrees rotated tot the right)
• -s --source: the ssh destination of the reMarkable (default: [email protected])
• -o --output: path of the output where the video should be recorded, as understood by ffmpeg; if this is -, the video is displayed in a new window and not recorded anywhere (default: -)
• -f --format: when recording to an output, this option is used to force the encoding format; if this is -, ffmpeg’s auto format detection based on the file extension is used (default: -).
• -w --webcam: record to a video4linux2 web cam device. By default the first found web cam is taken, this can be overwritten with -o. The video is scaled to 1280x720 to ensure compatibility with MS Teams, Skype for business and other programs which need this specific format. See Video4Linux Loopback for installation instructions.
• -m --measure: use pv to measure how much data throughput you have (good to experiment with parameters to speed up the pipeline)
• -t --title: set a custom window title for the video stream. The default title is "reStream". This option is disabled when using -o --output
• -u --unsecure-connection: send framebuffer data over an unencrypted TCP-connection, resulting in more fps and less load on the reMarkable. See Netcat for installation instructions.

If you have problems, don't hesitate to open an issue or send me an email.

Extra Dependencies

On your host machine:

• Video4Linux Loopback kernel module if you want to use --webcam
• netcat if you want to use --unsecure-connection

Video4Linux Loopback

To set your remarkable as a webcam we need to be able to fake one. This is where the Video4Linux Loopback kernel module comes into play. We need both the dkms and util packages. On Ubuntu you need to install:

# apt install v4l2loopback-utils v4l2loopback-dkms

In some package managers v4l2loopback-utils is found in v4l-utils.

After installing the module you must enable it with

# modprobe v4l2loopback

To verify that this worked, execute:

$ v4l2-ctl --list-devices

The result should contain a line with "platform:v4l2loopback".

Netcat

To use an unsafe and faster connection, we need the command nc, abbreviation of netcat.
If your system does not provide nc, the output of command -v nc is empty. In this case you need to install it.
Several implementations of netcat exists. On Ubuntu, you can install the version developed by OpenBSD, which is light and supports IPv6:

# apt install netcat-openbsd

Troubleshooting

Steps you can try if the script isn't working:

• Set up an SSH key
• Update ffmpeg to version 4.
• Make sure RSA keys are allowed on your system:
  • In some modern Unix distributions, RSA keys are considered "legacy" and will no longer work out of the box.
  • Therefore you need to add a section to your ~.ssh/config file to allow use of RSA ssh keys for specified hosts. (according to https://remarkablewiki.com/tech/ssh, Remarkable devices might not work with non-RSA keys, which is the reason for why this is necessary.)
  • This example should work without any additional configuration, although PubkeyAcceptedKeyTypes=ssh-rsa is required if you want to modify it:

    Host remarkable
        HostName 10.11.99.1
        User root
        PubkeyAcceptedKeyTypes=ssh-rsa
    

  • You can then use the -s flag to connect to the Remarkable: ./reStream.sh -s remarkable

Development

If you want to play with the restream code, you will have to install Rust and setup the reMarkable toolchain to do cross-platform development.