VDI Stream Client

A very tiny and low latency desktop streaming client for remote Windows guests with GPU passthrough which supports Nvidia NVENC, AMD VCE, VCN and Intel Quick Sync Video.

Overview

VDI Stream Client is a tiny and low latency Linux client which connects to Parsec Host running on Windows. It allows to run fully GPU accelerated Windows desktop environment on a remote machine while streaming the content to a local Linux system which process keyboard and mouse input. The remote server can be a virtual machine running on-top of on-premise deployments of Virtuozzo Hybrid Server, KVM or Xen. It can also connect to public clouds like Amazon (EC2 G3 Accelerated) or Microsoft Azure (NV6). It uses Simple DirectMedia Layer (SDL2) for low-level access to audio, video, keyboard, mouse and clipboard.

Motivation

I'm using Linux on Desktop since more than 20 years already for several reasons - customization, small and tiny floating window managers like Fluxbox, ideal platform for engineers and developers and many more. However over the past couple of years my daily job required more attention which rely on Microsoft Windows applications like Microsoft Office and full fledged groupware solution like Microsoft Outlook. There exist open source alternative like LibreOffice and Thunderbird plus various Exchange connectors or even SOGo. They are all good in their niche but they didn't reach compatibility to satisfy me. I tried a lot of different ways of solving the problem (see below in the comparison table) but at the end I have only three main goals:

1. GPU passthrough with remote support. Using hosted remote Windows desktop with full-fledged GPU acceleration for 3D, video decoding and encoding to run any kind of application with full GPU support as they would have been used locally.
2. Low latency network connection. Using laptop running Linux to connect from anywhere to the Windows desktop and do my daily work. This must work via fast network like ethernet, roaming wireless and low bandwidth with unstable mobile broadband.
3. Being very energy efficient on client. The laptop battery drain should not significantly increase while working on the remote desktop. Also the server should not become more energy hungry than needed for simple streaming.

Comparison

In Linux ecosystem there exist already wide range of options to run Windows guest environment as virtual machine on-top of a Linux host and access either its local display or via remote display protocol, all of them have their pros and cons. Look at the table below for brief comparison.

So why another streaming client is needed if one for Windows, Linux and macOS exist already? Well the Parsec client is focusing on gaming capabilities while VDI Stream Client is focusing on having a reliable daily working environment. The table below gives a brief overview about differences.

Requirements

Any recent GPU with OpenGL and VA-API support will work. When it comes to 4:4:4 color mode, part of the decoding work is made with FFmpeg (see notes below regarding 4:4:4 status). Nothing exist without drawbacks and that one for Parsec is that it is mandatory to have an account which is completely free. However communication between client and host is always made directly. Also the SDK is only available as pre-compiled library, so for those who fully rely on an open-source system, stop reading here. Some features are only available with a commercial subscription under Parsec Warp. It applies to 4:4:4 color mode which is required to encode images and streams without chroma subsampling for sharp and crystal clear text.

Features

• Fully CLI based customization. User can specify all required parameters via command line switches, allow perfect integration into different window managers.
• Desktop in window support with XGrabKeyboard and XUngrabKeyboard while leaving mouse pointer ungrabbed. Supporting Alt+Tab and Windows special keys grab, even if assigned to the window manager.
• SDL window is created without SDL_WINDOW_RESIZABLE flag set, so window cannot be resized by window manager and always uses native host resolution (no more blurry desktop).
• Host to client resolution sync with automatic window resize. User can change resolution in Windows control panel and client polls for the changes and adjust client window size.
• Specify client window size via command line and host will change native resolution to it once the connection has been established.
• Configurable mouse wheel sensitivity. User can specify mouse scroll speed via command line switch serving different needs and requirements.
• Modular architecture and can be extended with additional streaming host services like Nvidia GameStream via Moonlight libraries.
• Screen saver and screen locker support. By default screen saver support is enabled but user can specify command line switch to avoid setting SDL_EnableScreenSaver and disallow X server to lock the local screen.
• Built-in USB redirection with automatic reconnect support using usbredir protocol. User can specify via command line which local USB devices will be redirected to the host (e.g. to forward a webcam with microphone). However usbredir protocol is currently only supported if using KVM, Xen or Virtuozzo Hybrid Server with QEMU. Other virtualization solutions may use standard Linux USB/IP server and native Windows client driver.

Parsec Warp

• Support for disabling chroma subsampling to support color mode 4:4:4 with sharp and crisp text and better colors. Available for Nvidia Hosts running GTX 900 or better.

Known Issues

• Color mode 4:4:4 is not yet supported by the SDK. There is an open bug at Parsec SDK GitHub and Parsec team want to fix it with next SDK release. In official Parsec client it works already with some internal callbacks in the SDK.
• Resolution changes from client connected to the host are not persistent and only valid within the session. Once the last client disconnects the host restores original resolution.
• No macOS and Windows support yet. However porting should be fairly easy but I haven't tested it and pull requests are welcome.

Building

VDI Stream Client uses GNU Build System to configure, build and install the application. It requires sdl2, sdl2_ttf, libx11, libglvnd, libusb, usbredir and the Parsec SDK. The build system will search the SDK first in build directory and use DSO linking, the resulting binary will be redistributable but you need to ship Parsec library somehow. If not found, it will search in system-wide include and library directories and link accordingly, binary may not be redistributable. For build and install use the commands below and if --prefix=/usr is used, the make install command must be run as root user.

git clone https://github.com/parsec-cloud/parsec-sdk
./configure --prefix=/usr &&
make &&
make install

Arch Linux users can download ready-to-use PKGBUILD file available from Arch User Repository (AUR), following these build and install instructions.

Usage

VDI Stream Client requires that the Parsec Windows host (x86_64 or x86) is running and you have created a free account. There are several advanced configuration options for visual and network latency improvements described in the Parsec documentation in the "Hosting Settings" chapter.

The client requires a sessionID and a peerID obtained through the Parsec API to identify users to make secure connections. For convenience you can use tools/parsec-login script to retrieve list of available hosts. This is one-time operation whenever you add Parsec host application to another Windows machine.

USB Redirection

If you are using libvirt for virtualization, you can redirect local USB devices to your Windows host. It is highly recommended to add XHCI controller because it is the only one which supports USB 1.1, USB 2.0 and USB 3.0, the QEMU UHCI and EHCI controllers support only their respective USB standard. Windows 10 is shipped by default with an XHCI USB 3.0 driver. Add the following to your <devices> section in domain XML for an USB 3.0 controller:

<controller type='usb' model='qemu-xhci'/>

With the controller you can start using USB redirection via TCP/IP protocol. Each USB device is redirected through an independent port and the firewall of your server must allow incoming TCP/IP connection for that. VDI Stream Client supports monitoring of hotplug events (e.g. plug and unplug) of the redirected USB devices to allow automatic reassignment to the Windows host. Add the following to your <devices> section in domain XML to enable redirection of one local USB device and replace <ip> with the IP address of your virtualization host:

<redirdev bus='usb' type='tcp'>
  <source mode='bind' host='<ip>' service='4000'/>
</redirdev>

You need to add additional <redirdev> sections to redirect multiple devices and increase the port number accordingly. After reloading libvirt and starting the Virtual Machine with the configuration above, you can redirect a local USB device. You can get a list of available devices with their <vendorID> and <productID> with lsusb command.

vdi-stream-client --session <sessionID> --peer <peerID> --redirect <vendorID>:<productID>@<ip>#4000

Once connection is established it will redirect the local USB device to the host and setup drivers. Multiple USB devices can be redirected using , separator to the --redirect switch. They will be reassigned if the client reconnects to the host. Moreover, devices are reconnected to the host automatically when you unplug and plug them again to the USB port. If the devices are not connected during startup of the client, they are monitored and redirected as soon as they are attached to the client.

Notes

USB redirection integration doesn't support any kind of encryption. The main goal of this client is to support in-house desktop streaming between client and host. Please use a VPN like WireGuard if you are using it across WAN connections.

Future

Building a truly and fully open-source GPU accelerated desktop streaming solution requires a host service running inside the Windows environment. Hardware encoding is supported by FFmpeg for the major GPU vendors. VDI Stream Host application seems reasonable.

Thanks

A special thanks goes to Parsec Cloud, Inc. as they provided a Parsec Warp subscription to support this project.

Support

If you want to help out with development without providing code yourself, you can always donate to the project directly using the following platforms.

• GitHub
• PayPal
• Bitcoin - bc1qh2pssvhac7629k3ndmmpw3azsm4yjz9jvaaycr
• Litecoin - ltc1qfz93z928vr36d9ksp5mstt385t84mdx4shsv35

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