Direct USB passthrough is slow, but using SPICE is fast


New Member
Jul 29, 2023

I want to pass a USB device to a VM (namely a USB TV tuner for a TV server).
When I do it directly by adding a USB device to the VM with the vendor/device ID, it seems as if the device is sometimes slow to respond.
However, when I add a SPICE USB channel, change the display to SPICE, connect using remote-viewer, and share the USB-device from my PC, the speed/latency seems no problem.
How can it be that sharing a USB device over network (1 GBit/s LAN) is faster than directly sharing it to the VM?

Is there something I'm doing wrong? I have already read that sharing USB devices can be slow, but I don't understand why sharing through SPICE is no problem.

As a workaround, does someone know of a way I can share the USB device using SPICE without having a display connection (i.e., running some terminal-command in the background on the proxmox host, which just forwards the USB device using spice)?
I have already found the usbredir project. Can I tell proxmox to create a USB port that I can connect to using the usbredirect binary?

I already know that I could buy a PCIe USB card and share the full PCIe card to the VM, but that seems a bit overkill for a single USB 2.0 device.

Thank you for your help.
USB passthrough is not great for low-latency or high-bandwidth (like TV-tuners). Depending on your Proxmox version. make sure to enable USB3. I have no idea why it would work better via SPICE or how to do that in the background. You could try USB/IP instead maybe?
I run my TV-server in a unprivileged Ubuntu container for the least amount of overhead by loading the driver/firmware on the Proxmox host and bind-mounting /dev/dvb and setting up the right Linux group ID mapping. Several threads here about that.


The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!