Not sure it's related but I'm seeing this on the guest now when I use mpv --vo=drm on a tty:
[ 28.918606] xhci_hcd 0000:00:04.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 2 comp_code 13 [ 28.919816] xhci_hcd 0000:00:04.0: Looking for event-dma 000000012a8c7d80 trb-start 000000012a8c7d70 trb-end 000000012a8c7d70 seg-start 000000012a8c7000 seg-end 000000012a8c7ff0 [ 28.919818] xhci_hcd 0000:00:04.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 2 comp_code 13 [ 28.921019] xhci_hcd 0000:00:04.0: Looking for event-dma 000000012a8c7d90 trb-start 000000012a8c7d70 trb-end 000000012a8c7d70 seg-start 000000012a8c7000 seg-end 000000012a8c7ff0 [ 28.921023] xhci_hcd 0000:00:04.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 2 comp_code 13 [ 28.922203] xhci_hcd 0000:00:04.0: Looking for event-dma 000000012a8c7da0 trb-start 000000012a8c7d70 trb-end 000000012a8c7d70 seg-start 000000012a8c7000 seg-end 000000012a8c7ff0 Video is then a bit smoother. Diego On Sat, Dec 12, 2020 at 1:28 PM Diego Viola <diego.vi...@gmail.com> wrote: > > Hi, > > I'm experiencing a lot of choppiness in the video output when I pass > through my USB webcam to the guest using qemu-xhci as follows: > > qemu-system-x86_64 -enable-kvm -hda arch-zoom.qcow2 -m 4G -vga virtio > -device qemu-xhci,id=xhci -device > usb-host,bus=xhci.0,hostdevice=/dev/bus/usb/002/004 > > My webcam is: > > Bus 002 Device 004: ID 04f2:b449 Chicony Electronics Co., Ltd Integrated > Camera > > I am using mpv /dev/video0 from the guest. > > It works fine if I use usb-ehci instead, e.g.: > > qemu-system-x86_64 -enable-kvm -hda arch-zoom.qcow2 -m 4G -vga virtio > -device usb-ehci,id=ehci -device > usb-host,bus=ehci.0,hostdevice=/dev/bus/usb/002/004 > > In this case, the video output from mpv /dev/video0 is not choppy. > > My QEMU version is 5.2.0 -- I am running Arch Linux on the host and guest. > > Any ideas please? > > Thanks, > Diego