[RESPONDED] Hardware video decoding stutters when my TB4 dock is plugged in

Framework Laptop 13 Linux
1

Hi,

HW and SW
Framework 13 AMD 7840U with Radeon 780M.
BIOS – 3.05(beta), but was happening with 3.03 as well.
OS – Arch Linux, kernel 6.8.5-arch1-1.
Dock – Dell WD22TB4 Thunderbolt Dock.

Description
I have a TB4 dock that I use with my FW 13 AMD. When inserted into the Framework’s USB ports, then the HW video acceleration via VA-API drops frames consistently. At least VP9 and HEVC @ 4K is definitely affected. It is happening when the dock is connected via USB4 or USB3.2 port.

When playing video via MPV, there are visible dropped frames, also reported by MPV itself. When playing YouTube videos in Firefox, then some frames get randomly dropped, or the playback freezes at random times. YouTube then tends to restart the playback several times during a few seconds, until it just errors out.

When I pull the dock out during playback, then suddenly there are no more dropped frames.

It took some experimenting to find out that it was neither the video output, nor any of the cards I have inserted, but the dock itself. Even though there was nothing inserted into the dock, the video acceleration dropouts were happening.
I can reproduce it in 3 of 4 attempts; sometimes it just has no issues.

There are no warning or error lines in dmesg when this is happening.

It is not a new issue, it goes back at least to 6.7.0 kernels for me, but it has become pretty annoying.
In my case, I do not have another dock readily available to test, and I have quite a lot of devices to attach, so the dock helps immensely.

Potentially related (Framework 16 issue): Stuttering Videos

An observation that is probably not related to the issue - it is the “stuck CPU at low frequency” issue. When it happened, I had the dock connected. After I disconnected the dock, the CPU speed got unlocked again.

I would kill for any advice or what to try. Since it is not a supported OS, I can try and boot a Fedora 39 live ISO, but otherwise I don’t know what to try to debug this.

Thanks,
Pavel

2

Hi Pavel,

There are just some docks we don’t support or lacking full support, you may want to try other TB4 cables and see if issue goes away. :slight_smile:

3

Hi, thanks for the tip, and sorry for my late reply.

This particular dock has a TB4 cable that is permanently attached from the factory; I cannot easily replace it.
The issue usually goes away immediately after disconnecting the dock.

I also have issues with the laptop’s built-in audio jack (and the audio expansion, too) stuttering when the dock is present, and that also goes away when I disconnect the dock. Pipewire showed errors piling up in pw-top.
I suspect a hidden synchronization issue somewhere, because it definitely does not happen all the time. It could also be one of the USB devices, but the problem remained even though I disconnected all of them, and just the dock was connected.

4

Well, for the last couple of weeks, I no longer see this issue. I suspect that some of the kernel updates have fixed it - or it was the Virtualbox kernel drivers, which I have disabled. Either way, it’s no longer an issue for me. :slight_smile: