Enormous Input Lag

[Bunny-Head]

Hello there! Have been playing back some FPS these days and I found that the lag has a terrible input lag while plugged on DeskHop, is this a "side effect" of using DeskHop or could it be something related to my spercific mouse? 8BitDo Retro R8 Mouse wired connection. Thank you!

[hrvach]

I would love to help with this, but I don't have this mouse at hand and have no means to recreate the issue. This kind of lag is not something I've seen, but theoretically it could happen if the computer on the output port polls slower than the rate at which device polls the mouse.

What would help here is a check / assertion that this is never the case, and even if it is, to merge successive reports until the queue insert rate matches or drops below the poll rate. I haven't seen/heard this happens often, but features that interfere with the basic device functionality should have a very high priority, so I'll try to see if I could implement this.

[WilsonChiang]

This might be a similar issue @hrvach #215

[DelusionalLogic]

I'd like to help out here, since I also have this problem.

@hrvach You comment implies to me that the queue would be building up because the host might be polling slower than the mouse is generating reports. This does not seem to be the case. I added a log statement in the process_mouse_queue_task of the mouse_queue level and it shows no reports building up.

To describe the problem it feels like a constant latency. It's also seems to cause the keyboard to become unresponsive every once in a while, and the pico's led flash once every 4-5 seconds. The unresponsive keyboard happens right before the led flashes on the pico.

EDIT: The flashing seems to be caused by the all 3 hids remounting every 4-5 seconds when the mouse isn't moving. This doesn't happen when the mouse is moving, and is therefore unrelated to the latency issue.

I've bought a USB analyzer

[DelusionalLogic]

I think I (somewhat) figured it out. When the logitech receiver is connected directly to the PC, the endpoint descriptors report interval = 1 but when it's connected to the DeskHop it reports interval = 10. If I hack the firmware and set the interval lower, the mouse works basically correctly. I think there's some intermittent slowdown in the controller that causes some wonky laggy feeling. Why would 100Hz polling cause lag? I have no idea, could be a firmware bug in the dongle.

The question becomes what causes the difference in interval. I'm guessing it's the USB Full Speed limitation. The dongle is usually a High Speed device. I have to figure out some way to force it into full speed mode when connected to my PC to test that.

[DelusionalLogic]

I talked to Logitch support who told me that USB Full Speed (through what they called third party hubs) mode is not supported. We should probably not expect a firmware patch from them.

I'm currently still investigating an odd intermittent desync issue, but it takes like 5 hours to manifest so it's taking some time.

[hrvach]

This is very interesting, and a bit confusing to be honest! So, the receiver requests polling of 100 Hz from the box? The box requests the PC to poll it at 1000Hz, so emptying the bucket 10 times quicker than filling it shouldn't cause any issues. I'd expect problems in the opposite scenario (PC doing 100 Hz, mouse asking 1000).

Can you please clarify what firmware hack did you do exactly, i.e. did you convince the box to ignore interval=10 and keep polling at 1000 hz?

The scenario I can think of might be that the receiver reports 100 hz polling but generates 1000hz worth of data internally, which would explain such symptoms, probably due to an internal queue that gets filled way faster than emptied and operates at 100% constantly.

[WilsonChiang]

@DelusionalLogic Do you mind describing how you did If I hack the firmware and set the interval lower, the mouse works basically correctly.