Like a lot of people, I bought the HiSense Roku TV not knowing it would have unbelievable input lag with game consoles and that the "Game Mode" option came with a graphical output that stuttered. The lag for this TV is, by now, somewhat well-known and there are many topics on the Roku community website and Reddit and elsewhere that talk about it, but few by April 2025 seem to have offered up anything useful towards fixing it.
I don't claim to be the first person to help crack this problem, I'm just hoping to help provide frustrated owners more insight and relief than I see anyone else posting.
It's the sound. Sound output coming from a game console or PC is what's creating the input lag on the TV when Game Mode is off. It might not be the only thing contributing to it, but as of writing, it appears to be the element most present in all my experiments.
I came across this when I hooked up my non-gaming laptop to the HiSense Roku TV through HDMI and did not have any noticeable input lag from the mouse or keyboard when Game Mode is off.
Then I hooked up my gaming PC to the TV. I would get a lag-free mouse response UNTIL I started a game; any game. Then it would create nearly half a second in lag that would not go away until I shut the computer off entirely. Again, this is when Game Mode was off.
Hours of testing later, I was able to figure up a graphics setting for the PC that the 4Series-40 would let me game without lag and while Game Mode is still off. No sound was coming out and I discovered I had sound turned off. When I went to turn it on, lag would immediately start up and not go away until I shut down and started it up again.
Then just this moment, I tested the TV with a docked Nintendo Switch and a cheap PowerA wired controller with headphones hooked up to the controller itself. No noticeable lag while Game Mode is off. I plugged the controller and the headphones in before I put the console in the dock, so the audio never went through the TV. At this early point of testing, I can point towards the 4Series-40 TV taking in sound from an external device triggers the TV to create input lag for consoles and computers.
I'm not an expert computer guy or anything, but it also seems the sound input creating lag is more like a software bug than a design or mechanical shortcoming; because once I trigger the sound on from an external source, turning the sound off will not remove the input lag; I have to shut the console or PC all the way down (not sleep mode or restart) to get it to remove lag. And if the TV is capable of lag-free gaming without Game Mode on, which I discovered it is, then the only thing creating this lag is something in the firmware that could be fixed.
So the workaround at this early stage is this: Use a wired controller and the controller headphone jack before you turn on the console. Have your computer set to run audio through its integrated audio plugin like Realtek or whatever, then plug it into the TV and turn it on there. Do not run audio from the computer or console through the TV.
If this information is helpful, perhaps the Roku team could develop a new firmware patch to fix the software bug or include a new audio option where you could select the TV doesn't take audio data at all?
Thank you.
