HDMI IN on the Fire TV Cube 3 adds about 35 milliseconds of input lag

You can connect just about any HDMI device to the HDMI IN port on the 3rd-gen Fire TV Cube, as discussed here in my article all about how the new port works. While Amazon seems to expect cable and satellite TV set-top boxes to be the most common things connected, I expect game consoles will be commonly connected as well. Connecting a game console to the Fire TV Cube makes it very convenient to jump between gaming and streaming, however, be aware that the HDMI IN port adds some additional input latency and there’s an important setting you may need to adjust to reduce that latency.

While I don’t have any professional latency testing equipment, I slapped together a test that I believe does a decent enough job of testing input lag to ensure the latency difference between using the HDMI IN port of the new Fire TV Cube versus connecting directly to your TV. I took a wired USB mouse and wired an LED directly to the right-click micro switch of the mouse. This allowed me to easily see the moment the mouse button is pressed. I then recorded 240 fps slow motion videos of the mouse being used on various devices connected to the HDMI IN port of the Fire TV Cube and connected directly to the TV. By counting how many video frames passed between the LED lighting up and the button click’s action taking place on the screen, both through the HDMI IN port and bypassing the Cube completely, I was able to measure the input lag added by the HDMI IN port.

The accuracy of my testing is limited by the speed of my camera, which is 1 frame in a 240 fps video, or, in other words, about 4.16 milliseconds. That said, the data I collected was very consistent across all the devices I tested, so I’m fairly confident with the results. On average, I found that connecting a device to the HDMI IN port of the Fire TV Cube added about 33.4 milliseconds of input lag versus connecting the device directly to the TV. Given the plus or minus 4 millisecond margin of error, I’m comfortable calling it about 35 milliseconds of additional latency.

The Fire TV Cube 3 has a “Game Mode” setting under Settings > Display & Sounds > Display. The setting description states that “Game Mode reduces lag when you’re using supported gaming apps and connected gaming consoles.” The last bit about affecting gaming consoles indicates the mode applies to the device connected to the HDMI IN port. Sure enough, in my testing, I found that leaving this setting turned off resulted in about twice as much input lag through the Fire TV Cube’s HDMI IN port, or about 70 milliseconds more latency than if the HDMI device was connected directly to the TV. So you’ll definitely want to turn this on, even if your TV doesn’t support auto low latency mode.

It’s very subjective whether 35 milliseconds of additional latency is reason enough to not use the HDMI IN port for something like a game console. I expect that most serious gamers will forgo the convenience of the Cube’s HDMI IN port and connect directly to their TV to avoid the additional 35 milliseconds of input lag. For casual gaming or most other non-gaming HDMI devices, it’s probably not a big deal assuming your TV or other equipment isn’t already adding too much input lag, to begin with.

See all my 3rd-gen Fire TV Cube coverage here.

  1. RG Geiger says:

    Sounds like this means the end of support for the recast will be replaced with any other external OTA tuner, but will it be integrated I to the Amazon grid guide. Any answer to that question?

    • Rik Emmett says:

      I don’t see how amazon could determine the specific guide data to retrieve since the only connectivity to the external device is through HDMI.

    • HDMI IN on the Cube has nothing to do with the grid guide. If an external OTA tuner wants to be integrated into the guide, the device needs a Fire TV app, the app needs to be updated to pass guide data to the Fire TV, and the app/device needs to be approved by Amazon before it can show up in the guide. Basically, for HDHomeRun or Tablo to be in the guide, they need to reach out to Amazon for approval and update their Fire TV app.

      Long ago I was told by someone I trust that HDHomeRun reached out to Amazon about integration into the guide but things fell through for some reason. I don’t know if Tablo is interested in integrating.

  2. Ian King says:

    Does this Input lag result in any lip synch issues when used with a cable STB?

  3. Sadat says:

    Is there any reason not to have this setting always enabled? Do you get any additional video or sound processing to improve the quality of the output if you leave the setting off?

    • I wish I knew the answer to this. I know on TVs there are downsides to low latency “Game” modes, like a dimmer and/or lower quality picture, but I don’t know if any of that applies to the Fire TV Cube’s game mode.

  4. Andy lowrie says:

    Can I put a Yamaha amp into in hdmi
    Then run out into arc of my tv

  5. Stephen Thirkell says:

    Is the hdmi in 4k or limited to 1080p?

    • Scott Lewis says:

      If I recall it’s 4K but limited to 60fps. So again, just great for most and possibly not great for heavy duty gamers and people who care about 120fps dividing equally into a 24fps movie.

      I love the idea, although I’m not prepared to switch from what I have now. I had Caavo for awhile until the hardware got dated (no DolbyVision) and the company shifted directions to another segment.

  6. Tommattews says:

    Love my cube great job it is

  7. Basil says:

    Plug a dvd player in cube no sound only

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