Latency Comparison: LIQUID vs. Duet Display vs. Air Display

This report is meant to provide a baseline as to how our LIQUID v3 (that's used in Astropad and Luna Display) latency compares with competitors like Duet Display and Air Display.

In addition, we did a frame rate test to determine the maximum frame rate each product runs at.

Setup

For this test, we used a 2017 MacBook Pro 13" (MacOS 10.14.2) along with a 2018 iPad Pro 11” (iOS 12.1.1). It is worth noting that throughout the entirety of the tests, the computer was always plugged into a charger and a Razer LanceHead Mouse.

Software Versions

We made sure to run the latest version of the software, which included:

  • Luna Display 3.0
  • Duet Display (Mac: 2.0.4.6, iPad: 2.0.9)
  • Air Display 3.2

All software was configured to run at the highest quality setting when available, so that means 60FPS, highest quality unless otherwise noted.

Latency Test

For the latency test, we used this test page https://anydesk.com/benchmark/latency.html from AnyDesk. What we do is mirror the MacBook Pro screen to the iPad and then take a picture of both devices, then take the difference between the MacBook Pro number and the iPad number. This gives a timing what the end-to-end latency is. You can see an example below:

So, in this case, we would take the result on the Mac (7069) and subtract the value on the iPad (7052) giving us 7069 - 7052 = 17ms, which tell us the iPad is 17ms behind the Mac or about 1 frame running at 60FPS.

The USB connection test is straightforward; For Wifi, keep in mind that the network we tested on was a standard home network and the network wasn't the greatest. We had rather low quality but continued with the test as it's representative of real-world use.

You can access all the files of the raw captures here:

Latency Test Results

Results: You can find the test results here

To perform the test, we took 50 samples of each software and got the average latency from those samples. If you look at the above Sheets document the two columns on the left of each highlighted column is the raw data (MacBook on the left column, iPad on the right). To get the latency estimate we took the MacBook number minus the iPad number. The results are highlighted for visibility. The results are also summarized below:

Results of USB Connection:

Duet 60FPS

Duet 30FPS

Air Display

LIQUID V3

Average (ms)

95

98.5

52.9

11.3

Median (ms)

85

100

50

16

Standard Dev

23.5

14

13.7

9.8

Max (ms)

184

137

111

37

Min (ms)

64

79

31

0

 

 Results of Wireless Connection:

Duet 60FPS

Duet 30FPS

Air Display

LIQUID V3

Average (ms)

108.1

101.7

131.4

22.4

Median (ms)

100

100

133

17

Standard Dev

35.8

21.1

55.1

12.8

Max (ms)

300

184

416

86

Min (ms)

33

64

50

12

 

Potential errors: The engineering team mentioned there could potentially be some rendering issues within the browser itself that could skew the results. However, this should still give us an idea where each product is at. The fix would be to make sure that the browser is updating the timer on strict 60 FPS intervals.

For the network section, we would like to try this again on a strong, stable network. Due to the bad network, Duet had lots of lag issues and had a very hard time catching up. 

Frame Rate Test

For this test, we also used https://anydesk.com/benchmark/framerate.html. If you were to run this on your computer and choose something other than 60FPS, you should see the line spinning. In this case, we tested with 60FPS. You know you are around 60FPS if what you see looks like a cross and doesn't spin.

You can access the video samples we took by clicking below.

There are some additional videos in the raw files linked above as well.

Frame Rate Results

We found that both LIQUID is able to run at a consistent 60FPS on both Wifi and USB. Air Display and Duet Display, on the other hand, ran at slightly less than 60FPS on USB, and significantly less than 60FPS on Wifi.

USB 60FPS WiFi 60FPS

Air Display

No
No

Duet Display

No No

LIQUID v3

Yes Yes

 

How to interpret these videos

This is a comparison of Luna Display, Duet Display, Air Display and the built in Mac display to see how closely they run to 60FPS. Ideally, when running at 60 fps the graphic in the center appears as a cross that wiggles a little bit. If the graphic doesn't appear as a cross or rotates in one direction that means the display isn't running at a full 60FPS.

 

USB

 

Wireless