Tobii 5 – ONLY 33Hz for sampling frequency?

[Hongbin Zou]

Hi, I just tried the newest tobii_stream_engine 4.1.0.3 with the newest Tobii Eye Tracker 5.

I enumerated the available sampling frequencies with the api function below:
tobii_enumerate_output_frequencies
and it gave me two frequencies: 33 and 33. Yes, two same frequency options.

So I write some other tests, all of them indicates that the real sampling frequency is around 33. For 4C I am getting a stable sampling frequency of 90Hz.

But this post from Tobii implys Tobii 5 is capable of working at 133Hz (Image sampling rate – 90Hz vs 133Hz):
https://help.tobii.com/hc/en-us/articles/360008539058-What-s-the-difference-between-Tobii-Eye-Tracker-4C-and-5-

So am I able to get a 133Hz sampling rate? Why there are two same 33Hz options from the driver? Or the new Tobii 5 can only be 1/3 responsive of its predecessor?

I am quite confused by my test results. Did I do something wrong? Please explain these for me, Thanks.

[Hongbin Zou]

A datasheet from Tobii says the gaze data rate of IS5 is 33Hz(fine gaze) / 60Hz(fast gaze):
https://cdn2.hubspot.net/hubfs/1995689/is5/tobii_is5_evaluation-kit_data-sheet_v3_20190925.pdf

So, what is the benefit of a lower data rate? Stability? Or “optimum tracking over a large population”?

[Grant [Tobii]]

Hi @dragonus, thanks for your patience whilst we investigate this issue and will provide a full response soon. Best Wishes.

[Grant [Tobii]]

Hi @dragonus, thanks for the wait and thank you for spotting the error that had been made on our webpage regarding the ET5 statistics, much appreciated!

We can confirm that the ET5 has a sampling frequency of 33HZ (as compared to the 4C 30Hz) but crucially has an image capture rate far higher at 133Hz meaning more eye images are taken within one second that previous models.

The ET5 consumer eye tracker sampling frequency remains the same at 33HZ as reported in the stream engine which you mentioned.

With regards to the evaluation kit, this is something that our customers may purchase under special license for development or integration such as OEM applications.
With this advanced license, one may acquire 60Hz output, but for the ET5 consumer-level product this is not supported.

Further, the base evaluation kit has slightly different hardware configuration so one cannot make a direct comparison between this and the ET5.

Hopefully, this answers your query, please let us know otherwise. Best Wishes.

[Hongbin Zou]

OK, got it. Thanks.

[Grant [Tobii]]

You are very welcome 🙂 Please don’t hesitate to get in touch again should you require any additional information.

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