Hi @fenicento, thanks for your query. Firstly, with regard to purchasing the analytical licence and unlock file for using the 4C in conjunction with the Tobii Pro SDK please send an email to [email protected] and the team there will be able to provide you with a quote and instructions.
With regard to headstream data, yes you are right that for the time being this is only available in the Core SDK Stream Engine API together with the 4C whilst pupil size (along with individual eye data) is exposed only in the Pro SDK.
Whilst it may be possible to use both API’s, this is not supported as such as setup is untested. Certainly, should you wish to use Python, then the Pro SDK is the only one that supports this language binding. As you pointed, if you wished to use both SDK’s then this would indeed require using c#.
If you could kindly describe your intentions for the project, perhaps we can try to find a workaround for you that allows you to use only one SDK. In any event, please don’t hesitate to ask for any further information.