No videos and no audio

Currently, no videos can be embedded in z-Tree if z-Tree unleashed is used. This is due to Windows Media Player not being available on Linux.

Secondly, RFB (the network protocol behind noVNC, and therefore, z-Tree unleashed) is really ill-equipped to stream videos. Even if another method of opening a video would be used (such as with VLC, mplayer or mpv), the video would appear very choppy.

However, even if that were resolved, an even more pressing limitation is that audio is not available. Audio cannot be streamed over RFB. Therefore, no solution will ever be forthcoming (at least not in the current configuration of z-Tree unleashed).

POSSIBLE WORKAROUND: Upload the videos on YouTube (possibly using the “Not Listed” function) and tell subjects to enter the video’s URL in a separate browser tab when it is prudent. You might wish to use a URL shortening service to make the URL more user-friendly. Or you can send subjects the link to the video in the email with the participation link, if your experiment allows that. You could also show a QR code.

All leafs run on a single machine

z-Tree unleashed does its best to spread out the CPU load between all available cores. In contrast to oTree, z-Tree unleashed is fully parallelized! However, the central bottleneck of z-Tree unleashed cannot be totally avoided: All calculations and all rendering of screens takes place on the same device.

We have seen setups that run sessions with upwards of 80 simultaneous subjects—but the experiment is simple and works extremely well! But we have also seen setups with comparable hardware that have hardcore interactions or many updates to the screen, which radically reduces our recommended number of simultaneous subjects.

Perhaps, at this point, you should go back into the lab and run your z-Tree experiments there or use other experimental software for the web.