PiVR has been developed by David Tadres and Matthieu Louis (Louis Lab).

12. FAQ

12.1. Distorted Images


Why do my images/videos look distorted?


Every lens will introduce radial distortions to the image. Since the Raspbbery Pi Camera lens is not a high quality lens the radial distortion can become very obvious. The distortion is a function of the lens you are using meaning the distortion is identical for all videos/images taken by the same camera.

To get remove camera distortions in videos, please see here

12.2. Progress Bar


When running a tracking/virtual reality/video experiment on PiVR, why is there no progress bar?


PiVR was designed to process each frame as quickly as it can. This is necessary to produce realistic virtual realities. Having a progress bar undermines this goal as the act of updating the progress bar increase latency.

@ Developers: If you think this problem can be solved, please let us know - if there is a way to update a progress bar in less than a millisecond, this could and should be implemented.

12.3. Raspberry Pi does not turn on


I am unable to start the Raspberry Pi. It seems to start, but it never progresses to the Desktop.


We have observed this when the SD card was completely full! This can happen if you run experiments until you encounter an error saying that the experimental data can not be saved. If you then turn off the Raspberry Pi, the OS is unable to start.

We have been able to recover the data by removing the SD card from the PiVR setup and putting into a Ubunut workstation card reader. The files on the SD card can then be rescued. After removing the files, the Raspberry Pi was able to start again.

Alternatively, you can also just format the SD card and re-install Raspbian and PiVR, of course.

To avoid this error in the future, please always remove data before the SD card fills up!

12.4. PiVR won’t start a video/experiment


I want to record a video/start and experiment, but nothing happens.


There can be several causes for this. Usually, the terminal will be very helpful in troubleshooting why you are having a particular problem. Here, we list common problems and how to fix them. If you do not find your error message listed here, please take a picture/write it down and open an issue

  1. PermissionError: [Errno 13] Permission denied: …

    Please make sure to select a folder where the experiment should be saved. That is the button next to “Save in:”

  2. The camera is already using port %d ‘ % splitter_port) …

    We have seen this error after incorrectly closing the PiVR software. Restart the Raspberry Pi to fix this.

12.5. PiVR software won’t start


I can’t start the PiVR software on the Raspberry Pi


There could be several causes for this. To get to the bottom of the this bug please do the following:

  1. Restart the Raspberry Pi.

  2. Doubleclick on the desktop shortcut as if starting the software (this step is necessary!).

  3. Open the terminal.

  4. Change directory to the PiVR folder and start PiVR manually. If you installed PiVR with the provided script you would type:

    cd PiVR/PiVR
    python3 start_GUI.py
  5. See below if your error is explained below. If not, please take a picture/write it down and open an issue.

  1. Camera error


This could be due to several issues:

  • The camera might not have been enabled. The provided installation script normally enables the camera but it worth double-checking.

  • If this does not solve the problem, double-check whether the cable connecting the Raspberry Pi and the camera is plugged in with the correct orientation.

  • If this does not solve the problem it is likely that either the camera cable or the camera itself is faulty. It is more likely that the cable is faulty as we have experienced this more than once already. The solution is to buy a new camera cable and test it. If this does not fix the problem, try replacing the camera.

    Do note that we have seen batches of camera cables that seem to have a high (~50%) failure rates. We recommend using reputable sellers such as Mouser or DigiKey or better specialist sellers such as adafruit.

12.6. I have camera glitches/interference


I sometimes have lines appearing in my image.


It seems that this happens due to interference of the signal in the camera cable.

Make sure the camera cable is a short as possible. Ideally, the camera cable should be completely straight. If that doesn’t help you could try to shield the cable or use a completely different solution. Note that we haven not tested this but it claims to solve the problem.