Monday, 1 June 2015

Thor Camera Controls

Version 1.02 of Thor allows you to set various camera controls for your webcam.

To see all the controls scroll the screen:

Swipe vertically to scroll

The three blue buttons do the following:

Refresh Settings
Reads the value of each control from the camera and updates the user interface. Press this button to go back to your current settings.

Send To Camera
Sends the value of each control to the camera. Press this button after you've have made your changes to the control settings.

Reset All
Sets each of the controls on the screen to their default values, remember to press Send To Camera to send these values to the camera itself.

To quickly see your changes, press the GO TO CAMERA menu option in the top right corner. Please allow a few seconds for the camera to start up.

You can go back to the settings from the camera view by pressing the GO TO SETTINGS menu option in the top right corner. Please allow a few seconds for the camera to shutdown.

How To Use The Controls

Each camera has its own set of controls, where possible turn off any automatic settings such as White Light Balance and Exposure.

Experiment by changing only one setting at a time, you make notice that some controls do very little to the camera image. Most settings can be left set to their default values.

Important settings for the AutoMelt application will be the Gain, especially in low light situations.

Trouble Shooting

Pressing 'Send To Camera' says SEND ERROR. 

Go to the camera screen, wait a few seconds and then go back to the settings. If that fails try sending the default settings to the camera as some combinations of setting may cause the camera to send a fail response. If that still fails, power off the computer and reboot.

Have patience with the User Interface, there is a lot going on under the bonnet when communicating with the camera. Give a few seconds when sending new settings to the camera as the camera itself will be busy processing them.

Camera is not detected / does not work. 

Power off
Unplug the camera
Check the USB lead connection to the camera.
Plug in the camera.
Power on and reboot.

Swapping cameras does not work

If you wish to use another camera you will need to power off the computer, plug in the camera, power on and reboot.

Camera Settings Have No Effect

Remember to press 'Send To Camera' after changing a setting, wait a few seconds for the SEND OK response. Some camera settings may do very little such as Hue, Saturation and Gamma.

Camera Forgets its Settings

The current settings are lost when you power off, I recommend noting down camera settings that are to your liking. The idea of Thor is to allow you to experiment and research the camera optics and heating controls, it is not a full blown user product.

Some Controls Are Missing

Webcams will have differing capabilities and so have their own set of controls, out of the 3 webcams I have tried, only one had the Auto Exposure setting.

Programming Notes

Thor communicates directly to the Video 4 Linux drivers (V4L2), no third party UVC or USB libraries are used.

It is necessary that the Android build makes the /dev/video0 device available to the user for read/write operations:

Add the following code to the file /rootfs/ueventd.am335xevm.rc found on the SDCard
/dev/video0        0666  root       root

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