The Use and Capture of Images for Computer-Based Learning II

This report is also available as an Acrobat file.

Title

Screen Machine

Caveat:

This version of the card (and software) is the original (now called Screen Machine Lite, we believe) and there are likely to have been some updates to the system - although FAST seemed to imply that there were no major changes. Please take this into account when reading the following observations. There is a second version of this card - Screen Machine II.

Manufacturer

FAST

Appearance

Full length ISA card. 16 bit slot only.
4 jumpers (I/O address and wait state).
Various headers for option boards (SECAM, audio I/O, colour keying, RGB, TV tuner).

Connectors

Externally

VGA output, VGA and video input (both 15 pin HD D-sub, inputs via adapter cable)

Internally

Daughter board options as above.

Installation

Hardware

Select a suitable (free) I/O address. This was another card that clashed with the heatsink and, therefore, had to go in one specific slot. Connect the adapter cable between the VGA output and Screen Machine input, connect monitor to Screen Machine output (no drop in screen intensity).

Software

First attempt at installation wrote 0 length expanded files - corrupted some DLL's in the Windows directory (probably not checking for existence/date and overwriting with corrupt and/or of date versions of the same file).

Therefore a manual installation was performed. A few more problems were encountered before getting the card working properly:

make sure you have your video source connected to input 1 during SM_SETUP (the setup program), as there is no (apparent) way to choose the video source from this module û so there is no image on which to do the setup (unless you run SM Camera first, but you wouldn't normally do that until you've run setup!)
problems with the display card/driver. Forced to drop back to the standard VGA driver (640x480, 16 colour). Even then the setup.inf file had to be edited to get the image near to the correct position in its window û this is after setup, which then had to be run again to fine tune the position, size, proportion.
after the above the video image position (relative to its viewing window) would vary according to the viewing windowÆs position on the screen.
image quality on the monitor was slightly degraded compared to the output direct from the VGA card, more so at 800x600 - however images could not be grabbed at this resolution anyway (although it should handle it û and may with other VGA cards).

Capture times

Virtually instantaneous for capture (Note: will capture from moving source images), so these times are for the saves.
640x512x24 5s
640x512x8c 7s
640x512x8g 3s

Observations

The capture software provides three main modules : TV; camera; dark room

TV

provides a scaleable window; captured still images can be saved in a number of formats.

Camera

gives a fixed window and saves the captured images to a 'film strip', which can then be saved. Note : this is in Screen MachineÆs own FLM format.

Darkroom

used to 'develop' films, i.e. process the images in FLM format to other formats, colour depths, image size, rotation, resampling etc.

Both TV and Camera allow source setup (now they tell you!) which includes video input and type, composite colour on/off (for greyscale images), time base correction, prefilter, sharpness, noise, bandpass and hue filters (all 0-4 range). They also have control over the image brightness, contrast, saturation and RGB values, and size. But, although they both read the same settings file, only the TV module appears to be able to save these settings.

The manual briefly discusses the effect of the controls on image quality if they are not immediately obvious (e.g. explains that 'row correction off' will give higher resolutions from still image images). The 'Basics' chapter of the manual also briefly covers such issues as lossy compression, printing, colour models, palette optimisation, etc.

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