Frame Grabbers for SSTV

Newcomers often ask:

Where do I plug in my camcorder?

This is a very common question.

A dedicated scan converter, such as a Robot 1200C or Tasco TSC-70, has a place to plug in a TV camera and all the necessary circuitry to capture the signal. Very easy.

However, none of the current PC-based SSTV systems have built-in circuitry to capture an image from a standard video source such as a VCR or camera. When using a PC-based SSTV system you need an additional device known as a Frame Grabber, Video Digitizer, or Image Capture Card.

How do I send a picture of myself or my "shack?"

This can be rather cumbersome with different combinations of equipment and MS-DOS based SSTV software.
  1. Exit out of the SSTV program you are using.
  2. Run the program included with the frame grabber.
  3. Aim TV camera at subject and capture image into computer.
  4. Save image to a file such as WXYZ.BMP.
  5. Exit out of the frame grabber program.
  6. Run your favorite SSTV program.
  7. Read in the image file saved in earlier step.
However, if you are using Pasokon TV and a ComputerEyes/RT frame grabber, the procedure is:
  1. Click on the TV Camera icon.

Wow! That's easy. What's going on behind the scenes?

For maximum flexibility, Pasokon TV doesn't try to build in drivers for the wide variety of frame grabbers available. Instead, it is easily configured to run a program supplied by the frame grabber manufacturer.

For example, Digital Vision wrote the HAMCAP programs specifically for SSTV in response to customer demand. Here's how they are used.

When you click the TV Camera icon (in the paint tool box) or pick Digitize from the File menu, the system executes the commands in the DIGITIZE line of the configuration file. Let's look at an example.

        DIGITIZE RUN="HAMCAP TG=DIG~TMP" OPEN=DIG~TMP.TGA DELETE=DIG~TMP.TGA
This runs the HAMCAP program and tells it to automatically capture an image from the camera and save it into a file called DIG~TMP.TGA.

Many command line options are available. For instance, "SV=1" means use S-video input instead of usual composite video. "PM=0" and "KY=0" will eliminate the preview mode and user interaction. Consult the documentation for descriptions.

Next this temporary file is read into the SSTV program and deleted.

Why don't pictures from the Computer Eyes RT look so good with Pasokon TV version 3?

The original HAMCAP program was written to match the needs of Pasokon TV version 2. Specifically, it wrote a 320 x 240 TGA file with 32k colors.

The pictures don't look worse when read into Pasokon TV version 3. It's just that you have grown accustomed to the 640 x 480 images with 16 million colors so your expectations are now higher.

The solution is to use a newer version of HAMCAP that supports higher resolution and more colors. That way you don't lose anything when the image is copied to a temporary file.

Where do I get the latest software?

Right here for latest versions as of November 1996. Click on a file name below to download it.

Modify the PKTV.CFG file

Add the following option to the HAMCAP command:
        FT=3
This means save the image with 640 x 480 pixels and 16 million colors instead of the lower resolution default.

Thanks to Digital Vision

for responding to the needs of the ham radio community.
Back to SSTV Home Page.