ZL2AFP Narrow Band Digital NBTV

High speed PSK modem, image compression and noise-free pictures
Introduction     Transmitting     Receiving

 Picture Replay

Although the Digital NBTV system cannot transmit movies in real time, it can transmit them slowly. The receiver allows you to record a series of frames, and this Viewer can then be used to play the received pictures back at motion speed.

The Drag-and-Drop Viewer

The Viewer program accepts only .TV format files. However, it will also convert these files to .AVI format (using a range of different codecs). The program is very easy to use. Start the Viewer program Viewer_drag_drop.exe, and you will see the window shown above. Then, either select a .TV file from a folder view, and drag it onto the window, or use the 'File/Open' option on the menu to start a dialog allowing you to select a suitable file.

When a suitable file is opened, a second window, the Viewer itself, opens.

The replay TV Viewer

The movie sequence will start automatically, and will play over and over at the default speed (10 frames/sec). To view any individual frame, press the Pause button (marked ||) to the left of the progress bar, then slide the progress bar along to the frame of interest.

The TV Viewer window cannot be resized.

At this time you can save the individual frame as a .JPG, .BMP, .GIF etc image, by clicking on the TV Viewer window banner (making the Viewer 'in focus), then pressing the keys 'ALT + Print Scrn' together, which puts the image on the clipboard, and finally pasting the image into a graphics editor such as Paint or Paintshop.

The TV Viewer window cannot be resized, but of course once you have the image pasted into a graphics editor, you can make it any size you like.

As well as the File/Open business mentioned above, the menu also allows you to select a replay speed (10, 6, 3 or 1 frame per second), adjust the picture brightness and contrast (rarely needed), and switch the colour format (never needed, since the transmitter and receiver cannot generate the wrong colour format).

Making an AVI
Once the file is loaded, press Pause, then press the 'Make AVI' button. The dialog which opens allows you to select from a range of codecs. 'Cinepak Codec by Radius' works very well, and is compatible with Windows Media Player™. The file is saved in the current folder (same folder as the program) with the same name as the .TV file, but with the suffix .AVI. Since the .TV file is uncompressed (it is a series of bit map frames) and the .AVI file is compressed, the .AVI will be smaller.

Introduction     Transmitting     Receiving

Copyright © Con Wassilieff and Murray Greenman 2004-2009. All rights reserved.