VTR Clock
For the BBC Microcomputer, RISC OS and Windows™
Alan Pemberton wrote this
programme in BBC BASIC in 1983 in order to allow a BBC Microcomputer to
place a countdown and ident clock on video productions. The BBC Micro has a
625-line 50-field 1V composite video output which is suitable for feeding
directly into a video tape recorder. It is also easily modified with a
genlock board so that its signal can be fed synchronously into a video
mixer.
I adapted it to run natively on RISC OS and also on Windows using
BBC BASIC for Windows and Alan
has given permission for it to appear here.
Instructions
The program allows the user to type in the production details on the
slate. Use the cursor keys to move around within each box and Shift-Return
to move to the next box.
The countdown may be started at any ten-second point, and the take number is
incremented automatically.
When the clock is at rest, the following keys are recognised:
1 set the clock to 10 seconds
2 set the clock to 20 seconds
3 set the clock to 30 seconds
4 set the clock to 40 seconds
> increment the TAKE number
< decrement the TAKE number
SPACE start the countdown
S lets you type in the SHOT box
P lets you type in the PROG box
D lets you type in the DATE box
F set Auto-Fade on/off
B Blank display before countdown starts
C Continue countdown
E exit the program
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At any point pressing ESCAPE will display the menu.
The User Port is set to various values as the countdown
progresses. These can be used to control external equipment.
Each line goes to logical one as follows:
Bit 0 While the clock is counting
Bit 1 From 30s to 20s
Bit 2 From 20s to 15s
Bit 3 From 10s to 0s
Bit 4 From 6s to 0s
Bit 5 From 5s to 0s
Bit 6 From 3s to 0s
Giving the following bit pattern:
00000000 Before starting
00000001 40s
00000011 30s
00000101 20s
00000001 15s
00001001 10s
00011001 6s
00111001 5s
01111001 3s
00000000 0s
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Hosted by Force9 Internet -
Authored by J.G.Harston
Last update: 13-Dec-2006