schwarz@infbs.UUCP (07/06/87)
Is there anybody working with the AMIGA parallel device ? I use it
to read in slow picture data from weather satellites. The format of
these pictures is: 600 pixels per row in 0.25 sec and 200 rows per
picture (1 pixel = 1 Byte parallel = 256 colors). Therefore the bytes
arrive with a frequency of 2400 Hz.
The program is written in C and uses the DoIO-subroutine. There is
no exact handshake between picture source and Amiga parallel device
but only a strobe from source to the Amiga. The acknowledge from
Amiga is not used because the real time quality of the picture signal
allows no waiting of bytes before transfer to the Amiga.
Now the problem: Only 588 (+/- 10 Bytes) of 600 bytes (pixels) are
read in. The remaining 12 pixels are lost. So the picture shows a
non-vertical synchronization band and a randomized jitter on this band.
The latter is critical. Measurements showed that the Amiga stops
acknowledge pulses for a short period every 20 msec
(=> 50 Hz = German TV-frequency)
at the beginning of a new Amiga video frame. I think the machine needs
time to process the new frame (while reading the satellite picture this is
not shown on screen but only stored in fast memory area).
Is it possible to make the reading function secure without investing in
hardware (=> correct handshake mechanism: strobe and then ackn before
sending new byte) ?? I use an Amiga 2000 with 1.5 Mbytes.
Second question:
Is there anyone who has built a "real time video digitizer" or a genlock
interface and can send me more information ?
Thanks.
UUCP: ...!mcvax!unido!infbs!schwarz
BITNET/EARN: SCHWARZ @ DBSINF6
ADDRESS: Ulrich Schwarz
Technische Universitaet Braunschweig
Institut fuer Theoretische Informatik
Projekt Ausbildungstechnologien
Bueltenweg 74/75
D 3300 Braunschweig
West - Germany