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EnigmA Amiga Run 1997 July
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EnigmA AMIGA RUN 20 (1997)(G.R. Edizioni)(IT)[!][issue 1997-07 & 08][EAR-CD IV].iso
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colorframing.txt
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1996-12-09
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89 lines
The following should have some related information for
Lightwave users who wonder exactly what that Toaster card is doing. I
typed this up for the old LightWave mailing list.
-Karl
Karl Frederick
Antares Videomedia Ltd.
Email: frederik@teleport.com
=============================
Time Price Quality ... pick any two
The Toaster Manual tells you that each DVE buffer consists of
4 fields. When removing motion, these four fields are used to gain the
highest resolution inside the buffer. I went searching for the
Engineer's answer. After an hour, I ran across a fantastic resource
detaling all levels of the Video industry.
From an Engineer's point of view, I thought I would pass along
some data to describe EXACTLY why
1) the frame buffers use 4 fields
2) the frame buffers require motion removal
MASTERING TELEVISION TECHNOLOGY, A Cure for the Common Video
Newman Smith publishing 1988
ISBN# 0-929549-00-7
Congress CC# 88-90786
Starting on page 230, it details the makup of origional NTSC
as 60 fields per second. The author talks about the change to
59.94005996 fields per second, and how it interelates to the
subcarrier of 3,579,545.455 cycles per second. Further the book
describes about the number of subcarrier/sec divided by the number of
fields/sec = 59,718.75 Here we pay attention to -->.75<--
Now quoting:
Color Framing
The fractional number of cycles (xxx.75) in a field indicates
that between the beginning and end of a field there is a 1.0 - 0.75 =
.25 cycle (90 degree phase) difference in the subcarrier. With this
phase shift, returning to the original phase requires the completion
of 1 / 0.25 = 4 fields. The phase shift produced, when maintaining
subcarrier-to-horizontal (SCH) phase, effectively produces four fields
in the NTSC system:
COLOR FRAME A:
FIELD I starts after a line that is full of picture
information and has a positive-going subcarrier at the leading edge of
the sync pulse of Line 10 (where the burst first appears).
FIELD II starts after a line that is half full of picture
information and has a negative-going subcarrier (180 degrees out of
phase relative to FIELD I) at leading edge of the sync pulse of Line
10.
COLOR FRAME B:
FIELD III starts after a line that is full of picture
information and has a negative-going subcarrier at the leading edge of
the sync pulse of Line 10.
FIELD IV starts after a line that is half full of picture
information and has positive-going subcarrier at the leading edge of
the sync pulse of Line 10.
Examination of the totaled number of cycles at the beginning
of each of the color fields confirms the four field interval that is
necessary to return the subcarrier timing to the original phase. This
results to 360 degrees of subcarrier phase.
Summation: Four fields are stored in memory to track the
correct SCH timing. This insures that the Toaster Board has the most
complete color information about the frame you "grabbed".
I must say that the book covers several other topics as well:
Registration of tube cameras (good charts)
Interpreting Wave Form / Vector Scope Displays
Individual charts on video tape formats from 8MM, VHS, SVHS, MII,
BetaCam, 3/4 U-Matic, 3/4 SP, 1"-C, D-2. Good charts...
Digital Audio/Video Sampling
Proc Amp contols
Audio and Mic'ing
And more than I can mention....
This is one of those hard covered books with a bland-red
spline. Remarkable how much industry information is sealed within it's
cover. What your Toaster is doing is beyond the FREEZE FRAME,
found on most TBC's.