Belgian Amiga Club - ADF Collection/BS1 part 65.zip/BS1 part 65/VideoStudio v3.0 disk 2.adf/manual/test

Text File | 1992-04-19 | 13KB | 291 lines

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ZVP  TEST PATTERN GENERATOR  v3.0
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    This program is indispensible for ensuring that VCRs and
various video distribution feeds, mixers etc. are performing
(and continue to perform) as their manufacturers intended.  In
addition to a range of video tests, an audio function generator
with two channels is available for comprehensive audio checks too.

    It is also invaluable for keeping a look-out on the
progressive degradation of recorded quality of subsequent
generations of video tape copying.  To do this, a brief
recording is made on the initial part of a master tape,
before a recording begins.  Ten seconds or more will suffice.
All subsequent recordings will contain a 'N th' generation
copy of this for your inspection.  Particular defects such as
deterioration of luma and chroma definition, chroma mis-registration
and smearing (esp VHS), sync jitter and dropout (all formats),
and loss of low-level picture detail (VHS machines not equipped
with edge enhancement defeat/'edit' switch; most Beta ad V8 machines
have this as standard).  Beware of 'sharpness' controls... they don't
do quite what you'd expect.

    By carefully monitoring the video quality during post-production and
on subsequent genearation copies, any user-controlled variables, such
as tape quality, sharpness control and enhancer settings, (or even
which of two 'identical' video recorders to use!), each can be carefully
calibrated for best, and consistent results.  You can discover the truth
of which tapes are good, and which are awful (I'd better keep my mouth
shut just in case He Who Dares, gets sued!).  VCR(A) is a pattern
especially designed for visual evaluation of these parameters.  No serious
video-maker should be without this facility.  Few people actually get
they might out of their video equipment, so here at last is the means
to give you the edge in picture quality, and a little crucial know-how.

Use it... it could save you hundreds of pounds in unnecessary upgrades,
and it will help enormously in selecting which products are the best
to use. (i.e. borrow a mate's GXNFF-3000-XP/VC-F99 VCR and test it
before shelling out on one yourself.  Wicked... Huh...?)

THE PROGRAM

    All the patterns fortunately are vector-drawn for floppy
disk-space economy, efficient use of RAM, and of course, speed.

(IFF versions of these patterns and others, occupying a whole disk,
can be purchased as the VideoStudio PROFESSIONAL test pattern disk.
To use them you will also need a HARD drive and 1Mb CHIP memory
due to the buffer space needed for IFF files of this size).

GENERAL USE

    Each pattern is selected with a single lefthand mouse-button
click.  At this point a second click will dispay the pattern,
or alternatively the IDENT (the name overlay) or the AUDIO TONE
settings may be changed.

    The AUDIO level and frequency are separately adjusted by
clicking the appropriate +/- buttons corresponding to the channel
you wish to alter.  Each pattern has independent settings from
the others, and the channel 1/2 settings need not be the same,
permitting stereo testing.  The new settings can be saved
permanently upon clicking SAVE CONFIG.

    Clicking CHANGE IDENT will allow you to enter a new name,
or delete the existing name/callsign etc.  A separate ident is
independently available for each pattern, and this will be
permanently stored if you click SAVE CONFIG.

The patterns...

CROSSHATCH

    This principally is used to confirm the scanning linearity
of the horizontal and vertical deflection amplifiers of a
monitor.  The blocks are spaced at equal intervals, and this
may be confirmed by relative measurement at the face of the CRT.
This pattern is also useful for convergence checks, see below.

DOTS

    Normally used for focus and convergence checking/setting on
monitors.  The dots themselves should be crisply in focus at
the screen centre, and at the corners.  On colour monitors, any
divergence or red green and blue beams will be seen as a convergence
error.  This pattern is also interesting for observing dropout
behaviour on VCRs... record it and try it!

(The dropout compensation circuits of a VCR will repeat the previous
line if a dropout is detected.  The dots totally disappear if this
occurs when displaying this pattern, which is easy to observe.)

Deteriorating dropout behaviour may indicate worn or dirty video
heads.

MULTIBURST

    Sometimes referred to as Defintion Bars.  At line rate, six
different squarewave frequencies are available in turn, checking
the relative behaviour of different parts of the video spectrum.
Ideally they all should be displayed with equal intensity (or
seen as equal amplitude on an oscilloscope sychronised to line).
In fact, PAL G will only marginally display the top burst (over
600 lines) and S-VHS cannot display this, and will be very marginal
on the next burst down too (410 lines).

    Note that even quite expensive TVs (unlike computer monitors)
may not adequately resolve the top bars.  This is due to compromises
in the design of PAL decoders, and the choice of shadow-mask pitch
for the colour tube in TVs, which is coarser (hence cheaper to produce).
This applies frequently to modern FST sets.

    Viewing a recording on subsequent generations will show how
the video deteriorates due to recording non-linearities (especially
with VHS, Video-8, to a lesser extent the 'higher-band' domestic
S-VHS, Beta and Hi-8).  (A more flexible vesion of this is the
multiburst at four modulation levels. See VCR TEST A)

The defintions (in lines) are approximately 40, 60, 80, 160, 350, 700.

    The amplitude envelope may be viewed on an oscilloscope for a
much more useful assesment.  Very accurate measurement is entirely
possible if an allowance is made for the Commodore modulator.

COLOURBARS

     Two versions are provided.  Really only of value though for
checking chroma behaviour on an oscilloscope.  Look for equal
height of steps (luma linearity) crushing of chroma (esp. yellow,
i.e. the last-but-one step).

FLASHING H-BAR

     Checks the EHT regulation and that of scanning power supplies
in a monitor.  The vertical bars on either side of the screen ideally
should not be disturbed as the centre bar flashes.  However in
practice, the variation in beam current (due to the fluctuation of
average picture brightness) causes the EHT (Extra High Tension)
supply to the tube to drop, the electrons are accelerated less, so
for a constant deflection field, the picture grows and shrinks in
sympathy.  This sort of fault (over say 5%) is often exhibited on
old colour monitors, or some modern TVs of weak design.

PURITY

Six fully saturated colour screens to permit checking that the scanning
is uniformly registering with the appropriate colour phosphor dots
on the face of the tube.  Any purity irregularities will be seen
as changes in the colour in areas of the screen.  Most colour tubes
now are fully factory preset, so there may be no adjustment available.

These patterns are especially sensitive to static and varying magnetic
fields that may be close to, and interfering with a monitor.  Interference
from a loudspeaker magnet (for example) produces a mis-coloured blotch.
A transformer or motor will produce a slowly 'rolling' blotch (AC mains).

A permanent purity error may indicate that the shadow-mask of a tube
has become magnetised for some reason.  This is corrected by 'degaussing'
or exposing the tube to strong alternating magnetic field, using a
degaussing coil.  This is rather like erasing a tape.  This is sometimes
necessary after (for example) a hoover has been operated too close to
a colour tube.

Most sets have AUTOMATIC DEGAUSSING (upon switch-on) which should cope
with most minor magnetic disturbances.  Please note that this is why
you should NEVER place floppy disks (or video tapes for that matter)
near a colour tube, as they may be partly erased by this momentary
field.

CIRCLE AND DIAGONAL

     The eye is very sensitive to any lack of straightness of the
diagonals, as it also is to irregularity of the circle.  This pattern
is therefore better than the grid pattern (above) for linearity
settings and centreing, without the aid of a ruler.

COMPOSITE

     A combination of COLOUBARS and MULTIBURST patterns.

EBU COMPOSITE

     The design of this is credited to PHILIPS hence 'philips test
pattern'.

BREMA COMPOSITE

     British Radio Equipment Manufacturers agreed standard for
electronic test patterns.  More usually recognised as the Channel
Four test card.

VCR TEST

     A special VCR workout pattern designed by ZVP.  It is especially
sensitive to malfunctions peculiar to VCRs, namely:

     (a)  Jitter on verticals (see left and right bars for 'fizz')
     (b)  Wobble at top or discontinuity at head crossover. 'Flagging'.
     (c)  Chroma Bandwidth and shift (notched colour bars)
     (d)  Chroma Mis-Registration (see constant luma scale at bottom)
     (e)  Dropout (general disruption watch for D/O compensator)
     (f)  Luminance bandwidth deterioration (four modulation levels)

     The multiburst (definition bars) of progressively increasing
detail/frequency are at four different modulation levels, to draw
attention to the non-linearities and artificial sharpening tricks
that account for the loss of low-level picture detail.  The progressive
loss of sharpness (manifested by loss of detail in peoples faces
for example, a charcteristic of VHS recordings especially) can be
examined at various stages, and carefully monitored on subsequent
generations.  Careful attention to performance at EACH intermediate
generation will ensure best results at the final stage.  This will
be especially sentitive to prudent setting of sharpness controls
(if used).

     The colour blocks at the bottom are very special, and contain
little luminance detail, and maximum chroma detail.  Ideally the
blocks will be clearly and sharply defined on a good monitor
connected directly to the Amiga, using PAL composite video.  Once
recorded, varying degrees of smearing and mis-registration occur,
depending on the quality of the recorder and recording format in use.

     Please do not be too alarmed at the performance of 'domestic'
formats such as VHS, S-VHS (and professional).  This pattern is intended
for relative checking only.

TESTING (AND SELECTING) A GOOD MONITOR

     The best monitor to use for combined video work and use with the
Amiga will require careful selection.  It should have a good quality
wideband PAL composite input (plus optionally a RGB input IF you use the
Amiga for Non-Video applications).  The type of connector is probably
a BNC (ideally) but often the RCA-phono is used these days as a cheaper
alternative to keep cost down, and increase incompatiblilty.  If you
choose a set with a SCART connection only, you may well find you
end up needing a confusing selection of adaptors for various purposes,
so avoid the SCART/EUROCONNECTOR if at all possible.

     The set(s) you choose may or may not need to have a
TV tuner depending on what you need.  Ideal screen-size is very
subjective, but beware of smaller monitors (unless they are expensive)
because the shadow-mask pitch can be rather coarse, producing poor
definition (contrary to the impression visually, which is misleading).
To avoid spending a lot of money, a 20" domestic TV with the appropriate
connectors, from a reputable manufacturer (S*** or P********) is
a good bet.  Other brands are often of wildly varying quality.
Vision B/W should be flat to 6MHz (UK PAL) and not the lower 'universal'
'Euro' PAL based on the lower German bandwidth.  As a further clue
to quality, sets of UK manufacture (especially Wales) are generally
a good bet.

      Computer monitors (Such as the C**********) WOULD be useful as
they have a good tube and good video bandwidth, BUT they suffer from
being set up as monitors, having severe overscan and also have a
front-panel centering control.  These qualities mean that they cannot
reliably be used for video work since they can give no check of screen
composition and centring.  A properly set-up non-computer monitor is
needed.

      Don't forget to take your Amiga to the showroom before your
******-card is irretrievably debited. (!)  The definition bars should
be quite an eye-opener in D****S or C***T.  Look for artificial
'sharpening' implemented by marketing men (and not engineers) for
point-of-sale appeal only on the middle bars.

SOUND TESTING

     Recorders with EDGE (baseband) sound should be checked
periodically using the audio generator and a level meter.  The
recorded tone should be ideally at constant level independent
of frequency.  To check this, make a recording of the menu page
as you alter the frequency, then observe your level meters on
playback.  If the heads are out of alignment, dirty or worn,
this will be very evident from this test. VHS baseband should
be reasonably flat to about 6KHz.

!  WARNING

     Television receivers and computer monitors operate at very
high voltages.  Do not remove the covers of any mains equipment
while it is switched on.  Refer all adjustments and maintenance
to a qualified engineer.


iss 0  2 Dec 91
iss 1  3 Jan 92
iss 2  7 Jan 92