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The History of Videotape – part 4
Camcorders and Digital Video
By Ian Batty, Andre Switzer & Rod Humphris
As detailed in the previous three articles in this series, videotape
recording culminated in the incredibly popular VCR format. But it
was not really suitable for portable recording, being too bulky. Before
digital video totally replaced tape, there were still some significant
technological developments, mainly in the field of miniaturised tape
formats for more practical handheld video recording.
T
he camcorder began with Sony’s
record-only Betamovie. But what
led Sony to design such an oddball
machine?
Impressive as Betamax and VHS
were, their portable versions left much
to be desired. Lugging a klutzy VCRplus-camera kit was far from ideal.
Aside from colour recording and a longer running time, these weren’t much
better than the old half-inch reel-toreel Portapak.
The revolutionary ‘camcorder’
design put the camera and VCR
together into one case. The unit would
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have to sit on the operator’s shoulder,
which gave improved stability over
previous wobbly hand-held cameras.
So, leaving aside the inconvenience
of post-processing, why not stick with
a (smaller) 8mm movie camera with
colour film?
That is a question that users of Sony’s
Betamovie must have asked themselves. Sony has a history of going out
on a limb, and in this case, they appear
to have prioritised compactness over
practicality in their first camcorder.
It was a unitised design, but it had
no playback facility. To find out just
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what you had (or had not!) recorded,
you had to remove the tape from the
Betamovie and play it in a ‘proper’
Beta machine.
National Panasonic’s first outing,
the full-size M3 VHS camcorder, did
offer standard recording and playback.
But it was way bigger than a shoebox,
and so it was never going to be madly
popular.
The VHS-C cassette, at less than
30% the size of a standard cassette,
and giving 20 minutes of recording
time, helped to shrink the VHS camcorder. Reducing the size of the head
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drum from 62mm to 41.3mm helped,
but added complexity by demanding a
270° tape wrap and four video heads.
Even with VHS-C’s smaller size, cute
packaging and flip-out viewfinder/
playback screen, it wasn’t going to be
too long before someone went back to
the drawing board and came up with
a new format that would redefine portable video.
It would have to be something close
to the size of the extinct Super 8mm
film camera, with its unitised pointand-shoot convenience.
The Ultimate (analog) VCR:
Kodak/Sony’s Video8
The need for a new, compact format saw Sony and Kodak cooperate
in the early 1980s. The project was
announced by Kodak’s 1984 release
of the Kodavision 2200 and 2400
models.
At a base price of US$1600 (~$5700
today), sales were modest. 1985 saw
Sony release their cheaper, simpler
and smaller CCD-V8. Borrowing some
of the cachet from Super 8 movie film,
Video8 would become the last major
analog video tape format, and would
ultimately morph into a digital form.
Video8 used a 95 x 62.5 x 15mm cassette containing 8mm-wide tape running at 2.051cm/sec for standard play.
Using a smaller head drum (40mm)
than either Beta or VHS, the headto-tape speed was down to 313cm/s.
Like all other colour formats, Video8
used FM luminance and heterodyne
colour (4.2~5.4 MHz and around 734
kHz respectively).
The slow tape speed meant that linear audio recording would give very
poor results so Video8 only used FM
audio, similar to that of hifi Betamax
and hifi VHS.
Video8 was designed using Sony’s
U-loading system, developed two
generations back with U-matic. As
the M-load vs. U-load comparison in
Fig.56 shows, U-loading suffers from
the loading ring having to completely
encircle the head drum.
Video8 camcorder designers (needing to miniaturise the tape mechanism as much as possible) adopted the
M-loading system from VHS, keeping
Video8’s original record/playback format and speeds. This allowed Sony to
produce the much smaller CCD-FX270
Video8 and to realise the miniaturisation inherent in the Video8 format
(Fig.57).
siliconchip.com.au
Fig.51: reel-to-reel “portapaks” were the first truly portable video recording
system. Clearly, though, further reductions in size and weight would be
required! Source: www.rewindmuseum.com
Fig.52: the Akai VT-100S was an
improvement but still pretty awkward
to carry around. The hand-held
black/white camera VC-100 is shown
separately. Main image source:
https://youtu.be/iaPAyVcXz_0
Sub image: www.catawiki.com/
l/15944111-akai-vt-100s-video-set
Australia’s electronics magazine
June 2021 49
Needing to maximise tape real
estate, Video8’s designers dumped the
control track used to position the video
heads for exact tracking of the recorded
signal stripes in replay. Instead, a servo
signal embedded in the video tracks
allowed the head-positioning servo
in replay to correctly sync the video
heads to the tape.
The embedded Dynamic Track Following (DTF) servo had already been
pioneered by Philips in their ill-fated
Video 2000.
The embedded servo design,
rebranded as Automatic Track Following (ATF), was successful, but Video8
was unable to use the missing control
track pulses as a highly-accurate tape
counter. Video8 was forced to revert
to uncalibrated mechanical counters.
The slow head-to-tape speed forced
higher flux-change densities onto the
tape, so conventional oxide-particle
formulations were replaced by metal/
metal particle coatings. These had
been pioneered in audio cassettes, taking the Compact Cassette from its original ‘dictation quality’ (due to low-performing ferric oxide coatings) to true
high-fidelity in the best models.
Fig.53: a Sony Handycam from the late
90s. That’s much more like it!
The end of the road:
digital video
Digital measuring instruments had
been converting analog quantities to
digital signals since the mid-1950s,
and the principles of analog-to-digital
and digital-to-analog conversion were
well-understood by the 1970s.
Most digital audio recordings from
the 1980s were recorded on U-matic
tape via a Sony PCM-1600 audio interface. Digital audio has a wide signal
bandwidth, easily accommodated by
the luminance channel of U-matic.
Since the PCM-1600 was based on
U-matic record/play parameters, Compact Disc’s well-known 44.1kHz sampling rate was chosen to be compatible
with both NTSC and PAL video line
scanning rates. Digital audio, recorded
on U-matic tape, was the first system
used for mastering audio Compact
Discs in the early 1980s.
So it was just a matter of time before
VCR designers turned to digital signal processing for the video channel.
Video8 had already used Pulse Code
Modulated (PCM) audio in some models, but with a 32kHz sampling rate and
only 12-bit sampling (a 60dB dynamic
range), its audio performance was inferior to hifi Betamax/VHS.
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Silicon Chip
Fig.54: the National M3 was a full-size VHS Camcorder. You can see how big
it is in comparison to the later Sony Video8 Camcorder next to it.
Leaving aside the complexities, digital processing uses a codec (CoderDecoder) to store and retrieve signals.
The Digital Video (DV) codec borrows
an old idea: luminance and chrominance are processed separately. The
luminance signal is processed with
a 13.5MHz sampling rate, while the
separated U (yellow-blue) and V (redcyan) chroma signals are sampled at
the much lower rate of 3.375MHz.
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That’s pretty much what analog
VTRs/VCRs had done, allocating more
bandwidth for the luminance signal
and less for the extracted chroma.
Economising on signal processing
wasn’t enough though. Digitising the
video into 8-bit data streams gave a bit
rate greater than 100 megabits per second, so the digital images were compressed before recording, then decompressed in playback.
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DV. Using an even smaller cassette,
DV would finally produce a handycam smaller than a Super 8mm movie
camera, but with a lot more features!
Fig.55: this VHS-C Camcorder was much
more practical than the full-size VHS
units, but the 20-minute tape length
was pretty limiting, and it
wasn’t long before the
superior Video8 system
came along.
Nearly forgotten: Laserdisc
Yes, you can do all this on a video
disc. Just use the high-density optical
recording techniques developed for
Compact Disc, but lay down analog
audio and video signals.
Developed by an MCA-Philips consortium, the format was first demonstrated in 1972 and publicly released in
1978. Double-sided discs were limited
to a maximum of 64 minutes per side,
and could not be recorded on. Laserdisc’s high quality (equal to 1-inch
C-format videotape) could not overcome the convenience and home-recording features of Betamax and VHS.
G RING
ADIN
LO
Fig.56: a comparison
of the size required
for U-loading (blue)
and M-loading (red)
mechanisms. They
do more-or-less the
same job of wrapping
the tape around the
head drum, but with
M-loading taking up
barely half the space
outside of the cassette.
SUPPLY
REEL
The compression algorithm is lossy
– it works by discarding picture detail
that, in theory, won’t be missed. Picture an aeroplane flying across a uniform blue sky. We’ll need to portray
the ‘plane accurately and in fine detail
(high bit rate), but the sky can be broken up into blocks (low bit rate).
As you can imagine, such complex
processing demanded intensive and
innovative design.
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DC servos
TAKEUP
REEL
Digital8’s moderate success was a
matter of timing. Intended as a carryover medium for users already familiar with Video8, but not released until
1999, it actually followed Digital
Video’s 1995 launch.
Digital Video
The last iteration, before hard disk
drives and solid-state storage mostly
obsoleted tape, was Digital Video or
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Portable VTRs, lacking constantfrequency mains power, used several
types of capstan motors such as the
brushless servo motor. This used a
three-phase synchronous motor with
a permanent-magnet rotor. A threephase oscillator either drove the motor
directly, or supplied a power amplifier
to drive the capstan motor for constant
tape speed.
But this still left the VTR needing to
regulate the head drum according to
the control track. The simplest method
was to use an ordinary DC motor for
the head drum, regulated by a servo
and driven by a motor drive amplifier (MDA).
Ultimately, mains-powered VCRs
would adopt these techniques, and
would incorporate sophisticated
direct-drive motors for the capstan
and head drum.
While more complex mechanically
and electronically, these advanced
motor designs did not need speedreducing belts or gears, were lighter
and more reliable, could be controlled
more accurately, and could easily be
slowed or reversed for slow motion,
reverse play and other useful modes.
The incredible shrinking video camera
Continuing miniaturisation and
the adoption of digital processing
saw Canon deliver the truly compact
MV-800, which included two viewfinders: the conventional ‘peep’ sight,
and a handy swing-out screen; both
in colour!
June 2021 51
A Video8 cassette (https://w.wiki/nGy),
followed by a Hi8 cassette (https://w.
wiki/nGz). Both formats are in similar
packages and are analog. Fully digital
tapes didn’t come along until Digital8.
Fig.57: Video8 was the last hurrah for analog video recording before digital
tape systems like DV made it essentially obsolete. Of course, it wasn’t long
before DV was replaced with solid-state digital recording…
But the cassette’s end was in
sight. Somebody was going to take
the extreme miniaturisation of the
charge-coupled device (CCD) camera
chip and marry it with digital processing and solid-state memory. And
pack it all into a popular smartphone,
such as the Sony Xperia (bottom right
of Fig.58).
Conclusion
For some forty years between 1955
and 1995, analog (and then digital) videotape recording in its various incarnations embodied the most complex
combination of electrical, electronic
and mechanical designs of the day.
References
Fig.58: the incredible shrinking Camcorder. From top to bottom at left, VHS,
Video8, a smaller Video8 unit, then at right, a solid-state Handycam and a
modern mobile phone with superior video recording in terms of both quality
and duration (the Handycam still has much better zoom capability).
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Australia’s electronics magazine
• Video Cassette Recorders, Humphris, Rod, 1998, TAFE Course Notes
• How to use a Portapak: siliconchip.
com.au/link/ab5s
• U-matic development by Sony:
siliconchip.com.au/link/ab3i
• Technology Connections’ Youtube
channel: www.youtube.com/channel/
UCy0tKL1T7wFoYcxCe0xjN6Q
• An extensive picture gallery of
VTRs, Philips VCR, Beta and VHS:
www.oldtechnology.net
• The history of video tape recorders:
www.labguysworld.com
• Special thanks to Rewind Museum
for Fig.51: www.rewindmuseum.com
Lead images:
• https://w.wiki/nGs
• https://w.wiki/nGt
• https://w.wiki/nGu
SC
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