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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 48 Silicon Chip 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 Australia’s electronics magazine 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 siliconchip.com.au 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. 50 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. Australia’s electronics magazine 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. siliconchip.com.au 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. siliconchip.com.au 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 Australia’s electronics magazine 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). 52 Silicon Chip 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 siliconchip.com.au