Yeah, CDs are impressive or whatever, but have you ever seen the inside of a VCR?
What makes a VHS different from other options?
Many things! It’s entertainment predecessor, film, was dropped for a couple of reasons. Film is composed of individual images on thin, photosensitive tape, where magnetic tape is the image’s information translated into computer language. A reel film projector is shining a light behind the reel to show the image. If you shined a light behind a VHS’s tape, you’d see nothing but brown! Plus, you can pause VHS tapes. Pause a reel film on the projector without moving the tape, and you risk burning it.
Betamax, VHS’s primary competitor, is arguably superior in every way. Betamax had better resolution, better sound quality, etc. and it came out at the same time as the original VHSs. What separated the two was cost: a Betamax tape was more expensive than VHS, and since VHS was only marginally worse, companies picked it up. Secondly, VHS tapes could record more, but since most movies were under three hours anyway that didn’t do as much for it as pricing did. CED tapes, Hi8 tapes, better, smaller reel tapes, and the rest were also vying for the ‘primary choice’ crown – and the VHS beat them all with durability.
From the beginning, VHSs were kind of an underdog. Radically new tech was always coming and going, VHSs could be another flash in the pan and disappear the next day, like CEDs did. The first company to launch VHS tapes set up standards to prevent VHSs from dying out due to quality issues, but widespread adoption would be up to marketing and luck. Plenty of good ideas on paper died once they were actually put into manufacturing.
How does the tape itself work?
Where CDs and DVDs have no moving parts, VHS tapes are full of them. The tape itself moves on spools, and that forces VCRs to read the data linearly (instead of randomly). All that means is that that the VCR had to read the rest of the tape before it can get to the part you’re looking for, where something like a hard drive can pick a file without reading other files first.
Additionally, the tape is not a loop, it’s a strip. Many media types got caught up in trying to make a self-rewinding form of media, but the tech simply wasn’t there yet to do that cheaply. if you got to go to a Blockbuster before they switched away from tapes, they would kindly remind you to rewind the tape after you were done watching it so the next person to rent the movie doesn’t have to rewind it first. Since the reader works on the tape in both directions, having to do that can spoil the movie.
The information is encoded onto the tape in a couple of areas: there’s a control track, an audio track, and a visual track. The reader can’t read the tape without the audio or control track – trimming either off will cause the tape to fail. A reader head is actively looking for the control track to synchronize with the other tracks, which will ‘pulse’ in sync with each other to ensure correct alignment. If it can’t find it, it doesn’t have a backup plan!
Visual information is encoded onto the tape using two separate writing heads held at a slight angle. The data is magnetized into the tape in an almost herringbone-like pattern, which the VHS can read fast enough to generate smooth images on-screen. This has the added benefit of ‘self-correcting’ – each reader head only reads the data slots that are at its angle, so there’s no weird flashing or jumping between frames. Given the end-user is not doing something strange to the tape, VHSs run pretty smoothly as a result.
How does the reader work?
The reader is composed of a motor, some internal mechanisms to control the speed of the tape, and a couple of reading and writing heads. To play content, the VCR pulls the tape in front of it’s readers, which then decode the information written on the magnetic tape into video. The tape itself is divided into separate areas for audio and video, as well as a timing track. Different heads along the inside of the VCR read the tape as it’s pulled by, and rollers keep it taut between them to prevent tangling.
If one wants to write to a VHS tape, their VCR should be capable – all but the cheapest usually are. VCRs completely revolutionized the entertainment industry by enabling the consumer to record particular episodes or events cheaply. Suddenly, a TV show didn’t need to re-run an episode five or six times to be sure their fans saw it. Their other revolutionary trait was being able to do this when the user wasn’t home – again, all but the cheapest of VCRs were able to record at a set time, with minimal user interference.
VCRs are specially adapted to reuse VHS tapes. It’s possible to tape over other tapes because the VCR, while in writing mode, erases the tape as it goes by so that the writing head has a clean surface to write to. “Taping Over” something persists to this day, even though very few consumer devices use tape anymore!
Durability
VHS tapes are pretty durable – but they aren’t invincible. No form of media is! VHS tapes are vulnerable to many of the same things hard drives are: excessive heat may cause warping and a loss of quality, cold and radiation exposure can ruin the information on the tape. Unlike reel film, however, VHSs don’t become worthless when exposed to light. The tape shouldn’t be out of the container, but it’s not ruined if it somehow gets stuck outside the casing for a little while.
It takes a little bit of hunting to find working VCRs, but luckily they’re so simple that even broken ones can be used again. Replacement parts are still sold in specialty stores and online!
Assuming digital content really is the future forever and physical media declines, there are things you can do to convert tapes if you’re worried your home movies aren’t storing well in the attic. VHS-to-digital converters are available for purchase, for example, and places that do photo-printing also frequently offer mail-out services for conversion.
Sources:
http://repairfaq.cis.upenn.edu/sam/icets/vcr.htm
http://aperture.stanford.edu/lab/video/Tutorials/vhsvhsdub.html