Picture Dropout on Video Causes

It is my understanding that on video when the picture drops out on playback of a recording it's usually caused by the magnetic oxide (where the video is recorded) in the makeup of the tape beginning to shed and it generates a "hole" which manifests itself on screen as a few lines of interference as there is nothing there to "play".

I presume this is not unique to home video VHS because I've seen older episodes of various things on Challenge that have the same effect so I suspect the effect also applies to "professional" videotape - I suspect I'm referring to Betacam/Digibeta or anything a major step up from the home domestic formats.

I suppose my question is: What causes the magnetic oxide to shed on the tapes? Is it normally through overuse of the tape, an issue with the playback hardware (we all know how often VHS machines as they aged used to chew up the tapes given half a chance) or is it poor storage of them?

Drop-out is usually caused by either tape getting older (the 'glue' that keeps the oxide or similar metallic stuff on the plastic tape backing goes off and ceases to work as well) or being damaged through over-use/re-use (video tape relies on a physical contact between the tape and a large spinning metal head...) Poor alignment of the heads could also damage tape. This is permanent drop-out, but as the tape degrades particles flake off, and these can also 'clog' the replay heads, causing a drop-out on the replay (even where the recording is fine)

Decent analogue VTRs have 'drop out compensators' which detect the loss of RF and have a line-delay (so can replace the missing video with content from the line before) which will hide minor drop-out, but major drop out across multiple lines can be made very visible (as you get multiple lines of repeated video). This was particularly common on knackered Beta SP...

Digital tape recording formats like D3, D2 and DigiBeta have far better error correction and then error concealment systems which made digital VTRs a lot more robust. DigiBeta could cope with significant head clog ISTR without looking terrible. DVTRs also were able to warn you that they were getting errors - which could be useful warning to clean your heads etc.

You also see head-switching errors on Quad 2" and B-format 1" recordings (C-format 1" recorded an entire field in one track, whereas B-format used multiple tracks so had head switching) These head switching errors are far more obvious though, as they are regular dots or tears in a relatively fixed position.

An interesting video about the various different types of faults using 1" tape:

Unfortunate that there's a clip of Jim'll Fix It in there!

Most of the things in that clip I see show up quite often on TV show repeats and DVD released, I guess there's not much they can do about it at times. I've seen similar faults appear on shows I'dve thought post-dated 1" too, I'm guessing Beta/Beta SP can produce similar looking artifacts.

There's actually some quite interesting vintage footage shown there.

I noticed quite a bad videotape problem, whilst watching a repeat of the Monty Python 20 years compilation programme on Gold a few weeks ago (the one from 1989 with Steve Martin presenting). As far as I can tell it wasn't a problem with the programme itself, but rather a clip they used near the end which had a distortion line running right in the middle of the screen throughout the entire clip.

Luckily enough someone has uploaded one of Gold's broadcasts to YouTube so I can show you what it looks like:

https://youtu.be/q9nLYzraJhI?t=1h9m34s

Thanks Noggin and thanks Maaixuew for the video link. And thanks everybody else as well

Interesting video posted there by Maaixuew, what's that from, is that an internal training video of some sort?