VidFIRE
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VidFIRE, short for Video Field Interpolation Restoration Effect, is a restoration technique developed by Peter Finklestone. The basic idea behind VidFIRE is to restore the video-look to footage originally shot on videotape but which now exists only as a telerecording.
In the UK, television comprises 25 frames per second. Each frame contains two fields with either odd or even scanned lines that are interlaced together to make up the frame. The 1/50th of a second time difference between the two fields amounts to 50 discrete images per second, giving a fluid portrayal of motion. This is the "video look" that, to this day, soaps (such as Coronation Street and The Bill) and sports programmes use in order to maintain a "live" feel.
Back in the 1950s, however, the then new videotape technology was a huge investment; tapes were extremely costly and ate into a programme's budget. But their saving grace was that they were re-useable and frequently new recordings obliterated the previous images over and over again until the tape would literally fall apart. The alternative was to record a television programme off a specially-adapted monitor onto cheaper film (the resultant copies are commonly referred to as "telerecordings" in the UK, and "kinescopes" in the US). Film is durable compared to (early) videotape, and if a vintage programme survived the archive purges of the 1960s and 1970s it is most likely to exist as a film recording.
Film is a universal standard which allowed broadcasting a programme at a later date as well as offering easier saleability of shows to foreign broadcasters with otherwise incompatible television standards. The disadvantage is that the two separate fields in one video frame become "locked" together as one film frame. As both fields in the one frame are identical to the human eye the "video look" and fluid-feel to movement is lost. (This is down to the individual's perception as some claim not to be able to tell the difference between video and film.)
VidFIRE uses modern computing power to process these film recordings using "motion estimation" to create a brand new image that falls directly between two film frames. If, for example, it is applied to all frames in a 25-minute film recording the result is double the amount of frames and a new running length of 50-minutes. Playback at this stage (at 25 frames per second) gives movement at half speed, although this is fairly smooth due to the presence of the new in-between or "interpolated" images that were created.
The programme is further processed by halving the running time back to the original 25 minutes but using all available frames, which means the recording runs at 50 images per second. The trick here is to interlace two adjacent frames together - one the original film frame and the other the newly-created (interpolated) "in-between" frame - so that they act as if they were two FIELDS in an original video frame. The result is 25 frames or 50 fields (images) per second as each field now has its own 1/50th of a second of movement and a restored "video look".
Old film recordings are notorious for scratches and grainy images that "weave" subtly over a screen so it is imperative that only the best available copies are used; even then extensive cleaning and repairing may be necessary. The VidFIRE process works best on film images which are as clean and as stable as possible. Also, only images that were originally recorded from video should be processed as the lighting and picture balance are different to those originally shot on film. There is no technical reason why scenes that were originally shot on film cannot be processed, just that they don't quite look right - it's a matter of perception.
The self-appointed "Doctor Who Restoration Team" routinely VidFIRE all existing 1960s monochrome recordings of Doctor Who in preparation for DVD release. The process has also been applied to a small number of other programmes. The most famous example is two lost Dad's Army episodes ('Operation Kilt' and 'The Battle of Godfrey's Cottage') that were re-discovered in 2001. Both were quickly treated with VidFIRE and broadcast as part of a special "Dad's Army evening" on BBC2. The Dad's Army Series 1 and 2 DVD set contains VidFIRE'd versions of all the surviving monochrome episodes, and 1960s episodes of Sykes and Public Eye have also had the treatment for DVD.
The software used in the process now boasts an improved motion estimation engine which increases the video-effect. It retains more detail on estimated frames by producing sharper interpolated (in-between) images. This new version debuted in 2005 on the Quatermass and the Pit serial on the DVD release of Quatermass. Previous versions of VidFIRE used slightly softer estimated frames which lessened the effect slightly. Otherwise the technique - although critically applauded in the industry - has seen little exposure elsewhere, presumably due to the broadcasting industry's belief that there is not enough public interest in old monochrome programmes to justify the cost of processing.
Early in its development, the process was known jokingly as Video Field Artificial Restoration Technique—or VidFART.
[edit] External links
- [http://archive.whoniversity.co.uk/tech/index.html The Pamela Nash Experience -- 'TV Technology' (highly detailed articles on quadruplex videotape, film recording, and the BBC's early VERA system)
