VidFIRE

VidFIRE (Video Field Interpolation Restoration Effect) is a restoration technique intended to restore the video-like motion of footage originally shot with television cameras now existing only in formats with telerecording as their basis. The word is both a noun and a verb.

Background

Film recorded for the purposes of United Kingdom television production is usually recorded at 25 frames per second; there is an unrecorded temporal gap between each frame and the next. In contrast, video pictures are recorded as a stream of video fields. Each field can be loosely seen as half a frame, but each field is also a discrete image separated from the previous field by 1/50 second. This difference in the rate of change of the image is one of the factors contributing to the "video look," familiar to viewers as the more immediate, "live" feel seen in many soap operas and sports programmes.

When videotape technology was first created, in the 1950s, tapes were extremely costly; but their reusability meant that the cost of a single tape could be spread across several productions, with each successive production erasing and then reusing the tape from a previous one, with the result that relatively few programmes produced on videotape in the 1950s and 1960s still exist in their original format.

The expense of videotape and the various mutually incompatible television standards around the world made it impractical at the time for programme makers to sell their productions to foreign broadcasters in their original video form. Film, however, was considered a universal medium, and most broadcasters had the facility to broadcast from it. Before the devleopment of usuable video tape, programme makers such as the BBC developed the technology to record programmes--either live or for prerecording--from specially adapted monitors with a film camera. The resulting film recordings are called "telerecordings" in the UK and "kinescopes" in the United States.

Programmes often were copied in this way for rebroadcast or overseas sale before the original videotapes were reused. Most live- and videotape-originated television from this era exists today only as film recordings. However, the film recording system "locks" two video fields, previously separated by 1/50 second, into a single film frame. When the film is played back, the original video-like motion is lost.

Restoring the video look

VidFIRE was developed by Peter Finklestone to address the motion differences caused by the telerecording process. It uses motion estimation software to create an intermediate image, which exists temporally between two film frames. For example, if all frames of a twenty-five minute film recording were processed, the result would be double the amount of frames and a new running length of fifty minutes. Playback at this stage (at 25fps) gives smooth movement at half speed, due to the presence of interpolated images.

The programme is then further processed by interlacing adjacent frames, which halves the running time back to the original twenty-five minutes. The final result is video with fifty fields per second, alternate fields being sourced from the original film frame or the new interpolated image respectively. This has the effect of restoring the "video look" to the production.

Limitations

Depending on the quality of the film stock and how much care has been taken of the film in the years since it was first recorded, film recordings can be very grainy, dirty and scratched. The appearance of these film artefacts on the processed programme would break the illusion that the viewer is watching a videotape recording, therefore to maintain the VidFIRE effect it is imperative the image be as clean and stable as possible. The best available copy of the film-recorded programme should be used, preferably the original camera negative, and the film should be cleaned, digitally noise-reduced, and repaired, before processing.

A further, self-imposed limitation is that VidFIRE is used only to process material that originally was produced using video cameras. There is no technical reason why film-originated material cannot be processed, but it is not considered to be "in the spirit" of restoration. It is also possible that the difference in lighting and picture balance on film may mean the final processed images look subjectively "wrong."

Commercial use

The Doctor Who Restoration Team routinely VidFIRE 1960s episodes of "Doctor Who" when preparing them for release on DVD. The process has also been applied to a number of other programmes, including two previously lost episodes of the BBC sitcom "Dad's Army", which were rediscovered in 2001. The episodes, "Operation Kilt" and "The Battle of Godfrey's Cottage," were VidFIREd in preparation for their broadcast as part of a "Dad's Army" evening" on BBC Two. The remainder of series one and two of "Dad's Army" was later processed and released on DVD. Episodes of "Sykes" and "Public Eye" have also been treated for DVD.

A slightly revised version of the process, with an improved motion-estimation engine, was first used on the BBC's 2005 DVD release "The Quatermass Collection" and then on all subsequent relevant "Doctor Who" DVD releases.

Beyond this, the technique (although critically applauded) has seen relatively little exposure, perhaps because of a belief within the broadcasting industry that public interest in the kind of archive television that would benefit from VidFIRE is insufficient to justify the cost of processing.

Miscellaneous

* Early in its development, the process was known jokingly as "Video Field Artificial Restoration Technique" or "VidFART".
* The VidFIRE process is now owned by SVS Resources, a specialist archive film restoration company.
* An easter egg included on the DVD release of "The Tomb of the Cybermen" featured a brief clip from that serial with VidFIRE processing applied. This was an experiment by the Doctor Who Restoration Team to see how well VidFIRE would survive the MPEG-2 encoding process. The experiment demonstrated that the VidFIRE illusion was not diminished by MPEG encoding and so the next relevant DVD release, "The Aztecs" was VidFIREd in its entirety.

External links

* [http://www.restoration-team.co.uk Doctor Who Restoration Team]
* [http://www.whoniversity.co.uk/archive/tech/index.html The Pamela Nash Experience--"TV Technology"] (highly detailed articles on quadruplex videotape, film recording, and the BBC's early VERA system)
* [http://web.archive.org/web/20051224004340/http://www.keriallan.com/view_articles.asp?id=12 'Memories are Made of This'--clear introduction to techniques used to restore archive TV, including VidFIRE and advanced PAL decoding]
* [http://technology.guardian.co.uk/weekly/story/0,,1936559,00.html Interview with Peter Crocker of SVS Resources]