Information about Telecine

Telecine (IPA pronunciation: [ˈtɛləˌsɪni] or [ˌtɛləˈsɪni]; [ˌtɛləˈsɪnə]; also [ˌtɛləˈsiːn]. Phonetic: "tel-e-Sin-ee"; "tel-e-Sin-a" as 'cine' is the same root as in 'cinema'; also "tele-seen".) is the process of transferring motion picture film into electronic form, or the machine used in this process. Telecine enables a motion picture, captured originally on film, to be viewed with standard video equipment, such as televisions, video cassette decks or computers. This allows producers and distributors working in film to release their products on video and allows producers to use video production equipment to complete their film projects. “Telecine” is combination of “television” and “cinema.” Within the film industry, it is also referred to as a TK, as TC is already used to designate time code.

Basic principle

The telecine was invented to transfer motion picture film images into video signals. In all forms of telecine, light is projected through the film (whether negative or positive image) onto a pick-up device that translates the image into an electronic (or digital) video signal. This also allows the electronic (or digital) video signal to be processed and altered. See color grading for more information.

History of telecine

With the advent of popular television, broadcasters soon realized they needed more than live programming. By turning to film-originated material, they would have access to the wealth of films made for the cinema before television in addition to originating television programming on film that could be aired at different times. Broadcasters needed to find a way to record a live broadcast on film to re-broadcast later. The kinescope was the early tool for this.^[1] With the advent of color television, the film-chain tool—quite literally a film projector hooked to a video camera—came onto the scene. In the United States, this Film Chain was a film projector attached to a video camera with three vidicon image tubes. The image from the projector was separated via prism into the three primary colors, each directed at a vidicon tube. The three signals were then recombined to form the color video image.^[2]

In the United Kingdom, Rank Precision Industries was experimenting with the flying-spot scanner (FSS), which invented the cathode ray tube (CRT) concept of scanning using a television screen. The CRT emits a pixel-sized electron beam which is converted to a photon beam through the phosphors coating the envelope. This dot of light is then focused by a lens onto the film's emulsion, and finally collected by a pickup device. In 1950 the first Rank flying spot monochrome telecine was installed at the BBC's Lime Grove studios.^[3]

The advantage of the FSS is that colour analysis is done after scanning, so there can be no registration errors as can be produced by camera tubes where scanning is done after colour separation — it also allows simpler dichroics to be used. The modern telecine was born.

Flying spot scanner

In a flying spot scanner (FSS) or cathode-ray tube (CRT) telecine, a pixel-sized light beam is projected through exposed and developed motion picture film (either negative or positive) at a phosphor-coated envelope. This beam of light “scans” across the film image from left to right to record the vertical frame information. Horizontal scanning of the frame was then accomplished by moving the film past the CRT beam. This beam passes through the film image, projecting it pixel-by-pixel onto the pickup (phosphor-coated envelope). The light from the CRT passes through the film and is separated by dichroic mirrors and filters into red, green and blue bands. Photomultiplier tubes or avalanche photodiodes convert the light into separate red, green & blue electrical signals for further electronic processing. This can be accomplished in “real time”, 24 frames a second (or in some cases faster). Rank Precision-Cintel introduced the “Mark” series of FSS telecines, culminating in the MkIII (1975). Around this time advances were also made in CRTs, with increased light output producing a better signal-to-noise ratio and so allowing negative film to be run.

The problem with Flying Spots was the difference in frequencies between television field rates and film frame rates. This was solved first by the Mk1 Polygonal Prism system, then the Mk II Twin Lens and finally the Mk III Hopping Patch (jump scan). The Mk III series progressed from the original “jump scan” interlace scan to the MK IIIB which used a progressive scan and included a digital scan converter (Digiscan) to output interlaced video. The Mk IIIC was the most popular of the series and used a next generation Digiscan plus other improvements. The Mk I was remarkable in that the film could be run at any speed, and was optically sychronised to the television frame rate by the rotating prism. That series was then replaced by the Ursa (1989), the first in their line of telecines capable of producing digital data in 4:2:2 color space. The Ursa Gold (1993) stepped this up to 4:4:4 and then the Ursa Diamond (1997), which incorporated many third-party improvements on the Ursa system.^[4]

CCD

The Robert Bosch GmbH, Fernseh Div., which later became BTS inc. - Philips Digital Video Systems and is now part of Thomson's Grass Valley, introduced the worlds first CCD telecine (1979), the FDL-60. The FDL-60 designed and made in Darmstadt West Germany, was the first all solid state Telecine.

Rank Cintel (ADS telecine 1982) and Marconi Company (1985) both made CCD Telecines for a short time.

In a charge-coupled device (CCD) telecine, a “white” light is shone through the exposed film image into a prism, which separates out the image into the three primary colors, red, green and blue. Each beam of colored light is then projected at a different CCD, one for each color. The CCD converts the light into electrical impulses which the telecine electronics modulate into a video signal which can then be recorded onto video tape or broadcast.

Philips - BTS eventually evolved the FDL-60 into the FDL 90 (1989)/ Quadra (1993). In 1996 Philips working with Kodak introduced the Spirit DataCine (SDC 2000), which was capable of scanning the film image at HDTV resolutions and approaching 2K (1920 Luminance and 960 Chrominace RGB) x 1556 RGB. With the data option the Spirit DataCine can be used as a motion picture film scanner outputting 2K DPX data files as 2048 x 1556 RGB. In 2000 Philips introduced the Shadow Telecine (STE) this is a low cost version of the Spirit, with no Kodak parts. The Spirit DataCine, Cintel's C-Reality and ITK's Millennium opened the door to the technology of digital intermediates wherein telecine coloring tools were not just for video outputs, but could now be used for high-resolution data that would later be recorded back out to film.<ref name="filmtotape" />The Grass Valley Spirit 4k (2004) replaced the Spirit 1 Datacine and uses both 2K and 4k line array CCDs.

Digital intermediate systems and virtual telecines

Telecine technology is increasingly merging with that of Motion picture film scanners; high-resolution telecines, such as those mentioned above, can be regarded as film scanners that operate in real time.

As digital intermediate post-production becomes more common, the need to combine the traditional telecine functions of input devices, standards converters, and colour grading systems is becoming less important as the post-production chain changes to tapeless and filmless operation.

However, the parts of the workflow associated with telecines still remain, and are being pushed to the end, rather than the beginning, of the post-production chain, in the form of real-time digital grading systems and digital intermediate mastering systems, increasingly running in software on commodity computer systems. These are sometimes called virtual telecine systems.

Controllers

Main article: color grading

• For high-end systems most telecines are controlled by a Da Vinci Systems color corrector, 2k or 2k Plus, also called color grading.
• Some high-end systems are controlled by Pandora Int.'s Pogle, some with a their MegaDEF or a Pixi color grading system.
• For edit control Da Vinci Systems' TLC edit controller is used or Pandora Int.'s Pogle also has a built in edit control. The edit controller controls the telecine and a VTR(s) or other record devices for frame accurate film frame editing.
• Older systems are: Da Vinci Systems's: The Whiz (1982), Classic analog, Renaissance and 888; The Corporate Communications's System 60XL (1982-1989) and Copernicus-Sunburst; Bosch Fernseh's FRP-60 (1983-1989); Dubner (1978-1985?), Cintel's TOPSY (1978), Amigo (1983), and ARCAS (1992) systems. All of these older systems work only with standard-definition 525 and 625 video signals, and are considered near obsolete today.

Frame rate differences

Main article: Frame rate

The most complex part of telecine is the synchronization of the mechanical film motion and the electronic video signal. Every time the video part of the telecine samples the light electronically, the film part of the telecine must have a frame in perfect registration and ready to photograph. This is relatively easy when the film is photographed at the same frame rate as the video camera will sample, but when this is not true, a sophisticated procedure is required to change frame rate.

In countries that use the PAL or SECAM video standards, film destined for television is photographed at 25 frames per second. The PAL video standard broadcasts at 25 frames per second, so the transfer from film to video is simple; for every film frame, one video frame is captured. Theatrical features originally photographed at 24 frame/s are simply sped up by 4% to 25 frame/s. While this is usually not noticed in the picture it causes a slightly noticeable increase in audio pitch by about one semitone, which is sometimes corrected using a pitch shifter, though pitch shifting is a recent innovation and precedes an alternative method of telecine for 25 frames/s formats. However, a difference between the two is rarely noticed unless the original audio is compared side by side with the pitched audio.

Although the 4% speed increase has been standard since the early days of PAL and SECAM television, recently a new technique (see 2^12:3 pulldown, below) has gained popularity. This method converts every film frame to two video fields, except that every 12th frame is repeated, fitting exactly within 25 frames (50 fields) of video per second. The speed and pitch of the telecined presentation are identical to that of the original film.

In the United States and other countries that use the NTSC television standard, film is generally photographed at 24 frame/s. Color NTSC video is broadcast at 29.97 frame/s. For the film's motion to be accurately rendered on the video signal, an NTSC telecine must use a technique called the 3:2 pulldown to convert from 24 to 29.97 frame/s.

Similar techniques must be used for films shot at “silent speeds” of less than 24 frame/s (about 18fps), which include most silent movies themselves as well as many home movies.

Common pulldown patterns

3:2 pulldown

The process of converting 24 frame/s material to 29.97 frame/s is known as 3:2 pulldown. The term “pulldown” comes from the mechanical process of “pulling” the film down to advance it from one frame to the next at a repetitive rate (nominally 24 fps). This is accomplished in two steps. The first step is to slow down the film motion by 1/1.001. This speed change is unnoticeable to the viewer, and makes the film travel at 23.976 frame/s.

The second step of the 3:2 pulldown is the 3:2 (or 2:3, see below) step. At 23.976 frame/s, there are four frames of film for every five frames of NTSC video:

These four frames are “stretched” into five by exploiting the interlaced nature of NTSC video. For every NTSC frame, there are actually two complete images or fields, one for the odd-numbered lines of the image, and one for the even-numbered lines. There are, therefore, ten fields for every 4 film frames, and the telecine alternately places one film frame across two fields, the next across three, the next across two, and so on. The cycle repeats itself completely after four film frames have been exposed, and in the telecine cycle these are called the A, B, C, and D frames, thus:

Note that the pattern in this example is actually 2–3. A 3–2 pattern is identical to this except that it is shifted by one frame. For instance, starting with film frame B, followed by frame C, yields a 3–2 pattern (B-B-B-C-C). In other words, there is no difference between the two — it is only a matter of reference.

The above method is a "classic" 3:2, which was used before frame buffers allowed for holding more than one frame. The preferred method for doing a 3:2, creates only one dirty frame in every 5, while this method has a slight bit more judder, it allows for easier upconversion, and a better over all compression when encoding.

Display frame 1 and 2 for two fields each, and then frame 3 for three fields, and frame 4 for 3 fields. Honoring the original spatial placement of the fields. This results in Frame 4 of the new 5 frames being dirty. Diagram here

2^12:3, or 2:2:2:2:2:2:2:2:2:2:2:3 pulldown

This^[5] pulldown method^[6] is sometimes used in order to convert 24 frame/s material to 25 frame/s. Usually, this involves a film to PAL transfer without the aforementioned 4% speedup. For film at 24 frame/s, there are 24 frames of film for every 25 frames of PAL video. In order to accommodate this mismatch in frame rate, 24 frames of film have to be distributed over 50 PAL fields. This can be accomplished by inserting a pulldown field every 12 frames, thus effectively spreading 12 frames of film over 25 fields (or “12.5 frames”) of PAL video.

This method was born out of a frustration with the faster, higher pitched soundtracks that traditionally accompanied films telecined for PAL and SECAM audiences. More motion pictures are beginning to be telecined this way. It is particularly suited for films where the soundtrack is of special importance.

Other pulldown patterns

16 fps (actually 15.985) to NTSC 30 fps (actually 29.97), pulldown should be 3:4:4:4; 16 fps to PAL, pulldown is should be 3:3:3:3:3:3:3:4; 18 fps (actually 17.982) to NTSC, pulldown should be 3:3:4; 20 fps (actually 19.980) to NTSC, pulldown should be 3:3.

Telecine judder

The “3:2 pulldown” telecine process creates a slight error in the video signal compared to the original film frames that can be seen in the above image. This is one reason why NTSC films viewed on typical home equipment may not appear as smooth as when viewed in a cinema. The phenomenon is particularly apparent during slow, steady camera movements which appear slightly jerky when telecined. This process is commonly referred to as telecine judder. Reversing the 2-3 pulldown telecine is discussed below.

PAL material in which 2:2:2:2:2:2:2:2:2:2:2:3 pulldown has been applied, suffers from a similar lack of smoothness, though this effect is not usually called “telecine judder”. Effectively, every 12th film frame is displayed for the duration of 3 PAL fields (60 milliseconds), whereas the other 11 frames are all displayed for the duration of 2 PAL fields (40 milliseconds). This causes a slight “hiccup” in the video about twice a second.

Reverse telecine (a.k.a. IVTC/inverse telecine)

Some DVD players, line doublers, and personal video recorders are designed to detect and remove 2-3 pulldown from interlaced video sources, thereby reconstructing the original 24 frame/s film frames. This technique is known as “reverse” or “inverse” telecine. Benefits of reverse telecine include high-quality non-interlaced display on compatible display devices and the elimination of redundant data for compression purposes.

Reverse telecine is crucial when acquiring film material into a digital non-linear editing system such as an Avid or Final Cut Pro, since these machines produce negative cut lists which refer to specific frames in the original film material. When video from a telecine is ingested into these systems, the operator usually has available a “telecine trace,” in the form of a text file, which gives the correspondence between the video material and film original. Alternatively, the video transfer may include telecine sequence markers “burned in” to the video image along with other identifying information such as time code.

It is also possible, but more difficult, to perform reverse telecine without prior knowledge of where each field of video lies in the 2-3 pulldown pattern. This is the task faced by most consumer equipment such as line doublers and personal video recorders. Ideally, only a single field needs to be identified, the rest following the pattern in lock-step. However, the 2-3 pulldown pattern does not necessarily remain consistent throughout an entire program. Edits performed on film material after it undergoes 2-3 pulldown can introduce “jumps” in the pattern if care is not taken to preserve the original frame sequence (this often happens during the editing of television shows and commercials in NTSC format). Most reverse telecine algorithms attempt to follow the 2-3 pattern using image analysis techniques, e.g. by searching for repeated fields.

Algorithms that perform 2-3 pulldown removal also usually perform the task of deinterlacing. It is possible to algorithmically determine whether video contains a 2-3 pulldown pattern or not, and selectively do either reverse telecine (in the case of film-sourced video) or deinterlacing (in the case of native video sources).

Some product sheets refer to reverse telecine as “reverse 3:2 pulldown.?

Digital television, and high definition

Digital television and high definition standards provide several methods for encoding film material. 50 field/s formats such as 576i50 and 1080i50 can accommodate film content using a 4% speed-up like PAL. 59.94 field/s interlaced formats such as 480i60 and 1080i60 use the same 2-3 pulldown technique as NTSC. In 59.94 frame/s progressive formats such as 480p60 and 720p60, entire frames (rather than fields) are repeated in a 2-3 pattern, accomplishing the frame rate conversion without interlacing and its associated artifacts. Other formats such as 1080p24 can decode film material at its native rate of 24 or 23.976 frame/s.

All of these coding methods are in use to some extent. In PAL countries, 25 frame/s formats remain the norm. In NTSC countries, most digital broadcasts of 24 frame/s material, both standard and high definition, continue to use interlaced formats with 2-3 pulldown. Native 24 and 23.976 frame/s formats offer the greatest image quality and coding efficiency, and are widely used in motion picture and high definition video production. However, most consumer video devices do not support these formats.

DVDs

On DVDs, telecined material may be either hard telecined, or soft telecined. In the hard-telecined case, video is stored on the DVD at the playback framerate (29.97 frames/sec for NTSC, 25 frames/sec for PAL), using the telecined frames as shown above. In the soft-telecined case, the material is stored on the DVD at the film rate (24 or 23.976 frames/s) in the original progressive format, with special flags inserted into the MPEG-2 video stream that instruct the DVD player to repeat certain fields so as to accomplish the required pulldown during playback.^[7] Progressive scan DVD players additionally offer output at 480p by using these flags to duplicate frames rather than fields.

NTSC DVDs are often soft telecined, although lower-quality hard-telecined DVDs exist. In the case of PAL DVDs using 2:2 pulldown, the difference between soft and hard telecine vanishes, and the two may be regarded as equal. In the case of PAL DVDs using 2:3 pulldown, either soft or hard telecining may be applied.

See also

• Telecine (piracy), a pirated copy of a film created with a telecine.

References

External links

• XYHD: How a 3:2 Pull Down Cadence works when converting Film to Video
• (http://www.angelfire.com/film/tmtv/technical_info.html TMTV: Technical information on HDDTT film transfers
• IVTC Explained (brief)
• Explanation of telecine methods
• EBU I42 2004: Telecines for broadcasters — Technical information
• The Big Picture — 3:2 Pulldown and Inverse Telecine — In-depth explanation of interlaced and progressive frames, and the telecine process
• Tutorial Regarding Methods of Inverse Telecining

Hardware Products:

• Cintel: manufacturer of CRT and CCD based telecines and scanners
• Thomson's Grass Valley: manufacturer of CCD based telecines and scanners
• Moviestuff: manufacturer of 16mm and 8mm film telecine units for home transfers
• Motion picture film scanning system for virtual telecine
• Frame rate test video files