Progressive segmented frame
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Progressive segmented Frame (PsF, sF, SF) is a scheme designed to acquire, store, modify, and distribute progressive-scan video using interlaced equipment and media.
With PsF, a progressive frame is divided into two segments, with the odd lines in one segment and the even lines in the other segment. Technically, the segments are equivalent to interlaced fields, but unlike native interlaced video, there is no motion between the two fields that make up the video frame: both fields represent the same instant in time. This technique allows for a progressive picture to be processed through the same electronic circuitry that is used to store, process and route interlaced video.
The PsF technique is similar to 2:2 pulldown, which is widely used in 50 Hz television systems to broadcast 25 frame/s progressive material, but is rarely employed in 60 Hz systems as there is very little content of progressive 30 frame/s material. The 2:2 pulldown scheme had originally been designed for interlaced displays, so fine vertical details are usually filtered out to minimize interline twitter. PsF has been designed for transporting progressive content and therefore has no such filtering.
The term Progressive segmented frame is used predominantly in relation to high definition video. In the world of standard definition video it is also known as quasi-interlace[1] or progressive recording.
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[edit] History
PsF was designed to simplify the conversion of cinematic content to different video standards, and as a means of video exchange between networks and broadcasters worldwide.[2] Brought to life by the movie industry in the end of 1990s, the original PsF specification was focused on 24 frame/s content, resulting in existing interlaced equipment having to be modified for 48 Hz scanning rate in order to work properly with 24 frame/s content.
Not everyone welcomed the PsF standard, however. Some industry observers maintained that native 24p processing would have been a better and cleaner choice. Charles Poynton, an authority in digital television, made the following remark in his book: "Proponents of [PsF] scheme claim compatibility with interlaced processing and recording equipment, a dubious objective in my view."[1] William F. Schreiber, former Director of the Advanced Television Research Program at MIT, suspected that the continued advocacy of interlaced equipment originated from consumer electronics companies that were trying to get back the substantial investments they had made in obsolete technology.[3]
Despite the criticism, PsF quickly became a de-facto standard for high quality film-to-video transfer. One of the documented examples of PsF usage is the 2003 transfer of the film "Terminator 2" to DVD, performed by Artisan and THX. The original 24 frame/s movie was converted to PsF format and recorded to HD-D5 videotapes. This allowed for the creation of a digital master that was nearly identical to the original film, and made it possible to edit digitally at the native frame rate.[4] The same digital master appears to be used for the 2006 Blu-ray Disc transfer of the movie.[5]
PsF has been recognized by Recommendation ITU-R BT.709 as a legitimate way to transport progressive frames within an interlaced system. 25PsF and 30PsF rates have been added to the specification in addition to the more established 24PsF. "Fractional" frame rates, having the above values divided by 1.001, are also permitted; the resulting 23.976PsF and 29.97PsF rates are used in 60 Hz systems.
PsF became a means of initial image acquisition in professional Sony video cameras. It is employed in HDCAM and XDCAM video cameras, including the HDW-F900 CineAlta camera which was used by George Lucas for creating Star Wars, Episode 2, and by Alexander Sokurov for creating Russian Ark fully in the digital domain.
PsF is also used for 25-fps and 30-fps progressive-scan recording in some handheld Sony camcorders like the HVR-V1 and HVR-FX1000, in some consumer Canon HDV camcorders like the HV20/HV30/HV40 and in some Panasonic and Canon consumer AVCHD camcorders.[citation needed]
PsF recording mode is available on some DV camcorders under the name Progressive recording (Sony) or Frame mode (Panasonic and Canon). Here is how the progressive recording mode is described by Sony:
| “ | You can reduce image blur when recording moving pictures on tapes, intended for import to your computer as still images, by setting "Progressive Recording" to "On" (30p).
In a normal TV broadcast, the screen is divided into 2 finer fields and these are displayed in turn, every 1/60 of a second. Thus, the actual picture displayed in an instant covers only half of the apparent picture area. In progressive recording, the picture is fully displayed with all the pixels. A picture recorded in this mode appears clearer, but a moving subject may appear awkward. |
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—DCR-HC96 User's Guide, Sony Electronics |
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[edit] Variants
- 24PsF (48sF, 1080sf24, 1920x1080/24/1:1SF) is the original PsF format, which is used in professional equipment for film-to-video transfer, for high definition mastering and for video exchange between networks. This may be the first universal video standard which transcends continental boundaries, an area previously reserved for film.[6]
- 23.976PsF (1080sf23, 1920x1080/23.976/1:1SF) frame rate is often used in 60 Hz systems for HD production that originates on video and is targeted for television distribution. It is commonly used in organizations that also produce standard definition 525 line services (i.e. at 59.94Hz).[7]
- 25PsF (1080sf25, 1920x1080/25/1:1SF) is used in 50 Hz systems for production that originates on video and is targeted for television distribution.
- 30PsF (30p, 1080sf30, 1920x1080/30/1:1SF) and 29.97PsF (1080sf29, 1920x1080/29.97/1:1SF) formats are sometimes used in 60 Hz systems for sitcoms and music shows. These frame rates are gaining popularity as an acquisition format for Web video delivery.
[edit] References
- ^ a b "Charles Poynton, Digital Video and HDTV: Algorithms and Interfaces". http://books.google.com/books?id=ra1lcAwgvq4C&pg=RA1-PA62&sig=8ZAl0RqzUYnyxQSmjxiIw4ZJDbE.
- ^ "Jim Mendrala, A discussion of 24p frame and the new 48sF frame format". http://www.tech-notes.tv/Jim/Articles/24vs48sF.html.
- ^ "The history and politics of DTV". http://www.cinemasource.com/articles/hist_politics_dtv.pdf.
- ^ "Terminator 2: Extreme Edition". http://www.dtvforum.info/lofiversion/index.php/t16581.html.
- ^ "Terminator 2: Judgment Day (Blu-ray)". http://bluray.highdefdigest.com/terminator2.html.
- ^ "Steve Wiedemann, 24/P HDTV: The Fall of Film Production". http://www.filmmaking-careers.com/film-production.html.
- ^ "pro-bel, Vistek HD Poster". http://www.pro-bel.com/site_documents/Vistek_HD_Poster.pdf.
