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Toshiba developed the first progressive-scan player (SD5109, $800) in mid 1998, but didn't release it until fall of 1999 because of copy protection concerns. Panasonic also released a progressive-scan player (DVD-H1000, $3000) in fall of 1999. Many manufacturers have released progressive models since then. It's also possible to buy an external line multiplier to convert the output of a standard DVD player to progressive scanning. All DVD computers are progressive players, since the video is displayed on a progressive monitor, but quality varies a lot. (See 4.1 and 2.12.)
Converting interlaced DVD video to progressive video involves much more than putting film frames back together. There are essentially two ways to convert from interlaced to progressive:
1- Re-interleaving (also called weave). If the original video is from a progressive source, such as film, the two fields can be recombined into a single frame.
2- Line doubling (also called bob). If the original video is from an interlaced source, simply combining two fields will cause motion artifacts (the effect is reminiscent of a zipper), so each line of a single field is repeated twice to form a frame. Better line doublers use interpolation to produce new lines that are a combination of the lines above and below. The term line doubler is vague, since cheap line doublers only bob, while expensive line doublers (those that contain digital signal processors) can also weave.
(3- There's actually a third way, called field-adaptive de-interlacing, which examines individual pixels across three or more fields and selectively weaves or bobs regions of the picture as appropriate. Most systems that do this well cost $10,000 and up, so it will be a while before we see it in consumer DVD players.)
(4- And there's also a fourth way, called motion-adaptive de-interlacing, which examines MPEG-2 motion vectors or does massive image processing to identify moving objects in order to selectively weave or bob regions of the picture as appropriate. Most systems that do this well cost $50,000 and up (aside from the cool but defunct Chromatic Mpact2 chip).
There are three common kinds of de-interlacing systems:
1- Integrated. This is usually best, where the de-interlacer is integrated with the MPEG-2 decoder so that it can read MPEG-2 flags and analyze the encoded video to determine when to bob and when to weave. Most DVD computers use this method.
2- Internal. The digital video from the MPEG-2 decoder is passed to a separate deinterlacing chip. The disadvantage is that MPEG-2 flags and motion vectors may no longer available to help the de-interlacer determine the original format and cadence. (Some internal chips receive the repeat_first_field and top_field_first flags passed from the decoder, but not the progressive_scan flag.)
3- External. Analog video from the DVD player is passed to a separate de-interlacer (line multiplier) or to a display with a built-in de-interlacer. In this case, the video quality is slightly degraded from being converted to analog, back to digital, and often back again to analog. However, for high-end projection systems, a separate line multiplier (which scales the video and interpolates to a variety of scanning rates) may achieve the best results.
Most progressive DVD players use an internal Genesis gmVLX1A de-interlacing chip. The Princeton PVD-5000 uses a Sigma Designs decoder with integrated de-interlacing. The JVC XV-D723GD uses a custom decoder with integrated de-interlacing. Toshiba's "Super Digital Progressive" players and the Panasonic HD-1000 use 4:4:4 chroma oversampling, which provides a slight quality boost from DVD's native 4:2:0 format. Add-on internal de-interlacers such as the Cinematrix and MSB Progressive Plus are available to convert existing players to progressive-scan output. Faroudja and Silicon Image (DVDO) line multipliers are examples of external de-interlacers.
A progressive DVD player has to determine whether the video should be line-doubled or re-interleaved. When re-interleaving film-source video, the player also has to deal with the difference between film frame rate (24 Hz) and TV frame rate (30 Hz). Since the 2-3 pulldown trick can't be used to spread film frames across video fields, there are worse motion artifacts than with interleaved video. However, the increase in resolvable resolution more than makes up for it. Advanced progressive players such as the Princeton PVD-5000 and DVD computers can get around the problem by displaying at multiples of 24 Hz such as 72 Hz, 96 Hz, and so on.
A progressive player also has to deal with problems such as video that doesn't have clean cadence (as when it's edited after being converted to interlaced video, when bad fields are removed during encoding, when the video is speed-shifted to match the audio track, and so on). Another problem is that many DVDs are encoded with incorrect MPEG-2 flags, so the re-interleaver has to recognize and deal with pathological cases. In some instances it's practically impossible to determine if a sequence is 30-frame interlaced video or 30-frame progressive video. For example, the documentary on Apollo 13 is interlaced video encoded as if it were progressive. Other cases of improper encoding are Titanic, Fargo and More Tales of the City.
A growing problem is that many TVs with progressive input don't allow the aspect ratio to be changed. When a non-anamorphic signal is sent to these TVs, they stretch it out! Before you buy an HDTV, make sure that it allows aspect ratio adjustment on progressive input.
Just as early DVD computers did a poor job of progressive-scan display of DVDs, the first generation of progressive consumer players are also a bit disappointing. But as techniques improve, and as DVD producers become more aware of the steps they must take to ensure good progressive display, and as more progressive displays appear in homes, the experience will undoubtedly improve, bringing home theaters closer to real theaters.
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Про прогрессив из ФАКа (+) -- Kastor -- 15.03.01@15:13 (Чит.: 115)