Originally Posted by Vasant56
I heard recently that 1080p tv shows are still a ways a way.. and, I've read that a lot of modern 1080p sets can de-interlace 1080i into 1080p.. does that mean that the shows filmed in 1080i will have a 1080p (or near 1080p) image?
This confuses me a little, as on one hand there are arguments saying 1080p sets aren't needed for hi-def tv watchers as nothing is filmed in 1080p, and on the other hand, couldnt you get a 1080p tv show by de-interlacing the 1080i signal?
Just about every drama-oriented production is captured on 1080/24p master tapes, either directly with 1080/24PsF (segmented-frame) cameras/recorders, or optically telecined from 24p films. U.S. broadcasters deliver digital copies of these 1080/24p recordings through pulldown (inserting extra TV fields/frames) to convert 24 fps into the broadcast rate for 1080i/720p (60 Hz).
Displays or video processors, using inverse-pulldown circuits, can discard these extra fields/frames, which can introduce motion judder in images, then recreate 1080/24p images. 1080/24p master tapes, typically with 270, 440 or more Mbps storage, are further compressed (~17 Mbps maximum video payload
for OTA/cable/DBS or 40 Mbps peak for HD discs). This can trim effective resolution
(resolvable detail) and filter PQ in other ways. But movie master tape PQ and final home delivery, because of 'artistic' camera filtering and other factors
, has quite limited effective resolution
to start with (~800--1100 lines) compared with a potential 4000-plus lines (equivalent) on film negatives. (This pdf paper
details why film on theater screens approximates 1280X720p HD resolution.)
Hardware to view 1080/24p varies widely, with a growing number of displays, after inverse pulldown, able to repeat extracted 24 fps at even multiples, avoiding judder, instead of at 60 fps, the same rate typically used after deinterlacing 1080/60i (30i) or displaying 720/60p. HD disc players may deliver movies at 1080/60i, 1080p60 (@74 MHz sampling, not @148 Mhz), or 1080/24p for U.S. viewing.
1080p displays with measured 1920X1080 resolution from test patterns--not all are capable
--could resolve gradual enhancements to HD effective resolution. But a startling number of displays employ a basic, inadequate, type of deinterlacing that can halve vertical resolution (see Gary Merson's three sublinked articles
Live or recorded 1080i, already typically appearing crisper than 720p with half the format/spatial resolution, has more headroom for resolution gains. Estimates vary, but ~1450 lines maximum effective horizontal resolution today could theoretically be boosted closer to full 1920X1080 by oversampling, say with ~4k cinema-type digital cameras, or 4k telecines of film negatives/prints, then downconversion to 1920X1080. (Some HD discs are produced this way, although updated measurements
similar to sspears' several years ago haven't been published/posted AFAIK
.) Standard ~74-MHz 1080 sampling today has a limiting resolution (see effective resolution link) of ~1700 lines. Oversampling/downconversion can boost this limiting resolution. -- John