Recently, an anonymous person added this comment to my post:
I stopped reading your article partway through because you obviously know NOTHING about the DVD standard. NTSC DVD's support both "30fps" (interlaced video) and 24fps (progressive scan video); in fact, most Hollywood DVD's use 24fps when the original source is film to save on disc space (by eliminating 6 fps of interpolated data), as the DVD player will do 2:3 pulldown as necessary when outputting to an interlaced display. Blu-ray just adds extra resolution to the image, not a "breakthru" in frame rates or progressive scanning. Bother to do your research before blathering on the internet like you are some sort of expert. I don't know everything, but I do know something about DVD's, as I work with encoding and authoring them everyday for my job.
Now, I can take being called names like "Bonehead" when my name-caller has any kind of a good point to make. In this case though, not only was the anonymous commenter rude, but he was just plain wrong, to boot. So here is my rejoinder:
Sorry, you who so impolitely called me "Bonehead," but I beg to differ:
On DVDs sold in the United States, film-derived video is recorded in such a way as to result in 480i output from a standard DVD player — that is, interlaced video with two fields per video frame, separated by a time interval of approx. 1/60 second between fields. The frame rate is thus approx. 30 frames per second.
The typical "progressive scan" DVD player (one that does no "upconversion") can derive 30 complete, non-interlaced frames per second from film-based video on an NTSC DVD and output those frames as 480p video on a component-video connection, into a TV whose component-video input can handle the bandwidth of 480p. It cannot, however, output progressive video at 24 fps. Only a Blu-ray player, using a Blu-ray disc, can do that.
To derive progressive output at 30 frames per second from film-based material, the progressive scan DVD player can simply take each video field and "double" the scan lines in it, to make up a full frame with 480 scan lines. This is the "line doubler" approach.
A smarter approach is to do "3:2 pulldown compensation," a.k.a. "2:3 pulldown compensation" or "inverse telecine." Ideally, this process faithfully recreates the 24 frames per second of the original film —— but then 6 of those 24 frames are repeated(!) to bring the video-output frame rate up to 30 frames per second. This is done because few if any of the TVs that were available when progressive scan DVD players were introduced were able to accept video at 24 frames per second.
On the DVD itself, the encoding is 480i. However, film-based material is usually — but not always — encoded in such a way that the video fields that need to be repeated (in "2:3 pulldown") to change the 24 frames per second of film into the 30 frames (or 60 fields) per second of NTSC video are flagged, with the DVD player being expected to use the flags to re-output the fields as necessary.
This use of flags to tell the player how to do 2:3 pulldown is called "soft telecine." In "hard telecine," the fields are actually repeated on the disc. Few progressive scan DVD players know how to compensate for "hard telecine." They typically do know how to compensate for "soft telecine" — but, unfortunately, many DVDs using that type of encoding have portions where the flags are missing or improperly used, resulting in imperfections in the output cadence until the flags get back in sync.
"Soft telecine" 480i DVDs record exactly 24 frames per second, or 48 fields per second. They accordingly bear a superficial resemblance to the "24p" recording of a film on Blu-ray, but the latter is truly recorded as progressive video at 24 frames per second, while the former records discrete fields of interlaced video at 48 fields per second.
In saying the above, I realize that I am in disagreement with the Wikipedia article on 24p.
The section "24p on DVD" states, "DVDs, however, are capable of storing the native 24p frames." This is possibly true. It also states, "Every Hollywood movie is laid to disc as a 24p ... stream." This is definitely not true.
True 24p is at best an optional way to encode DVDs that is rarely if ever used. It is not actually used for "every Hollywood movie." See this page at the website dedicated to the Handbrake video transcoder software, if you don't believe me about most or all film-based NTSC DVDs being either "soft" or "hard" telecined. Also see this page about the MPlayer and MEncoder software. The format discussed at "188.8.131.52. Telecined" is the one used on virtually every film-based NTSC DVD.
Still don't believe me? Let me refer you to perhaps the ultimate authority on DVDs, Jim Taylor, who wrote the book DVD Demystified and maintains the Official DVD FAQ. He says, in "What's a progressive DVD player?":
A progressive-scan DVD player converts the interlaced (480i or 576i) video from DVD into progressive (480p or 576p) format for connection to a progressive-scan display (31.5 kHz or higher) ... There's enormous confusion about whether DVD video is progressive or interlaced. Here's the one true answer: Progressive-source video (such as from film) is usually encoded on DVD as interlaced field pairs that can be reinterleaved by a progressive player to recreate the original progressive video.
OK, that's about the size of it, then. Virtually all NTSC DVDs in the United States that were sourced from film have telecined video encoded on them, which means interlaced, not progressive, video. Any more questions, Anonymous?