In an earlier post, I described some of my findings with respect to cadence breaks and changes in 2:3 pulldown flag patterns on commercial DVD discs.

I went back to some very early (circa 1992) literature on the development of the MPEG-2 standard, and found some references to the motivations for the 2:3 pulldown features of MPEG. As it turns out, the designers of MPEG-2 anticipated these choppy cadences of 2:3 pulldown material as such sequences are commonly produced by non-linear editing systems when the final product is 29.97i.

So this brings my understanding full circle. The first time I noticed breaks and changes in 2:3 pulldown flags was in evaluating and comparing two different releases of a Hollywood DVD: the original theatrical release vs. the directors cut.

It was clear that the director's cut was reworked on a non-linear editing system, and then released straight to DVD. They probably did the director's cut in 29.97i, using additional 2:3 telecine material (ie. scenes not in the theatrical release). This would account for the fact that 99% of the DVD has a regular 2:3 pulldown cadence and just a very few scenes have true 29.97i material.

Nevertheless, DVD discs which contain mixed pulldown cadences will undoubtedly cause a great deal of trouble for people ripping discs and re-encoding.

In further evaluation of voOM, I have a specific example of artifacts in the video presentation. In this case, it is an HD channel, HBOHD. The scene in question is from the recent HD presentation of the Matrix (original 1999). It's approximately 2/3 of the way through the film, just after Neo and Trininty decimate the foyer of the building where Morpheus is held captive by the 3 agents on the upper floor. They get into the elevator, and then onto the roof of the elevator where Neo sets an explosive device. Then he says, "there is no spoon", the device detonates, and he and Trinity hang onto the elevator cable as the explosion goes down into the shaft. During the explosion (flames etc.) there was a series of frames, perhaps as long as 3/4 of a second, where serious block artifacts occur. I'm assuming the stream is 24p, although I don't have any way to verify that. So we're looking at about 18 (3/4 of 24) frames that have serious artifacts. It detracted from the presentation of the movie.

Since HBOHD is on both voOM and DirecTV, I am wondering if HBO provides a compressed MPEG-2 feed to the DTV broadcasters - so it would seem, as the header for an HD film reads "in HD where available".