About how unclear it was if the DVD Video specification supported progressive scan content or not. This was a question I'd been asking for years with no clear answers being given by anyone. It was rekindled when last night I decided to rip two of my DVDs, one a film and one a TV show. When playing back the ripped files with no deinterlacing filters applied, they had NO interlacing artifacts to speak of. One ripped at a solid 23.976fps, the other a solid 29.97fps, not interlaced, progressive. Despite many forumites over the years insisting it was impossible.
So I'm about to start writing this post and I go look up the DVD-Video Wikipedia article so I can just get some dates right... And right there is the "Video data" section that describes exactly what I just discovered, laying it all out plain as day, as if this was common knowledge that everyone had always possessed.
At a display rate of 29.97 frames per second, interlaced or progressive scan (commonly used in regions with 60 Hz image scanning frequency, compatible with analog 525-line NTSC): 720 × 480 pixels (D-1 resolution, 4:3 or 16:9)
The MPEG-1 Part 2 format does not support interlaced video. The H.262/MPEG-2 Part 2 format supports both interlaced and progressive-scan content, and can handle different frame rates from the ones mentioned above by using pulldown. This is most commonly used to encode 23.976 frame/s content for playback at 29.97 frame/s. Pulldown can be implemented directly while the disc is mastered, by actually encoding the data on the disc at 29.97 frames/s; however, this practice is uncommon for most commercial film releases, which provide content optimized for display on progressive-scan television sets.
Alternatively, the content can be encoded on the disc itself at one of several alternative frame rates, and use flags that identify scanning type, field order and field repeating pattern. Such flags can be added in video stream by the H.262/MPEG-2 Part 2 encoder.[12][13] A DVD player uses these flags to convert progressive content into interlaced video in real time during playback, producing a signal suitable for interlaced TV sets. These flags also allow reproducing progressive content at their original, non-interlaced format when used with compatible DVD players and progressive-scan television sets.[14][15]
I feel both incredibly stupid and incredibly relieved that this years-long mystery is over and my soul can rest. For the most part. DVD-Video is still really fucked up in a lot of ways.