MPEG2 2.21:1 aspect ratio - Why not used?

[JanBing]

Reading that the MPEG2-format supports an aspect ratio-flag of 2.21:1, I was wondering, why it's unused on commercial DVDs?

Taking a PAL-DVD with a 2.35:1-movie as a basis, the standard anamorphic encoding (at 16:9) allows a vertical resolution of 436 pixels for that kind of image-AR, whereas encoding it at 2.21:1 would keep a vertical res of 542 pixels, almost the complete height of the image! Why isn't this done?

With today's HDTV-sets, wouldn't it make sense to just scale the image to the full resolution of the panel? (1366x768 or better)

After all, anamorphic encoding is used to keep as much vertical resolution as possible - which is true for 16:9-productions. Why not 2.21:1-encoding for "wider" movies?

[drmpeg]

Because there are no (or exceedingly few) 2.21:1 displays. A 2:21 aspect ratio DVD would have to be vertically downsampled (just like a 16:9 DVD is vertically downsampled for a 4:3 display) for a 16:9 display, negating the resolution advantage.

Ron

[JanBing]

Because there are no (or exceedingly few) 2.21:1 displays. A 2:21 aspect ratio DVD would have to be vertically downsampled (just like a 16:9 DVD is vertically downsampled for a 4:3 display) for a 16:9 display, negating the resolution advantage.

Ron

But that's why I mentioned HDTVs, which wouldn't require downsampling, but upsampling.

[manono]

DVD allows only 4:3 and 16:9. 2.21:1 is allowed for MPEG-2 in general but not for the more restricted DVD.