Jason_Hall wrote:Interesting stuff! I had no idea there could be 4:3 anamorphic video.
It seems like the only fool-proof way is a visual inspection. I did test a few DVDs and they were correctly reported but looks like that's not always going to be the case. I don't think any tool exists that will take a screenshot, strip out borders and determine aspect ratio, attempt to scale, again strip borders and determine aspect ratio, and then report the results.
ah well. Would've been nice
DVD is a 4:3 format with the same pixels in 4:3 or 16:9. A correct 16:9 transfer is encoded squeezed (with more horizontal information in each square pixel while gaining resolution vertically that would be sacrificed to just black matting in 1.78:1 letterbox 4.3 and losing less with 2.35:1 since the player adds the black matte with 4:3 playback). A file flag stretches the native 4:3 to 16:9 just as a file flag in Dolby Digital 2.0 tracks will turn on ProLogic decoding if your receiver is set to automatic (which is why we add “Surround” only to 2.0 tracks that are flagged not 2.0 tracks that just sound good with ProLogic turned on).
Playing a dvd in VLC with the default window size (not clicked to fill the frame) should display the disc in 4:3 or 16:9, although the player can hiccup once in a while if the menu is 16:9 and the film 4:3 or vice versa like the UK dvd of La Captive which plays its 4:3 letterbox transfer stretched because the menu is anamorphic, although I haven’t checked that disc on newer versions of the player). The VLC screenshots will be 4:3 (720x540 NTSC or 768x576 PAL) or 16:9 (853x480 NTSC or 1024x576 PAL) and aspect ratio for matted films is determined by cropping the mattes away and dividing width by height).
High-definition is native 16:9 with a 1.78:1 image made up of square pixels requiring no squeezing but requiring pillarboxing for 1.66:1, 1.33:1, and narrower silent film formats like 1.19:1 (or Xavier Dolan’s 1:1 square format for his latest film)