Hybrid Vs UAR – a simple guide
Maybe someone has encountered a so-called “Hybrid” version, and does not know what it is about; and I bet many don’t know about UAR as well! So, this post would try to clarify this – I hope so!
Note: in this article, we use the following terms for the most used aspect ratios
fullscreen=1.33:1 (but could be also up to 1.66:1), open matte=1.78:1 (but could be also down to 1.66:1), letterbox=2.40:1 (but could be also down to 1.85:1)
Hybrid: obtained overlapping the source with higher quality on top of lower quality one; borders (if any) are straight; image aspect ratio is the same of one of the sources.
PROs: retains the same AR for the whole movie; improved quality of the center “slice”
CONs: usually does not preserve OAR; sometimes sources are cropped, and, if not stated, it is difficult to know that; “ambilight” version could be annoying for someone
UAR: previously known as AAP-AR (axis-aligned polygon aspect ratio), this is obtained overlapping two or more sources; borders are not straight, but stairsteps-like.
PROs: more image than any single source; improved quality of the source overlaid on top; two sources version can retain OAR using YAO hack
CONs: three sources version can’t preserve OAR; “stairsteps” borders and/or VAR could be annoying for someone
This is the classic situation where high quality letterbox source, usually BD, is placed on top of lower quality open matte, usually WEB-DL or HDTV; when no BD of a given movie exists, letterbox could be WEB-DL or HDTV 1080p, where open matte could be WEB-DL or HDTV 720p, or even DVD. This would preserve the open matte AR.
WARNING: when letterbox has more image on one or both sides, it must be cropped unless the open matte is full, hence both sources have the same frame width
NOTE: here open matte is full, apart two or three shots, hence it is mainly uncropped, apart those brief ones.
Another example of hybrid; the letterbox/open matte could usually be BD, WEB-DL, HDTV, where fullscreen is often a DVD.
WARNING: the letterbox/open matte would be cropped at both sides, to preserve the fullscreen AR, unless both frames have the same width (AFAIK no title does that for the whole duration of the film)
NOTE: indeed, this will be an UAR version, but in some shots it happens that both sources perfectly match their frame width, hence no cropping.
A rare case where a fullscreen (cropped or pan&scan) version has better quality than letterbox/open matte; I could think of HDTV for fullscreen and DVD for letterbox. WARNING: the fullscreen would usually be cropped on top and/or bottom, to preserve the letterbox AR.
NOTE: indeed, this test used HDTV as fullscreen and BD as letterbox; in theory HDTV, having an higher resolution, *could* held a better quality; top and bottom slices are still there and would be cropped in an hybrid version.
In this version, one or both sources are cropped, to get a “custom” open matte AR – which is more or less between fullscreen and letterbox; so, you would get a bit more image on top and bottom in comparison to letterbox, and a bit more image on one or both sides in comparison to fullscreen; still, image would be cropped in comparison of a “pure” UAR version. Black corners would be unavoidable, but in this instance they could be filled with so-called “ambilight” or “frosty borders” (a feasible option), or inpainted (still to find out an inpaint technique that would works well in video… let’s wait for a great neural net/deep learning technology!)
NOTE: in some shots the “ambilight” corners pass unnoticed, whereas in others are quite noticeable. As usual, is up to the single viewer to prefer this version, an UAR, or simply neither.
UAR using two sources; letterbox/open matte could be BD, WEB-DL, HDTV, while fullscreen could be DVD. UAR would get as much image as possible.
Resident Evil: Afterlife UAR (raw test made in paint, 2.40:1+1.33:1)
Here we have a better quality open matte source, usually WEB-DL or HDTV, placed on top of lower quality letterbox, usually DVD; at the contrary, if the letterbox has higher quality, like a BD or HD-DVD, it could be put on top of open matte.
Here you can get as much image as possible, using three sources; stairsteps borders are even more evident in this case.
In this case, where letterbox and fullscreen sources are of comparable quality, it is possible to mix them (percentage varies according to quality of each source) to let the sources blend better and improve the final result.
Q: I want to watch a movie in its OAR; should I go for hybrid, or UAR version?
A: Surely not for UAR; in some cases hybrid could retain OAR; you should compare the OAR of that movie, and the one of the hybrid version to be sure.
Q: When I should watch an hybrid version?
A: Every time you like to see that movie in the hybrid AR, even if it’s not in its OAR; you would get a better quality than “plain” bigger source, and more image than “plain” smaller source.
Q: When I should watch an experimental hybrid version?
A: The “experimental” term here is used for those hybrid versions that use “ambilight” corners; so, for the same reasons above, plus if you can stand those corners filled with “imaginary” image – where an algorithm decides what parts of the surround image could be used to fill the empty corners.
Q: When I should watch an UAR version?
A: When you want to see as much image as possible – indeed, it is a composited image of two or more sources, often bringing the whole visible image close to what it was present in the negative film (or digital) frame; and you can stand VAR and stairsteps borders. Do note that UAR versions could have fullscreen, open matte or letterbox shots when two or three sources simply overlap perfectly, without more image on top/bottom/sides, or when one is it completely enclosed inside another, or in SFX shots that were filmed only in one AR; this doesn’t occur frequently, though. Also, you should expect any “tetris-like” image shape, in particular when three sources are used. In rare cases, you have one source “shift” from top to bottom (and vice versa) or left to right (and vice versa) to stay aligned with the other source. So, actually an UAR could contain pure UAR shots (stairsteps borders), shots with the same AR of the sources (letterbox, open matte, fullscreen), or hybrid shots.
Q: I don’t think I will like this kind of borders, and variable aspect ratio…
A: Is it possible, or course. But I’d give it a try, because our brain would be used to not notice it after few minutes, and then you could focus on the bigger image, where previously hidden details could be discovered now.
Q: What’s about props, mics, unfinished effects that could be now seen?
A: Albeit is it possible to spot them in theory, in practice (almost) all versions available don’t contain them; in an unfortunate event they do, it is care of the UAR maker to NOT include them!
Q: Wouldn’t be the “seams” between sources visible? And “slices” from sources with different quality? And what’s about sources with different color gradings?
A: Seams would be noticeable in few cases, in particular when a source has an high quality, like BD, and the other has low quality, like DTV; of course, there are various method to let them as unnoticeable as possible, like color grading and diffused noise. Also, final quality of the sources should be evened before overlapping, so needed noise reduction, deblocking, sharpening, grains should be applied; even higher quality source could be degraded a bit if needed to be closer to enhanced lower quality one. Different color gradings, and contrasts, should be matched as much as possible; even here we could find few shots where the difference between sources could be noticed, usually barely. Finally, a grain plate helps a lot to cover such eventual problems, and improves overall perceived details.
Hybrid & UAR projects list
Restoration tips: Overlap matching
Restoration tips: Axis-Aligned Polygon Aspect Ratio™ (a.k.a. UAR™)
Restoration tips: Soft+Open Matte™ (a.k.a. YAO™)
Frosty Borders – avisynth plugin
Inpaint – Wikipedia