Cropping Aspect Ratio

[Roldy]

Long time user, first time poster please go easy.

So I have a preference for ensuring that the output aspect ratio matches the input aspect ratio exactly. So for a 4:3 source if I am downsizing I make sure that the width / height equals 1.25 and the display width / height equals 1.33 and that everything divdes by exactly 16. If the source needs cropping though then this means that crop width / height also must equal 1.25. I wonder though if I am just being too OCD about this process?

If I'm only encoding the one file then sorting out this cropping is easy enough but if I have multipe files then it becomes pretty tedious. To speed things up I went ahead and wrote a batch script to first run a 1 second capture of the source for the purpose of obtaining the autocrop settings that handbrake detects. Using the autocrop settings supplied by handbrake I then do a bit of checking and math to convert it into numbers that equal the desired 1.25. With the converted autocrop numbers I then can encode my source using my hardset crop numbers.

The script makes the process virtually instant but it seems a lot of work for something that I thought handbrake might (should?) be able to natively do. I noticed that there was once an option called --loose-crop which appeared to do something of this nature. Anyone know if a feature like this has been discussed in the past?

Anyway I guess I'm just looking for some feedback here or perhaps even a link to some standardised conventions if such a thing exists?

[Smithcraft]

I would say that you are being too OCD about it.

Why are you sticking to a MOD value of 16? Does your playback system require it?

SC

[Deleted User 13735]

Simplest solution: don't crop.
Where did you come up with 1.25? Is it PAL?

[TedJ]

Yes, 1.25:1 / 5:4 is PAL storage resolution.

[Roldy]

Thanks very much for the thoughts. Does anyone know of any standards or guides for this type of thing?

Why are you sticking to a MOD value of 16? Does your playback system require it?

I've been using a mod value of 16 as that's what I 'think' is being recommended in the handbrake anamorphic guide https://trac.handbrake.fr/wiki/AnamorphicGuide#macro. My playback device is generally MPC-HC so I don't imagine it cares about mod 16. Am I missinterpreting the guide?

Simplest solution: don't crop.
Where did you come up with 1.25? Is it PAL?

Yeah I'm from Oz so hence PAL 1.25 as Ted says. Is not to crop really the best way to go though? Say if you're working with 4:3 standard definition video content from the early 90s. As an example think TV shows from this period; the final edit wasn't done on 35mm hence the DVD's generally have uneven black borders around the frame. Wouldn't most folk prefer these removed?

[TedJ]

That part of the guide is a little out of date. The reasoning behind enforcing mod16 was that it was believed that it improved compression efficiency, which according to one of the x264 developers is no longer relevant. I tend to work on mod4 dimensions myself as some hardware based decoders can choke on mod2 encodes.

The black borders were usually added to compensate for the overscan found on CRT televisions of the day. If you're playing back on a flatscreen monitor or TV these can be safely removed.

[Deleted User 13735]

I tend to work on mod4 dimensions myself as some hardware based decoders can choke on mod2 encodes.

Correct, mod 2 is not as widely supported as mod 4, but I stick with mod 8 because it is common to all standard pixel dimensions I can think of. I do not do any cropping if I can avoid it, and if necessary I conform it to multiples of 8. The thin irregular black bars on the sides of some OTA recordings are either cropped off by overscan, or not readily noticed (if your screen has a black bezel).

BTW, I've always wondered about the 16:9 widescreen ratio standard. 9:5 is much easier to work with (one can do the calculations mentally), supports many more screen sizes, and it is just 1% different ratio.

[Flo]

BTW, I've always wondered about the 16:9 widescreen ratio standard.

Wikipedia has an explanation for that.

[Deleted User 13735]

Very interesting explanation, thank you.
But as a "compromise" format (as Wikipedia describes it), 1.8 is a much more extensible and ergonomic ratio than 1.778, and they should have seen that. Researchers sometimes don't see the forest for all the trees. Just look at all the resolutions available for 9:5 delivery, and all mod 8! (try that with 16:9).

216 x 120
288 x 160
360 x 200
432 x 240
504 x 280
576 x 320
648 x 360
720 x 400
792 x 440
864 x 480
936 x 520
1008 x 560
1080 x 600
1152 x 640
1224 x 680
1296 x 720
1368 x 760
1440 x 800
1512 x 840
1584 x 880
1656 x 920
1728 x 960
1800 x 1000
1872 x 1040
1944 x 1080
2016 x 1120
2088 x 1160
2160 x 1200
2232 x 1240
2304 x 1280

[Deleted User 11865]

Quite easy to calculate. There are 1.8 times as many mod8 resolutions for 1.8:1 when compared to 16:9. But that's about it.

Compare that to 2:1 (9x as many mod8 resolutions)

[Deleted User 13735]

US "flat" widescreen cinema, for whatever reason, is 1.85, which is actually 37:20.
Once again, 9:5 (36:20) or even 5:3 (1.667, which was the European flat widescreen standard) would have been so much easier on this tired brain.
The aesthetics of 2:1 SAR (or greater) is one discussion I have chosen not to participate in, and there are many that will argue that monitor resolution (1.6) is still the best

[Flo]

If you're going to ignore previous formats you might as well go with 2:1. Doesn't get much "easier to work with" than that.

But the whole point is moot. The world isn't likely to adopt a new TV aspect ratio anytime soon.

[Deleted User 13735]

If you're going to ignore previous formats you might as well go with 2:1.

Well, the answer to that would seem to depend entirely on one's viewing preferences, as was strongly alluded to in my previous post.
A 2:1 image would require a complete redesign of my living space to accommodate a reasonably sized screen viewing area, even if I felt compelled to choose it.

As a point of reference, the "wider is better" trend reached its apex quite some time ago (like in the 1970s ?) . . .
So as long as we're referencing Wikipedia, this one is definitely worth a look:
http://en.wikipedia.org/wiki/Golden_ratio
;?)

[Flo]

A 2:1 image would require a complete redesign of my living space to accommodate a reasonably sized screen viewing area, even if I felt compelled to choose it.

But now you're making the same "mistake" as the people who originally decided on 16:9... trying to accommodate other variables instead of picking a ratio that would be "easy to work with"

[Deleted User 13735]

You're right of course; I am quite comfortable viewing 1.6 to 1.85, and my tastes probably won't change that much, nor would I consider 2:1 just for the sake of arithmetic convenience alone. 1.8 is convenient "enough" for me to figure without a calculator, and is only 1% away from actual 16:9, so it "fits" with the vast viewing majority, whether on home TV or internet. By comparison, 2:1 is a full 12.5% departure from 16:9.

I knew I shouldn't have taken this discussion so far off topic -- my apologies to the OP