Find a video's true aspect ratio when frame width/height doesn't work

[planetrock]

How can I find the aspect ratio (width divided by height) of videos as they are actually played in real life which sometimes can not - I repeat NOT - be found by dividing frame width by frame height as they're reported in the file's metadata?

For example I have a video whose frame width and height are 718 x 480 which would mean the ratio is 1.5 : 1 (718 divided by 480) but the ratio as actually played in the real world is 1.85 : 1 which I know from holding up a physical ruler to the monitor and measuring in mm, and that's the correct ratio of the movie as it actually played in theaters. The video as played is 100% correct in its framing and is not stretched or squeezed or letterboxed or pan-and-scan or anything.

I'm NOT ripping or encoding or editing or recording anything. The only thing I'm asking for here is how to find the real-world as-played aspect ratios of existing videos without holding up a ruler to the monitor. For most videos doing the calculation using width and height from the metadata gives the ratio as actually viewed so this is just about the occasional video where that's not the case.

[Sharc]

Many sources (like DVDs) are stored 'anamorphic', means they are stored different (distorted) from the 'real life' width/height for technical reasons.
The relation is
DAR = SAR x PAR
DAR: Display Aspect Ratio (what you call 'real life' aspect ratio)
SAR: Storage Aspect Ratio. How the video frame is stored as widht and hight in pixels (your 'metadata')
PAR: Pixel Aspect Ratio. The 'shape' of a pixel. This ratio is standardized for various video formats (and can be taken from catalogs).

Applied to your case:
The PAR of a 16:9 NTSC DVD is 32/27 (value taken from "catalog"), the SAR is 720/480=1.5. So DAR=720/480x32/27=1.7778=16:9.
A 1.85 movie is padded with black bars on top and bottom of 8 pixels height to fit the 720x480 DVD frame, so the height of the remaining active picture is (480-16)=464 pixels.
Now applying the equation DAR=SARxPAR gives DAR= 720/464x32/27=1.84 which is - within rounding - 1.85:1 (there are no 'fractional' pixels).

All this is confusing at the beginning, and there are many posts about the subject in this forum. It's even more confusing as the same acronyms (e.g. SAR and PAR) can have a different meaning.

See also
https://en.wikipedia.org/wiki/Pixel_aspect_ratio

Simply put:
- Blu-ray sources usually have PAR=1/1 ("square pixels"), so DAR=SAR and the anamorphic distortion does not exist.
- DVD's (including any black borders of the movie) have to be played back as either 4:3 or 16:9. This is a player/TV setting which has to be set according to the label on the DVD box.
- If your source is some oddly ripped footage - possibly wrongly encoded and/or wrongly flagged - you have to do the maths, or solve it by tinkering.

[planetrock]

Many thanks. Yes, DAR is what I was looking for and didn't know the name of, nor SAR or PAR.

Is there any freeware that can show DAR for all the videos in a folder at the same time since AFAIK Windows Explorer and other ordinary file managers can't? I found Media-Player-Classic shows DAR in Properties > Media Info but that means you have to open each video one by one. I have programs for managing a great many metadata fields in photos that can't be seen in file managers but they don't work with video.

As for black borders I know all about them but encounter them encoded into videos so infrequently that I'm pretty sure it'll make a lot more sense for my purposes to just hold up a ruler to the monitor than wrestle with still other complicated software that can detect the width/height of the actual filmed image excluding the bars, if such a thing exists. It seldom happens and when it does I don't need accuracy down to a couple pixels.

[aramkolt]

My explanation won't be as good as Sharc's, but basically it's more about knowing what type of aspect ratio the original display was supposed to be. Typically players will allow you to force the aspect ratio to 4:3, or it might assume that the aspect ratio is 4:3 if it sees a starting resolution of 720x480, though the 718 pixels horizontally you mentioned might be throwing things off since that is not a standard resolution for anything to my knowledge. Technically, there should be some black bars on the left and right that total 16 pixels to make the actual video resolution 704x480 for traditionally captured 4:3 content. This originally did not matter at the time because most TVs were overscanning to the point where the side black bars weren't visible.

You can also specify DAR and SAR as flags in the video file (even without re-encoding the video usually), but it's up to the player itself as to whether it actually honors those flags or decides to just display the pixels as square anyway.

[Kakujitsu]

MediaInfo


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