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[Solved] Display Aspect Ratios and Pixel Aspect Ratios - ntsc

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I'm working with a large collection of varied video formats going back decades. I want to make sure I can quickly see the pixel aspect ratio of a video to make sure we have the correct copies and formats digitzed.

MovieScanner2 provides the resolution and the 'Display Aspect Ratio' but in some cases I suspect it may be showing me the Storage Aspect Ratio. (I may be misunderstanding something!)

For instance -

A file opens in quicktime, and the inspector tells me that it is 720 × 480 (640 × 480) - DV/DVCPRO - NTSC. So I will assume that the Display Aspect Ratio should be 4:3, and the Storage Aspect Ratio is 720 x 840, and therefore a pixel aspect ratio of 0.889... - standard NTSC. (link)

However, MovieScanner is telling me the file's 'Display Aspect Ratio' is 3:2 - which makes me think it is reading the 720 × 480 dimensions, and not the 640 × 480.

Can we clarify this? (or correct my misunderstanding?)

Can we display an explicit Pixel Aspect Ratio value? 

(fixed funky link)

This topic was modified 6 days ago 2 times by Hans

   
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 Hans
(@hans)
Famed Member Admin
Joined: 10 years ago
Posts: 2407
 

Let's start with apologies for the late reply ... 😁 

Maybe I should start with that MovieScanner isn't a pro-tool, and my video knowledge is limited to "good enough" for what I use it for.

As for the aspect ratio, this is calculated based on width and height as provided as the video stream "width" and "height" by ffProbe.
Not to be confused with coded_with and coded_height (right click a scanned video in MovieScanner and select "Copy ffProbe output to clipboard" so you can copy it to a text editor).

So maybe see if we can learn something from that - I'd be more than happy to learn something new and improve my "calculation".

Note that you may see a sample_aspect_ratio and a display_aspect_ratio, like this example:

sample_aspect_ratio=1\:1
display_aspect_ratio=4\:3

However, often enough there is no aspect ratio defined and we will see something like this:

sample_aspect_ratio=N/A
display_aspect_ratio=N/A

So I had to make a function to calculate the aspect ratio and with the best of my abilities I came to the width:height ratio (as it should be).
This will however at times result in very weird numbers. For example: a width of 1268 and a height of 720 would result in a 317:180 ratio - which makes no sense for most users of course. Here the 16:9 ratio makes more sense for the user.

This is why I made a function that brings ratios closer to more normal or common aspect ratio's. Of course this could potentially come with aspect ratio's that a re little "off", although I would hope this is not the case in your situation. I hope that makes sense 😜 

I'm open to suggestions and improvements! 😁 


   
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 Hans
(@hans)
Famed Member Admin
Joined: 10 years ago
Posts: 2407
 

Just to clarify:

The pixels displayed is the "width" and "height" as provided by ffProbe. 

MovieScanner will try to get a useful aspect ratio, straight from ffProbe, by using display_aspect_ratio.
If that value does not exist, or is set to "N/A", or cannot be found in the list of "usual aspect ratio's", then an aspect ratio is calculated based in "width" and "height" as presented by the ffProbe output.

If you could provide an example video, then I wouldn't mind looking into this. Always room for improvements 😁 

p.s. you will not be able to upload the video in the forum. Too big, and you're not yet allowed to post attachments. You could use WeTransfer, or a share on Google Drive or something like that.


   
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