Anamophic aspect ratio workflow

Hello. I am creating anamorphic videos. I set the custom video size and rate to the stretched size (2560x1080 for HD) when I make the video project from the beginning.

Then when I import my videos I have to individually change the aspect ratio to 21:9 for each video.

I am guessing this is because each video is being process according to it’s properties when it’s been imported (even though the project is set at 21:9 and 2560x1080).

Is there a way for the videos to honor the aspect ration and pixels? Ie ignore HD?

I think there will be a way to do this in bulk in ffmpeg (haven’t looked into it) if I can’t do it in shotcut.

Thanks to any responders. Thank you Dan and everyone else who makes it possible.

If I’m understanding this right, your footage was captured at 16:9 with an anamorphic lens, presumably at 1.33x squeeze, and now you need to de-squeeze it to 21:9 in post?

If so, the easy way is to put a Size, Position, & Rotate filter on a track head rather than an individual clip. Then all clips on that track automatically get de-squeezed. Remember to set the SP&R mode to Distort.

When setting up your Video Mode, also note that the aspect ratio of 2560x1080 is 64:27 in order to retain perfectly square pixels. 21:9 is a marketing term, not a mathematically correct aspect ratio.

In theory, it would be possible for FFmpeg to rewrite your sources with 64:27 display aspect ratio (DAR) instead of 16:9. It would burn a lot of write cycles on your disks during the remux, but it could be done.

Why not change the aspect ratio in properties?

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It would have to be done to every one of potentially hundreds of clips. Unless there is a place to set aspect ratio for a track that I’m not aware of.

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Yes, the track filter is the quick and dirty way, but much heavier and possibly less quality.

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Thank you for the speedy reply Austin.

That’s correct about the desqueeze. I forgot about the 64:27 thing. Thanks for the reminder.

I tried the SPR filter just now and found my computer is struggling with the filter on the track. Also feeling a bit thick because I can’t see it doing anything when I apply it. But not too worried as I’m not going to use that technique because of the dropped frames.

Going to have a think a bit more about this workflow problem… Thanks again

That only affects preview, and is affected by interpolation and preview scaling in the settings menu.

Proxy helps a lot too. And preview scaling.

Sorry Dan, missed your posts. I mean this is the question as far as I can see it. It’s a matter of going into each video clip and editing the properties as the properties in the overall project file don’t seem to cascade into each individual clip.

I’ve been trying that out and I will try it out again.

That is intentional. Also you can edit one of the files with the aspect ratio, open the project file in a text editor, find the <property> tags it added for the aspect ratio override, and copy them to all the other clips.

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Out of curiosity, what is the resolution of the source footage? I’m playing with the idea of making the Video Mode natively match one side of the source footage. This means the SP&R filter would not be scaling up from lower-than-output resolution. Then the Export > Advanced resolution override can bring it back down to 2560x1080. It would be a hack, but could be faster than editing MLT XML for every project.

Source is 1920x1080 8bit 24fps. It can be 4k but not super fussed either way as my computer doesn’t cope… 1.33x squeeze as mentioned.

In that case, whether you modify the aspect ratio in MLT XML or whether you stretch the track headers with SP&R, the exact same scaling (stretch) is going to happen. You’re essentially upscaling with both methods since the source is lower resolution than the final. So you get to choose whichever method you feel is easier without fearing a quality penalty. To Dan’s point, there would be less processing involved and higher preview performance by editing the MLT XML. But the final output would theoretically be identical from a quality standpoint.

The story would be different if the source was 4K and being scaled down to the output resolution.

Since this is an upscale, you’ll probably benefit from using Lanczos interpolation in the Export > Advanced panel.

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