BMA Blackmagic Camera App iPhone desqueeze renders 'extra pi

Hello all,

I am trying to switch from Protake 4.0 to the Blackmagic Camera App 2.0 (BMA) as the go-to video app on my iPhones. I like to shoot with a Sandmarc 1.33x anamorphic lens now-and-then.

While testing with a last-generation iPhone SE in 4k, I notice that BMA has a different way to desqueeze than I was used to with Protake. Since I'm clueless as to what BMA is doing 'under the hood' I was hoping someone here can shine some light on this.

This is the 'test':

Shooting normal 4k footage in the iPhone typically renders 3840x2160 px clips. When 1.33x anamorphic desqueeze is turned on in Protake, it compresses the vertical resolution by a factor 1/1.33333 = 0,75 to render a 3840x1620 clip in 2.37 aspect ratio, preserving the horizontal resolution.

However, when 1.33x anamorphic desqueeze is turned on in BMA, it seems to stretch the horizontal resolution by a factor 5107/3840 = 1,32995 to render a 5107x2160 clip in 2.36 aspect ratio, preserving the vertical resolution.

Inspecting the file information on a Mac provides the information as depicted below. When opened in Quicktime, the inspector window shows two resolutions for the BMA desqueezed file: "3840 x 2160 (5107 x 2160)".

How would BMA create a clip that has 5107 pixels horizontally when my iPhone SE only has a sensor capable of capturing up to 4032 pixels horizontally? Is BMA using algorithms to 'invent' additional horizontal pixels when it is asked to desqueeze? What am I missing or misunderstanding?

Who has a proper workflow for using anamorphic footage out of BMA in post-production, either with or without the desqueeze option turned on?

Thanks for helping!

File info comparison:

BMA desqueeze.jpg (464.88 KiB) Viewed 2167 times

Multiple clip resolutions:

BMA desqueeze 2.jpg (102.11 KiB) Viewed 2167 times

I have this question too.

When shooting on an iPhone 16 Pro and the Blackmagic 1.33 desqueeze is applied to the footage in-camera, the resolution is shown in the Quicktime inspector as 3840 x 2160 (5107 x 2160).

What is the Blackmagic Camera app doing here, and what is the correct way to handle the footage in FCP? The message when using the FCP automatic timeline feature is that this is non-standard footage.

So far I have just been using the standard 3840 x 2160 4K settings. In this case FCP creates letterboxed footage at the correct aspect ratio, but I wonder if this is the best way to handle the anamorphic image to get the best image quality from the desqueeze?

Any definitive answers are much appreciated!

Blackmagic saves the "original" resolution unsqueezed, but it tags the file with metadata for the pixel aspect ratio. Then it's up to the player/NLE to unsqueeze according to the metadata. That's why some apps show both resolutions.

I'd say the BMD way is correct as that maintains the resolution of the file until you yourself do the desqueeze the way you want to.

Thanks Roger.

I subsequently found this youtube video which suggests that the "correct" way to handle the footage is to retain the vertical resolution, and increase the horizontal by a factor of 1.33x.

The technical reasons for this are explained in the video, and sound convincing enough. Unfortunately I am not allowed to post the URL, but doing a search on youtube for "How to Desqueeze Anamorphic Footage the Right Way" should bring it up.

Hope this helps anyone else with the question.

If the metadata is there Resolve usually does the desqueeze automatically. Or are you not using Resolve?

Edit: Ah, Final Cut.