ID 152798 - If Nuke cannot find the pixel aspect ratio (anamorphic squeeze) in a file, its default format will be set to the first format in the list which matches the width and height

Problem summary
If Nuke cannot find the pixel aspect ratio in a file, its default format will be set to the first format in the list which matches the width and height.
This can result in images being read in with the incorrect pixel aspect ratio applied.

Customer reported version
Nuke 12.2v3

Customer reported platform
Linux

Steps to reproduce

1) Open Nuke.

2) Open the Project Settings (press the S key in the Node Graph) and from the full size format dropdown, select new.

3) In the dialog that appears, enter a width of 1000 and a height of 1000 and a pixel aspect of 2. Name the format 'Test1'.

4) Then create a second format, also with a width of 1000 and a height of 1000 but a pixel aspect of 1. Name the format 'Test2'.

5) With the full size format set to 'Test2', write out a PNG file. This can simply be a ColorWheel connected to a Write node.

6) Change the full size format to PC_Video 640x480.

7) Read back in the PNG file you rendered out in step 5.

8) The Format knob of this Read node will be incorrectly set to 'Test1' (with a pixel aspect of 2).

Expected behaviour
Nuke should read files with the correct format and pixel aspect ratio.
If the pixel aspect ratio cannot be found in the file, it would be preferable for Nuke to assume that it should be set to 1. 

Actual behaviour
If Nuke cannot find the pixel aspect ratio in a file, it will set its default format to the first one in the list with the same width and height, regardless of aspect ratio.

Workaround
You can manually change the Format knob of the Read node. 

Alternatively, the following Reformat node uses expressions to change the pixel aspect ratio, based on the metadata. If the input/pixel_aspect metadata value does not exist, it will default to 1:

Reformat {type "to box"box_width {{width}}box_height {{height}}box_fixed truebox_pixel_aspect {{"[if {[metadata input/pixel_aspect] ==\"\"} {return \"1\"} {return \"[metadata input/pixel_aspect]\"}]"}}resize nonecenter false} 

Reproduced by support
This bug has been reproduced in:

Nuke 13.0v2 - Windows 10 - macOS 10.15 (Catalina) - Linux CentOS 7

Nuke 8.0v1 - Windows 10 - macOS 10.15 (Catalina)

Earliest version tested
Nuke 8.0v1
- This issue appears to be in all versions of the product