Pixel Aspect Ratio Incorrectly Interpreted as 1.778 Instead of 1.0

There has been a long-standing regression affecting both Premiere and Media Encoder, introduced between versions 26.0 and 26.2, and is still present.

With certain H.264 footage that has a 1.0 pixel aspect ratio, Premiere and Media Encoder incorrectly interpret it as 1.778 instead. This results in the footage being displayed with the wrong aspect ratio and requires manually changing the interpretation and/or applying a transform to correct it.

The same footage is correctly interpreted as 1.0 by other media players and applications, including After Effects. The issue also does not occur in the 2025 versions of Premiere or Media Encoder.

Steps to reproduce:

1. Import the affected H.264 footage into Media Encoder.

2. Check the interpreted pixel aspect ratio.

3. Observe that it is incorrectly detected as 1.778 instead of 1.0.

Other bug reports on Premiere reporting the regression:
 

Please fix this long standing issue once and for all. Issue happening on both software should be a good starting point.