OK this is complex.
The move from analogue to digital required that none of the analogue image was cropped horizontally.
The actual pixel count is 720×576 for PAL
And of that 704 is active picture. Allowing 16 pixels blanking to be retained. This would vary by a few pixels left and right based on the timing of the original analogue signal.
But that’s 4:3 aspect pixels (or later 26:9 aspect pixels)
To view them correctly in our square pixel world of computers and HD you have to scale horizontal.
So for 4:3 it becomes 768×576 and for 26:9 it becomes 1024×576.
But this includes the original blanking scaled up as well.
To retain aspect you must zoom expanding width and height.
But this will soften the image more.
Remember you have already expanded the width from 720 anyway.
One solution is to crop the black edges using a pip effect and use the active edge of the original zoomed image underneath. It basically repeats the edges slight.
Hope that helps.
Pat Horridge
Broadcast & Post Consultant, Trainer, Avid Certified Instructor
Free online Tutorials at VET digital media academy online https://vimeo.com/channels/752951
pat@vet.co.uk