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How does FCP handle PAL SD blanking (black borders)?

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Graham Stewart
How does FCP handle PAL SD blanking (black borders)?
on Apr 29, 2020 at 9:59:49 pm

I'm dealing with digitised PAL 4:3 video, which originally came from tape, and is hosted on my company's content management system. My aim is to repurpose this video for online (and also publish screenshots as .jpegs).

When I export the files they come in MPEG IMX 625/50 format (.mxf file container).

If I open this file in QuickTime Player there are NO vertical blanking bars (well, maybe a couple of pixels either side but nothing major). QT's inspector pane shows the video as: "720 x 576 (767 x 576), 4:3 (pixel aspect 59:54)". What this says to me is "these are non-square pixels, but we've converted them to square pixel equivalent". Great — just as I'd expect!

However, while Final Cut Pro also says the video is "720 x 576 Rec. 601 (PAL)", it shows much wider vertical black bars. And likewise, when I export my edited video in Compressor using the "Apple Devices" setting the same black bars show (Compressor outputs at "768 x 576"). (Screenshot below shows the exported file in QT Player, but it looks the same in FCP)

A few questions...
1. Why the difference in the handling of the same file?
2. Why does FCP show "720" and not just convert to "768"? (after all, I'm on a computer monitor where the pixels are square!) Is the software assuming editors might be spitting the file back out to conventional TVs again rather than online?
3. How do I fix it? Should I scale the x-axis before I export from FCP and, if so, is this maintaining the proper 4:3 aspect ratio? Or should I be scaling both x- and y- axis in proportion? In otherwords, is that active picture area that I can see in proportion or not?!

My head hurts!

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