MP4 not opening in PS

"How to open an AVC file.

To open an H.264 file format, you’ll need a media player with enough processing power to handle the intensive encoding and decoding required. Software like VideoLAN VLC Media Player is a common choice for most professional and consumer level users looking to watch AVC files on their computer.

You might need to right-click on the AVC file and select “Open With,” choosing VLC (or your chosen platform) as the option. That’s because selected media players may not automatically recognize H.264 files as playable video content."

"Is AVC an MP4?

No, but the two are similar." [read that section for yourself; I won't reproduce it here, for brevity]

"What type of files can I convert AVC into?

You’ll need to convert your H.264 into an editable file format if you want to make changes. You can convert into files like MOV and MP4. Once you’ve converted your video file, you can make changes in your chosen software." [implying that AVC needs to be converted before editing in Ps?]

"H.264s are for displaying video only, so you can’t edit them natively. To edit an H.264, you’ll need to convert the video into a codec suitable for your particular software, like MPEG, MP4, or even a MOV file. Then you’ll be able to edit in programs like Adobe Premiere Pro."

And just like that, my brain is on E.