I saw a post about this from 3 years ago, but wanted to give my own account of this issue in 2022.
I do a lot of movie montages for various LA studios and clients. I am ussually given MP4 files to edit with, but always prefer editing with ProRes Proxy for the smoothness of playback.
But of course, ProRes takes up far more space. I've always wanted a workflow where I could have the convenience of editing in ProRes, but the small storage space of H264 files.
In one sense, Premiere's Proxy workflow should be a dream come true. I should be able to convert those pesky MP4 files into ProRes, have a smooth editing experience, but when the project is done delete the Proxies and have a much more compressed project size to archive.
But in reality, it NEVER works this way. I will convert all of my films given to me to ProRes via the Proxy workflow. But when I go to toggle, the proxies are almost always 2-3 frames off sync. That means with edited feature films, I have flash frames galore in my cuts.
I've tried this with Premiere's internal settings via Media Encoder. I've also tried this with third-party apps like EditReady and Compressor, and attaching the Proxies manually. Same thing every time. Every time I update Premiere, I think maybe this is fixed. I just went to 2022, and thought I'd try it. But disappointingly the same issue occurs.
Is no one else having this problem?
My only guess is that it is a framerate issue. Sometimes footage comes in and Premiere interprets it as 23.98 instead of 23.976. Even then, I will conform and interpret the footage to 23.976, make the Proxies, and the same frame-off issue occurs.
I'm sorry about that. I am currently on vacation, but I can look into this when I get back into the office. Contact Adobe Support if you need immediate assistance.
I think I've seen this complaint before and looked into it. Forgive me if I am wrong about this, as my memory can sometimes play tricks on me!
As I recall, the issue is that any time you have Long GOP-based source footage and create proxies from that footage, there might be some frame errors. I guess you could describe your problem as the nature of the "H.264 beast." The codec was not initially designed for use in post-production, so we have to live with some of its shortcomings (like frame accuracy on transcodes).
A workflow to get around the Long GOP frame-accurate flakiness is what you might try to achieve. You might try ProRes LT, 422, or HQ transcodes and cut with those. Take the extra step of creating ProRes Proxy proxies if you like or for portability's sake. See if your proxies match your transcodes then. If they do, you can verify it's a source footage issue.
You could archive the .mp4 files and transcode again if you ever need to restore a project, which is usually rare (except for certain edge cases). You'd have to fix those flash frames, etc., probably. Archiving the ProRes files might take up too much room for most people. Otherwise, you can delete all these ProRes files after the project is wrapped.
Yup, I personally hate H.264 which is why I don't cut with it. The workflow you suggested is my standard workflow.
I just hoped this might be a good solution as an automated one. It's SO close to be EXACTLY what I need! And it's always consistantly off by 2-3 frames depending on the video (and sometimes not off at all).
It would be awesome if there were some sort of "correction" feature built into the Proxy Workflow, where if things are off by a frame or two, you could manaully tell Premiere to correct for it. And obviously, Premiere's AI is smart enough to read frames, like in your amazing scene edit detection feature. Would be great if there was a way for the AI to "check" the frame was accurate before linking them.