A7s III 4:2:2 choppy and stuttering playback on premiere pro 2022 (can't fix)

I'm facing the same problem. Sony files with subscrediting - 4:2:2 10 Bit 200 Mb, does not work smoothly in Premiere. And that's the trouble. More and more often we have to work with such a video format for client requests. Now 4K is becoming almost the main dominance of content in social networks. And 10-bit formats are increasingly coming and soon, if the situation is not corrected, Premiere will stall.

That rig just can't produce 120 frames per second of H.264 playback. The larger formats you specified almost certainly were in intra-frame codecs, where every frame is complete by itself, simply compressed.

The H.264/long-GOP codec works by only making a complete frame every 10-30 'actual' frames, and in-between, it stores a matrix or chart of the pixels that 1) have changed since the last complete or " i-frame " ... or 2) will change before the next i-frame ... or 3) both.

So the computer has to decompress and decode a bunch of frames at the same time simply to play each frame. Vastly higher computer resource demand.

And it's hard enough for 'normal' speed work, 24-30fps. You're running this at 120 fps! Yea, it's a ton of load on the computer.

You will probably need to make proxies of those clips to get smooth playback ... do say half-resolution Cineform or ProRes proxies, they'll play back so much better.

Neil