I'm dealing with footage from two Sony cameras recorded internally in UHD 3840 x 2160 at 23.976.
A Sony FS5 recorded in MXF OP1a, XAVC Long QFHD, h264/MPEG-4 8bit 4:2:0 at 100Mbps. Clips have 4 mono audio channels.
A Sony A7RII recorded in MP4, XAVC-S, h264/MPEG-4 AVC Long Gop 8bit 4:2:0 at 100Mbps. Clips have one stereo audio channel.
Importing original MXF and MP4 footage into PP is no problem, but PP playback of original UHD footage is very clunky for both the A7RII MP4 and the FS5 MXF at any settings: full, 1/2, 1/4.
So I created two Proxy and Ingest Presets in AME, one for each audio config, and I'm transcoding to Prores Proxy HD 1920x1080.
It took approximately 4 hours for AME to transcode 120GB of footage overnight which is about 2hrs and 15min. in duration. So roughly TWICE real time. The resulting proxy files are roughly HALF the size of the originals.
Premiere hanged during that process, I had to restart the app. On restart, all the footage from Day2 was not in the project. I re-imported the footage from Day2 in PP. The Proxies didn't show in the Browser.
I selected all clips and selected Proxy/Attach Proxies and then pointed at the first Proxy file. All files got reconnected automatically to their proxies.
I have separate folders for Day1 and Day2, both for originals and Proxies. This is due to the fact that I have duplicated clip names, so I want to keep things compartmented.
Toggling Original and proxy footage is seamless, just use the toggle button. Playback of proxies is smooth.
Export Media automatically reverts to using the original UHD footage. Exporting a 5min. UHD Timeline (or HD Timeline with all clips at 50% scale)\ to Prores Proxy 1080p or to h264 720p takes about 6min., so a little more than real time.
OK, so that's Proxies so far.
Now instead of working with the proxy workflow, I can upfront convert the UHD XAVC footage to Prores UHD. PP is perfectly capable of smooth 4K Prores playback on my machine. Export Media time also falls to near real time. So, it is not 4K that taxes the machine as much as it is the Sony XAVC codec.
If I edit 50% scaled UHD Prores clips into a HD Timeline, PP playback is flawless as well. Export Media time is below real time.
AME conversion time to transcode to Prores UHD is roughly twice that of transcoding to HD Proxies. In this case it will take 8 hours vs. 4 hours as mentioned above. That's one drawback.
So, ultimately I think I will use the non proxy workflow. I don't see why I would want to go back to a clunky codec at any time during post. Remember with PP proxy workflow, you are dealing with original media XAVC codec on export. That is a real slowdown.
Transcoding to UHD Prores has all the advantages: UHD frame size allowing for repo in a HD Timeline, an easy to deal with codec for the computer, and relatively fast export times. If something is not right with a Prores clip, it's easy to re-transcode from the original.
Granted files are bigger in UHD Prores HQ, five time as big as the original XAVC files, that's the second drawback, but drive space is cheap, so not an issue on this project.
Transcoded to Prores HD, the size would be somewhat less, and it might take less time for AME to transcode, but it would restrict the reframing possibilities that UHD has to offer.
