This is rather urgent. I've just finished rendering a video I've been working on. The general frame rate is 29.97 progressive and I took a specific shot at 59.94 progressive to use for a slow motion speed. After transcoding, I took them into premiere and used time remapping to turn part of the 60p video to 50 percent speed, which I thought would work smoothly since the frames already existed. In playback, it was choppy, but I attributed that to my HDD, which is the significant bottleneck in my system. Anyway, after export the video remained choppy in playback.
I've seen tutorials with time mapping 30p video which must create intermediate frames that don't look good, and I'm wondering if premiere pro did that to me or if you are aware of some other reason for this behavior.
Nope, once it's in a 30p timeline, for all intent and purpose that clip is now 30p... it's dropping frames.
I would work slightly backwards. In your library/bin, right click and go to properties > interpret footage. Set your framerate to 29.97. This will play back the 60p footage slower; a natural slow motion. I would then time remap the portions that need to be faster. This is in contrast to you trying to time remap the slower portions. I think you'll find the result more acceptable.