Got my Vegas Pro15 yesterday.
Good - MP4 Nvidia encoder when run on GeForce GTX 680 cuts rendering time in about half - CPU is i5-4670K no overclocking. Fantastic!
Bad - Editing multi(3)-track (2xGH4 4K streams, 1xAVCHD 1080p, all @24fps) is unacceptably slow. VegasPro 13 has no problems with those. Am I missing something?
I understand your argument if VP13 can edit those formats, why is VP15 struggling. With VP15 it sounds like vegas is attempting to use NVENC hardware for both encode(render) and decode(timeline.) This is a dramatic shift in from the way VP13 handled timeline footage. more than likely the 680 is over loaded with tasks, or the software is just not optimized for that generation of hardware and drivers. VP15 was most likely tested with the latest gear and not that heavily tested with legacy gear.
I would read some of the many posts on optimizing your pc for vegas. Also look up the VP15 minimum hardware for 4K and then improve on that by double if you can.
Alex, you're not the only one as Vegas Pro 14 handles files so much better than Vegas Pro15 on my system as well. Vegas 15 struggles with 4K 60fps MP4 files (to even preview let alone edit) from my c200 while VP14 handles them perfectly. VP15 struggles to preview even an 1080p HD clip with effects. The VP15 timeline lags heavily when editing. I still am editing in VP14 due to the lack of speed in VP15. The specs of my system should easily handle 4K files in VP15:
Processor: Core i7-5930K 3.5GHz 6-Core Processor
Graphics Card: Radeon R9 390 8GB
RAM: 32GB DDR4
Hard Drive: Videos files are edited from 512GB M.2-2280 Solid State Drive