OK, heard back directly from Sony, so this is definitive:
1) For timeline video processing, Vegas uses OpenCL and only OpenCL. It also uses only one video card, so it will not leverage multiple cards. The card you choose is the one it will use, and it will not use more than that one.
2) For rendering MainConcept AVC and Sony AVC, it will leverage CUDA, OpenCL, or Intel QSV. This is set separately from the video processing GPU acceleration, so you can choose a separate card from the one you're using for video processing. Or you can choose the same card. This, too, uses only one card, and will not leverage multiple cards.
3) For GPU acceleration on the Preview Device, it uses the same card as you choose for video processing (not render processing), but can be seperately disabled for Preview Device purposes if there's a driver issue.
So . . .
Multiple cards will be beneficial if you wanted to use, say, CUDA for rendering AVC and AMD OpenCL for video processing. But multiple cards of the same type (like those two 580s) won't do you any good; Vegas is only ever using one card at a time.
A system with both Nvidia CUDA and AMD OpenCL could be utilized for separate functions (one for video processing, one for rendering AVC). However, as said, I would not mix competing video drivers.
I've asked a follow-up concerning SLi (or Crossfire).
As for AMD/ATi/Radeon vs. Nvidia by itself, well, people are making some persuasive arguments in favor of AMD cards for Vegas. I'm an Nvidia guy myself, for purposes wider than just Vegas, but if Vegas is your only concern, perhaps AMD is the way to go. I can't speak to it from experience (unlike with Intel vs. AMD processors).
1) For timeline video processing, Vegas uses OpenCL and only OpenCL. It also uses only one video card, so it will not leverage multiple cards. The card you choose is the one it will use, and it will not use more than that one.
2) For rendering MainConcept AVC and Sony AVC, it will leverage CUDA, OpenCL, or Intel QSV. This is set separately from the video processing GPU acceleration, so you can choose a separate card from the one you're using for video processing. Or you can choose the same card. This, too, uses only one card, and will not leverage multiple cards.
3) For GPU acceleration on the Preview Device, it uses the same card as you choose for video processing (not render processing), but can be seperately disabled for Preview Device purposes if there's a driver issue.
So . . .
Multiple cards will be beneficial if you wanted to use, say, CUDA for rendering AVC and AMD OpenCL for video processing. But multiple cards of the same type (like those two 580s) won't do you any good; Vegas is only ever using one card at a time.
A system with both Nvidia CUDA and AMD OpenCL could be utilized for separate functions (one for video processing, one for rendering AVC). However, as said, I would not mix competing video drivers.
I've asked a follow-up concerning SLi (or Crossfire).
As for AMD/ATi/Radeon vs. Nvidia by itself, well, people are making some persuasive arguments in favor of AMD cards for Vegas. I'm an Nvidia guy myself, for purposes wider than just Vegas, but if Vegas is your only concern, perhaps AMD is the way to go. I can't speak to it from experience (unlike with Intel vs. AMD processors).
