The Google VP8 libvpx encoding library doesn't scale so well to all available 12-threads, with the stock i7-3960X performance being close to the i5-2500K Sandy Bridge, but when overclocked its performance jumped by 22%.
The Intel Core i7 3960X did much better with the x264 encoding benchmark over the other Sandy Bridge processors tested.
Interestingly, for the FFmpeg benchmark, the FX-8150, Core i5 2400S, and Core i5 2500K all did better than the Core i7 3960X for this video encoding test. This is quite odd, but this is not the most demanding video encoding test either.
For FLAC audio encoding, the Core i7 3960X returned to being the frontrunner.
The LAME MP3 encoding performance was also favorable to the Sandy Bridge-E processor.