I just did an quick test with my usual setup, assuming you mean Full Resolution 2.1 DNG-Files.
I used My Adobe After Effects CS6, running on even older Hardware, an 4 Core i7 (i7-4720HQ+GTX960M, Laptop), though i dont really know how much After Effects used the GPU for this operation. I put a 100 DNG-Frame Sequence in, didnt change anything on them, no effects added, no denoise, nothing, just the DNG with untouched Settings, exporting as h.264 with a Setting of 8 MBps Bitrate. Did take 31 Seconds to finish the Render for the 100 Frames, so should be around 3,2fps export speed. Gets quite a bit slower if denoising and or sharpening is added, Whitebalance and general Color adjustments seem to slow it down a bit, but by far not as much as denoise and Sharpening.
Isnt really that fast, but Image Quality is very good from the Internal Adobe Camera Raw Converter.
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#EDIT: Also, should say, will propably run quite a bit faster on more Recent hardware with the Newest CC Version of After Effects, would at least expect somewhere between 10-30fps or even more on an fast CPU/ GPU combination