### Encoder denoiser performance improvement

The denoiser function was modified to reduce the computational complexity. 1. The denoiser c function modification: The original implementation calculated pixel's filter_coefficient based on the pixel value difference between current raw frame and last denoised raw frame, and stored them in lookup tables. For each pixel c, find its coefficient using filter_coefficient[c] = LUT[abs_diff[c]]; and then apply filtering operation for the pixel. The denoising filter costed about 12% of encoding time when it was turned on, and half of the time was spent on finding coefficients in lookup tables. In order to simplify the process, a short cut was taken. The pixel adjustments vs. pixel diff value were calculated ahead of time. adjustment = filtered_value - current_raw = (filter_coefficient * diff + 128) >> 8 The adjustment vs. diff curve becomes flat very quick when diff increases. This allowed us to use only several levels to get a close approximation of the curve. Following the denoiser algorithm, the adjustments are further modified according to how big the motion magnitude is. 2. The sse2 function was rewritten. This change made denoiser filter function 3x faster, and improved the encoder performance by 7% ~ 10% with the denoiser on. Change-Id: I93a4308963b8e80c7307f96ffa8b8c667425bf50

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