Bayer bilateral denoising on TriMedia3270

Digital cameras are now commonly included in several digital devices such as mobile phones. They are present everywhere and have become the principal image capturing tool. Inherent to light and semiconductors properties, sensor noise [10] continues to be an important factor of image quality [12], especially in low light conditions. Removing the noise with mathematical solutions appears thus unavoidable to obtain an acceptable image quality. However, embedded devices are limited by processing capabilities and power consumption and thus cannot make use of the full range of complex mathematical noise removing solutions. The bilateral filter [6] appears to be an interesting compromise between implementation complexity and noise removing performances. Especially, the Bayer [5] bilateral filter proposed in [11] is well adapted for single sensor devices. In this paper, we simulate and optimize the Bayer bilateral filter execution on a common media-processor: the TM3270 [4] from the NXP Semiconductors TriMedia family. To do so we use the TriMedia Compilation System (TCS). We applied common optimization techniques (such as LUT, loop unrolling, convenient data type representation) as well as custom TriMedia operations. We finally propose a new Bayer bilateral filter formulation dedicated to the TM3270 architecture that yields an execution improvement of 99.6% compared to the naïve version. This improvement results in real-time video processing at VGA resolution at the 350MHz clock rate.