1. Developing the Demosaicing Algorithm in GPGPU Ping Xiang Electrical engineering and computer science

2. Outline Background Algorithm Implementation Experiment Results Future Work

3. Background 1.Color Filter Array. A mosaic of color filters in front of the image sensor

4. Background Demosaicing algorithm is to reconstruct a full color image from the data collected by the color filtering array.

5. Algorithm Bilinear interpolation: The red value of a non-red pixel is computed by the average of the two or four adjacent red pixels, and similarly for blue and green.

6. Algorithm

8. For Green Channels

9. Algorithm For Red or Blue Channels

10. Implementation Optimization: 1. Vectorize the pixel data to be processed 2. use shared memory to reduce the data transfer

11. Implementation 1. Vectorize the pixel data to be processed

12. Implementation 2. Use shared memory to reduce the data transfer

13. Experiment Results Platform: ATI Radeon™ HD 4870 Brook+ 1.4 Nvidia GeForce 8800 GTX CUDA 2.1 Dual Core AMD Opteron(tm) 2212 Frequency 2.0GHz

14. Experiment Results For small data size, GPU is not always a good choice a. Memory transfer time dominates the kernel execution time b. Computation is not that complex enough

15. Experiment Results When the data size is small, CUDA has better performance. When the data size increases to 4K, the brook+ performance catches up with CUDA

16. Experiment Results Explanation ? Memory SpeedStream processing Units HD 48708008*5*10*2 GTX 8800128(16*8)

17. Experiment Results Shared Register Usage Read data into shared register and try to reuse the data

18. Experiment Results

19. Future Work 1. Shared memory usage for further optimization 2. Integrate the code with proper interface to import image data and export pixel data 3. Report

20. Reference 1. High-Quality linear interpolation for Demosaicing of Bayer-patterned color images, Henrique S. Malvar, Li-wei He, and Ross Cutler 2. An Improved Demosaicing Algorithm Alexey Lukin, Denis Kubasov Questions?