The discrete cosine transform (DCT) is widely used in image/video coding standards. However, since most DCT coefficients will be quantized to zeros, a large number of redundant computations are introduced. This paper presents an early detection algorithm to predict zero-quantized DCT coefficients for fast JPEG encoding. Based on the theoretical analysis for 2-D DCT and quantization in JPEG standard, we derive a sufficient condition under which each quantized coefficient becomes zero. Finally, the transform of the zero-quantized coefficients is omitted. Experimental results show that the proposed algorithm can significantly reduce the redundant computations and speed up the image encoding. Moreover, it doesn't cause any performance degradation. Computational reduction also implies longer battery lifetime and energy economy for digital applications.
['Jin Li', 'Jarmo Takala', 'Moncef Gabbouj', 'Hexin Chen']
A detection algorithm for zero-quantized DCT coefficients in JPEG