A detection algorithm for zero-quantized DCT coefficients in JPEG

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.