Fast Thumbnail Generation in Integer DCT Domain for H.264/AVC

In this paper, we propose a simple and efficient method for generating a thumbnail or 1/4 reduced-size image in integer Discrete Cosine Transform (DCT) domain for H.264/AVC video streams. To accomplish this, we first obtain the integer DCT coefficients of a prediction residual using a newly-defined re-scaling operation of inverse quantization, and then perform a transform domain intra prediction in integer DCT domain through simplified matrix multiplication by using only shift operation and integer addition. Finally, we generate a thumbnail directly from a H.264/AVC intra frame. Experimental results demonstrate that the proposed algorithm can reduce the total computational complexity about 16% on average, while maintaining almost the same image quality as compared to the existing method(1).