Fast generating thumbnail in MBAFF mode of H.264/AVC intra-coded

In this paper, we propose a method for generating thumbnail images from the intra-sliced macroblock-adaptive frame/field coding mode in H.264/AVC bit stream. The pixel value of thumbnail image is combined by two elements: the average value of residual pixels, which is extracted in the transform domain, and the average value of estimated pixels, which is calculated in the pixel domain. Also, the pixels only required for the intra prediction in the pixel domain is reconstructed by using the reduced form of inverse integer discrete cosine transform. The thumbnail images produced by the proposed method are indistinguishable to the ones by the method that decodes the H.264/AVC-I slice bit streams and then scales them down. For most of images, the proposed method also executes at least 2 times faster than the full decoding method at frequently used bandwidths.