All-zero block detecting algorithm based on look-up threshold tables in H.264

In H.264 video coding, there are a substantial number of all-zero discrete cosine transform (DCT) coefficient blocks. This is a waste of computational resources because these all-zero blocks do not require forward transform and quantization. Most of the proposed algorithm before only used the characteristics of both DCT formula and quantization to get the thresholds to decide a block whether is an all-zero block or not is. However, using the DCT formula and quantization cannot get the best thresholds to early terminate, and the thresholds are all been calculated from relative formula and this consumes a lot of time. This paper established a lookup threshold table that derived from statistics characteristics of all-zero blocks. The threshold can be look-up from the threshold table and the thresholds are more accurate. By using the proposed algorithm to H.264 video encoding, the simulation results show that the all-zero block detection ratio is about 10%-18% higher and it achieves up to 21% computational saving with no video quality degradation, compared with results of the existing method.