A fast video transcoder with adaptive drifting error control is proposed in this paper. Firstly, similar to the traditional close-loop transcoder, the proposed transcoder still accumulates the re-quantization errors of each I or P picture. However, the accumulated errors are not always introduced into the transcoding loop in every block. A triple-threshold algorithm is proposed to adaptively utilize the accumulated errors at block level so as to control the drifting error under an acceptable level. Secondly, the re-quantization process can be simply implemented by looking up table, which significantly reduces the complexity of the re-quantization process. The experimental results show that the picture quality obtained from the proposed transcoder is close to that of the traditional closed-loop one while about 50% blocks are not updated with the accumulated errors. In this case, the speed of the proposed transcoder is much faster than that of the traditional close-loop one, and even faster than that of the traditional open-loop one. Furthermore, the proposed transcoder provides the desired flexibility between picture quality and transcoding complexity in CPU-awareness applications.