Patent ID: 8902973

Claim:
A method of transcoding a coded video bitstream in a video transcoding system, comprising the steps of: receiving, at the video transcoding system from an external video encoder, a coded video bitstream including a plurality of video frames, each video frame including a plurality of macroblocks (MBs), the coded video bitstream being encoded in a first coding format, at least some of the plurality of MBs being encoded in accordance with a predetermined coding mode; decoding the plurality of video frames in the coded video bitstream; extracting predetermined information from the coded video bitstream; calculating, using at least some of the predetermined information, a likelihood value indicative of a likelihood that the coded video bitstream has been previously processed at the external video encoder to account for one or more perceptual insensitivity characteristics of a human visual system; performing a comparison of the likelihood value and a predetermined threshold value; in response to the comparison indicating the likelihood of the coded video bitstream being previously processed at the external video encoder, for each of at least some of the plurality of video frames in the coded video bitstream: calculating, using at least some of the predetermined information, a distortion imperceptibility value for each of at least some of the plurality of MBs in the video frame as a function of at least a difference between an actual quantization parameter (QP) used by the external video encoder to encode the macroblock (MB), and an average QP used by the external video encoder to encode the respective MBs, the distortion imperceptibility value representing the imperceptibility of a presence of distortion in the MB with respect to the human visual system; determining one or more quantization parameters (QPs) for the respective MBs encoded in accordance with the predetermined coding mode; adjusting the distortion imperceptibility value for each of at least some of the plurality of MBs in the video frame based at least on one or more of the determined QPs for the respective MBs encoded in accordance with the predetermined coding mode; calculating a QP for each of at least some of the plurality of MBs in the video frame using the adjusted distortion imperceptibility values for the respective MBs in the video frame; and encoding the video frame in a second coding format using the calculated QPs for the respective MBs in the video frame; and providing the plurality of video frames in an output video bitstream.