Patent ID: 9100656
Filing Date: 2015-08-04
Classification: H04N

Abstract:
1. A method of improving efficiency in transcoding a video sequence comprised of input Inter frames, each input Inter frame comprising one or more input macro blocks of pixels encoded in a first format, into a sequence of output Inter frames, each output Inter frame comprising one or more output macro blocks of pixels encoded in a second format, the method comprising: (a) determining a set of candidate coding modes for a macro block of the second format depending on coding modes used for coding macro blocks of the first format, comprising limiting the set of candidate coding modes based on comparison of residual information of a macro block of the first format, which is to be transcoded into the macro block in the second format, and residual information of two or more macro blocks of the first format already transcoded for one or more of the previous frames in the sequence of input frames; (b) determining, for each candidate coding mode in the set of the candidate coding modes, a value of a cost function, characterizing distortion and bitrate for the macro block; (c) selecting a coding mode for the macro block of the second format from among the set of the candidate coding modes, the selected coding mode having the lowest value of the cost function; and (d) refining motions vectors for the candidate coding modes except those where a coding mode for the macro block in the first format is the same as a coding mode for the macro block in the second format, and where a residual information of the macro block of the first format does not exceed a threshold associated with average relative residual information of two or more macro blocks of the first format already transcoded for one of the previous frames in the sequence of input frames, the macro block in the first format and the two or more macro blocks of the first format being coded in the same coding mode.