Patent ID: 8588296

Claim:
A method of performing rate control in a video transcoding system, comprising the steps of: receiving, by the video transcoding system, an input video bitstream including a plurality of frames in an input video sequence, wherein each frame in the input video bitstream is in a first coding format; for each of at least some of the plurality of frames in the input video bitstream: decoding the respective frame using a predetermined type of video decoder; obtaining complexity information indicative of the complexity of the respective frame after decoding, the complexity information including a number of bits used by the respective frame, an average quantization parameter (QP avg ) used to encode the respective frame, and an indication of the predetermined type of video decoder used in the decoding of the respective frame; in a first calculating step, calculating an estimated number of bits to allocate for the respective frame; in a second calculating step, calculating, using a rate estimation model, a picture cost for the respective frame based on the estimated number of bits to allocate for the respective frame, and a model parameter for the rate estimation model; in a third calculating step, calculating a target number of non-zero discrete cosine transform (DCT) coefficients for the respective frame based at least in part on the picture cost for the respective frame, and the complexity information obtained for the respective frame after decoding; in a fourth calculating step, calculating a quantization parameter (QP) that, when used to quantize the plurality of DCT coefficients, a number of non-zero quantized coefficients approximately equal to the target number of non-zero DCT coefficients is generated; and encoding the respective frame using the calculated QP; and providing the respective frames encoded in the second coding format in an output video bitstream.