Patent ID: 7991048

Claim:
A device for double pass encoding of a video data stream comprising: a first type encoding means performing the first encoding pass, a second type encoding means different from the first type encoding means performing the second encoding pass using encoding information originating from the first encoding pass, means of regulating the bit rate of the data stream originating from the second pass encoding means comprising: prediction means which compute a relative weight of the image to be encoded in the reference period, regulation means which compute a target cost of the image to be encoded by the second type encoding means on the basis of a target bit rate received from the second type encoding means and the relative weight of the image to be encoded in the reference period, means of quantizing second type encoding which compute the quantization step to be applied to each image to be encoded by the second type encoding means on the basis of the target cost of the image and wherein the prediction means comprise: computing a ratio, known as non-reducible cost ratio, of the non-reducible encoding cost of the first pass over the non-reducible encoding cost of the second pass for each image to be encoded, computing a ratio, known as complexity ratio, of the complexity of first pass encoding over the complexity of second pass encoding for each image to be encoded, updating a complexity ratio averaged on the basis of the complexity ratio of the last images encoded and updating a non-reducible cost ratio averaged on the basis of the non-reducible cost ratio of the last images encoded, estimating the complexity of the current image to be encoded by the second type encoding means on the basis of the averaged complexity ratio and of the complexity of second type encoding of the said image, estimating the non-reducible cost of the current image to be encoded by the second type encoding means on the basis of the ratio of averaged non-reducible cost and the non-reducible cost of first type encoding of the said image, estimating the non-reducible cost of the reference period to which the current image belongs, computing the complexity of the reference period to which the current image belongs, computing the relative weight of the current image as being the ratio between the complexity of the current image and the total complexity of the reference period to which the current image belongs.