Methods for RDO (rate-distortion optimization) based on fit-curves and apparatuses using the same
A method for RDO (Rate-Distortion Optimization) based on fit-curves contains at least the following steps: calculating a first fit-curve and a second fit-curve according to information regarding a first frame; carrying information regarding a second frame into the first and second fit-curves to calculate fit distortions and fit bit counts; calculating costs according to the fit distortions and the fit bit counts; determining the best block-division mode for the second frame according to the costs; and dividing the second frame into blocks according to the best block-division mode and encoding the second frame.
1. A method for RDO (Rate-Distortion Optimization) based on fit-curves, comprising:
calculating a first fit-curve and a second fit-curve according to information regarding a first frame;
carrying information regarding a second frame into the first and second fit-curves to calculate a plurality of fit distortions and a plurality of fit bit counts;
calculating a plurality of costs according to the fit distortions and the fit bit counts;
determining the best block-division mode for the second frame according to the costs; and
dividing the second frame into blocks according to the best block-division mode and encoding the second frame;
wherein the step for calculating a first fit-curve and a second fit-curve according to information regarding a first frame further comprises:
obtaining a plurality of first distortions between a plurality of original pixel values and a plurality of predicted pixel values of a plurality of PUs (Prediction Units) of the first frame;
obtaining a plurality of second distortions between the original pixel values and a plurality of reconstructed pixel values of the PUs of the first frame;
calculating the first fit-curve according to the first distortions and the second distortions;
obtaining a plurality of first absolute values of syntax of residuals of the PUs of the first frame;
obtaining a plurality of bit counts required to encode the first frame; and
calculating the second fit-curve according to the first absolute values of syntax of residuals and the bit counts;
wherein the step for calculating the first fit-curve according to the first distortions and the second distortions further comprises:
calculating the first fit-curve using Equations (1) and (2):
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wherein x i1 indicates the distortion between the original pixel value and the predicted pixel value of the i-th PU and y i1 indicates the distortion between the original pixel value and the reconstructed pixel value of the i-th PU, and a 1 , b 1 , c 1 and d 1 indicates coefficients of the first fit-curve; and
calculating the second fit-curve using Equations (3) and (4):
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wherein x i2 indicates the first absolute value of syntax of residual of the i-th PU and y i2 indicates the bit count required to encode the syntax of the i-th PU, and a 2 , b 2 , c 2 , and d 2 indicates coefficients of the second fit-curve.
2. The method of claim 1 , wherein the first fit-curve and the second fit-curve are third-order functions.
3. The method of claim 1 , wherein the step for carrying information regarding a second frame into the first and second fit-curves to calculate a plurality of fit distortions and a plurality of fit bit counts further comprises:
obtaining a plurality of third distortions between a plurality of original pixel values and a plurality of predicted pixel values of a plurality of PUs of the second frame;
carrying the third distortions into the first fit-curve to calculate the fit distortions;
obtaining a plurality of second absolute values of syntax of residuals of the PUs of the second frame; and
carrying the second absolute values of syntax of residuals into the second fit-curve to calculate a plurality of fit bit counts.
4. The method of claim 3 , wherein the step for calculating a plurality of costs according to the fit distortions and the fit bit counts further comprises:
calculating the costs using Equation (5):
min{ J},J=D+λ·R (5)
wherein λ indicates a Lagrange constant, D′ indicates the fit distortions, R′ indicates a total amount of the fit bit counts, and J indicates the costs.
5. An apparatus for RDO (Rate-Distortion Optimization) based on fit-curves, comprising:
an intra-frame/inter-frame prediction module;
an RD cost calculation module; and
a curve-fitting module,
wherein the curve-fitting module calculates a first fit-curve and a second fit-curve according to information regarding a first frame; and carries information regarding a second frame into the first and second fit-curves to calculate a plurality of fit distortions and a plurality of fit bit counts,
wherein the RD cost calculation module calculates a plurality of costs according to the fit distortions and the fit bit counts, and
wherein the intra-frame/inter-frame prediction module determines the best block-division mode for the second frame according to the costs; and divides the second frame into blocks according to the best block-division mode and encodes the second frame;
wherein the apparatus further comprises:
a distortion calculation module; and
an entropy coding module,
wherein the curve-fitting module obtains a plurality of first distortions between original pixel values and a plurality of predicted pixel values of a plurality of PUs (Prediction Units) of the first frame from the intra-frame/inter-frame prediction module; obtains a plurality of second distortions between the original pixel values and a plurality of reconstructed pixel values of the PUs of the first frame from the distortion calculation module; calculates the first fit-curve according to the first distortions and the second distortions; obtains a plurality of first absolute values of syntax of residuals of the PUs of the first frame from the intra-frame/inter-frame prediction module; obtains a plurality of bit counts required to encode the first frame from the entropy coding module; and calculates the second fit-curve according to the first absolute values of syntax of residuals and the bit counts;
wherein the first fit-curve is calculated using Equations (1) and (2):
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wherein x i1 indicates the distortion between the original pixel value and the predicted pixel value of the i-th PU and y i1 indicates the distortion between the original pixel value and the reconstructed pixel value of the i-th PU, and a 1 , b 1 , c 1 and d 1 indicates coefficients of the first fit-curve; and
wherein the second fit-curve is calculated using Equations (3) and (4):
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wherein x i2 indicates the first absolute value of syntax of residual of the i-th PU and y i2 indicates the bit count required to encode the syntax of the i-th PU, and a 2 , b 2 , c 2 and d 2 indicates coefficients of the second fit-curve.
6. The apparatus of claim 5 , wherein the first fit-curve and the second fit-curve are third-order functions.
7. The apparatus of claim 5 , wherein the curve fitting module obtains a plurality of third distortions between a plurality of original pixel values and a plurality of predicted pixel values of PUs of the second frame from the intra-frame/inter-frame prediction module; carries the third distortions into the first fit-curve to calculate the fit distortions; obtains a plurality of second absolute values of syntax of residuals of the PUs of the second frame from the intra-frame/inter-frame prediction module; and carries the second absolute values of syntax of residuals into the second fit-curve to calculate fit bit counts.
8. The apparatus of claim 7 , wherein the costs is calculated using Equation (5):
min{ J},J=D+λ·R (5)
wherein λ indicates a Lagrange constant, D′ indicates the fit distortions, R′ indicates a total amount of the fit bit counts, and J indicates the costs.