Method and apparatus for control of rate-distortion tradeoff by mode selection in video encoders
A Method And Apparatus For Control of Rate-Distortion Tradeoff by Mode Selection in Video Encoders is Disclosed. The system of the present invention first selects a distortion value D near a desired distortion value. Next, the system determines a quantizer value Q using the selected distortion value D. The system then calculates a Lagrange multiplier lambda using the quantizer value Q. Using the selected Lagrange multiplier lambda and quantizer value Q, the system begins encoding pixelblocks. If the system detects a potential buffer overflow, then the system will increase the Lagrange multiplier lambda. If the Lagrange multiplier lambda exceeds a maximum lambda threshold then the system will increase the quantizer value Q. If the system detects a potential buffer underflow, then the system will decrease the Lagrange multiplier lambda. If the Lagrange multiplier lambda falls below a minimum lambda threshold then the system will decrease the quantizer value Q.
1. A method of controlling rate distortion in a video compression and encoding system, said method comprising:
selecting a distortion value D near a desired distortion value;
determining quantizer value Q using said distortion value D;
calculating a Lagrange multiplier lambda using said quantizer value Q;
encoding a pixelblock using said Lagrange multiplier lambda and said quantizer value Q;
increasing said Lagrange multiplier lambda when a buffer exceeds an overflow threshold value and increasing said quantizer value Q if said Lagrange multiplier lambda exceeds a maximum lambda threshold; and
decreasing said Lagrange multiplier lambda when a buffer falls below an underflow threshold value and decreasing said quantizer value Q if said Lagrange multiplier lambda falls below a minimum lambda threshold.
2. The method as claimed in claim 1 , said method further comprising:
recalculating said Lagrange multiplier lambda if said quantizer value Q is adjusted.
3. The method as claimed in claim 1 , said method further comprising wherein said Lagrange multiplier lambda is increased or decreased by an amount dependent upon said quantizer value Q.
4. A method of controlling rate distortion in a video compression and encoding system, said method comprising:
selecting a distortion value D near a desired distortion value;
determining a quantizer value Q using said distortion value D;
calculating a Lagrange multiplier lambda using said quantizer value Q;
encoding a pixelblock using said Lagrange multiplier lambda and said quantizer value Q;
calculating a visual mask value M; and
increasing said Lagrange multiplier lambda when said visual mask value M times said Lagrange multiplier lambda is less than a maximum threshold for said Lagrange multiplier lambda.
5. The method as claimed in claim 4 wherein said maximum threshold for said Lagrange multiplier lambda is dependent upon said quantizer value Q.
6. The method as claimed in claim 4 , said method further comprising:
increasing said Lagrange multiplier lambda when a buffer exceeds an overflow threshold value and increasing said quantizer value Q if said Lagrange multiplier lambda exceeds a maximum lambda threshold; and
decreasing said Lagrange multiplier lambda when a buffer falls below an underflow threshold value and decreasing said quantizer value Q if said Lagrange multiplier lambda falls below a minimum lambda threshold.
7. The method as claimed in claim 6 , said method further comprising:
recalculating said Lagrange multiplier lambda if said quantizer value Q is adjusted.
8. A computer-readable medium, said computer-readable medium containing a set of computer instructions for implementing a method of controlling rate distortion in a video compression and encoding system with the following steps:
selecting a distortion value D near a desired distortion value;
determining a quantizer value Q using said distortion value D;
calculating a Lagrange multiplier lambda using said quantizer value Q;
encoding a pixelblock using said Lagrange multiplier lambda and said quantizer value Q;
increasing said Lagrange multiplier lambda when a buffer exceeds an overflow threshold value and increasing said quantizer value Q if said Lagrange multiplier lambda exceeds a maximum lambda threshold; and
decreasing said Lagrange multiplier lambda when a buffer falls below an underflow threshold value and decreasing said quantizer value Q if said Lagrange multiplier lambda falls below a minimum lambda threshold.
9. The computer-readable medium as claimed in claim 8 wherein said set of computer instructions further implement the steps of:
recalculating said Lagrange multiplier lambda if said quantizer value Q is adjusted.
10. The computer-readable medium as claimed in claim 8 wherein said Lagrange multiplier lambda is increased or decreased by an amount dependent upon said quantizer value Q.
11. A computer-readable medium, said computer-readable medium containing a set of computer instructions for implementing a method of controlling rate distortion in a video compression and encoding system with the following steps:
selecting a distortion value D near a desired distortion value;
determining a quantizer value Q using said distortion value D;
calculating a Lagrange multiplier lambda using said quantizer value Q;
encoding a pixelblock using said Lagrange multiplier lambda and said quantizer value Q;
calculating a visual mask value M; and
increasing said Lagrange multiplier lambda when said visual mask value M times said Lagrange multiplier lambda is less than a maximum threshold for said Lagrange multiplier lambda.
12. The computer-readable medium as claimed in claim 11 wherein said maximum threshold for said Lagrange multiplier lambda is dependent upon said quantizer value Q.
13. The computer-readable medium as claimed in claim 11 wherein said set of computer instructions further implement the steps of:
increasing said Lagrange multiplier lambda when a buffer exceeds an overflow threshold value and increasing said quantizer value Q if said Lagrange multiplier lambda exceeds a maximum lambda threshold; and
decreasing said Lagrange multiplier lambda when a buffer falls below an underflow threshold value and decreasing said quantizer value Q if said Lagrange multiplier lambda falls below a minimum lambda threshold.
14. The computer-readable medium as claimed in claim 13 wherein said set of computer instructions further implement the steps of:
recalculating said Lagrange multiplier lambda if said quantizer value Q is adjusted.