Activity normalization for video encoding

1. A method for calculating a quantization value used during encoding of a video sequence, the method comprising the steps of:

a) providing a predetermined activity metric for a portion of the video sequence;

b) determining a minimum normalized activity value and a maximum normalized activity value for the portion of the video sequence;

c) calculating, on one or more microprocessors, a set of normalization activity parameters based at least in part on the minimum normalized activity value and the maximum normalized activity value;

d) determining, on the one or more microprocessors, a normalized activity value as a function of the set of normalization parameters;

e) determining, on the one or more microprocessors, a quantization value based at least in part on the normalized activity value; and

f) encoding, on the one or more microprocessors, the portion of the video sequence using the quantization value.

2. The method of claim 1 wherein the portion of the video sequence comprises a frame of the video sequence.

3. The method of claim 1 wherein the minimum normalized activity value is greater than 0 and less than 1.

4. The method of claim 1 wherein the maximum normalized activity value is greater than 1.

5. The method of claim 1 wherein the determination of the normalization activity parameters assures that the average normalized activity value is equal to 1 for the portion of the video sequence regardless of the predetermined activity metric.

6. The method of claim 1 wherein the set of normalization activity parameters comprises a first parameter C, a second parameter D, and third parameter m, and the function for determining the normalized activity value for the portion of the video sequence comprises adding C to the predetermined activity metric for the portion, and dividing the result by the sum of D and the product of m and the predetermined activity metric.

7. A method for encoding a video sequence, the method comprising the steps of:

selecting a method of assessment of video quality based on a human visualization system;

calculating, on one or more microprocessors, a normalized activity value that optimizes the encoding of the video sequence according to the chosen method of assessment;

calculating, on the one or more microprocessors, a quantization step size based on the normalized activity metric; and

encoding, on the one or more microprocessors, the video sequence using the quantization step size.

8. The method of claim 7 further comprising calculating, on the one or more microprocessors, the normalized activity value for each block within a frame of the video sequence.

9. The method of claim 8 wherein the normalized activity value calculated for each block is based on a predetermined activity metric.

10. A non-transitory computer-readable medium encoded with a program for calculating a quantization value used during the encoding of a video sequence, that, when executed by at least one microprocessor, performs a method comprising:

a) providing a predetermined activity metric for a portion of the video sequence;

b) determining a minimum normalized activity value and a maximum normalized activity value for each portion of the video sequence;

c) determining a set of normalization activity parameters based at least in part on the minimum normalized activity value and the maximum normalized activity value;

d) determining a normalized activity value as a function of the set of normalization parameters; and

e) determining a quantization step size based at least in part on the normalized activity value; and

f) encoding each portion of the video sequence using the quantization step size.

11. An apparatus for encoding video data, comprising:

at least one microprocessor configured to

select an activity metric;

select a method of assessment of encoded video quality based on a human visualization system;

select an optimal minimum normalized activity value and optimal maximum normalized activity value based on the selected activity metric and the human visualization system;

calculate a set of normalization activity parameters;

calculate a normalized activity value to be used for encoding the video data based on the activity value and the normalization activity parameters;

calculate a quantization value based on the normalized activity value; and

encode the video data using the quantization value.

12. The apparatus of claim 11 wherein the at least one microprocessor is further configured to calculate the normalized activity value for each block within a frame of the video sequence.

13. The apparatus of claim 11 wherein the at least one microprocessor is further configured to calculate the normalized activity value for each block based on the selected activity metric and the calculated set of normalization activity parameters.

14. An apparatus for determining a quantization value used during encoding of a video sequence, comprising:

at least one microprocessor configured to

provide a predetermined activity metric for a portion of the video sequence;

determine a minimum normalized activity value and a maximum normalized activity value for the predetermined activity metric;

determine a set of normalization activity parameters;

determine a normalized activity value as a function of the set of normalization parameters and the predetermined activity metric;

determine a quantization step size based at least in part on the normalized activity value; and

encode the portion of the video sequence using the quantization step size.

15. The apparatus of claim 14 wherein the portion of the video sequence comprises a frame of the video sequence.

16. The method of claim 14 wherein the minimum normalized activity value is greater than 0 and less than 1.

17. The method of claim 14 maximum normalized activity metric is greater than 1.

18. The method of claim 14 wherein the determination of the normalization activity parameters assures that the average normalized activity value is equal to 1 for the a number of portions of the video sequence regardless of the predetermined activity metric.

19. The method of claim 14 wherein the set of normalization activity parameters comprises a first parameter C, a second parameter D, and third parameter m, and the function for determining the normalized activity value for the portion of the video sequence comprises adding C to the predetermined activity value for the portion, and dividing the result by the sum of D and the product of m and the predetermined activity value.