Estimation of I frame average rate quantization parameter (QP) in a group of pictures (GOP)

1. A method of Rate-QP estimation for an I picture, comprising:

(a) providing an input group of pictures (GOP);

(b) selecting an input I picture within the input group of pictures; and

(c) outputting, to a computer readable medium, a bit rate corrected Rate-QP, R(QP), for the input I picture, comprising:

calculating an intra luma (Y) Rate-QP estimate from an intra luma (Y) histogram;

calculating an intra chroma (C) Rate-QP estimate from an intra chroma (C) histogram;

offsetting the intra chroma (C) Rate-QP estimate to form an offset intra chroma (C) estimate; and

setting a Rate-QP for the input I picture to a sum of:

(i) the intra luma (Y) Rate-QP estimate; and

(ii) the offset intra chroma (C) Rate-QP estimate.

2. The method of claim 1 , wherein the outputting the bit rate corrected Rate-QP step comprises correcting the Rate-QP of the input I picture to produce the bit rate corrected Rate-QP, R(QP).

3. The method of claim 2 , wherein the correcting the bit rate corrected Rate-QP step comprises:

(a) partitioning a set of ordered pairs of (QP, Rate-QP) into a plurality of correction regions; and

(b) applying mapping functions for QP values in each of the correction regions to produce the bit rate corrected Rate-QP, R(QP).

4. The method of claim 3 , wherein the plurality of correction regions comprise:

(a) a high bit rate correction region;

(b) a medium bit rate correction region; and

(c) a low bit rate correction region.

5. The method of claim 4 , further comprising applying a linear interpolation for QP values in the high bit rate correction region.

6. The method of claim 4 , further comprising applying a medium bit rate correction for QP values in the medium bit rate correction region.

7. The method of claim 4 , further comprising applying a low bit rate correction for QP values in the low bit rate correction region.

8. The method of claim 1 , wherein the intra luma (Y) histogram, and the intra chroma (C) histogram are accumulated, for every macroblock in the group of pictures, in steps comprising:

(a) forming an estimate of a set of intra prediction coefficients;

(b) for each macroblock, separating the set of intra prediction coefficients into an output accumulated intra luma (Y) histogram and an accumulated intra chroma (C) histogram.

9. The method of claim 8 , wherein the selecting the intra mode step comprises:

(a) selecting the intra mode that has a lowest Sum of Absolute Transformed Differences (SATD) among intra modes using a set of inputs [x], H pos , V pos , {right arrow over (h)}, and {right arrow over (v)};

(b) wherein [x] is a 4×4 block of pixels within the input P picture and

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(c) wherein H pos is a horizontal pixel position of the 4×4 block within the image;

(d) wherein V pos is a vertical pixel position of the 4×4 block within the image;

(e) wherein {right arrow over (h)} is a vector immediately left of the 4×4 block [x], defined as {right arrow over (h)}≡(x 0,−1 ,x 1,−1 ,x 2,−1 ,x 3,−1 ) T relative to the indexing of the elements of [x];

(f) wherein {right arrow over (v)} is a vector immediately above the 4×4 block [x], defined as {right arrow over (v)}≡(x −1,0 ,x −1,1 ,x −1,2 ,x −1,3 ) T relative to the indexing of the elements of [x]; and

(g) wherein the lowest SATD intra mode is determined among a group comprising:

(i) a horizontal intra mode;

(ii) a vertical intra mode; and

(iii) a steady state (DC) intra mode.

10. The method of claim 9 , wherein the selecting the lowest SATD intra mode step comprises:

(a) calculating a horizontal predictor {right arrow over (H)}≡(H 0 , H 1 , H 2 , H 3 ) T , a vertical predictor {right arrow over (V)}≡(V 0 , V 1 ,V 2 ,V 3 ) T , and a steady state (DC) predictor D;

(b) calculating a horizontal cost precursor C hs and a vertical cost precursor C vs using the horizontal predictor {right arrow over (H)}, the vertical predictor {right arrow over (V)}, and the steady state (DC) predictor D; and

(c) calculating a horizontal intra mode cost C H , a vertical intra mode cost C V , and a steady state (DC) intra mode cost C D using the horizontal cost precursor C hs and the vertical cost precursor C vs .

11. The method of claim 10 , wherein the calculating of the horizontal predictor {right arrow over (H)}, the vertical predictor {right arrow over (V)}, and the steady state (DC) predictor D comprises:

(a) when H pos ≠0 and V pos ≠0 then:

(i) setting {right arrow over (H)}=(H 0 , H 1 , H 2 , H 3 ) T =[NDCT 4 ]{right arrow over (h)}

where {right arrow over (h)}≡(h 0 ,h 1 ,h 2 ,h 3 ) T (x 0,−1 ,x 1,−1 ,x 2,−1 ,x 3,−1 ) T ;

(ii) setting {right arrow over (V)}≡(v 0 ,v 1 ,v 2 ,v 3 ) T =[NDCT 4 ]{right arrow over (v)}

where {right arrow over (v)}≡(v 0 ,v 1 ,v 2 ,v 3 )≡(x −1,0 ,x −1,1 ,x −1,2 ,x −1,3 ) T ;

(iii) setting D=(H 0 +V 0 )/2;

(b) when H pos =0 and V pos ≠0 then:

(i) setting {right arrow over (H)}=(2 15 −1,0,0,0) T ;

(ii) setting {right arrow over (V)}≡(V 0 , V 1 ,V 2 ,V 3 ) T =[NDCT 4 ]{right arrow over (v)}

where {right arrow over (v)}≡(v 0 ,v 1 ,v 2 ,v 3 )≡(x −1,0 ,x −1,1 ,x −1,2 ,x −1,3 ) T ;

(iii) setting D=V 0 ;

(c) when H pos ≠0 and V pos =0 then:

(i) setting {right arrow over (H)}≡(H 0 ,H 1 ,H 2 ,H 3 ) T =[NDCT 4 ]{right arrow over (h)}

where {right arrow over (h)}≡(h 0 ,h 1 ,h 2 ,h 3 ) T ≡(x 0,−1 ,x 1,−1 ,x 2,−1 ,x 3,−1 ) T ;

(ii) setting {right arrow over (V)}=(2 15 −1,0,0,0) T ;

(iii) setting D=H 0 ; and

(d) when H pos =0 and V pos =0 then:

(i) setting {right arrow over (H)}=(2 15 −1,0,0,0) T ;

(ii) setting {right arrow over (V)}=(2 15 −1,0,0,0) T ; and

(iii) setting D=128×16.

12. The method of claim 10 , wherein the calculating of the horizontal cost precursor C hs and the vertical cost precursor C vs comprises:

(a) calculating the values X i,0 ,X 0,i , for iε0, 1, 2, 3 using the relationships

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(b) calculating the horizontal cost precursor

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(c) calculating the vertical cost precursor

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13. The method of claim 12 , wherein calculating the horizontal intra mode cost C H comprises calculating

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14. The method of claim 12 , wherein calculating the vertical intra mode cost C V comprises calculating

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15. The method of claim 12 , wherein calculating the steady state (DC) intra mode cost C D comprises calculating C D =|D−X 0,0 |+C hs +C vs .

16. The method of claim 10 , further comprising selecting the lowest SATD intra mode with a lowest associated intra mode cost among the group consisting of: the horizontal intra mode cost C H , the vertical intra mode cost C V , and the steady state (DC) intra mode cost C D .

17. A method of Rate-QP estimation for an I picture, comprising:

(a) providing an input group of pictures (GOP);

(b) selecting an input I picture within the input group of pictures; and

(c) outputting, to a computer readable medium, a bit rate corrected Rate-QP, R(QP), for the input I picture by correcting the Rate-QP of the input I picture to produce the bit rate corrected Rate-QP, R(QP);

(d) wherein correcting said Rate-QP comprises:

(i) partitioning a set of ordered pairs of (QP, Rate-QP) into a plurality of correction regions; and

(ii) applying mapping functions for QP values in each of the correction regions to produce the bit rate corrected Rate-QP, R(QP);

(e) wherein said plurality of correction regions comprise a high bit rate correction region, a medium bit rate correction region, and a low bit rate correction region.

18. The method of claim 17 , further comprising applying a linear interpolation for QP values in the high bit rate correction region.

19. The method of claim 17 , further comprising applying a medium bit rate correction for QP values in the medium bit rate correction region.

20. The method of claim 17 , further comprising applying a low bit rate correction for QP values in the low bit rate correction region.

21. A method of Rate-QP estimation for an I picture, comprising:

(a) providing an input group of pictures (GOP);

(b) selecting an input I picture within the input group of pictures; and

(c) outputting, to a computer readable medium, a bit rate corrected Rate-QP, R(QP), for the input B picture by correcting the Rate-QP of the input B picture to produce the bit rate corrected Rate-QP, R(QP);

(d) wherein correcting said Rate-QP comprises:

(i) partitioning a set of ordered pairs of (QP, Rate-QP) into a plurality of correction regions; and

(ii) applying mapping functions for QP values in each of the correction regions to produce the bit rate corrected Rate-QP, R(QP);

(e) wherein said correction regions comprise a low, medium, and high bit rate correction regions; and

(f) applying a linear interpolation for QP values in the high bit rate correction region.

22. The method of claim 21 , further comprising:

applying a medium bit rate correction for QP values in the medium bit rate correction region; and

applying a low bit rate correction for QP values in the low bit rate correction region.