Claims
- 1. A method of video bitrate transcoding comprising:extracting information comprising motion vectors and picture/macroblock (MB) type for all frames in a GOP from a bitstream; calculating a number of bits for encoding discrete cosine transform (DCT) coefficients by VLC decoding and transforming the bitstream into a DCT bitstream; determining a bitrate difference; dropping DCT coefficients based-upon the information in order to achieve the bitrate difference in the DCT bitstream; wherein the bitrate difference D is distributed into Intra-MB and Inter-MB groups based upon D=Dintra-MB+Dinter-MB(Dintra-MB)(Dinter-MB)=(A′p+A′b)(Ai+Ap+Ab) where A is the average bit count, i represents anchor frames, p represents predicted frames and b represents bidirectional frames.
- 2. A method in accordance with claim 1 wherein the bitrate difference is determined by a dynamic recurrence algorithm D1= NiNi+Np+Nb×Dintra-MBD2= NpNi+Np+Nb×Dintra-MBD3= NbNi+Np+Nb×Dintra-MBD4= Np′Np′+Nb′×Dinter-MBD5= Nb′Np′+Nb′×Dinter-MBwhere 1<=i<=5.
- 3. A method in accordance with claim 2 further comprising pre-analyzing the bitstream by parsing the bitstream and calculating coding complexity for the DCT bitstream.
- 4. A method in accordance with claim 3 wherein the coding complexity is determined with average bits for frame types by a dynamic recurrence algorithmA{i,p,b}=T{i,p,b}/N{i.p.b} and A′{p,b}=T′{p,b}/N′{p,b}where T(i,p,b) (T′(i,p,b)) are the total bit counts for an intra-MB (inter-MB) in frame I, P and B, respectively, N(i,p,b) (N′(i,p,b)) are the total number of intra-MBs (inter-MBs) in frame I, P and B, respectively, and I represents anchor frames, P represents predicted frames and B represents bidirectional frames.
- 5. A method in accordance with claim 4 wherein reference links are calculated for each picture/macroblock (MB) type based upon the motion vectors and the bitrate difference is determined by a dynamic recurrence algorithmDi=di1+di2+ . . . +din, anddi1·m1=di2·m2= . . . =di1·mn, where n is the number of MBs in category i, 1≦i≦5 and mi is the number of reduction bits.
- 6. A method of video bitrate transcoding comprising:extracting information comprising motion vectors and picture/macroblock (MB) type for all frames in a GOP from a bitstream; calculating a number of bits for encoding discrete cosine transform (DCT) coefficients by VLC decoding and transforming the bitstream into a DCT bitstream; determining a bitrate difference; dropping DCT coefficients based upon the information in order to achieve the bitrate difference in the DCT bitstream; wherein the bitrate difference is achieved by proportionally distributing DCT coefficients to be dropped among anchor frames, predicted frames and bidirectional frames, and wherein priority for proportionally distributing the DCT coefficients to be dropped is anchor frame<predicted frame<bidirectional frame.
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Application No. 60/355,187 filed Feb. 8, 2002 which is herein incorporated by reference for all purposes.
US Referenced Citations (8)
Provisional Applications (1)
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Number |
Date |
Country |
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60/355187 |
Feb 2002 |
US |