Method and system for video transcoding

1. A system for transcoding compressed video signals, including a plurality of pictures, comprising:

a decoder to completely or partially decode an input compressed video signal,

a look-ahead estimator to gather information from said input compressed video signal prior to input to said decoder to estimate future signal characteristics of one or more future incoming pictures, and to gather information from said decoder to estimate current signal characteristics of a current picture; and

an encoder to compress the reconstructed video signal according to a coding scheme derived from said current and future signal characteristics from said look-ahead estimator.

2. The transcoding system according to claim 1 , wherein said look-ahead estimator derives a complexity of said current picture being transcoded.

3. A transcoding system according to claim 2 , wherein said picture complexity is estimated by a function of the total bits and the average quantization step size used to code the picture in the first coding scheme.

4. A transcoding system according to claim 2 , wherein said picture complexity is estimated by a function of the total bits and average quantization step size used to code the portion of the picture in the first coding scheme.

5. The transcoding system according to claim 1 , wherein said look-ahead estimator estimates a complexity of each portion of said current picture.

6. The transcoding system according to claim 5 , wherein said portion is a slice of said current picture.

7. The transcoding system according to claim 5 , wherein said portion is a macroblock of said current picture.

8. A method for video transcoding, comprising:

decoding, at least partially, a compressed video signal to produce an at least partially reconstructed video signal, said compressed video signal being a data stream coded by a first coding scheme;

determining a current picture complexity for at least a portion of a current picture in said at least partially reconstructed video signal;

looking ahead to estimate complexities of one of more future pictures or portions thereof, said future pictures in said compressed video signal prior to input to said decoder;

selecting a second coding scheme based on said current picture complexity and said future picture complexities; and

encoding said current picture using said second coding scheme and said current picture complexity.

9. The method according to claim 8 , further comprising: determining current signal characteristics for said current picture; and using said current signal characteristics in selecting said second coding scheme.

10. The method according to claim 9 , further comprising using said current signal characteristics in encoding said current picture.

11. The method according to claim 8 , further comprising:

determining a future picture complexity for at least a portion of a future picture;

using said future picture complexity in selecting said second coding scheme; and

using said future picture complexity in encoding said current picture.

12. The method according to claim 8 , further comprising:

determining a future picture complexity for at least a portion of a future picture;

using said future picture complexity in selecting said second coding scheme;

determining future signal characteristics for said future picture; and

using said future signal characteristics in selecting said second coding scheme.

13. The method according to claim 12 , further comprising using said future signal characteristics in encoding said current picture.

14. The method according to claim 8 , wherein said portion of said future picture is a slice.

15. The method according to claim 8 , wherein said portion of said future picture is a macroblock.

16. The method according to claim 15 , further comprising determining a macroblock complexity for said macroblock; and

using said macroblock complexity in selecting said second coding scheme.

17. The method according to claim 16 , further comprising using said macroblock complexity in encoding said current picture.

18. The method according to claim 16 , wherein said macroblock complexity is determined by a function of total bits and an average quantization step size used to code said data stream.

19. The method according to claim 16 , wherein said macroblock complexity is determined by a function of total bits and an average quantization step size used to code said macroblock.

20. The method according to claim 8 , wherein said current picture complexity is determined by a function of total bits and an average quantization step size used to code said data stream.

21. The method according to claim 8 , further comprising:

determining a future picture complexity for at least a portion of a future picture; and

using said future picture complexity in selecting said second coding scheme;

wherein said future picture complexity is determined by a function of total bits and an average quantization step size used to code said data stream.

22. The method according to claim 8 , wherein said current picture complexity is determined by a function of total bits and an average quantization step size used to code said portion.

23. The method according to claim 8 , further comprising:

determining a future picture complexity for at least a portion of a future picture; and

using said future picture complexity in selecting said second coding scheme;

wherein said future picture complexity is determined by a function of total bits and an average quantization step size used to code said portion.