Reduced cost decoder using bitstream editing for image cropping

1. A method for decoding variable length encoded digital video data including pictures, to a size less than the full size of the pictures, each picture including a plurality of macroblocks, the method comprising the steps of:

parsing the digital video data to identify macroblocks included in the digital video data;

discarding from the digital video data those macroblocks not associated with a picture region substantially corresponding to one of a safe-title picture region and safe-action picture region; and

storing the digital video data in a decoder input buffer, said digital video data stored in said decoder buffer including fewer macroblocks per picture than identified during said step of parsing.

2. The method of claim 1 , wherein:

said step of parsing comprises the step of extracting, from the digital video data, one of a macroblock address indicium and a slice position indicium; and

said step of discarding comprises the step of discarding macroblocks associated with a predetermined macroblock address indicium or a predetermined slice position indicium.

3. The method of claim 1 , further comprising the step of:

identifying non-discarded macroblocks that utilize predictive information associated with discarded macroblocks; and

in the case of said identified non-discarded macroblocks additionally utilizing predictive information associated with non-discarded macroblocks, utilizing only said prediction information associated with non-discarded macroblocks to form said identified non-discarded macroblocks.

4. The method of claim 3 , wherein:

in the case of said identified non-discarded macroblocks utilizing only predictive information associated with non-discarded macroblocks, performing the steps of:

identifying, for each identified non-discarded macroblock, a respective proximately displayed macroblock region;

utilizing, for each identified non-discarded macroblock, said respective proximately displayed macroblock region to estimate a respective regional motion compensation parameter; and

calculating, for each identified non-discarded macroblock, a motion compensation parameter utilizing said respective regional motion compensation parameter.

5. The method of claim 1 , further comprising the step of:

identifying non-discarded macroblocks that utilize predictive information associated with discarded macroblocks;

identifying, for each identified non-discarded macroblock, a respective proximately displayed macroblock region;

utilizing, for each identified non-discarded macroblock, said respective proximately displayed macroblock region to estimate a respective regional motion compensation parameter; and

calculating, for each identified non-discarded macroblock, a motion compensation parameter utilizing said respective regional motion compensation parameter.

6. An apparatus for use in a system for decoding variable length encoded digital video data including pictures, to a size less than the full size of the pictures, each picture including a plurality of macroblocks, the apparatus comprising:

a bitstream trimmer, for parsing the digital video data to identify macroblocks included in the digital video data, and for discarding from the digital video data those macroblocks not associated with a predefined picture region to produce data reduced encoded digital video data, said data reduced encoded digital video data including fewer macroblocks per picture than present in said digital video data; and

a video decoder, coupled to said bitstream trimmer, for decoding said data reduced encoded digital video data to produce a video signal.

7. The apparatus of claim 6 , further comprising:

a buffer memory, coupled to said bitstream trimmer and said video decoder, for buffering said data reduced encoded digital video data prior to said data reduced encoded digital video data being decoded by said decoder.

8. The apparatus of claim 7 , wherein said bitstream trimmer, in response to a rate control signal, responsively modifies a data rate parameter of said data reduced encoded digital video data.

9. The apparatus of claim 8 , wherein rate control signal is generated by said buffer memory and is indicative of a level of memory utilization within said buffer memory.

10. The apparatus of claim 6 , wherein said bitstream trimmer, in response to a display mode indicium signal, responsively discards macroblocks associated with picture areas not relevant to said indicated display mode.

11. The apparatus of claim 6 , wherein:

said video decoder includes a motion compensator responsive to motion predictive information included within said digital video data.

12. The apparatus of claim 11 , wherein:

said motion compensator, in the case of a macroblock utilizing motion predictive information from a discarded macroblock, estimates said discarded motion compensation information.

13. The apparatus of claim 12 , wherein:

said motion compensator estimates said motion compensation information by utilizing an average motion estimation of a macroblock region proximate to said macroblock requiring said motion compensation information.

14. The apparatus of claim 13 , wherein:

said macroblock region comprises a region calculated using at least one of a predetermined spatial displacement parameter, and a predetermined temporal parameter.

15. A method for decoding variable length encoded digital video data including pictures, to a size less than the full size of the pictures, each picture including a plurality of macroblocks, the method comprising the steps of:

parsing the digital video data to identify macroblocks included in the digital video data;

discarding from the digital video data only those macroblocks not associated with a picture region substantially corresponding to one of a safe-title picture region and safe-action picture region; and

storing the digital video data in a decoder input buffer.

16. The method of claim 15 , wherein:

said step of parsing comprises the step of extracting, from the digital video data, one of a macroblock address indicium and a slice position indicium; and

said step of discarding comprises the step of discarding macroblocks associated with a predetermined macroblock address indicium or a predetermined slice position indicium.

17. The method of claim 15 , further comprising the step of:

identifying non-discarded macroblocks that utilize predictive information associated with discarded macroblocks; and

in the case of said identified non-discarded macroblocks additionally utilizing predictive information associated with non-discarded macroblocks, utilizing only said prediction information associated with non-discarded macroblocks to form said identified non-discarded macroblocks.

18. The method of claim 17 , wherein:

in the case of said identified non-discarded macroblocks utilizing only predictive information associated with non-discarded macroblocks, performing the steps of:

identifying, for each identified non-discarded macroblock, a respective proximately displayed macroblock region;

utilizing, for each identified non-discarded macroblock, said respective proximately displayed macroblock region to estimate a respective regional motion compensation parameter; and

calculating, for each identified non-discarded macroblock, a motion compensation parameter utilizing said respective regional motion compensation parameter.

19. The method of claim 15 , further comprising the step of:

identifying non-discarded macroblocks that utilize predictive information associated with discarded macroblocks;

identifying, for each identified non-discarded macroblock, a respective proximately displayed macroblock region;

utilizing, for each identified non-discarded macroblock, said respective proximately displayed macroblock region to estimate a respective regional motion compensation parameter; and

calculating, for each identified non-discarded macroblock, a motion compensation parameter utilizing said respective regional motion compensation parameter.

20. An apparatus for use in a system for decoding variable length encoded digital video data including pictures, to a size less than the full size of the pictures, each picture including a plurality of macroblocks, the apparatus comprising:

a bitstream trimmer, for parsing the digital video data to identify macroblocks included in the digital video data, and for discarding from the digital video data only those macroblocks not associated with a predefined picture region to produce data reduced encoded digital video data; and

a video decoder, coupled to said bitstream trimmer, for decoding said data reduced encoded digital video data to produce a video signal.

21. The apparatus of claim 20 , further comprising:

a buffer memory, coupled to said bitstream trimmer and said video decoder, for buffering said data reduced encoded digital video data prior to said data reduced encoded digital video data being decoded by said decoder.

22. The apparatus of claim 21 , wherein said bitstream trimmer, in response to a rate control signal, responsively modifies a data rate parameter of said data reduced encoded digital video data.

23. The apparatus of claim 22 , wherein rate control signal is generated by said buffer memory and is indicative of a level of memory utilization within said buffer memory.

24. The apparatus of claim 20 , wherein said bitstream trimmer, in response to a display mode indicium signal, responsively discards macroblocks associated with picture areas not relevant to said indicated display mode.

25. The apparatus of claim 20 , wherein:

said video decoder includes a motion compensator responsive to motion predictive information included within said digital video data.

26. The apparatus of claim 25 , wherein:

said motion compensator, in the case of a macroblock utilizing motion predictive information from a discarded macroblock, estimates said discarded motion compensation information.

27. The apparatus of claim 26 , wherein:

said motion compensator estimates said motion compensation information by utilizing an average motion estimation of a macroblock region proximate to said macroblock requiring said motion compensation information.

28. The apparatus of claim 27 , wherein:

said macroblock region comprises a region calculated using at least one of a predetermined spatial displacement parameter, and a predetermined temporal parameter.