Method and system for transcoding video data
View Patent ↗A first method of transcoding video data is disclosed that generates a motion vector for a macroblock encoded as a dual prime macro block that has a direct motion vector, and differential motion vector for its two fields respectively. Another method of transcoding includes replacing a skipped P-macroblock that has been used to backward predict a B-Frame with a P-macroblock having a motion vector of zero. Another method of transcoding includes replacing a skipped B-macroblock with a macroblock having a motion vector from a macroblock of the same frame of the skipped B-macroblock that is not co-located.
1. A method comprising:
receiving a first data stream comprising encoded image data; and
transcoding the first data stream to generate a second data stream, the transcoding comprising:
determining whether the first data stream is characterized by one of:
a skipped P macroblock and a first B-macroblock that is forward predicted from image data associated with an image location of the skipped P-macroblock; and
a skipped B-macroblock;
responsive to the first data stream including the skipped P-macroblock and the first B-macroblock:
encoding a first P-macroblock based on the image data at the image location of the skipped P-macroblock; and
implementing the first P-macroblock in the second data stream in place of the skipped P-macroblock; and
responsive to the first data stream including the skipped B-macroblock:
encoding a second B-macroblock based on a prediction error data set to zero; and
implementing the second B-macroblock in the second data stream in place of the skipped B-macroblock.
2. The method of claim 1 , wherein the first data stream includes the skipped P-macroblock and the first B-macroblock.
3. The method of claim 2 , wherein encoding the first P-macroblock comprises encoding the first P-macroblock with a motion vector value of zero.
4. The method of claim 2 , wherein encoding the first P-macroblock comprises encoding the first P-macroblock based on a second P-macroblock associated with the image location of the skipped P-macroblock.
5. The method of claim 4 , wherein encoding the first P-macroblock based on the second P-macroblock comprises encoding the first P-macroblock based on decoded texture data from the second P-macroblock.
6. The method of claim 2 , wherein encoding the first P-macroblock comprises transcoding the skipped P-macroblock via an open-loop transcoder to generate the first P-macroblock.
7. The method of claim 1 , wherein the first data stream is encoded based on a first protocol and the second data stream is encoded based on a second protocol different than the first protocol.
8. The method of claim 7 , wherein the first protocol comprises an MPEG2 protocol and the second protocol comprises an MPEG4 protocol.
9. The method of claim 1 , wherein the first data stream includes the skipped B-macroblock.
10. The method of claim 9 , wherein encoding the second B-macroblock comprises encoding the second B-macroblock based on a motion vector of a third B-macroblock in the same frame as the skipped B-macroblock.
11. The method of claim 10 , wherein the third B-macroblock is a macroblock to be rendered prior to the second B-macroblock.
12. The method of claim 10 , wherein the third B-macroblock comprises image data to be displayed immediately adjacent to the second B-macroblock.
13. The method of claim 9 , wherein encoding the second B-macroblock comprises encoding the second B-macroblock based on a motion vector of zero responsive to the skipped B-frame being associated with an initial image location of a frame sequence.
14. The method of claim 9 , wherein encoding the second B-macroblock comprises encoding the second B-macroblock via an open-loop transcoder.
15. An electronic device comprising:
a transcoder configured to transcode a first data stream comprising encoded image data to generate a second data stream by:
determining whether the first data stream is characterized by one of:
a skipped P macroblock and a first B-macroblock that is forward predicted from image data associated with an image location of the skipped P-macroblock; and
a skipped B-macroblock;
responsive to the first data stream including the skipped P-macroblock and the first B-macroblock:
encoding a first P-macroblock based on the image data at the image location of the skipped P-macroblock; and
implementing the first P-macroblock in the second data stream in place of the skipped P-macroblock; and
responsive to the first data stream including the skipped B-macroblock:
encoding a second B-macroblock based on a prediction error data set to zero; and
implementing the second B-macroblock in the second data stream in place of the skipped B-macroblock.
16. The electronic device of claim 15 , wherein the first data stream includes the skipped P-macroblock and the first B-macroblock.
17. The electronic device of claim 16 , wherein the transcoder is configured to encode the first P-macroblock by encoding the first P-macroblock with a motion vector value of zero.
18. The electronic device of claim 16 , wherein the transcoder is configured to encode the first P-macroblock based on a second P-macroblock associated with the image location of the skipped P-macroblock.
19. The electronic device of claim 18 , wherein the transcoder is configured to encode the first P-macroblock based on decoded texture data from the second P-macroblock.
20. The electronic device of claim 16 , wherein the transcoder comprises an open-loop transcoder configured to transcode the skipped P-macroblock to generate the first P-macroblock.
21. The electronic device of claim 15 , wherein the first data stream is encoded based on a first protocol and the second data stream is encoded based on a second protocol different than the first protocol.
22. The electronic device of claim 21 , wherein the first protocol comprises an MPEG2 protocol and the second protocol comprises an MPEG4 protocol.
23. The electronic device of claim 15 , wherein the first data stream includes the skipped B-macroblock
24. The electronic device of claim 23 , wherein the transcoder is configured to encode the second B-macroblock based on a motion vector of a third B-macroblock in the same frame as the skipped B-macroblock.
25. The electronic device of claim 24 , wherein the third B-macroblock is a macroblock to be rendered prior to the second B-macroblock.
26. The electronic device of claim 24 , wherein the third B-macroblock comprises image data to be displayed immediately adjacent to the second B-macroblock.
27. The electronic device of claim 23 , wherein the transcoder is configured to encode the second B-macroblock based on a motion vector of zero responsive to the skipped B-frame being associated with an initial image location of a frame sequence.
28. The electronic device of claim 23 , wherein the transcoder comprises an open-loop transcoder configured to encode the second B-macroblock.