Bidirectionally predicted pictures or video object planes for efficient and flexible video coding
A method is provided for decoding a bit stream representing an image that has been encoded The method includes the steps of: performing an entropy decoding of the bit stream to form a plurality of transform coefficents and a plurality of motion vectors; performing an inverse transformation on the plurality of transform coefficients to form a plurality of error blocks; determining a plurality of predicted blocks based on bidirectional motion estimation that employs the motion vectors, wherein the bidirectional motion estimation includes a direct prediction mode and a second prediction mode; and, adding the plurality of error blocks to the plurality of predicted blocks to form the image. The second prediction mode may include forward, backward, and interpolated prediction modes.
1. A method for decoding a block in a B-picture, the method comprising:
receiving an indication that a prediction mode associated with a block in a B-picture is a direct prediction mode;
deriving a motion vector to determine a predicting block from a listing of blocks that is to be used for decoding the block in the B-picture;
determining the predicting block using a forward scaling of the derived motion vector;
determining a second predicting block using a backward scaling of the derived motion vector; and
predicting data for the content of the block in the B-picture based on at least the predicting block and the second predicting block.
2. The method of claim 1 , wherein the motion vector is derived using a block in a listing of blocks that is spatially coincident with the block in the B-picture.
determining a second predicting block using a backward scaling of the derived motion vector, wherein predicting data for the content of the block further comprises using the predicting block and the second prediction block.
3. The method of claim 1 , wherein the predicting block is determined from a listing of blocks that is temporally previous to the block in the B-picture.
4. The method of claim 3 , wherein the second predicting block is determined from a listing of blocks that is temporally ahead of the block in the B-picture.
5. A computer-readable medium storing instructions for controlling a computing device to decode a block in a B-picture, the instructions comprising:
receiving an indication that a prediction mode associated with a block in a B-picture is a direct prediction mode;
deriving a motion vector to determine a predicting block from a listing of blocks that is to be used for decoding the block in the B-picture;
determining the predicting block using a forward scaling of the derived motion vector;
determining a second predicting block using a backward scaling of the derived motion vector; and
predicting data for the content of the block in the B-picture based on at least the predicting block and the second predicting block.
6. The computer-readable medium of claim 5 , wherein the motion vector is derived using a block in a listing of blocks that is spatially coincident with the block in the B-picture.
7. The computer-readable medium of claim 5 , wherein the predicting block is determined from a listing of blocks that is temporally previous to the block in the B-picture.
8. The computer-readable medium of claim 7 , wherein the second predicting block is determined from a listing of blocks that is temporally ahead of the block in the B-picture.
9. A computing device for decoding a block in a B-picture, the computing device comprising:
a module configured to receive an indication that a prediction mode associated with a block in a B-picture is a direct prediction mode;
a module configured to identify a motion vector to determine a predicting block from a listing of blocks that is to be used for decoding the block in the B-picture; and
a module configured to predict data for the content of the block in the B-picture based on at least the predicting block, wherein the module configured to predict data for the content of the block of the B-picture further:
determines the predicting block using a forward scaling of the derived motion vector; and
determines a second predicting block using a backward scaling of the derived motion vector, wherein predicting data for the content of the block further comprises using the predicting block and the second predicting block.
10. The computing device of claim 9 , wherein the motion vector is derived using a block in a listing of blocks that is spatially coincident with the block in the B-picture.
11. The computing device of claim 9 , wherein the predicting block is determined from a listing of blocks that is temporally previous to the block in the B-picture.
12. The computing device of claim 11 , wherein the second predicting block is determined from a listing of blocks that is temporally ahead of the block in the B-picture.
13. A computing device for decoding a block in a B-picture, the computing device comprising:
means for receiving an indication that a prediction mode associated with a block in a B-picture is a direct prediction mode;
means for deriving a motion vector to determine a predicting block from a listing of blocks that is to be used for decoding the block in the B-picture; and
means for predicting data for the content of the block in the B-picture based on at least the predicting block, wherein the means for predicting data for the content of the block of the B-picture further:
determining the predicting block using a forward scaling of the derived motion vector;
determining a second predicting block using a backward scaling of the derived motion vector, wherein predicting data for the content of the block further comprises using the predicting block and the second predicting block.
14. The computing device of claim 13 , wherein the motion vector is derived using a block in a listing of blocks that is spatially coincident with the block in the B-picture.
15. The computing device of claim 14 , wherein the predicting block is determined from a listing of blocks that is temporally previous to the block in the B-picture.
16. The computing device of claim 15 , wherein the second predicting block is determined from a listing of blocks that is temporally ahead of the block in the B-picture.