Adaptive weighting of reference pictures in video decoding
View Patent ↗A video decoder, encoder, and corresponding methods for processing video signal data for an image block and a particular reference picture index to predict the image block are disclosed that utilize adaptive weighting of reference pictures to enhance video compression, where a decoder includes a reference picture weighting factor unit for determining a weighting factor corresponding to the particular reference picture index; an encoder includes a reference picture weighting factor assignor for assigning a weighting factor corresponding to the particular reference picture index; and a method for decoding includes receiving a reference picture index with the data that corresponds to the image block, determining a weighting factor for each received reference picture index, retrieving a reference picture for each index, motion compensating the retrieved reference picture, and multiplying the motion compensated reference picture by the corresponding weighting factor to form a weighted motion compensated reference picture.
1. A video decoder for decoding video data for an image block and a particular reference picture index to predict the image block, the decoder comprising a reference picture weighting factor unit having an output for determining an offset corresponding to the particular reference picture index,
wherein the reference picture weighting factor unit receives the particular reference picture index, the particular reference picture index is used for independently indicating, without use of another index, (1) one of a plurality of reference pictures from which the image block is predicted and (2) the offset corresponding to the particular reference picture index.
2. A video decoder as defined in claim 1 wherein the reference picture weighting factor unit has a second output for determining a weighting factor.
3. A video decoder as defined in claim 1 , further including a variable length decoder in communication with the reference picture weighting factor unit for providing the particular reference picture index to the reference picture weighting factor unit.
4. A video decoder as defined in claim 1 , further including a motion compensator in communication with the reference picture weighting factor unit for providing motion compensated reference pictures responsive to the reference picture weighting factor unit.
5. A video decoder as defined in claim 4 , further including a multiplier in communication with the motion compensator and the reference picture weighting factor unit for applying a weighting factor to a motion compensated reference picture.
6. A video decoder as defined in claim 5 , further including an adder in communication with the motion compensator and the reference picture weighting factor unit for applying the offset to a motion compensated reference picture.
7. A video decoder as defined in claim 1 , wherein the video data includes block transform coefficients.
8. A video decoder as defined in claim 1 , usable with bi-predictive picture predictors, the decoder further including:
prediction means for forming first and second predictors from two different reference pictures;
averaging means for averaging the first and second predictors together using their corresponding weighting factors to form a single averaged predictor.
9. A video decoder as defined in claim 8 wherein the two different reference pictures are both from the same direction relative to the image block.
10. A method for decoding video data for an image block, the method including:
receiving at least one reference picture index with the data for the image block, each corresponding to a particular reference picture;
determining a weighting factor for use with at least one of the received at least one reference picture index;
retrieving a reference picture corresponding to at least one of the received at least one reference picture index;
motion compensating the retrieved reference picture;
varying the motion compensated reference picture by the corresponding weighting factor to form a weighted motion compensated reference picture;
determining an offset corresponding to at least one of the received at least one reference picture index; and
adjusting the weighted motion compensated reference picture with the corresponding offset,
wherein the at least one reference picture index independently indicates, without use of another index, (1) the corresponding particular reference picture from which the image block is predicted and (2) the offset corresponding to the at least one reference picture index.
11. A method as defined in claim 10 , further including:
combining the weighted motion compensated reference picture to the data for the image block to predict the image block; and
storing the predicted image block as a reference picture for future retrieval.
12. A method as defined in claim 10 , wherein the video data includes block transform coefficients.
13. A method as defined in claim 10 , wherein bi-predictive picture predictors are used, the method further including:
forming first and second predictors from two different reference pictures, motion compensating each of the first and second predictors;
combining the first and second predictors together using their corresponding weighting factors to form a single combined predictor.
14. A method as defined in claim 13 , further including:
determining first and second offsets corresponding to each of the first and second predictors; and
combining the first and second predictors with the corresponding first and second offsets, respectively.
15. A method as defined in claim 13 wherein the two different reference pictures are both from the same direction relative to the image block.
16. A non-transitory computer readable media readable by machine, tangibly embodying a program of instructions executable by the machine to perform program steps for decoding video data for an image block, the program steps including:
receiving at least one reference picture index with the data for the image block, each corresponding to a particular reference picture;
determining a weighting factor for use with at least one of the received at least one reference picture index;
retrieving a reference picture corresponding to at least one of the received at least one reference picture index;
motion compensating the retrieved reference picture;
varying the motion compensated reference picture by the corresponding weighting factor to form a weighted motion compensated reference picture;
determining an offset corresponding to at least one of the received at least one reference picture index; and
adjusting the weighted motion compensated reference picture with the corresponding offset,
wherein the at least one reference picture index independently indicates, without use of another index, (1) the corresponding particular reference picture from which the image block is predicted and (2) the offset corresponding to the at least one reference picture index.
17. A non-transitory computer readable media as defined in claim 16 , the program steps further including combining the weighted motion compensated reference picture to the data for the image block to predict the image block.
18. A non-transitory computer readable media tangibly embodying data of encoded video corresponding to an image block and a particular reference picture index, the reference picture index used for encoding the image block, the encoder assigning an offset corresponding to the particular reference picture index,
wherein the particular reference picture index independently indicates, without use of another index, (1) a particular reference picture corresponding to the particular reference picture index and (2) the offset corresponding to the particular reference picture index.