Inter-Prediction Candidate Index Coding Independent of Inter-Prediction Candidate List Construction in Video Coding

• US 20120320984A1
• Filed: 06/14/2012
• Published: 12/20/2012
• Est. Priority Date: 06/14/2011
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Zhou, Minhua
• Granted Patent: US 9,866,859 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: H04N 19/109 among a plurality of temporal predictive coding modes
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/463 by compressing encoding parameters before transmission
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/625 using discrete cosine transform [DCT]

Abstract

Methods are provided for inter-prediction candidate index coding independent of the construction of the corresponding inter-prediction candidate list, i.e., a merging candidate list or an advanced motion vector predictor list. A maximum allowed number of inter-prediction candidates for an inter-prediction candidate list is used for encoding the inter-prediction candidate index in an encoded bit stream. The maximum allowed number may be pre-determined or may be selected by the encoder and encoded in the bit stream. A decoder may then decode the index using the maximum allowed number of inter-prediction candidates independent of the construction of the corresponding inter-prediction candidate list.

Claims

1. A method for decoding an encoded video bit stream in a video decoder, the method comprising:

constructing an inter-prediction candidate list for a prediction unit (PU);

decoding a candidate index for the PU inter-prediction candidate list, wherein a maximum allowed number of inter-prediction candidates for an inter-prediction candidate list is used as a maximum codeword size for truncated unary decoding of the candidate index; and

decoding the PU using an inter-prediction candidate in the inter-prediction candidate list indicated by the candidate index.

2. The method of claim 1, further comprising:

decoding an indicator of the maximum allowed number of inter-prediction candidates from the encoded bit stream.

3. The method of claim 1, wherein constructing an inter-prediction candidate list comprises:

deriving native inter-prediction candidates for the PU;

pruning the inter-prediction candidate list when a number of native inter-prediction candidates in the inter-prediction candidate list is larger than the maximum allowed number of inter-prediction candidates, wherein sufficient low priority native inter-prediction candidates are removed from the inter-prediction candidate list to reduce the number of native inter-prediction candidates to the maximum allowed number; and

adding virtual inter-prediction candidates to the inter-prediction candidate list when the number of native inter-prediction candidates is less than the maximum allowed number, wherein a total number of native inter-prediction candidates and virtual inter-prediction candidates in the inter-prediction candidate list is equal to the maximum allowed number of inter-prediction candidates.

4. The method of claim 3, wherein the inter-prediction candidate list is an AMVP candidate list, a native inter-prediction candidate is a native motion vector predictor (MVP) candidate, and a virtual inter-prediction candidate is a zero MVP candidate.

5. The method of claim 4, wherein the maximum allowed number of inter-prediction candidates is pre-determined.

6. The method of claim 3, wherein the inter-prediction candidate list is a merging candidate list, a native inter-prediction candidate is a native merging candidate, and a virtual inter-prediction candidate is a virtual merging candidate.

7. The method of claim 6, wherein a virtual merging candidate is one selected from a group consisting of a zero motion vector merging candidate and a combined bi-predictive merging candidate.

8. The method of claim 7, wherein adding virtual inter-prediction candidates comprises adding a combined bi-predictive merging candidate to the inter-prediction candidate list according to a pre-determined priority, wherein the combined bi-predictive merging candidate is generated from a forward component of a first native merging candidate in the inter-prediction candidate list and a backward component of a second native merging candidate in the inter-prediction candidate list selected according to the pre-determined priority.

9. A method for decoding an encoded video bit stream in a video decoder, the method comprising:

constructing a merging candidate list for a prediction unit (PU);

decoding a merging candidate index for the merging candidate list, wherein a maximum allowed number of merging candidates for a merging candidate list is used as a maximum codeword size for truncated unary decoding of the merging candidate index; and

decoding the PU using a merging candidate in the merging candidate list indicated by the merging candidate index.

10. The method of claim 9, further comprising:

decoding an indicator of the maximum allowed number of merging candidates from the encoded bit stream.

11. The method of claim 9, wherein constructing a merging candidate list comprises:

deriving native merging candidates for the PU; and

adding virtual merging candidates to the merging candidate list when a number of native merging candidates is less than the maximum allowed number, wherein a total number of native merging candidates and virtual merging candidates in the merging candidate list is equal to the maximum allowed number of merging candidates.

12. The method of claim 11, wherein a virtual merging candidate is one selected from a group consisting of a zero motion vector merging candidate and a combined bi-predictive merging candidate.

13. The method of claim 12, wherein adding virtual merging candidates comprises adding a combined bi-predictive merging candidate to the inter-prediction candidate list according to a pre-determined priority, wherein the combined bi-predictive merging candidate is generated from a forward component of a first native merging candidate in the merging candidate list and a backward component of a second native merging candidate in the merging candidate list selected according to the pre-determined priority.

14. The method of claim 9, further comprising

constructing an advanced motion vector predictor (AMVP) candidate list for another prediction unit (PU);

decoding an AMVP candidate index for the AMVP candidate list, wherein a maximum allowed number of motion vector predictor (MVP) candidates for an AMVP candidate list is used as a maximum codeword size for truncated unary decoding of the AMVP candidate index; and

decoding the another PU using an MVP candidate in the AMVP candidate list indicated by the AMVP candidate index.

15. The method of claim 14, wherein constructing an AMVP candidate list comprises:

deriving native MVP candidates for the PU; and

adding virtual MVP candidates to the AMVP candidate list when a number of native MVP candidates is less than the maximum allowed number of MVP candidates, wherein a total number of native MVP candidates and virtual MVP candidates in the AMVP candidate list is equal to the maximum allowed number of MVP candidates.

16. The method of claim 14, wherein the maximum allowed number of MVP candidates is pre-determined.

17. A method for encoding a video stream in a video encoder to generate an encoded bit stream, the method comprising:

constructing an inter-prediction candidate list for a prediction unit (PU);

selecting a candidate index for the PU inter-prediction candidate list; and

encoding the candidate index into the encoded bit stream, wherein a maximum allowed number of inter-prediction candidates for an inter-prediction candidate list is used as a maximum codeword size for truncated unary coding of the candidate index.

18. The method of claim 17, further comprising:

selecting the maximum allowed number of inter-prediction candidates for an inter-prediction candidate list for a slice comprising the PU; and

signaling the maximum allowed number of inter-prediction candidates in the encoded bits stream in header information for the slice.

19. The method of claim 17, wherein constructing an inter-prediction candidate list comprises:

deriving native inter-prediction candidates for the PU;

pruning the inter-prediction candidate list when a number of native inter-prediction candidates in the inter-prediction candidate list is larger than the maximum allowed number of inter-prediction candidates, wherein sufficient low priority native inter-prediction candidates are removed from the inter-prediction candidate list to reduce the number of native inter-prediction candidates to the maximum allowed number; and

adding virtual inter-prediction candidates to the inter-prediction candidate list when the number of native inter-prediction candidates is less than the maximum allowed number, wherein a total number of native inter-prediction candidates and virtual inter-prediction candidates in the inter-prediction candidate list is equal to the maximum allowed number of inter-prediction candidates.

20. The method of claim 19, wherein the inter-prediction candidate list is an AMVP candidate list, a native inter-prediction candidate is a native motion vector predictor (MVP) candidate, and a virtual inter-prediction candidate is a zero MVP candidate.

21. The method of claim 20, wherein the maximum allowed number of inter-prediction candidates is pre-determined.

22. The method of claim 19, wherein the inter-prediction candidate list is a merging candidate list, a native inter-prediction candidate is a native merging candidate, and a virtual inter-prediction candidate is a virtual merging candidate.

23. The method of claim 22, wherein a virtual merging candidate is one selected from a group consisting of a zero motion vector merging candidate and a combined bi-predictive merging candidate.

24. The method of claim 23, wherein adding sufficient virtual inter-prediction candidates comprises adding a combined bi-predictive merging candidate to the inter-prediction candidate list according to a pre-determined priority, wherein the combined bi-predictive merging candidate is generated from a forward component of a first native merging candidate in the inter-prediction candidate list and a backward component of a second native merging candidate selected according to the pre-determined priority.