Parsing friendly and error resilient merge flag coding in video coding
Methods and apparatus for parsing friendly and error resilient merge flag coding in video coding are provided. In some methods, in contrast to merging candidate list size dependent coding of the merge flag in the prior art, a merge flag is always encoded in the encoded bit stream for each inter-predicted prediction unit (PU) that is not encoded using skip mode. In some methods, in contrast to the prior art that allowed the merging candidate list to be empty, one or more zero motion vector merging candidates formatted according to the prediction type of the slice containing a PU are added to the merging candidate list if needed to ensure that the list is not empty and/or to ensure that the list contains a maximum number of merging candidates.
1. A method for decoding an encoded bit stream for a picture in a video decoder, the method comprising:
decoding a merge flag for a non skip mode inter-predicted prediction unit (PU) from the encoded bit stream;
constructing a merge mode motion data vector (merging candidate) list with a maximum number of motion vector merging candidates for the non skip mode inter-predicted PU for a first value of the merge flag;
adding a sufficient number of zero motion vector merging candidates to the merging candidate list to ensure that the maximum number of motion vector merging candidates is obtained wherein adding each zero motion vector merging candidate to the merging candidate list comprises determining a content of the zero motion vector merging candidate based on a prediction type of a slice containing the non skip mode inter-predicted PU wherein the zero motion vector merging candidate comprises a motion vector with a value of zero if the slice is a forward predicted slice, and the zero motion vector merging candidate comprises two motion vectors with values of zero if the slice is a bi-directionally predicted slice; and
reconstructing the non skip mode inter-predicted PU based on the merging candidate list.
2. The method of claim 1 further comprising a first prediction list utilization flag and a second prediction list utilization flag, and when the slice containing the non skip mode inter-predicted PU is a bi-directionally predicted slice, both the first prediction list utilization flag and the second prediction list utilization flag are set to one.
3. A method for decoding an encoded video bit stream in a video decoder, the method comprising:
decoding a merge flag for a inter-predicted prediction unit (PU) from the encoded bit stream;
constructing a merge mode motion data vector (merging candidate) list with a maximum number of motion vector merging candidates for the inter-predicted PU;
adding a sufficient number of zero motion vector merging candidates to the merging candidate list to ensure that the maximum number of motion vector merging candidates is obtained wherein the content of each added zero motion vector merging candidate is determined based on a prediction type of a slice containing the inter-predicted PU; and
reconstructing the inter-predicted PU based on a value of the merge flag.
4. The method of claim 3 , wherein a merge flag is always encoded in the encoded bit stream for each inter-predicted PU that is not encoded using skip mode.
5. The method of claim 3 , wherein each added zero motion vector merging candidate comprises a motion vector with a value of zero if the slice is a forward predicted slice, and the zero motion vector merging candidate comprises two motion vectors with values of zero if the slice is a bi-directionally predicted slice.
6. The method of claim 5 , wherein the prediction direction indicator comprises a first prediction list utilization flag and a second prediction list utilization flag, and when the slice is a bi-directionally predicted slice, both the first prediction list utilization flag and the second prediction list utilization flag are set to one.
7. A method for decoding an encoded bit stream for a picture, the method comprising:
decoding a merge flag for a inter-predicted prediction unit (PU) not encoded using skip mode from the encoded bit stream;
constructing a merge mode motion data vector (merging candidate) list with a maximum number of motion vector merging candidates for the inter-predicted PU for a first value of the merge flag;
adding a sufficient number of zero motion vector merging candidates to the merging candidate list to ensure that the maximum number of motion vector merging candidates is obtained wherein adding each zero motion vector merging candidate to the merging candidate list comprises determining a content of the zero motion vector merging candidate based on a prediction type of a slice containing the inter-predicted PU wherein the zero motion vector merging candidate comprises a motion vector with a value of zero if the slice is a forward predicted slice, and the zero motion vector merging candidate comprises two motion vectors with values of zero if the slice is a bi-directionally predicted slice;
reconstructing the inter-predicted PU based on the merging candidate list;
reconstructing the picture using the reconstructed inter-predicted PU; and
displaying the picture on a display.
8. The method of claim 7 further comprising a first prediction list utilization flag and a second prediction list utilization flag, and when the slice containing the non skip mode inter-predicted PU is a bi-directionally predicted slice, both the first prediction list utilization flag and the second prediction list utilization flag are set to one.