METHOD AND APPARATUS FOR VIDEO CODING AND DECODING
There are disclosed various methods, apparatuses and computer program products for video encoding and decoding. In some embodiments diagonal inter-layer prediction is enabled by providing an indication of a reference picture. In some embodiments the indication is provided as a combination of a temporal picture identifier and a layer identifier of the reference picture in another layer than the picture to be predicted. In an encoding method a first picture of a first layer representing a first time instant is encoded; a second picture representing a second time instant on a second layer is predicted by using the first picture as a reference picture; and a temporal picture identifier and an indication of the first layer are provided to indicate the first picture.
1 . A method comprising:
decoding a first picture of a first layer representing a first time instant;
decoding a temporal picture identifier and an indication of a first layer to determine a reference picture for decoding a second picture of a second layer representing a second time instant;
concluding based on the temporal picture identifier and the indication of the first layer that the first picture is the reference picture;
predicting the second picture by using the first picture as the reference picture, the first layer being a reference layer for inter-layer prediction of the second layer.
2 . The method according to claim 1 , wherein the temporal picture identifier comprises one or more of the following:
a picture order count value;
a part of the picture order count value;
a frame number value;
a variable derived from the frame number value;
a temporal reference value;
a decoding timestamp;
a composition timestamp;
an output timestamp;
a presentation timestamp;
an index of a long-term reference picture.
3 . The method according to claim 1 , wherein the layer identifier comprises one or more of the following:
a dependency_id,
a quality_id;
a priority_id;
a view_id;
a view order index;
a DepthFlag;
a generalized layer identifier.
4 . The method according claim 1 further comprising:
receiving one or more reference picture sets including information of pictures which may be used as reference pictures;
concluding that no picture of the first layer and of the second time instant is used for prediction of the second picture;
on the basis of said concluding, decoding a reference picture set concerning reference pictures of the first layer that may be used for prediction of the second picture, wherein the reference picture set indicates the first picture.
5 . The method according to claim 1 further comprising:
identifying for a current block a co-located block in another picture;
determining a picture used as a reference for the co-located block;
determining a default target picture on the basis of the picture used as a reference for the co-located block;
determining whether the picture used as a reference for the co-located block resides in the same layer as the default target picture;
if so, using the default target picture as the reference for the current block;
if not so, deriving a different target picture as the first picture in a reference picture list having the same layer identifier as that of the picture used as the reference for the co-located block.
6 . The method according to claim 1 further comprising:
decoding an indication of the second picture to be a diagonal stepwise layer access picture, wherein no picture following, in decoding order, the diagonal stepwise layer access picture in the second layer is predicted from any picture in the second layer that precedes, in decoding order, the diagonal stepwise layer access picture.
7 . The method according to claim 6 further comprising one of the following:
decoding an indication that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer; or
deducing that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer.
8 . An apparatus comprising at least one processor and at least one memory, said at least one memory stored with code thereon, which when executed by said at least one processor, causes an apparatus to perform at least the following:
decode a first picture of a first layer representing a first time instant;
decode a temporal picture identifier and an indication of a first layer to determine a reference picture for decoding a second picture of a second layer representing a second time instant;
conclude based on the temporal picture identifier and the indication of the first layer that the first picture is the reference picture; and
predict the second picture by using the first picture as the reference picture.
9 . The apparatus according to claim 8 , wherein the temporal picture identifier comprises one or more of the following:
a picture order count value;
a part of the picture order count value;
a frame number value;
a variable derived from the frame number value;
a temporal reference value;
a decoding timestamp;
a composition timestamp;
an output timestamp;
a presentation timestamp;
an index of a long-term reference picture.
10 . The apparatus according to claim 8 , wherein the layer identifier comprises one or more of the following:
a dependency_id,
a quality_id;
a priority_id;
a view_id;
a view order index;
a DepthFlag;
a generalized layer identifier.
11 . The apparatus according to claim 8 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
receive one or more reference picture sets including information of pictures which may be used as reference pictures;
conclude that no picture of the first layer and of the second time instant is used for prediction of the second picture;
on the basis of said concluding, decode a reference picture set concerning reference pictures of the first layer that may be used for prediction of the second picture, wherein the reference picture set indicates the first picture.
12 . The apparatus according to claim 8 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
identify for a current block a co-located block in another picture;
determine a picture used as a reference for the co-located block;
determine a default target picture on the basis of the picture used as a reference for the co-located block;
determine whether the picture used as a reference for the co-located block resides in the same layer as the default target picture;
if so, use the default target picture as the reference for the current block;
if not so, derive a different target picture.
13 . The apparatus according to claim 8 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
decode an indication of the second picture to be a diagonal stepwise layer access picture, wherein no picture following, in decoding order, the diagonal stepwise layer access picture in the second layer is predicted from any picture in the second layer that precedes, in decoding order, the diagonal stepwise layer access picture.
14 . The apparatus according to claim 13 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
decoding an indication that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer; or
deduce that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer.
15 . A method comprising:
encoding a first picture of a first layer representing a first time instant;
predicting a second picture representing a second time instant on a second layer by using the first picture as a reference picture; and
providing a temporal picture identifier and an indication of the first layer to indicate the first picture.
16 . The method according to claim 15 , wherein the temporal picture identifier comprises one or more of the following:
a picture order count value;
a part of the picture order count value;
a frame number value;
a variable derived from the frame number value;
a temporal reference value;
a decoding timestamp;
a composition timestamp;
an output timestamp;
a presentation timestamp;
an index of a long-term reference picture.
17 . The method according to claim 15 , wherein the layer identifier comprises one or more of the following:
a dependency_id,
a quality_id;
a priority_id;
a view_id;
a view order index;
a DepthFlag;
a generalized layer identifier.
18 . The method according to claim 15 further comprising:
providing one or more reference picture sets including information of pictures which may be used as reference pictures.
19 . The method according to claim 15 further comprising:
identifying for a current block a co-located block in another picture;
determining a picture used as a reference for the co-located block;
determining a default target picture on the basis of the picture used as a reference for the co-located block;
determining whether the picture used as a reference for the co-located block resides in the same layer as the default target picture;
if so, using the default target picture as the reference for the current block;
if not so, deriving a different target picture as the first picture in a reference picture list having the same layer identifier as that of the picture used as the reference for the co-located block.
20 . The method according to claim 15 further comprising:
encoding an indication of the second picture to be a diagonal stepwise layer access picture, wherein no picture following, in decoding order, the diagonal stepwise layer access picture in the second layer is predicted from any picture in the second layer that precedes, in decoding order, the diagonal stepwise layer access picture.
21 . The method according to claim 20 further comprising one of the following:
encoding an indication that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer; or
deducing that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer.
22 . An apparatus comprising at least one processor and at least one memory, said at least one memory stored with code thereon, which when executed by said at least one processor, causes an apparatus to perform at least the following:
encode a first picture of a first layer representing a first time instant;
predict a second picture representing a second time instant on a second layer by using the first picture as a reference picture; and
provide a temporal picture identifier and an indication of the first layer to indicate the first picture.
23 . The apparatus according to claim 22 , wherein the temporal picture identifier comprises one or more of the following:
a picture order count value;
a part of the picture order count value;
a frame number value;
a variable derived from the frame number value;
a temporal reference value;
a decoding timestamp;
a composition timestamp;
an output timestamp;
a presentation timestamp;
an index of a long-term reference picture.
24 . The apparatus according to claim 22 , wherein the layer identifier comprises one or more of the following:
a dependency_id,
a quality_id;
a priority_id;
a view_id;
a view order index;
a DepthFlag;
a generalized layer identifier.
25 . The apparatus according to claim 22 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
provide one or more reference picture sets including information of pictures which may be used as reference pictures.
26 . The apparatus according to claim 22 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following in said marking the first picture to be a long-term reference picture:
identify for a current block a co-located block in another picture;
determine a picture used as a reference for the co-located block;
determine a default target picture on the basis of the picture used as a reference for the co-located block;
determine whether a picture used as a reference for the co-located block resides in the same layer as a default target picture;
if so, use the default target picture as the reference for the current block;
if not so, derive a different target picture as the first picture in a reference picture list having the same layer identifier as that of the picture used as the reference for the co-located block.
27 . The apparatus according to claim 22 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
encode an indication of the second picture to be a diagonal stepwise layer access picture, wherein no picture following, in decoding order, the diagonal stepwise layer access picture in the second layer is predicted from any picture in the second layer that precedes, in decoding order, the diagonal stepwise layer access picture.
28 . The apparatus according to claim 27 , said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least the following:
encoding an indication that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer; or
deducing that no picture having the second time instant or later, in decoding order, in the first layer is used for prediction of the diagonal stepwise layer access picture or any picture following, in decoding order, the diagonal stepwise layer access picture in the second layer.