Picture encoding and picture decoding with selective decoded picture buffer storage based on reference layer number sets

1 . An encoder comprising:

a memory configured to store instructions; and

one or more processors coupled to the memory and configured to execute the instructions to cause the encoder to:

determine a first reference frame number of a current picture based on first channel feedback information, wherein the first channel feedback information indicates first information about a second picture frame of a decoder side;

obtain a first reference layer number set of a first picture frame corresponding to the first reference frame number, wherein the first reference layer number set comprises layer numbers of N1 layers, wherein 1≤N1<L1, and wherein L1 indicates a total quantity of layers of the first picture frame;

determine a first reference layer number of the current picture based on the first channel feedback information and the first reference layer number set;

obtain a reconstructed picture corresponding to the first reference frame number and the first reference layer number from a decoded picture buffer (DPB) that stores only reconstructed pictures of the N1 layers for the first picture frame;

set the reconstructed picture as a reference picture; and

perform video encoding on the current picture based on the reference picture to obtain a bitstream.

2 . The encoder of claim 1 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

obtain pieces of the first channel feedback information, wherein the pieces indicate frame numbers, and wherein the first channel feedback information further indicates a first frame number of the second picture frame; and

set a second frame number that is in the frame numbers and that is closest to a third frame number of the current picture as the first reference frame number.

3 . The encoder of claim 2 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

determine a highest layer number from second channel feedback information indicating the first reference frame number as a target layer number;

set the target layer number as the first reference layer number when the first reference layer number set comprises the target layer number; and

set a first layer number that is in the first reference layer number set and that is less than and closest to the target layer number as the first reference layer number when the first reference layer number set does not comprise the target layer number.

4 . The encoder of claim 1 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

obtain groups of second channel feedback information corresponding to decoder sides, wherein each of the groups comprises pieces of third channel feedback information, and wherein the third channel feedback information indicates a first frame number of a third picture frame of a corresponding decoder side;

determine one or more common frame numbers based on the groups, wherein each of the one or more common frame numbers is indicated by at least one piece of the third channel feedback information in each of the groups; and

determine the first reference frame number based on the one or more common frame numbers.

5 . The encoder of claim 4 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

obtain a highest layer number indicated by fourth channel feedback information that is in each of the groups and that indicates the first reference frame number;

determine a smallest highest layer number among highest layer numbers as a target layer number; and

further determine the first reference layer number based on the target layer number.

6 . The encoder of claim 1 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

obtain pieces of second channel feedback information, wherein the second channel feedback information indicates a first frame number of the second picture frame;

determine a second frame number that is in frame numbers indicated by the pieces of the second channel feedback information and that is closest to a third frame number of the current picture as a target frame number; and

set the target frame number as the first reference frame number when a first highest layer number indicated by third channel feedback information indicating the target frame number is greater than or equal to a second highest layer number in a second reference layer number set, wherein the second reference layer number set is of a third picture frame corresponding to the target frame number.

7 . The encoder of claim 6 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

identify that the first highest layer number is less than the second highest layer number; and

set, in response to identifying that the first highest layer number is less than the second highest layer number, a fourth frame number in the frame numbers as the first reference frame number.

8 . The encoder of claim 3 , wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

identify that the first reference layer number set does not comprise the target layer number and a second layer number less than the target layer number; and

in response to identifying that the first reference layer number set does not comprise the target layer number and the second layer number less than the target layer number:

set a second reference frame number of a previous frame of the current picture as the first reference frame number; and

set a second reference layer number of the previous frame as the first reference layer number.

9 . The encoder of claim 1 , wherein the current picture is a picture slice, wherein the first channel feedback information comprises a first picture slice number of the second picture frame and a first layer number corresponding to the first picture slice number, and wherein the one or more processors are further configured to execute the instructions to cause the encoder to:

set the first layer number as a target layer number when a second picture slice number of the current picture is the same as the first picture slice number;

set the target layer number as the first reference layer number when the first reference layer number set comprises the target layer number; and

set a second layer number that is in the first reference layer number set and that is less than and closest to the target layer number as the first reference layer number when the first reference layer number set does not comprise the target layer number.

10 . A decoder comprising:

a memory configured to store instructions; and

one or more processors coupled to the memory and configured to execute the instructions to cause the decoder to:

obtain a bitstream;

parse the bitstream to obtain a first reference frame number of a current picture;

obtain a first reference layer number set of a first picture frame corresponding to the first reference frame number, wherein the first reference layer number set comprises layer numbers of N2 layers, wherein 1≤N2<L2, and wherein L2 indicates a first total quantity of layers of the first picture frame;

determine a first reference layer number of the current picture based on the first reference layer number set;

obtain a reconstructed picture corresponding to the first reference frame number and the first reference layer number from a decoded picture buffer (DPB) that stores only reconstructed pictures of the N2 layers for the first picture frame;

set the reconstructed picture as a reference picture; and

perform video decoding based on the reference picture to obtain a first reconstructed picture of the current picture.

11 . The decoder of claim 10 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to:

store reconstructed pictures of N3 layers of the current picture in the DPB, wherein a second reference layer number set of the current picture comprises layer numbers of M layers, wherein the M layers comprise the N3 layers, wherein 1≤M<L3, and wherein L3 indicates a second total quantity of layers of the current picture; or

store a second reconstructed picture of a highest layer among the N3 layers in the DPB.

12 . The decoder of claim 11 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to display a third reconstructed picture of an L4 th layer of the current picture, and wherein L4 indicates a layer number of a highest layer from decoding the current picture.

13 . The decoder of claim 10 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to:

determine a highest layer number among layer numbers corresponding to reconstructed pictures that are from decoding and that are of the first picture frame;

set the highest layer number as the first reference layer number when the first reference layer number set comprises the highest layer number; and

set a first layer number that is in the first reference layer number set and that is less than and closest to the highest layer number as the first reference layer number when the first reference layer number set does not comprise the highest layer number.

14 . The decoder of claim 13 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to:

identify that the first reference layer number set does not comprise the highest layer number and a second layer number less than the highest layer number; and

in response to identifying that the first reference layer number set does not comprise the highest layer number and the second layer number:

set a second reference frame number of a previous frame of the current picture as the first reference frame number; and

set a second reference layer number of the previous frame as the first reference layer number.

15 . The decoder of claim 10 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to:

determine a first frame number and a first layer number of a received picture frame; and

send channel feedback information to an encoder side, wherein the channel feedback information indicates the first frame number and the first layer number.

16 . The decoder of claim 15 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to further send the channel feedback information to the encoder side when it is determined, based on a second frame number in the bitstream, that a second frame starts to be parsed, wherein the channel feedback information further indicates a third frame number of a first frame and a second layer number of a highest layer of the first frame, and wherein the first frame is a previous frame of the second frame.

17 . The decoder of claim 15 , wherein the one or more processors are further configured to execute the instructions to cause the decoder to further send the channel feedback information to the encoder side when it is determined, based on the first layer number, that a first frame is completely received, and wherein the first frame is a previous frame of a second frame.

18 . A method comprising:

determining a reference frame number of a current picture based on first channel feedback information, wherein the first channel feedback information indicates first information about a second picture frame of a decoder side;

obtaining a reference layer number set of a first picture frame corresponding to the reference frame number, wherein the reference layer number set comprises layer numbers of N1 layers, wherein 1≤N1<L1, and wherein L1 indicates a total quantity of layers of the first picture frame;

determining a reference layer number of the current picture based on the first channel feedback information and the reference layer number set;

obtaining a reconstructed picture corresponding to the reference frame number and the reference layer number from a decoded picture buffer (DPB) storing only reconstructed pictures of the N1 layers for the first picture frame;

setting the reconstructed picture as a reference picture; and

performing video encoding on the current picture based on the reference picture to obtain a bitstream.

19 . The method of claim 18 , further comprising:

obtaining pieces of the first channel feedback information, wherein the pieces indicate frame numbers, and wherein the first channel feedback information further indicates a first frame number of the second picture frame; and

setting a second frame number that is in the frame numbers and that is closest to a third frame number of the current picture as the reference frame number.

20 . The method of claim 19 , further comprising:

determining a highest layer number from second channel feedback information indicating the reference frame number as a target layer number;

setting the target layer number as the reference layer number when the reference layer number set comprises the target layer number; and

setting a layer number that is in the reference layer number set and that is less than and closest to the target layer number as the reference layer number when the reference layer number set does not comprise the target layer number.