# US 12,015,761 B2 · Reference picture management in video coding

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- Number: US 12,015,761 B2
- Document ID: US12015761B2
- Status: Granted
- Kind: B2
- Application number: 17/176,594
- Filed: 2021-02-16
- Published: 2021-06-03
- Granted: 2024-06-18
- Earliest claimed: 2018-08-17
- Assignees: Huawei Technologies Co., Ltd.
- Applicants: Huawei Technologies Co., Ltd.
- Inventors: Fnu Hendry; Ye-Kui Wang
- Web page: https://patentgrep.com/patent/US12015761B2

## CPC

- H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
- A61C 7/002: {Orthodontic computer assisted systems}
- A61C 7/02: Tools for manipulating or working with an orthodontic appliance {(tools for placement of brackets A61C7/146; instruments for attaching elastic bands A61C7/306)}
- A61C 7/08: Mouthpiece-type retainers {or positioners, e.g. for both the lower and upper arch (arch-shaped medicament applicators for teeth or gums A61C19/063; mouthguards for protecting the teeth of sportsmen A63B71/085)}
- B29C 51/30: Moulds
- B29C 51/46: Measuring, controlling or regulating
- H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
- H04N 19/174: the region being a slice, e.g. a line of blocks or a group of blocks
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/44: Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
- H04N 19/46: Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence)
- H04N 19/58: Motion compensation with long-term prediction, i.e. the reference frame for a current frame not being the temporally closest one (H04N19/23 takes precedence)
- H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards
- H04N 21/44004: {involving video buffer management, e.g. video decoder buffer or video display buffer}
- B29L 2031/753: {Medical equipment; Accessories therefor (bloodbags, medical bags B29L2031/7148; artificial eyes B29L2011/0008)}
- G06T 1/60: Memory management
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- A61C: DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE (non-driven toothbrushes A46B; {tongue scrapers A61B17/24;} preparations for dentistry A61K6/00; preparations for cleaning the teeth or mouth A61K8/00, A61Q11/00)
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

A method of decoding a coded video bitstream is provided. The method includes obtaining a reference picture list structure for a current slice represented in the coded video bitstream; constructing a reference picture list for the current slice based on the reference picture list structure such that a number of entries in the reference picture list and an order of the entries in the reference picture list are both the same as in the reference picture list structure, wherein the reference picture list contains a plurality of active entries and a plurality of inactive entries; and obtaining, based on at least one active entry of the reference picture list, at least one reconstructed block of the current slice.

## Claims

### Claim 1

A method of decoding a coded video bitstream implemented by a video decoder, the method comprising:
obtaining a reference picture list syntax structure for a current slice represented in the coded video bitstream, wherein the reference picture list syntax structure contains a number of entries;
constructing a reference picture list for the current slice based on the reference picture list syntax structure such that a number of entries in the reference picture list and an order of entries in the reference picture list are both the same as in the reference picture list syntax structure, wherein first entries in the reference picture list are always a plurality of active entries followed by a plurality of inactive entries, wherein one or more of the entries in the reference picture list are equal to “no reference picture” because corresponding pictures are not present in a decoded picture buffer (DPB), wherein each inactive entry in the reference picture list equal to the “no reference picture” is ignored, and wherein an unintentional picture loss is inferred for each active entry in the reference picture list equal to the “no reference picture”;
obtaining, based on at least one active entry from the plurality of active entries in the reference picture list, at least one reconstructed block of the current slice; and
obtaining a reference picture list flag from an active sequence parameter set (SPS) of the coded video bitstream, wherein the reference picture list flag equal to 1 specifies that reference picture list i of a current picture is derived based on a reference picture list structure in the active SPS, and wherein the reference picture list flag equal to 0 specifies that reference picture list i of the current picture is derived based on a reference picture list structure directly included in a slice header of the current picture,
wherein a num_ref_idx_active_override_flag equal to 1 specifies that syntax element num_ref_idx_active_minus1[0] is present for P and B slices and that syntax element num_ref_idx_active_minus1[1] is present for B slices, and when the current slice is a B slice and the num_ref_idx_active_override_flag is equal to 0, NumRefIdxActive[i] is inferred to be equal to num_ref_idx_default_active_minus1[i]+1.

### Claim 2 (depends on 1)

The method of claim 1, wherein each entry in the reference picture list syntax structure describes a corresponding reference picture in the reference picture list.

### Claim 3 (depends on 1)

The method of claim 1, wherein the reference picture list for the current slice is constructed without using a reference picture list initialization process or a reference picture list modification process.

### Claim 4 (depends on 1)

The method of claim 1, wherein the at least one reconstructed block is used to generate an image displayed on a display of an electronic device.

### Claim 5 (depends on 1)

The method of claim 1, wherein the reference picture list comprises a list of reference pictures used for inter prediction of the at least one reconstructed block.

### Claim 6 (depends on 1)

The method of claim 1, wherein the current slice is a P slice or for a B slice.

### Claim 7

A method of encoding a coded video bitstream implemented by a video encoder, the method comprising:
constructing a reference picture list for a current slice, wherein first entries in the reference picture list are always a plurality of active entries followed by a plurality of inactive entries, wherein one or more of the entries in the reference picture list are equal to “no reference picture” because corresponding pictures are not present in a decoded picture buffer (DPB), wherein each inactive entry in the reference picture list equal to the “no reference picture” is ignored, and wherein an unintentional picture loss is inferred for each active entry in the reference picture list equal to the “no reference picture”;
obtaining, based on at least one active entry from the plurality of active entries in the reference picture list, at least one reconstructed block of the current slice;
encoding a reference picture list syntax structure for the current slice into the coded video bitstream, wherein the reference picture list syntax structure contains a number of entries used to derive the entries in the reference picture list, and wherein the number of entries in the reference picture list and an order of entries in the reference picture list are both the same as in the reference picture list syntax structure; and
obtaining a reference picture list flag from an active sequence parameter set (SPS) of the coded video bitstream, wherein the reference picture list flag equal to 1 specifies that reference picture list i of a current picture is derived based on a reference picture list structure in the active SPS, and wherein the reference picture list flag equal to 0 specifies that reference picture list i of the current picture is derived based on a reference picture list structure directly included in a slice header of the current picture,
wherein a num_ref_idx_active_override_flag equal to 1 specifies that syntax element num_ref_idx_active_minus1[0] is present for P and B slices and that syntax element num_ref_idx_active_minus1[1] is present for B slices, and when the current slice is a B slice and the num_ref_idx_active_override_flag is equal to 0, NumRefIdxActive[i] is inferred to be equal to num_ref_idx_default_active_minus1[i]+1.

### Claim 8 (depends on 7)

The method of claim 7, wherein each entry in the reference picture list syntax structure describes a corresponding reference picture in the reference picture list.

### Claim 9 (depends on 7)

The method of claim 7, wherein the reference picture list for the current slice is constructed without using a reference picture list initialization process or a reference picture list modification process.

### Claim 10 (depends on 7)

The method of claim 7, wherein the reference picture list comprises a list of reference pictures used for inter prediction of the at least one reconstructed block.

### Claim 11 (depends on 7)

The method of claim 7, wherein the current slice is a P slice or for a B slice.

### Claim 12 (depends on 7)

The method of claim 7, further comprising storing the coded video bitstream in a memory of the video encoder.

### Claim 13 (depends on 7)

The method of claim 7, further comprising transmitting the coded video bitstream toward a video decoder.

### Claim 14

An encoding device, comprising:
a memory storing instructions; and
one or more processors coupled to the memory, the one or more processors configured to execute the instructions stored in the memory to cause the encoding device to:
construct a reference picture list for a current slice, wherein first entries in the reference picture list are always a plurality of active entries followed by a plurality of inactive entries, wherein one or more of the entries in the reference picture list are equal to “no reference picture” because corresponding pictures are not present in a decoded picture buffer (DPB), wherein each inactive entry in the reference picture list equal to the “no reference picture” is ignored, and wherein an unintentional picture loss is inferred for each active entry in the reference picture list equal to the “no reference picture”;
obtain, based on at least one active entry from the plurality of active entries in the reference picture list, at least one reconstructed block of the current slice;
encode a reference picture list syntax structure for the current slice into a coded video bitstream, wherein the reference picture list syntax structure contains a number of entries used to derive the entries in the reference picture list, and the number of entries in the reference picture list and an order of entries in the reference picture list are both the same as in the reference picture list syntax structure; and
obtain a reference picture list flag from an active sequence parameter set (SPS) of the coded video bitstream, wherein the reference picture list flag equal to 1 specifies that reference picture list i of a current picture is derived based on a reference picture list structure in the active SPS, and wherein the reference picture list flag equal to 0 specifies that reference picture list i of the current picture is derived based on a reference picture list structure directly included in a slice header of the current picture,
wherein a num_ref_idx_active_override_flag equal to 1 specifies that syntax element num_ref_idx_active_minus1[0] is present for P and B slices and that syntax element num_ref_idx_active_minus1[1] is present for B slices, and when the current slice is a B slice and the num_ref_idx_active_override_flag is equal to 0, NumRefIdxActive[i] is inferred to be equal to num_ref_idx_default_active_minus1[i]+1.

### Claim 15 (depends on 14)

The encoding device of claim 14, wherein each entry in the reference picture list syntax structure describes a corresponding reference picture in the reference picture list.

### Claim 16

A decoding device, comprising:
a receiver configured to receive a coded video bitstream;
a memory coupled to the receiver, the memory storing instructions; and
one or more processors coupled to the memory, the one or more processors configured to execute the instructions stored in the memory to cause the decoding device to:
obtain a reference picture list syntax structure for a current slice represented in the coded video bitstream, wherein the reference picture list syntax structure contains a number of entries;
construct a reference picture list for the current slice based on the reference picture list syntax structure such that the number of entries in the reference picture list and an order of entries in the reference picture list are both the same as in the reference picture list syntax structure, wherein first entries in the reference picture list are always a plurality of active entries followed by a number of inactive entries, wherein one or more of the entries in the reference picture list are equal to “no reference picture” because corresponding pictures are not present in a decoded picture buffer (DPB), wherein each inactive entry in the reference picture list equal to the “no reference picture” is ignored, and wherein an unintentional picture loss is inferred for each active entry in the reference picture list equal to the “no reference picture”;
obtain, based on at least one active entry of the reference picture list, at least one reconstructed block of the current slice; and
obtain a reference picture list flag from an active sequence parameter set (SPS) of the coded video bitstream, wherein the reference picture list flag equal to 1 specifies that reference picture list i of a current picture is derived based on a reference picture list structure in the active SPS, and wherein the reference picture list flag equal to 0 specifies that reference picture list i of the current picture is derived based on a reference picture list structure directly included in a slice header of the current picture,
wherein a num_ref_idx_active_override_flag equal to 1 specifies that syntax element num_ref_idx_active_minus1[0] is present for P and B slices and that syntax element num_ref_idx_active_minus1[1] is present for B slices, and when the current slice is a B slice and the num_ref_idx_active_override_flag is equal to 0, NumRefIdxActive[i] is inferred to be equal to num_ref_idx_default_active_minus1[i]+1.

### Claim 17 (depends on 16)

The decoding device of claim 16, further comprising a display configured to display an image based on the at least one reconstructed block.

### Claim 18 (depends on 16)

The decoding device of claim 16, wherein each entry in the reference picture list syntax structure describes a corresponding reference picture in the reference picture list.

### Claim 19 (depends on 17)

The decoding device of claim 17, wherein the reference picture list for the current slice is constructed without using a reference picture list initialization process or a reference picture list modification process, wherein the reference picture list comprises a list of reference pictures used for inter prediction of the at least one reconstructed block, and wherein the current slice is a P slice or for a B slice.

### Claim 20

A non-transitory storage medium which includes an encoded bitstream, the encoded bitstream being generated by dividing a current picture of a video signal or an image signal into a plurality of slices, and comprising a plurality of syntax elements, wherein the plurality of syntax elements comprises a reference picture list syntax structure for a current slice, wherein the reference picture list syntax structure contains a number of entries, wherein first entries in a reference picture list constructed based on the reference picture list syntax structure are always a plurality of active entries followed by a plurality of inactive entries, wherein one or more of the entries in the reference picture list are equal to “no reference picture” because corresponding pictures are not present in a decoded picture buffer (DPB), wherein each inactive entry in the reference picture list equal to the “no reference picture” is ignored, and wherein an unintentional picture loss is inferred for each active entry in the reference picture list equal to the “no reference picture”,
wherein a reference picture list flag is obtained from an active sequence parameter set (SPS) of a coded video bitstream, wherein the reference picture list flag equal to 1 specifies that reference picture list i of the current picture is derived based on a reference picture list structure in the active SPS, and wherein the reference picture list flag equal to 0 specifies that reference picture list i of the current picture is derived based on a reference picture list structure directly included in a slice header of the current picture,
wherein a num_ref_idx_active_override_flag equal to 1 specifies that syntax element num_ref_idx_active_minus1[0] is present for P and B slices and that syntax element num_ref_idx_active_minus1[1] is present for B slices, and when the current slice is a B slice and the num_ref_idx_active_override_flag is equal to 0, NumRefIdxActive[i] is inferred to be equal to num_ref_idx_default_active_minus1[i]+1.