) ( 2 International Patent Classification: 1909701.3 05 July 2019 (05.07.2019) GB H04N /33 (2014.01) H04N 19/136 (2014.01) 1909724.5 06 July 2019 (06.07.2019) GB H04N 19/107 2014.01) H04N 19/18 (2014.01) 1909997.7 11 July 2019 ( 11.07.2019) GB H04N 19/109 (2014.01) H04N 19/48 (2014.01) 1910674.9 25 July 2019 (25.07.2019) GB H04N / 70 (2014.01) H04N 19/503 (2014.01) 191 1467.7 09 August 2019 (09.08.2019) GB 191 1546.8 13 August 2019 (13.08.2019) GB (21) International Application Number: 1914215.7 02 October 2019 (02. 10.2019) GB PCT/GB2020/050695 1914414.6 06 October 2019 (06. 10.2019) GB (22) International Filing Date: 1914634.9 10 October 2019 (10. 10.2019) GB 18 March 2020 (18.03.2020) 1915553.0 25 October 2019 (25. 10.2019) GB 1916090.2 05 November 2019 (05. 11.2019) GB (25) Filing Language: English 1918099. 1 10 December 2019 (10. 12.2019) GB (26) Publication Language: English 2000430.5 12 January 2020 (12.01.2020) GB 2000483.4 13 January 2020 (13.01.2020) GB (30) Priority Data: 2000600.3 15 January 2020 (15.01.2020) GB 1903844.7 20 March 2019 (20.03.2019) GB 2000668.0 16 January 2020 (16.01.2020) GB 1904014.6 23 March 2019 (23.03.2019) GB 2001408.0 31 January 2020 (3 1.01.2020) GB 1904492.4 29 March 2019 (29.03.2019) GB 62/984,261 02 March 2020 (02.03.2020) US 1905325.5 15 April 2019 (15.04.2019) GB (54) Title: LOW COMPLEXITY ENHANCEMENT VIDEO CODING (57) Abstract: Examples of a low complexity enhancement video coding are described. Encoding and decoding methods are described, as well as corresponding encoders and decoders. The enhancement coding may operate on top of a base layer, which may provide base encoding and decoding. Spatial scaling may be applied across different layers. Only the base layer encodes full video, which may be at a lower resolution. The enhancement coding instead operates on computed sets of residuals. The sets of residuals are computed for a plurality of layers, which may represent different levels of scaling in one or more dimensions. A number of encoding and decoding components or tools are described, which may involve the application of transformations, quantization, entropy encoding and temporal buffering. At an example decoder, an encoded base stream and one or more encoded enhancement streams may be independently decoded and combined to reconstruct an original video. [Continued on nextpage] (71) Applicant: V-NOVA INTERNATIONAL LIMITED [GB/GB]; 8thFloor 1 Sheldon Square, Paddington, London W2 6TT (GB). (72) Inventors: MEARDI, Guido; V-Nova International Lim¬ ited, 8th Floor 1 Sheldon Square, Paddington, London W2 6TT (GB). FERRARA, Simone; V-Nova International Limited, 8th Floor 1 Sheldon Square, Paddington, London W2 6TT (GB). CICCARELLI, Lorenzo; V-Nova Inter¬ national Limited, 8th Floor 1 Sheldon Square, Paddington, London W2 6TT (GB). DAMNJANOVIC, Ivan; V-Nova International Limited, 8thFloor 1 Sheldon Square, Padding¬ ton, London W2 6TT (GB). CLUCAS, Richard; V-Nova International Limited, 8thFloor 1 Sheldon Square, Padding¬ ton, London W2 6TT (GB). LITTLEWOOD, Sam; V- Nova International Limited, 8th Floor 1 Sheldon Square, Paddington, London W2 6TT (GB). (74) Agent: GILL JENNINGS & EVERY LLP; The Broadgate Tower, 20 Primrose Street, London EC2A 2ES (GB). (81) Designated States (unless otherwise indicated, for every kind of national protection available) : AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IR, IS, JO, JP, KE, KG, KH, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, WS, ZA, ZM, ZW. (84) Designated States (unless otherwise indicated, for every kind of regional protection available) : ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, Cl, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Published: LOW COMPLEXITY ENHANCEMENT VIDEO CODING TECHNICAL FIELD The present invention relates to a video coding technology. In particular, the present invention relates to methods and systems for encoding and decoding video data. In certain examples, the methods and systems may be used to generate a compressed representation for streaming and/or storage. BACKGROUND Typical comparative video codecs operate using a single-layer, block-based approach, whereby an original signal is processed using a number of coding tools in order to produce an encoded signal which can then be reconstructed by a corresponding decoding process. For simplicity, coding and decoding algorithms or processes are often referred to as “codecs”; the term “codec” being used to cover one or more of encoding and decoding processes that are designed according to a common framework. Such typical codecs include, but are not limited, to MPEG-2, AVC/H.264, HEVC/H.265, VP8, VP9, AVI. There are also other codecs that are currently under development by international standards organizations, such as MPEG/ISO/ITU as well as industry consortia such as Alliance for Open Media (AoM). In recent years, adaptations to the single-layer, block-based approach have been suggested. For example, there exists a class of codecs that operate using a multi-layer, block-based approach. These codecs are often known as “scalable” codecs within the video coding industry. They typically replicate operations performed by a single-layer, block- based approach over a number of layers, where a set of layers are obtained by down- sampling an original signal. In certain cases, efficiencies in the single-layer, block-based approach may be achieved by re-using information from a lower layer to encode (and decode) an upper layer. These scalable codecs are meant to provide scalability features to operators, in the sense that they need to guarantee that the quality of the scaled-down decoded signal (e.g., the lower resolution signal) satisfies the quality requirements for existing services, as well as ensuring that the quality of the non-scaled decoded signal (e.g., higher resolution signal) is comparable with that produced by a corresponding single-layer codec. An example of a “scalable” codec is Scalable Video Coding - SVC (see for example “The Scalable Video Coding Extension of the H.264/AVC Standard”, H . Schwarz and M . Wien, IEEE Signal Processing Magazine, March 2008, which is incorporated herein by reference). SVC is the scalable version of the Advanced Video Coding standard - AVC (AVC also being known as H.264). In SVC, each scalable layer is processed using the same AVC-based single-layer process, and upper layers receive information from lower layers (e.g., interlayer predictions including residual information and motion information) which is used in the encoding of the upper layer to reduce encoded information at the upper layer. Conversely, in order to decode, an SVC decoder needs to receive various overhead information as well as decode the lower layer in order to be able to decode the upper layer. Another example of a scalable codec is the Scalable Extension of the High Efficiency Video Coding Standard (HEVC) - SHVC (see for example “Overview of SHVC: Scalable Extensions of the High Efficiency Video Coding Standard”, J . Boyce, Y. Ye, J . Chen and A . Ramasubramonian, IEEE Trans. On Circuits and Systems for Video Technology, Vol. 26, No. 1, Jan 2016, which is incorporated by reference herein). Similar to SVC, SHVC also uses the same HEVC-based process for each scalable layer, but it allows for the lower layer to use either AVC or HEVC. In SHVC, the upper layer also receives information from the lower layer (e.g., inter layer processing including motion information and/or the up-sampled lower layer as an additional reference picture for the upper layer coding) in the encoding of the upper layer to reduce encoded information at the upper layer. Again, similarly to SVC, an SHVC decoder needs to receive various overhead information as well as decode the lower layer in order to be able to decode the upper layer. Both SVC and SHVC may be used to encode data in multiple streams at different levels of quality. For example, SVC and SHVC may be used to encode e.g. a SD (standard definition) and an HD (high definition) stream or an HD and a UHD (ultra-high-definition) stream. The base stream (at the lowest level of quality) is typically encoded so that the quality of the base stream is the same as if the base stream were encoded as a single stream, separately from any higher-level streams. Both SVC and SHVC may be thought of primarily as a set of parallel copies of a common encoder and decoder structure, where the outputs of these parallel copies are respectively multiplexed and demultiplexed. In more detail, within an example SVC encoding, a UHD stream (e.g.