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The Daala Project Techniques Lapped Daala: Building a Next-Generation Video Codec from Unconventional Technology Jean-Marc Valin, Timothy B. Terriberry Nathan E. Egge, Thoma$ J. Daede mozilla research %ushin Cho, Christo&her Montgomery Michael Bebenita The Daala Project 'erceptual Vector Quantization Deringing Filter -BMC Pro(ect goal$: Gain-shape vector 2uantization based on a -verview: Blending "ased on 4-8 mesh ● )oyalty-free video codec $&herical projection of the &yramid vector ● Conditional replacement filter ● Only dou"le MV$ for each level 2uantizer in N dimensions ● )eplacing traditional tool$ *ith ● Directional @A-tap /Ax7) separable 8lter ● Gain = contrast ne*+uncommon ones ● Decoder-side direction estimation ● ● =hape = details #xploring new ideas *ithout constraint$ ● Computed on Cx8 block$ ● Number of pulses K "ased on gain #ffort is now part of the ,lliance for Open ● =trength signaled on super"locks /64x64) Media’s /,-M) ,V1 codec ● Completely vectorizable /=9MD) Chroma from Luma (CfL) Techniques Conditional replacement filter 3uma and chroma are highly correlated so ?iltered *e can &redict chroma from luma Main Daala techiques: 'ixel ● Chroma shape is &redicted from luma ● 3apped transform$ Input D; C DD DA D: D@ CE ,verage < DG ● Code gain and sign ● -verlapped-block motion compensation K<@ /A!DA "its) K=4 /;!E4 bit$0 K<; /B!1G bits) K=8 /C!E1 bit$0 )eplacement ● 1 E 1 1 1 1 E 3uma optionally do*n-sampled (4:D:E0 (OBMC) ma$4 for T = A U$ing prediction: ● 'erceptual vector 2uantization /'V60 Input after ● D; DA DD DA D: D@ DA ,verage < D: Multi-=ym"ol #ntropy Coder =u"tracting prediction from in&ut replacement ● Chroma from luma /CfL0 prediction ● Transform input using &rediction Entro&y decoding is a (serial) "ottlenec4 in ● Directional ?iltering: Haar DC ● video decoding! Fe can reduce the cost "y U$e Householder reflection to align ● ● B-tap 8lter along direction increasing the alphabet size and coding Multi-symbol entro&y coding &rediction with one axis ● fewer $ymbol$! Daala uses alphabet sizes up ● A-tap 8lter acro$$ lines (lo*er threshold0 Deringing filter ● 9ntroduce angle θ "etween in&ut and to 1;! *eight$: [1 2 3 (:) 3 2 1J *eight$: [1 1 (1) 1 1J In ,V1 Considered for ,V1 Not considered for ,V1 &rediction CE ● N D@ Alliance for Open Media Code $&here in -1 dimensions D: 3a&ped Transforms ● DA =econd 8lter Optional no reference coding DD ,-M’s new ,V1 codec based on 4x4 to ;:x64 DCT$ *ith 4-&oint la&&ing C ?iltered pixel ● D; ,ll of VP9 (Google) #ffective spatial ● ,dvantages: $upport 'arts of Daala /Hiph!Org+Mo5illa0 'rediction ● No bloc4ing artefacts ● 'arts of Thor /CI=C-0 In&ut Direction estimation: ● ● Better energy compaction θ New contributions 'rediction ● Minimi5e error compared to directional ● 'erfect reconstruction 9n&ut line averages )esult$ Disadvantages: ● ?ast, vectorizable algebraic Progress over the &ast 3 year$ ● Cannot use traditional intra &rediction simplifications ● Have to use 8xed $ize lapping (search) 'V6 can ta4e advantage of contrast ma$4ing ● Better re$olution for small gain u& and left Haar DC ● Quantize companded gain i$ "etter Hierarchically code DC coefficients using ● Can be done with no signaling 76 %ouTu"e Haar transform 4x: =plit coeffs in bands CxC 16x1; 36 Video Compensate for lack of intra predictor Conference ● DC coded separately Jan ● )ecursive subdivision ● =plit per octave Threshold based on signaled global 7!D;A May threshold signaled super"lock adjustment, ● =plit per direction Jun non-signaled "lock variance measurement ,pr ,pr Nov Nov ?e".
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