1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/media/libtheora/lib/quant.c Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,127 @@
1.4 +/********************************************************************
1.5 + * *
1.6 + * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. *
1.7 + * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
1.8 + * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
1.9 + * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
1.10 + * *
1.11 + * THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2009 *
1.12 + * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
1.13 + * *
1.14 + ********************************************************************
1.15 +
1.16 + function:
1.17 + last mod: $Id: quant.c 17307 2010-06-27 06:02:15Z tterribe $
1.18 +
1.19 + ********************************************************************/
1.20 +
1.21 +#include <stdlib.h>
1.22 +#include <string.h>
1.23 +#include <ogg/ogg.h>
1.24 +#include "quant.h"
1.25 +#include "decint.h"
1.26 +
1.27 +/*The maximum output of the DCT with +/- 255 inputs is +/- 8157.
1.28 + These minimum quantizers ensure the result after quantization (and after
1.29 + prediction for DC) will be no more than +/- 510.
1.30 + The tokenization system can handle values up to +/- 580, so there is no need
1.31 + to do any coefficient clamping.
1.32 + I would rather have allowed smaller quantizers and had to clamp, but these
1.33 + minimums were required when constructing the original VP3 matrices and have
1.34 + been formalized in the spec.*/
1.35 +static const unsigned OC_DC_QUANT_MIN[2]={4<<2,8<<2};
1.36 +static const unsigned OC_AC_QUANT_MIN[2]={2<<2,4<<2};
1.37 +
1.38 +/*Initializes the dequantization tables from a set of quantizer info.
1.39 + Currently the dequantizer (and elsewhere enquantizer) tables are expected to
1.40 + be initialized as pointing to the storage reserved for them in the
1.41 + oc_theora_state (resp. oc_enc_ctx) structure.
1.42 + If some tables are duplicates of others, the pointers will be adjusted to
1.43 + point to a single copy of the tables, but the storage for them will not be
1.44 + freed.
1.45 + If you're concerned about the memory footprint, the obvious thing to do is
1.46 + to move the storage out of its fixed place in the structures and allocate
1.47 + it on demand.
1.48 + However, a much, much better option is to only store the quantization
1.49 + matrices being used for the current frame, and to recalculate these as the
1.50 + qi values change between frames (this is what VP3 did).*/
1.51 +void oc_dequant_tables_init(ogg_uint16_t *_dequant[64][3][2],
1.52 + int _pp_dc_scale[64],const th_quant_info *_qinfo){
1.53 + /*Coding mode: intra or inter.*/
1.54 + int qti;
1.55 + /*Y', C_b, C_r*/
1.56 + int pli;
1.57 + for(qti=0;qti<2;qti++)for(pli=0;pli<3;pli++){
1.58 + /*Quality index.*/
1.59 + int qi;
1.60 + /*Range iterator.*/
1.61 + int qri;
1.62 + for(qi=0,qri=0;qri<=_qinfo->qi_ranges[qti][pli].nranges;qri++){
1.63 + th_quant_base base;
1.64 + ogg_uint32_t q;
1.65 + int qi_start;
1.66 + int qi_end;
1.67 + memcpy(base,_qinfo->qi_ranges[qti][pli].base_matrices[qri],
1.68 + sizeof(base));
1.69 + qi_start=qi;
1.70 + if(qri==_qinfo->qi_ranges[qti][pli].nranges)qi_end=qi+1;
1.71 + else qi_end=qi+_qinfo->qi_ranges[qti][pli].sizes[qri];
1.72 + /*Iterate over quality indicies in this range.*/
1.73 + for(;;){
1.74 + ogg_uint32_t qfac;
1.75 + int zzi;
1.76 + int ci;
1.77 + /*In the original VP3.2 code, the rounding offset and the size of the
1.78 + dead zone around 0 were controlled by a "sharpness" parameter.
1.79 + The size of our dead zone is now controlled by the per-coefficient
1.80 + quality thresholds returned by our HVS module.
1.81 + We round down from a more accurate value when the quality of the
1.82 + reconstruction does not fall below our threshold and it saves bits.
1.83 + Hence, all of that VP3.2 code is gone from here, and the remaining
1.84 + floating point code has been implemented as equivalent integer code
1.85 + with exact precision.*/
1.86 + qfac=(ogg_uint32_t)_qinfo->dc_scale[qi]*base[0];
1.87 + /*For postprocessing, not dequantization.*/
1.88 + if(_pp_dc_scale!=NULL)_pp_dc_scale[qi]=(int)(qfac/160);
1.89 + /*Scale DC the coefficient from the proper table.*/
1.90 + q=(qfac/100)<<2;
1.91 + q=OC_CLAMPI(OC_DC_QUANT_MIN[qti],q,OC_QUANT_MAX);
1.92 + _dequant[qi][pli][qti][0]=(ogg_uint16_t)q;
1.93 + /*Now scale AC coefficients from the proper table.*/
1.94 + for(zzi=1;zzi<64;zzi++){
1.95 + q=((ogg_uint32_t)_qinfo->ac_scale[qi]*base[OC_FZIG_ZAG[zzi]]/100)<<2;
1.96 + q=OC_CLAMPI(OC_AC_QUANT_MIN[qti],q,OC_QUANT_MAX);
1.97 + _dequant[qi][pli][qti][zzi]=(ogg_uint16_t)q;
1.98 + }
1.99 + /*If this is a duplicate of a previous matrix, use that instead.
1.100 + This simple check helps us improve cache coherency later.*/
1.101 + {
1.102 + int dupe;
1.103 + int qtj;
1.104 + int plj;
1.105 + dupe=0;
1.106 + for(qtj=0;qtj<=qti;qtj++){
1.107 + for(plj=0;plj<(qtj<qti?3:pli);plj++){
1.108 + if(!memcmp(_dequant[qi][pli][qti],_dequant[qi][plj][qtj],
1.109 + sizeof(oc_quant_table))){
1.110 + dupe=1;
1.111 + break;
1.112 + }
1.113 + }
1.114 + if(dupe)break;
1.115 + }
1.116 + if(dupe)_dequant[qi][pli][qti]=_dequant[qi][plj][qtj];
1.117 + }
1.118 + if(++qi>=qi_end)break;
1.119 + /*Interpolate the next base matrix.*/
1.120 + for(ci=0;ci<64;ci++){
1.121 + base[ci]=(unsigned char)(
1.122 + (2*((qi_end-qi)*_qinfo->qi_ranges[qti][pli].base_matrices[qri][ci]+
1.123 + (qi-qi_start)*_qinfo->qi_ranges[qti][pli].base_matrices[qri+1][ci])
1.124 + +_qinfo->qi_ranges[qti][pli].sizes[qri])/
1.125 + (2*_qinfo->qi_ranges[qti][pli].sizes[qri]));
1.126 + }
1.127 + }
1.128 + }
1.129 + }
1.130 +}
