Line data Source code
1 : /********************************************************************
2 : * *
3 : * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. *
4 : * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
5 : * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
6 : * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
7 : * *
8 : * THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2009 *
9 : * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
10 : * *
11 : ********************************************************************
12 :
13 : function:
14 : last mod: $Id: quant.c 17307 2010-06-27 06:02:15Z tterribe $
15 :
16 : ********************************************************************/
17 :
18 : #include <stdlib.h>
19 : #include <string.h>
20 : #include <ogg/ogg.h>
21 : #include "quant.h"
22 : #include "decint.h"
23 :
24 : /*The maximum output of the DCT with +/- 255 inputs is +/- 8157.
25 : These minimum quantizers ensure the result after quantization (and after
26 : prediction for DC) will be no more than +/- 510.
27 : The tokenization system can handle values up to +/- 580, so there is no need
28 : to do any coefficient clamping.
29 : I would rather have allowed smaller quantizers and had to clamp, but these
30 : minimums were required when constructing the original VP3 matrices and have
31 : been formalized in the spec.*/
32 : static const unsigned OC_DC_QUANT_MIN[2]={4<<2,8<<2};
33 : static const unsigned OC_AC_QUANT_MIN[2]={2<<2,4<<2};
34 :
35 : /*Initializes the dequantization tables from a set of quantizer info.
36 : Currently the dequantizer (and elsewhere enquantizer) tables are expected to
37 : be initialized as pointing to the storage reserved for them in the
38 : oc_theora_state (resp. oc_enc_ctx) structure.
39 : If some tables are duplicates of others, the pointers will be adjusted to
40 : point to a single copy of the tables, but the storage for them will not be
41 : freed.
42 : If you're concerned about the memory footprint, the obvious thing to do is
43 : to move the storage out of its fixed place in the structures and allocate
44 : it on demand.
45 : However, a much, much better option is to only store the quantization
46 : matrices being used for the current frame, and to recalculate these as the
47 : qi values change between frames (this is what VP3 did).*/
48 0 : void oc_dequant_tables_init(ogg_uint16_t *_dequant[64][3][2],
49 : int _pp_dc_scale[64],const th_quant_info *_qinfo){
50 : /*Coding mode: intra or inter.*/
51 : int qti;
52 : /*Y', C_b, C_r*/
53 : int pli;
54 0 : for(qti=0;qti<2;qti++)for(pli=0;pli<3;pli++){
55 : /*Quality index.*/
56 : int qi;
57 : /*Range iterator.*/
58 : int qri;
59 0 : for(qi=0,qri=0;qri<=_qinfo->qi_ranges[qti][pli].nranges;qri++){
60 : th_quant_base base;
61 : ogg_uint32_t q;
62 : int qi_start;
63 : int qi_end;
64 0 : memcpy(base,_qinfo->qi_ranges[qti][pli].base_matrices[qri],
65 : sizeof(base));
66 0 : qi_start=qi;
67 0 : if(qri==_qinfo->qi_ranges[qti][pli].nranges)qi_end=qi+1;
68 0 : else qi_end=qi+_qinfo->qi_ranges[qti][pli].sizes[qri];
69 : /*Iterate over quality indicies in this range.*/
70 0 : for(;;){
71 : ogg_uint32_t qfac;
72 : int zzi;
73 : int ci;
74 : /*In the original VP3.2 code, the rounding offset and the size of the
75 : dead zone around 0 were controlled by a "sharpness" parameter.
76 : The size of our dead zone is now controlled by the per-coefficient
77 : quality thresholds returned by our HVS module.
78 : We round down from a more accurate value when the quality of the
79 : reconstruction does not fall below our threshold and it saves bits.
80 : Hence, all of that VP3.2 code is gone from here, and the remaining
81 : floating point code has been implemented as equivalent integer code
82 : with exact precision.*/
83 0 : qfac=(ogg_uint32_t)_qinfo->dc_scale[qi]*base[0];
84 : /*For postprocessing, not dequantization.*/
85 0 : if(_pp_dc_scale!=NULL)_pp_dc_scale[qi]=(int)(qfac/160);
86 : /*Scale DC the coefficient from the proper table.*/
87 0 : q=(qfac/100)<<2;
88 0 : q=OC_CLAMPI(OC_DC_QUANT_MIN[qti],q,OC_QUANT_MAX);
89 0 : _dequant[qi][pli][qti][0]=(ogg_uint16_t)q;
90 : /*Now scale AC coefficients from the proper table.*/
91 0 : for(zzi=1;zzi<64;zzi++){
92 0 : q=((ogg_uint32_t)_qinfo->ac_scale[qi]*base[OC_FZIG_ZAG[zzi]]/100)<<2;
93 0 : q=OC_CLAMPI(OC_AC_QUANT_MIN[qti],q,OC_QUANT_MAX);
94 0 : _dequant[qi][pli][qti][zzi]=(ogg_uint16_t)q;
95 : }
96 : /*If this is a duplicate of a previous matrix, use that instead.
97 : This simple check helps us improve cache coherency later.*/
98 : {
99 : int dupe;
100 : int qtj;
101 : int plj;
102 0 : dupe=0;
103 0 : for(qtj=0;qtj<=qti;qtj++){
104 0 : for(plj=0;plj<(qtj<qti?3:pli);plj++){
105 0 : if(!memcmp(_dequant[qi][pli][qti],_dequant[qi][plj][qtj],
106 : sizeof(oc_quant_table))){
107 0 : dupe=1;
108 0 : break;
109 : }
110 : }
111 0 : if(dupe)break;
112 : }
113 0 : if(dupe)_dequant[qi][pli][qti]=_dequant[qi][plj][qtj];
114 : }
115 0 : if(++qi>=qi_end)break;
116 : /*Interpolate the next base matrix.*/
117 0 : for(ci=0;ci<64;ci++){
118 0 : base[ci]=(unsigned char)(
119 0 : (2*((qi_end-qi)*_qinfo->qi_ranges[qti][pli].base_matrices[qri][ci]+
120 0 : (qi-qi_start)*_qinfo->qi_ranges[qti][pli].base_matrices[qri+1][ci])
121 0 : +_qinfo->qi_ranges[qti][pli].sizes[qri])/
122 0 : (2*_qinfo->qi_ranges[qti][pli].sizes[qri]));
123 : }
124 : }
125 : }
126 : }
127 0 : }
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