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Diffstat (limited to 'media/libtheora/lib/quant.c')
| -rw-r--r-- | media/libtheora/lib/quant.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/media/libtheora/lib/quant.c b/media/libtheora/lib/quant.c new file mode 100644 index 0000000000..c3f3f47713 --- /dev/null +++ b/media/libtheora/lib/quant.c @@ -0,0 +1,127 @@ +/******************************************************************** + * * + * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. * + * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS * + * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE * + * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. * + * * + * THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2009 * + * by the Xiph.Org Foundation and contributors http://www.xiph.org/ * + * * + ******************************************************************** + + function: + last mod: $Id: quant.c 17307 2010-06-27 06:02:15Z tterribe $ + + ********************************************************************/ + +#include <stdlib.h> +#include <string.h> +#include <ogg/ogg.h> +#include "quant.h" +#include "decint.h" + +/*The maximum output of the DCT with +/- 255 inputs is +/- 8157. + These minimum quantizers ensure the result after quantization (and after + prediction for DC) will be no more than +/- 510. + The tokenization system can handle values up to +/- 580, so there is no need + to do any coefficient clamping. + I would rather have allowed smaller quantizers and had to clamp, but these + minimums were required when constructing the original VP3 matrices and have + been formalized in the spec.*/ +static const unsigned OC_DC_QUANT_MIN[2]={4<<2,8<<2}; +static const unsigned OC_AC_QUANT_MIN[2]={2<<2,4<<2}; + +/*Initializes the dequantization tables from a set of quantizer info. + Currently the dequantizer (and elsewhere enquantizer) tables are expected to + be initialized as pointing to the storage reserved for them in the + oc_theora_state (resp. oc_enc_ctx) structure. + If some tables are duplicates of others, the pointers will be adjusted to + point to a single copy of the tables, but the storage for them will not be + freed. + If you're concerned about the memory footprint, the obvious thing to do is + to move the storage out of its fixed place in the structures and allocate + it on demand. + However, a much, much better option is to only store the quantization + matrices being used for the current frame, and to recalculate these as the + qi values change between frames (this is what VP3 did).*/ +void oc_dequant_tables_init(ogg_uint16_t *_dequant[64][3][2], + int _pp_dc_scale[64],const th_quant_info *_qinfo){ + /*Coding mode: intra or inter.*/ + int qti; + /*Y', C_b, C_r*/ + int pli; + for(qti=0;qti<2;qti++)for(pli=0;pli<3;pli++){ + /*Quality index.*/ + int qi; + /*Range iterator.*/ + int qri; + for(qi=0,qri=0;qri<=_qinfo->qi_ranges[qti][pli].nranges;qri++){ + th_quant_base base; + ogg_uint32_t q; + int qi_start; + int qi_end; + memcpy(base,_qinfo->qi_ranges[qti][pli].base_matrices[qri], + sizeof(base)); + qi_start=qi; + if(qri==_qinfo->qi_ranges[qti][pli].nranges)qi_end=qi+1; + else qi_end=qi+_qinfo->qi_ranges[qti][pli].sizes[qri]; + /*Iterate over quality indicies in this range.*/ + for(;;){ + ogg_uint32_t qfac; + int zzi; + int ci; + /*In the original VP3.2 code, the rounding offset and the size of the + dead zone around 0 were controlled by a "sharpness" parameter. + The size of our dead zone is now controlled by the per-coefficient + quality thresholds returned by our HVS module. + We round down from a more accurate value when the quality of the + reconstruction does not fall below our threshold and it saves bits. + Hence, all of that VP3.2 code is gone from here, and the remaining + floating point code has been implemented as equivalent integer code + with exact precision.*/ + qfac=(ogg_uint32_t)_qinfo->dc_scale[qi]*base[0]; + /*For postprocessing, not dequantization.*/ + if(_pp_dc_scale!=NULL)_pp_dc_scale[qi]=(int)(qfac/160); + /*Scale DC the coefficient from the proper table.*/ + q=(qfac/100)<<2; + q=OC_CLAMPI(OC_DC_QUANT_MIN[qti],q,OC_QUANT_MAX); + _dequant[qi][pli][qti][0]=(ogg_uint16_t)q; + /*Now scale AC coefficients from the proper table.*/ + for(zzi=1;zzi<64;zzi++){ + q=((ogg_uint32_t)_qinfo->ac_scale[qi]*base[OC_FZIG_ZAG[zzi]]/100)<<2; + q=OC_CLAMPI(OC_AC_QUANT_MIN[qti],q,OC_QUANT_MAX); + _dequant[qi][pli][qti][zzi]=(ogg_uint16_t)q; + } + /*If this is a duplicate of a previous matrix, use that instead. + This simple check helps us improve cache coherency later.*/ + { + int dupe; + int qtj; + int plj; + dupe=0; + for(qtj=0;qtj<=qti;qtj++){ + for(plj=0;plj<(qtj<qti?3:pli);plj++){ + if(!memcmp(_dequant[qi][pli][qti],_dequant[qi][plj][qtj], + sizeof(oc_quant_table))){ + dupe=1; + break; + } + } + if(dupe)break; + } + if(dupe)_dequant[qi][pli][qti]=_dequant[qi][plj][qtj]; + } + if(++qi>=qi_end)break; + /*Interpolate the next base matrix.*/ + for(ci=0;ci<64;ci++){ + base[ci]=(unsigned char)( + (2*((qi_end-qi)*_qinfo->qi_ranges[qti][pli].base_matrices[qri][ci]+ + (qi-qi_start)*_qinfo->qi_ranges[qti][pli].base_matrices[qri+1][ci]) + +_qinfo->qi_ranges[qti][pli].sizes[qri])/ + (2*_qinfo->qi_ranges[qti][pli].sizes[qri])); + } + } + } + } +} |